修改 JavaDoc。

.gitignore

@@ -12,6 +12,8 @@ target
 *.iws
 *.log
 .idea
-
 *.conf
 *.PNG
+
+.vscode/
+*.class

HISTORY

@@ -1,3 +1,8 @@
+Version 1.30  2023-01-29
+  * support tracker server fail over
+    If the tracker server is not specified, when the tracker server fails to
+    get the connection, it will try to get the connection from other tracker servers.
+    The maximum number of attempts is the number of tracker servers minus 1
 
 Version 1.29  2020-01-03
   * support active test for connection pool.

README.md

@@ -26,7 +26,7 @@ mvn install:install-file -DgroupId=org.csource -DartifactId=fastdfs-client-java
 <dependency>
     <groupId>org.csource</groupId>
     <artifactId>fastdfs-client-java</artifactId>
-    <version>1.29-SNAPSHOT</version>
+    <version>1.30-SNAPSHOT</version>
 </dependency>
 ```
 

pom.xml

@@ -4,7 +4,7 @@
 
   <groupId>org.csource</groupId>
   <artifactId>fastdfs-client-java</artifactId>
-  <version>1.29-SNAPSHOT</version>
+  <version>1.30-SNAPSHOT</version>
   <name>fastdfs-client-java</name>
   <description>fastdfs client for java</description>
   <packaging>jar</packaging>
@@ -14,8 +14,8 @@
     <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
     <maven.test.failure.ignore>true</maven.test.failure.ignore>
     <maven.test.skip>true</maven.test.skip>
-    <jdk.version>1.6</jdk.version>
-    <slf4j.version>1.7.26</slf4j.version>
+    <jdk.version>1.8</jdk.version>
+    <slf4j.version>1.7.36</slf4j.version>
   </properties>
 
   <dependencies>

src/main/java/org/csource/common/IniFileReader.java

@@ -155,13 +155,13 @@ public class IniFileReader {
     } finally {
       try {
         if (in != null) in.close();
-        //System.out.println("loadFrom...finally...in.close(); done");
       } catch (Exception ex) {
         ex.printStackTrace();
       }
     }
   }
 
+  @SuppressWarnings("unchecked")
   private void readToParamTable(InputStream in) throws IOException {
     this.paramTable = new Hashtable();
     if (in == null) return;
@@ -206,7 +206,6 @@ public class IniFileReader {
       try {
         if (bufferedReader != null) bufferedReader.close();
         if (inReader != null) inReader.close();
-        //System.out.println("readToParamTable...finally...bufferedReader.close();inReader.close(); done");
       } catch (Exception ex) {
         ex.printStackTrace();
       }

src/main/java/org/csource/common/MyException.java

@@ -16,6 +16,7 @@ package org.csource.common;
  */
 public class MyException extends Exception {
   public MyException(String s, Exception e) {
+    super(s, e);
   }
 
   public MyException(String message) {

src/main/java/org/csource/fastdfs/ClientGlobal.java

@@ -48,7 +48,6 @@ public class ClientGlobal {
   public static final String PROP_KEY_CONNECTION_POOL_MAX_IDLE_TIME = "fastdfs.connection_pool.max_idle_time";
   public static final String PROP_KEY_CONNECTION_POOL_MAX_WAIT_TIME_IN_MS = "fastdfs.connection_pool.max_wait_time_in_ms";
 
-
   public static final int DEFAULT_CONNECT_TIMEOUT = 5; //second
   public static final int DEFAULT_NETWORK_TIMEOUT = 30; //second
   public static final String DEFAULT_CHARSET = "UTF-8";
@@ -180,7 +179,6 @@ public class ClientGlobal {
     String poolMaxCountPerEntry = props.getProperty(PROP_KEY_CONNECTION_POOL_MAX_COUNT_PER_ENTRY);
     String poolMaxIdleTime  = props.getProperty(PROP_KEY_CONNECTION_POOL_MAX_IDLE_TIME);
     String poolMaxWaitTimeInMS = props.getProperty(PROP_KEY_CONNECTION_POOL_MAX_WAIT_TIME_IN_MS);
-
     if (connectTimeoutInSecondsConf != null && connectTimeoutInSecondsConf.trim().length() != 0) {
       g_connect_timeout = Integer.parseInt(connectTimeoutInSecondsConf.trim()) * 1000;
     }
@@ -221,7 +219,7 @@ public class ClientGlobal {
    *                       server之间用逗号','分隔
    */
   public static void initByTrackers(String trackerServers) throws IOException, MyException {
-    List<InetSocketAddress> list = new ArrayList();
+    List<InetSocketAddress> list = new ArrayList<InetSocketAddress>();
     String spr1 = ",";
     String spr2 = ":";
     String[] arr1 = trackerServers.trim().split(spr1);

src/main/java/org/csource/fastdfs/ProtoStructDecoder.java

@@ -27,6 +27,7 @@ public class ProtoStructDecoder<T extends StructBase> {
   /**
    * decode byte buffer
    */
+  @SuppressWarnings("unchecked")
   public T[] decode(byte[] bs, Class<T> clazz, int fieldsTotalSize) throws Exception {
     if (bs.length % fieldsTotalSize != 0) {
       throw new IOException("byte array length: " + bs.length + " is invalid!");

src/main/java/org/csource/fastdfs/StorageClient.java

@@ -73,15 +73,18 @@ public class StorageClient {
      * upload file to storage server (by file name)
      *
      * @param local_filename local filename to upload
-     * @param file_ext_name  file ext name, do not include dot(.), null to extract ext name from the local filename
+     * @param file_ext_name  file ext name, do not include dot(.), null to extract
+     *                       ext name from the local filename
      * @param meta_list      meta info array
      * @return 2 elements string array if success:<br>
-     * <ul><li>results[0]: the group name to store the file </li></ul>
-     * <ul><li>results[1]: the new created filename</li></ul>
-     * return null if fail
+     *         <ul>
+     *         <li>results[0]: the group name to store the file</li>
+     *         <li>results[1]: the new created filename</li>
+     *         </ul>
+     *         return null if fail
      */
     public String[] upload_file(String local_filename, String file_ext_name,
-                                NameValuePair[] meta_list) throws IOException, MyException {
+            NameValuePair[] meta_list) throws IOException, MyException {
         final String group_name = null;
         return this.upload_file(group_name, local_filename, file_ext_name, meta_list);
     }
@@ -91,15 +94,18 @@ public class StorageClient {
      *
      * @param group_name     the group name to upload file to, can be empty
      * @param local_filename local filename to upload
-     * @param file_ext_name  file ext name, do not include dot(.), null to extract ext name from the local filename
+     * @param file_ext_name  file ext name, do not include dot(.), null to extract
+     *                       ext name from the local filename
      * @param meta_list      meta info array
      * @return 2 elements string array if success:<br>
-     * <ul><li>results[0]: the group name to store the file </li></ul>
-     * <ul><li>results[1]: the new created filename</li></ul>
-     * return null if fail
+     *         <ul>
+     *         <li>results[0]: the group name to store the file</li>
+     *         <li>results[1]: the new created filename</li>
+     *         </ul>
+     *         return null if fail
      */
     protected String[] upload_file(String group_name, String local_filename, String file_ext_name,
-                                   NameValuePair[] meta_list) throws IOException, MyException {
+            NameValuePair[] meta_list) throws IOException, MyException {
         final byte cmd = ProtoCommon.STORAGE_PROTO_CMD_UPLOAD_FILE;
         return this.upload_file(cmd, group_name, local_filename, file_ext_name, meta_list);
     }
@@ -110,15 +116,18 @@ public class StorageClient {
      * @param cmd            the command
      * @param group_name     the group name to upload file to, can be empty
      * @param local_filename local filename to upload
-     * @param file_ext_name  file ext name, do not include dot(.), null to extract ext name from the local filename
+     * @param file_ext_name  file ext name, do not include dot(.), null to extract
+     *                       ext name from the local filename
      * @param meta_list      meta info array
      * @return 2 elements string array if success:<br>
-     * <ul><li>results[0]: the group name to store the file </li></ul>
-     * <ul><li>results[1]: the new created filename</li></ul>
-     * return null if fail
+     *         <ul>
+     *         <li>results[0]: the group name to store the file</li>
+     *         <li>results[1]: the new created filename</li>
+     *         </ul>
+     *         return null if fail
      */
     protected String[] upload_file(byte cmd, String group_name, String local_filename, String file_ext_name,
-                                   NameValuePair[] meta_list) throws IOException, MyException {
+            NameValuePair[] meta_list) throws IOException, MyException {
         File f = new File(local_filename);
         FileInputStream fis = new FileInputStream(f);
 
@@ -146,12 +155,14 @@ public class StorageClient {
      * @param file_ext_name file ext name, do not include dot(.)
      * @param meta_list     meta info array
      * @return 2 elements string array if success:<br>
-     * <ul><li>results[0]: the group name to store the file</li></ul>
-     * <ul><li>results[1]: the new created filename</li></ul>
-     * return null if fail
+     *         <ul>
+     *         <li>results[0]: the group name to store the file</li>
+     *         <li>results[1]: the new created filename</li>
+     *         </ul>
+     *         return null if fail
      */
     public String[] upload_file(byte[] file_buff, int offset, int length, String file_ext_name,
-                                NameValuePair[] meta_list) throws IOException, MyException {
+            NameValuePair[] meta_list) throws IOException, MyException {
         final String group_name = null;
         return this.upload_file(group_name, file_buff, offset, length, file_ext_name, meta_list);
     }
@@ -166,12 +177,14 @@ public class StorageClient {
      * @param file_ext_name file ext name, do not include dot(.)
      * @param meta_list     meta info array
      * @return 2 elements string array if success:<br>
-     * <ul><li>results[0]: the group name to store the file</li></ul>
-     * <ul><li>results[1]: the new created filename</li></ul>
-     * return null if fail
+     *         <ul>
+     *         <li>results[0]: the group name to store the file</li>
+     *         <li>results[1]: the new created filename</li>
+     *         </ul>
+     *         return null if fail
      */
     public String[] upload_file(String group_name, byte[] file_buff, int offset, int length,
-                                String file_ext_name, NameValuePair[] meta_list) throws IOException, MyException {
+            String file_ext_name, NameValuePair[] meta_list) throws IOException, MyException {
         return this.do_upload_file(ProtoCommon.STORAGE_PROTO_CMD_UPLOAD_FILE, group_name, null, null, file_ext_name,
                 length, new UploadBuff(file_buff, offset, length), meta_list);
     }
@@ -183,12 +196,14 @@ public class StorageClient {
      * @param file_ext_name file ext name, do not include dot(.)
      * @param meta_list     meta info array
      * @return 2 elements string array if success:<br>
-     * <ul><li>results[0]: the group name to store the file</li></ul>
-     * <ul><li>results[1]: the new created filename</li></ul>
-     * return null if fail
+     *         <ul>
+     *         <li>results[0]: the group name to store the file</li>
+     *         <li>results[1]: the new created filename</li>
+     *         </ul>
+     *         return null if fail
      */
     public String[] upload_file(byte[] file_buff, String file_ext_name,
-                                NameValuePair[] meta_list) throws IOException, MyException {
+            NameValuePair[] meta_list) throws IOException, MyException {
         final String group_name = null;
         return this.upload_file(group_name, file_buff, 0, file_buff.length, file_ext_name, meta_list);
     }
@@ -201,12 +216,14 @@ public class StorageClient {
      * @param file_ext_name file ext name, do not include dot(.)
      * @param meta_list     meta info array
      * @return 2 elements string array if success:<br>
-     * <ul><li>results[0]: the group name to store the file</li></ul>
-     * <ul><li>results[1]: the new created filename</li></ul>
-     * return null if fail
+     *         <ul>
+     *         <li>results[0]: the group name to store the file</li>
+     *         <li>results[1]: the new created filename</li>
+     *         </ul>
+     *         return null if fail
      */
     public String[] upload_file(String group_name, byte[] file_buff,
-                                String file_ext_name, NameValuePair[] meta_list) throws IOException, MyException {
+            String file_ext_name, NameValuePair[] meta_list) throws IOException, MyException {
         return this.do_upload_file(ProtoCommon.STORAGE_PROTO_CMD_UPLOAD_FILE, group_name, null, null, file_ext_name,
                 file_buff.length, new UploadBuff(file_buff, 0, file_buff.length), meta_list);
     }
@@ -220,12 +237,14 @@ public class StorageClient {
      * @param file_ext_name file ext name, do not include dot(.)
      * @param meta_list     meta info array
      * @return 2 elements string array if success:<br>
-     * <ul><li>results[0]: the group name to store the file</li></ul>
-     * <ul><li>results[1]: the new created filename</li></ul>
-     * return null if fail
+     *         <ul>
+     *         <li>results[0]: the group name to store the file</li>
+     *         <li>results[1]: the new created filename</li>
+     *         </ul>
+     *         return null if fail
      */
     public String[] upload_file(String group_name, long file_size, UploadCallback callback,
-                                String file_ext_name, NameValuePair[] meta_list) throws IOException, MyException {
+            String file_ext_name, NameValuePair[] meta_list) throws IOException, MyException {
         final String master_filename = null;
         final String prefix_name = null;
 
@@ -240,15 +259,18 @@ public class StorageClient {
      * @param master_filename the master file name to generate the slave file
      * @param prefix_name     the prefix name to generate the slave file
      * @param local_filename  local filename to upload
-     * @param file_ext_name   file ext name, do not include dot(.), null to extract ext name from the local filename
+     * @param file_ext_name   file ext name, do not include dot(.), null to extract
+     *                        ext name from the local filename
      * @param meta_list       meta info array
      * @return 2 elements string array if success:<br>
-     * <ul><li>results[0]: the group name to store the file </li></ul>
-     * <ul><li>results[1]: the new created filename</li></ul>
-     * return null if fail
+     *         <ul>
+     *         <li>results[0]: the group name to store the file</li>
+     *         <li>results[1]: the new created filename</li>
+     *         </ul>
+     *         return null if fail
      */
     public String[] upload_file(String group_name, String master_filename, String prefix_name,
-                                String local_filename, String file_ext_name, NameValuePair[] meta_list) throws IOException, MyException {
+            String local_filename, String file_ext_name, NameValuePair[] meta_list) throws IOException, MyException {
         if ((group_name == null || group_name.length() == 0) ||
                 (master_filename == null || master_filename.length() == 0) ||
                 (prefix_name == null)) {
@@ -266,8 +288,8 @@ public class StorageClient {
         }
 
         try {
-            return this.do_upload_file(ProtoCommon.STORAGE_PROTO_CMD_UPLOAD_SLAVE_FILE, group_name, master_filename, prefix_name,
-                    file_ext_name, f.length(), new UploadStream(fis, f.length()), meta_list);
+            return this.do_upload_file(ProtoCommon.STORAGE_PROTO_CMD_UPLOAD_SLAVE_FILE, group_name, master_filename,
+                    prefix_name, file_ext_name, f.length(), new UploadStream(fis, f.length()), meta_list);
         } finally {
             fis.close();
         }
@@ -283,20 +305,23 @@ public class StorageClient {
      * @param file_ext_name   file ext name, do not include dot(.)
      * @param meta_list       meta info array
      * @return 2 elements string array if success:<br>
-     * <ul><li>results[0]: the group name to store the file</li></ul>
-     * <ul><li>results[1]: the new created filename</li></ul>
-     * return null if fail
+     *         <ul>
+     *         <li>results[0]: the group name to store the file</li>
+     *         <li>results[1]: the new created filename</li>
+     *         </ul>
+     *         return null if fail
      */
     public String[] upload_file(String group_name, String master_filename, String prefix_name,
-                                byte[] file_buff, String file_ext_name, NameValuePair[] meta_list) throws IOException, MyException {
+            byte[] file_buff, String file_ext_name, NameValuePair[] meta_list) throws IOException, MyException {
         if ((group_name == null || group_name.length() == 0) ||
                 (master_filename == null || master_filename.length() == 0) ||
                 (prefix_name == null)) {
             throw new MyException("invalid arguement");
         }
 
-        return this.do_upload_file(ProtoCommon.STORAGE_PROTO_CMD_UPLOAD_SLAVE_FILE, group_name, master_filename, prefix_name,
-                file_ext_name, file_buff.length, new UploadBuff(file_buff, 0, file_buff.length), meta_list);
+        return this.do_upload_file(ProtoCommon.STORAGE_PROTO_CMD_UPLOAD_SLAVE_FILE, group_name, master_filename,
+                prefix_name, file_ext_name, file_buff.length, new UploadBuff(file_buff, 0, file_buff.length),
+                meta_list);
     }
 
     /**
@@ -311,21 +336,23 @@ public class StorageClient {
      * @param file_ext_name   file ext name, do not include dot(.)
      * @param meta_list       meta info array
      * @return 2 elements string array if success:<br>
-     * <ul><li>results[0]: the group name to store the file</li></ul>
-     * <ul><li>results[1]: the new created filename</li></ul>
-     * return null if fail
+     *         <ul>
+     *         <li>results[0]: the group name to store the file</li>
+     *         <li>results[1]: the new created filename</li>
+     *         </ul>
+     *         return null if fail
      */
     public String[] upload_file(String group_name, String master_filename, String prefix_name,
-                                byte[] file_buff, int offset, int length, String file_ext_name,
-                                NameValuePair[] meta_list) throws IOException, MyException {
+            byte[] file_buff, int offset, int length, String file_ext_name,
+            NameValuePair[] meta_list) throws IOException, MyException {
         if ((group_name == null || group_name.length() == 0) ||
                 (master_filename == null || master_filename.length() == 0) ||
                 (prefix_name == null)) {
             throw new MyException("invalid arguement");
         }
 
-        return this.do_upload_file(ProtoCommon.STORAGE_PROTO_CMD_UPLOAD_SLAVE_FILE, group_name, master_filename, prefix_name,
-                file_ext_name, length, new UploadBuff(file_buff, offset, length), meta_list);
+        return this.do_upload_file(ProtoCommon.STORAGE_PROTO_CMD_UPLOAD_SLAVE_FILE, group_name, master_filename,
+                prefix_name, file_ext_name, length, new UploadBuff(file_buff, offset, length), meta_list);
     }
 
     /**
@@ -339,30 +366,35 @@ public class StorageClient {
      * @param file_ext_name   file ext name, do not include dot(.)
      * @param meta_list       meta info array
      * @return 2 elements string array if success:<br>
-     * <ul><li>results[0]: the group name to store the file</li></ul>
-     * <ul><li>results[1]: the new created filename</li></ul>
-     * return null if fail
+     *         <ul>
+     *         <li>results[0]: the group name to store the file</li>
+     *         <li>results[1]: the new created filename</li>
+     *         </ul>
+     *         return null if fail
      */
     public String[] upload_file(String group_name, String master_filename,
-                                String prefix_name, long file_size, UploadCallback callback,
-                                String file_ext_name, NameValuePair[] meta_list) throws IOException, MyException {
-        return this.do_upload_file(ProtoCommon.STORAGE_PROTO_CMD_UPLOAD_SLAVE_FILE, group_name, master_filename, prefix_name,
-                file_ext_name, file_size, callback, meta_list);
+            String prefix_name, long file_size, UploadCallback callback,
+            String file_ext_name, NameValuePair[] meta_list) throws IOException, MyException {
+        return this.do_upload_file(ProtoCommon.STORAGE_PROTO_CMD_UPLOAD_SLAVE_FILE, group_name, master_filename,
+                prefix_name, file_ext_name, file_size, callback, meta_list);
     }
 
     /**
      * upload appender file to storage server (by file name)
      *
      * @param local_filename local filename to upload
-     * @param file_ext_name  file ext name, do not include dot(.), null to extract ext name from the local filename
+     * @param file_ext_name  file ext name, do not include dot(.), null to extract
+     *                       ext name from the local filename
      * @param meta_list      meta info array
      * @return 2 elements string array if success:<br>
-     * <ul><li>results[0]: the group name to store the file </li></ul>
-     * <ul><li>results[1]: the new created filename</li></ul>
-     * return null if fail
+     *         <ul>
+     *         <li>results[0]: the group name to store the file</li>
+     *         <li>results[1]: the new created filename</li>
+     *         </ul>
+     *         return null if fail
      */
     public String[] upload_appender_file(String local_filename, String file_ext_name,
-                                         NameValuePair[] meta_list) throws IOException, MyException {
+            NameValuePair[] meta_list) throws IOException, MyException {
         final String group_name = null;
         return this.upload_appender_file(group_name, local_filename, file_ext_name, meta_list);
     }
@@ -372,15 +404,18 @@ public class StorageClient {
      *
      * @param group_name     the group name to upload file to, can be empty
      * @param local_filename local filename to upload
-     * @param file_ext_name  file ext name, do not include dot(.), null to extract ext name from the local filename
+     * @param file_ext_name  file ext name, do not include dot(.), null to extract
+     *                       ext name from the local filename
      * @param meta_list      meta info array
      * @return 2 elements string array if success:<br>
-     * <ul><li>results[0]: the group name to store the file </li></ul>
-     * <ul><li>results[1]: the new created filename</li></ul>
-     * return null if fail
+     *         <ul>
+     *         <li>results[0]: the group name to store the file</li>
+     *         <li>results[1]: the new created filename</li>
+     *         </ul>
+     *         return null if fail
      */
     protected String[] upload_appender_file(String group_name, String local_filename, String file_ext_name,
-                                            NameValuePair[] meta_list) throws IOException, MyException {
+            NameValuePair[] meta_list) throws IOException, MyException {
         final byte cmd = ProtoCommon.STORAGE_PROTO_CMD_UPLOAD_APPENDER_FILE;
         return this.upload_file(cmd, group_name, local_filename, file_ext_name, meta_list);
     }
@@ -394,12 +429,14 @@ public class StorageClient {
      * @param file_ext_name file ext name, do not include dot(.)
      * @param meta_list     meta info array
      * @return 2 elements string array if success:<br>
-     * <ul><li>results[0]: the group name to store the file</li></ul>
-     * <ul><li>results[1]: the new created filename</li></ul>
-     * return null if fail
+     *         <ul>
+     *         <li>results[0]: the group name to store the file</li>
+     *         <li>results[1]: the new created filename</li>
+     *         </ul>
+     *         return null if fail
      */
     public String[] upload_appender_file(byte[] file_buff, int offset, int length, String file_ext_name,
-                                         NameValuePair[] meta_list) throws IOException, MyException {
+            NameValuePair[] meta_list) throws IOException, MyException {
         final String group_name = null;
         return this.upload_appender_file(group_name, file_buff, offset, length, file_ext_name, meta_list);
     }
@@ -414,14 +451,16 @@ public class StorageClient {
      * @param file_ext_name file ext name, do not include dot(.)
      * @param meta_list     meta info array
      * @return 2 elements string array if success:<br>
-     * <ul><li>results[0]: the group name to store the file</li></ul>
-     * <ul><li>results[1]: the new created filename</li></ul>
-     * return null if fail
+     *         <ul>
+     *         <li>results[0]: the group name to store the file</li>
+     *         <li>results[1]: the new created filename</li>
+     *         </ul>
+     *         return null if fail
      */
     public String[] upload_appender_file(String group_name, byte[] file_buff, int offset, int length,
-                                         String file_ext_name, NameValuePair[] meta_list) throws IOException, MyException {
-        return this.do_upload_file(ProtoCommon.STORAGE_PROTO_CMD_UPLOAD_APPENDER_FILE, group_name, null, null, file_ext_name,
-                length, new UploadBuff(file_buff, offset, length), meta_list);
+            String file_ext_name, NameValuePair[] meta_list) throws IOException, MyException {
+        return this.do_upload_file(ProtoCommon.STORAGE_PROTO_CMD_UPLOAD_APPENDER_FILE, group_name, null, null,
+                file_ext_name, length, new UploadBuff(file_buff, offset, length), meta_list);
     }
 
     /**
@@ -431,12 +470,14 @@ public class StorageClient {
      * @param file_ext_name file ext name, do not include dot(.)
      * @param meta_list     meta info array
      * @return 2 elements string array if success:<br>
-     * <ul><li>results[0]: the group name to store the file</li></ul>
-     * <ul><li>results[1]: the new created filename</li></ul>
-     * return null if fail
+     *         <ul>
+     *         <li>results[0]: the group name to store the file</li>
+     *         <li>results[1]: the new created filename</li>
+     *         </ul>
+     *         return null if fail
      */
     public String[] upload_appender_file(byte[] file_buff, String file_ext_name,
-                                         NameValuePair[] meta_list) throws IOException, MyException {
+            NameValuePair[] meta_list) throws IOException, MyException {
         final String group_name = null;
         return this.upload_appender_file(group_name, file_buff, 0, file_buff.length, file_ext_name, meta_list);
     }
@@ -449,14 +490,16 @@ public class StorageClient {
      * @param file_ext_name file ext name, do not include dot(.)
      * @param meta_list     meta info array
      * @return 2 elements string array if success:<br>
-     * <ul><li>results[0]: the group name to store the file</li></ul>
-     * <ul><li>results[1]: the new created filename</li></ul>
-     * return null if fail
+     *         <ul>
+     *         <li>results[0]: the group name to store the file</li>
+     *         <li>results[1]: the new created filename</li>
+     *         </ul>
+     *         return null if fail
      */
     public String[] upload_appender_file(String group_name, byte[] file_buff,
-                                         String file_ext_name, NameValuePair[] meta_list) throws IOException, MyException {
-        return this.do_upload_file(ProtoCommon.STORAGE_PROTO_CMD_UPLOAD_APPENDER_FILE, group_name, null, null, file_ext_name,
-                file_buff.length, new UploadBuff(file_buff, 0, file_buff.length), meta_list);
+            String file_ext_name, NameValuePair[] meta_list) throws IOException, MyException {
+        return this.do_upload_file(ProtoCommon.STORAGE_PROTO_CMD_UPLOAD_APPENDER_FILE, group_name, null, null,
+                file_ext_name, file_buff.length, new UploadBuff(file_buff, 0, file_buff.length), meta_list);
     }
 
     /**
@@ -468,16 +511,19 @@ public class StorageClient {
      * @param file_ext_name file ext name, do not include dot(.)
      * @param meta_list     meta info array
      * @return 2 elements string array if success:<br>
-     * <ul><li>results[0]: the group name to store the file</li></ul>
-     * <ul><li>results[1]: the new created filename</li></ul>
-     * return null if fail
+     *         <ul>
+     *         <li>results[0]: the group name to store the file</li>
+     *         <li>results[1]: the new created filename</li>
+     *         </ul>
+     *         return null if fail
      */
     public String[] upload_appender_file(String group_name, long file_size, UploadCallback callback,
-                                         String file_ext_name, NameValuePair[] meta_list) throws IOException, MyException {
+            String file_ext_name, NameValuePair[] meta_list) throws IOException, MyException {
         final String master_filename = null;
         final String prefix_name = null;
 
-        return this.do_upload_file(ProtoCommon.STORAGE_PROTO_CMD_UPLOAD_APPENDER_FILE, group_name, master_filename, prefix_name,
+        return this.do_upload_file(ProtoCommon.STORAGE_PROTO_CMD_UPLOAD_APPENDER_FILE, group_name, master_filename,
+                prefix_name,
                 file_ext_name, file_size, callback, meta_list);
     }
 
@@ -489,7 +535,8 @@ public class StorageClient {
      * @param local_filename    local filename to append
      * @return 0 for success, != 0 for error (error no)
      */
-    public int append_file(String group_name, String appender_filename, String local_filename) throws IOException, MyException {
+    public int append_file(String group_name, String appender_filename, String local_filename)
+            throws IOException, MyException {
         File f = new File(local_filename);
         FileInputStream fis = new FileInputStream(f);
 
@@ -508,8 +555,10 @@ public class StorageClient {
      * @param file_buff         file content/buff
      * @return 0 for success, != 0 for error (error no)
      */
-    public int append_file(String group_name, String appender_filename, byte[] file_buff) throws IOException, MyException {
-        return this.do_append_file(group_name, appender_filename, file_buff.length, new UploadBuff(file_buff, 0, file_buff.length));
+    public int append_file(String group_name, String appender_filename, byte[] file_buff)
+            throws IOException, MyException {
+        return this.do_append_file(group_name, appender_filename, file_buff.length,
+                new UploadBuff(file_buff, 0, file_buff.length));
     }
 
     /**
@@ -523,7 +572,7 @@ public class StorageClient {
      * @return 0 for success, != 0 for error (error no)
      */
     public int append_file(String group_name, String appender_filename,
-                           byte[] file_buff, int offset, int length) throws IOException, MyException {
+            byte[] file_buff, int offset, int length) throws IOException, MyException {
         return this.do_append_file(group_name, appender_filename, length, new UploadBuff(file_buff, offset, length));
     }
 
@@ -537,7 +586,7 @@ public class StorageClient {
      * @return 0 for success, != 0 for error (error no)
      */
     public int append_file(String group_name, String appender_filename,
-                           long file_size, UploadCallback callback) throws IOException, MyException {
+            long file_size, UploadCallback callback) throws IOException, MyException {
         return this.do_append_file(group_name, appender_filename, file_size, callback);
     }
 
@@ -551,7 +600,7 @@ public class StorageClient {
      * @return 0 for success, != 0 for error (error no)
      */
     public int modify_file(String group_name, String appender_filename,
-                           long file_offset, String local_filename) throws IOException, MyException {
+            long file_offset, String local_filename) throws IOException, MyException {
         File f = new File(local_filename);
         FileInputStream fis = new FileInputStream(f);
 
@@ -573,7 +622,7 @@ public class StorageClient {
      * @return 0 for success, != 0 for error (error no)
      */
     public int modify_file(String group_name, String appender_filename,
-                           long file_offset, byte[] file_buff) throws IOException, MyException {
+            long file_offset, byte[] file_buff) throws IOException, MyException {
         return this.do_modify_file(group_name, appender_filename, file_offset,
                 file_buff.length, new UploadBuff(file_buff, 0, file_buff.length));
     }
@@ -590,7 +639,7 @@ public class StorageClient {
      * @return 0 for success, != 0 for error (error no)
      */
     public int modify_file(String group_name, String appender_filename,
-                           long file_offset, byte[] file_buff, int buffer_offset, int buffer_length) throws IOException, MyException {
+            long file_offset, byte[] file_buff, int buffer_offset, int buffer_length) throws IOException, MyException {
         return this.do_modify_file(group_name, appender_filename, file_offset,
                 buffer_length, new UploadBuff(file_buff, buffer_offset, buffer_length));
     }
@@ -606,7 +655,7 @@ public class StorageClient {
      * @return 0 for success, != 0 for error (error no)
      */
     public int modify_file(String group_name, String appender_filename,
-                           long file_offset, long modify_size, UploadCallback callback) throws IOException, MyException {
+            long file_offset, long modify_size, UploadCallback callback) throws IOException, MyException {
         return this.do_modify_file(group_name, appender_filename, file_offset,
                 modify_size, callback);
     }
@@ -617,11 +666,14 @@ public class StorageClient {
      * @param group_name        the group name of appender file
      * @param appender_filename the appender filename
      * @return 2 elements string array if success:<br>
-     * <ul><li> results[0]: the group name to store the file</li></ul>
-     * <ul><li> results[1]: the new created filename</li></ul>
-     * return null if fail
+     *         <ul>
+     *         <li>results[0]: the group name to store the file</li>
+     *         <li>results[1]: the new created filename</li>
+     *         </ul>
+     *         return null if fail
      */
-    public String[] regenerate_appender_filename(String group_name, String appender_filename) throws IOException, MyException {
+    public String[] regenerate_appender_filename(String group_name, String appender_filename)
+            throws IOException, MyException {
         byte[] header;
         boolean bNewStorageServer;
         Connection connection = null;
@@ -700,13 +752,15 @@ public class StorageClient {
      * @param callback        the write data callback object
      * @param meta_list       meta info array
      * @return 2 elements string array if success:<br>
-     * <ul><li> results[0]: the group name to store the file</li></ul>
-     * <ul><li> results[1]: the new created filename</li></ul>
-     * return null if fail
+     *         <ul>
+     *         <li>results[0]: the group name to store the file</li>
+     *         <li>results[1]: the new created filename</li>
+     *         </ul>
+     *         return null if fail
      */
     protected String[] do_upload_file(byte cmd, String group_name, String master_filename,
-                                      String prefix_name, String file_ext_name, long file_size, UploadCallback callback,
-                                      NameValuePair[] meta_list) throws IOException, MyException {
+            String prefix_name, String file_ext_name, long file_size, UploadCallback callback,
+            NameValuePair[] meta_list) throws IOException, MyException {
         byte[] header;
         byte[] ext_name_bs;
         String new_group_name;
@@ -731,7 +785,6 @@ public class StorageClient {
 
         try {
             connection = this.storageServer.getConnection();
-
             ext_name_bs = new byte[ProtoCommon.FDFS_FILE_EXT_NAME_MAX_LEN];
             Arrays.fill(ext_name_bs, (byte) 0);
             if (file_ext_name != null && file_ext_name.length() > 0) {
@@ -747,8 +800,8 @@ public class StorageClient {
                 masterFilenameBytes = master_filename.getBytes(ClientGlobal.g_charset);
 
                 sizeBytes = new byte[2 * ProtoCommon.FDFS_PROTO_PKG_LEN_SIZE];
-                body_len = sizeBytes.length + ProtoCommon.FDFS_FILE_PREFIX_MAX_LEN + ProtoCommon.FDFS_FILE_EXT_NAME_MAX_LEN
-                        + masterFilenameBytes.length + file_size;
+                body_len = sizeBytes.length + ProtoCommon.FDFS_FILE_PREFIX_MAX_LEN
+                        + ProtoCommon.FDFS_FILE_EXT_NAME_MAX_LEN + masterFilenameBytes.length + file_size;
 
                 hexLenBytes = ProtoCommon.long2buff(master_filename.length());
                 System.arraycopy(hexLenBytes, 0, sizeBytes, 0, hexLenBytes.length);
@@ -862,7 +915,7 @@ public class StorageClient {
      * @return return true for success, false for fail
      */
     protected int do_append_file(String group_name, String appender_filename,
-                                 long file_size, UploadCallback callback) throws IOException, MyException {
+            long file_size, UploadCallback callback) throws IOException, MyException {
         byte[] header;
         boolean bNewStorageServer;
         Connection connection = null;
@@ -955,7 +1008,7 @@ public class StorageClient {
      * @return return true for success, false for fail
      */
     protected int do_modify_file(String group_name, String appender_filename,
-                                 long file_offset, long modify_size, UploadCallback callback) throws IOException, MyException {
+            long file_offset, long modify_size, UploadCallback callback) throws IOException, MyException {
         byte[] header;
         boolean bNewStorageServer;
         Connection connection = null;
@@ -1081,7 +1134,7 @@ public class StorageClient {
      * @return 0 for success, none zero for fail (error code)
      */
     public int truncate_file(String group_name, String appender_filename,
-                             long truncated_file_size) throws IOException, MyException {
+            long truncated_file_size) throws IOException, MyException {
         byte[] header;
         boolean bNewStorageServer;
         Connection connection = null;
@@ -1164,7 +1217,8 @@ public class StorageClient {
      * @param download_bytes  download bytes, 0 for remain bytes from offset
      * @return file content/buff, return null if fail
      */
-    public byte[] download_file(String group_name, String remote_filename, long file_offset, long download_bytes) throws IOException, MyException {
+    public byte[] download_file(String group_name, String remote_filename, long file_offset, long download_bytes)
+            throws IOException, MyException {
         boolean bNewStorageServer = this.newReadableStorageConnection(group_name, remote_filename);
         Connection connection = this.storageServer.getConnection();
 
@@ -1204,7 +1258,7 @@ public class StorageClient {
      * @return 0 success, return none zero errno if fail
      */
     public int download_file(String group_name, String remote_filename,
-                             String local_filename) throws IOException, MyException {
+            String local_filename) throws IOException, MyException {
         final long file_offset = 0;
         final long download_bytes = 0;
         return this.download_file(group_name, remote_filename,
@@ -1222,8 +1276,8 @@ public class StorageClient {
      * @return 0 success, return none zero errno if fail
      */
     public int download_file(String group_name, String remote_filename,
-                             long file_offset, long download_bytes,
-                             String local_filename) throws IOException, MyException {
+            long file_offset, long download_bytes,
+            String local_filename) throws IOException, MyException {
         boolean bNewStorageServer = this.newReadableStorageConnection(group_name, remote_filename);
         Connection connection = this.storageServer.getConnection();
         try {
@@ -1244,17 +1298,18 @@ public class StorageClient {
                 long remainBytes = header.body_len;
                 int bytes;
 
-                //System.out.println("expect_body_len=" + header.body_len);
+                // System.out.println("expect_body_len=" + header.body_len);
 
                 while (remainBytes > 0) {
                     if ((bytes = in.read(buff, 0, remainBytes > buff.length ? buff.length : (int) remainBytes)) < 0) {
-                        throw new IOException("recv package size " + (header.body_len - remainBytes) + " != " + header.body_len);
+                        throw new IOException(
+                                "recv package size " + (header.body_len - remainBytes) + " != " + header.body_len);
                     }
 
                     out.write(buff, 0, bytes);
                     remainBytes -= bytes;
 
-                    //System.out.println("totalBytes=" + (header.body_len - remainBytes));
+                    // System.out.println("totalBytes=" + (header.body_len - remainBytes));
                 }
 
                 return 0;
@@ -1293,7 +1348,7 @@ public class StorageClient {
      * @return 0 success, return none zero errno if fail
      */
     public int download_file(String group_name, String remote_filename,
-                             DownloadCallback callback) throws IOException, MyException {
+            DownloadCallback callback) throws IOException, MyException {
         final long file_offset = 0;
         final long download_bytes = 0;
         return this.download_file(group_name, remote_filename,
@@ -1311,8 +1366,8 @@ public class StorageClient {
      * @return 0 success, return none zero errno if fail
      */
     public int download_file(String group_name, String remote_filename,
-                             long file_offset, long download_bytes,
-                             DownloadCallback callback) throws IOException, MyException {
+            long file_offset, long download_bytes,
+            DownloadCallback callback) throws IOException, MyException {
         int result;
         boolean bNewStorageServer = this.newReadableStorageConnection(group_name, remote_filename);
         Connection connection = this.storageServer.getConnection();
@@ -1332,7 +1387,7 @@ public class StorageClient {
             long remainBytes = header.body_len;
             int bytes;
 
-            //System.out.println("expect_body_len=" + header.body_len);
+            // System.out.println("expect_body_len=" + header.body_len);
 
             while (remainBytes > 0) {
                 if ((bytes = in.read(buff, 0, remainBytes > buff.length ? buff.length : (int) remainBytes)) < 0) {
@@ -1345,7 +1400,7 @@ public class StorageClient {
                 }
 
                 remainBytes -= bytes;
-                //System.out.println("totalBytes=" + (header.body_len - remainBytes));
+                // System.out.println("totalBytes=" + (header.body_len - remainBytes));
             }
 
             return 0;
@@ -1407,14 +1462,18 @@ public class StorageClient {
      * @param remote_filename filename on storage server
      * @param meta_list       meta item array
      * @param op_flag         flag, can be one of following values: <br>
-     *                        <ul><li> ProtoCommon.STORAGE_SET_METADATA_FLAG_OVERWRITE: overwrite all old
-     *                        metadata items</li></ul>
-     *                        <ul><li> ProtoCommon.STORAGE_SET_METADATA_FLAG_MERGE: merge, insert when
-     *                        the metadata item not exist, otherwise update it</li></ul>
+     *                        <ul>
+     *                        <li>ProtoCommon.STORAGE_SET_METADATA_FLAG_OVERWRITE:
+     *                        overwrite all old
+     *                        metadata items</li>
+     *                        <li>ProtoCommon.STORAGE_SET_METADATA_FLAG_MERGE:
+     *                        merge, insert when
+     *                        the metadata item not exist, otherwise update it</li>
+     *                        </ul>
      * @return 0 for success, !=0 fail (error code)
      */
     public int set_metadata(String group_name, String remote_filename,
-                            NameValuePair[] meta_list, byte op_flag) throws IOException, MyException {
+            NameValuePair[] meta_list, byte op_flag) throws IOException, MyException {
         boolean bNewStorageServer = this.newUpdatableStorageConnection(group_name, remote_filename);
         Connection connection = this.storageServer.getConnection();
         try {
@@ -1455,7 +1514,7 @@ public class StorageClient {
 
             header = ProtoCommon.packHeader(ProtoCommon.STORAGE_PROTO_CMD_SET_METADATA,
                     2 * ProtoCommon.FDFS_PROTO_PKG_LEN_SIZE + 1 + groupBytes.length
-                            + filenameBytes.length + meta_buff.length, (byte) 0);
+                    + filenameBytes.length + meta_buff.length, (byte) 0);
             OutputStream out = connection.getOutputStream();
             byte[] wholePkg = new byte[header.length + sizeBytes.length + 1 + groupBytes.length + filenameBytes.length];
             System.arraycopy(header, 0, wholePkg, 0, header.length);
@@ -1517,7 +1576,7 @@ public class StorageClient {
         }
 
         if (file_type == FileInfo.FILE_TYPE_SLAVE ||
-                file_type == FileInfo.FILE_TYPE_APPENDER) { //slave file or appender file
+                file_type == FileInfo.FILE_TYPE_APPENDER) { // slave file or appender file
             FileInfo fi = this.query_file_info(group_name, remote_filename);
             if (fi == null) {
                 return null;
@@ -1529,7 +1588,7 @@ public class StorageClient {
 
         int create_timestamp = ProtoCommon.buff2int(buff, 4);
         if ((file_size >> 63) != 0) {
-            file_size &= 0xFFFFFFFFL;  //low 32 bits is file size
+            file_size &= 0xFFFFFFFFL; // low 32 bits is file size
         }
         int crc32 = ProtoCommon.buff2int(buff, 4 * 4);
 
@@ -1619,7 +1678,7 @@ public class StorageClient {
             TrackerClient tracker = new TrackerClient();
             this.storageServer = tracker.getStoreStorage(this.trackerServer, group_name);
             if (this.storageServer == null) {
-                throw new MyException("getStoreStorage fail, errno code: " + tracker.getErrorCode());
+                throw new MyException("getStoreStorage fail, error code: " + tracker.getErrorCode());
             }
             return true;
         }
@@ -1632,7 +1691,8 @@ public class StorageClient {
      * @param remote_filename filename on storage server
      * @return true if create a new connection
      */
-    protected boolean newReadableStorageConnection(String group_name, String remote_filename) throws IOException, MyException {
+    protected boolean newReadableStorageConnection(String group_name, String remote_filename)
+            throws IOException, MyException {
         if (this.storageServer != null) {
             return false;
         } else {
@@ -1652,7 +1712,8 @@ public class StorageClient {
      * @param remote_filename filename on storage server
      * @return true if create a new connection
      */
-    protected boolean newUpdatableStorageConnection(String group_name, String remote_filename) throws IOException, MyException {
+    protected boolean newUpdatableStorageConnection(String group_name, String remote_filename)
+            throws IOException, MyException {
         if (this.storageServer != null) {
             return false;
         } else {
@@ -1672,7 +1733,8 @@ public class StorageClient {
      * @param group_name      the group name of storage server
      * @param remote_filename filename on storage server
      */
-    protected void send_package(byte cmd, String group_name, String remote_filename, Connection connection) throws IOException {
+    protected void send_package(byte cmd, String group_name, String remote_filename, Connection connection)
+            throws IOException {
         byte[] header;
         byte[] groupBytes;
         byte[] filenameBytes;
@@ -1793,7 +1855,8 @@ public class StorageClient {
         }
 
         /**
-         * send file content callback function, be called only once when the file uploaded
+         * send file content callback function, be called only once when the file
+         * uploaded
          *
          * @param out output stream for writing file content
          * @return 0 success, return none zero(errno) if fail

src/main/java/org/csource/fastdfs/TrackerClient.java

@@ -71,6 +71,71 @@ public class TrackerClient {
         return this.getStoreStorage(trackerServer, groupName);
     }
 
+    public Connection getConnection(TrackerServer trackerServer) throws IOException, MyException {
+        Connection connection = null;
+        int length = this.tracker_group.tracker_servers.length;
+        boolean failOver = length > 1 && trackerServer == null;
+        try {
+            if (trackerServer == null) {
+                trackerServer = getTrackerServer();
+                if (trackerServer == null) {
+                    throw new MyException("tracker server is empty!");
+                }
+            }
+            connection = trackerServer.getConnection();
+        } catch (IOException e) {
+            if (failOver) {
+                System.err.println("trackerServer get connection error, emsg:" + e.getMessage());
+            } else {
+                throw e;
+            }
+        } catch (MyException e) {
+            if (failOver) {
+                System.err.println("trackerServer get connection error, emsg:" + e.getMessage());
+            } else {
+                throw e;
+            }
+        }
+        if (connection != null || !failOver) {
+            return connection;
+        }
+        //do fail over
+        int currentIndex = 0;
+        if (trackerServer != null) {
+            currentIndex = trackerServer.getIndex();
+        }
+        int failOverCount = 0;
+        while (failOverCount < length - 1) {
+            failOverCount++;
+            currentIndex++;
+            if (currentIndex >= length) {
+                currentIndex = 0;
+            }
+            try {
+                trackerServer = this.tracker_group.getTrackerServer(currentIndex);
+                if (trackerServer == null) {
+                    throw new MyException("tracker server is empty!");
+                }
+                return trackerServer.getConnection();
+            } catch (IOException e) {
+                System.err.println("fail over trackerServer get connection error, failOverCount:" + failOverCount + "," + e.getMessage());
+                if (failOverCount == length - 1) {
+                    throw e;
+                }
+
+            } catch (MyException e) {
+                System.err.println("fail over trackerServer get connection error, failOverCount:" + failOverCount + ", " + e.getMessage());
+                if (failOverCount == length - 1) {
+                    throw e;
+                }
+            }
+
+
+        }
+        return null;
+    }
+
+
     /**
      * query storage server to upload file
      *
@@ -85,12 +150,7 @@ public class TrackerClient {
         byte cmd;
         int out_len;
         byte store_path;
-        Connection connection;
-
-        if (trackerServer == null) {
-            trackerServer = getTrackerServer();
-        }
-        connection = trackerServer.getConnection();
+        Connection connection = getConnection(trackerServer);
         OutputStream out = connection.getOutputStream();
 
         try {
@@ -170,16 +230,7 @@ public class TrackerClient {
         int port;
         byte cmd;
         int out_len;
-        Connection connection;
-
-        if (trackerServer == null) {
-            trackerServer = getTrackerServer();
-            if (trackerServer == null) {
-                return null;
-            }
-        }
-
-        connection = trackerServer.getConnection();
+        Connection connection = getConnection(trackerServer);
         OutputStream out = connection.getOutputStream();
 
         try {
@@ -343,15 +394,7 @@ public class TrackerClient {
         int len;
         String ip_addr;
         int port;
-        Connection connection;
-
-        if (trackerServer == null) {
-            trackerServer = getTrackerServer();
-            if (trackerServer == null) {
-                return null;
-            }
-        }
-        connection = trackerServer.getConnection();
+        Connection connection = getConnection(trackerServer);
         OutputStream out = connection.getOutputStream();
 
         try {
@@ -473,16 +516,7 @@ public class TrackerClient {
         byte cmd;
         int out_len;
         byte store_path;
-        Connection connection;
-
-        if (trackerServer == null) {
-            trackerServer = getTrackerServer();
-            if (trackerServer == null) {
-                return null;
-            }
-        }
-
-        connection = trackerServer.getConnection();
+        Connection connection = getConnection(trackerServer);
         OutputStream out = connection.getOutputStream();
 
         try {
@@ -548,15 +582,7 @@ public class TrackerClient {
         byte[] bGroupName;
         byte[] bs;
         int len;
-        Connection connection;
-
-        if (trackerServer == null) {
-            trackerServer = getTrackerServer();
-            if (trackerServer == null) {
-                return null;
-            }
-        }
-        connection = trackerServer.getConnection();
+        Connection connection = getConnection(trackerServer);
         OutputStream out = connection.getOutputStream();
 
         try {

src/main/java/org/csource/fastdfs/TrackerGroup.java

@@ -18,84 +18,83 @@ import java.net.InetSocketAddress;
  * @version Version 1.17
  */
 public class TrackerGroup {
-  public int tracker_server_index;
-  public InetSocketAddress[] tracker_servers;
-  protected Integer lock;
+    public int tracker_server_index;
+    public InetSocketAddress[] tracker_servers;
+    protected Integer lock;
 
-  /**
-   * Constructor
-   *
-   * @param tracker_servers tracker servers
-   */
-  public TrackerGroup(InetSocketAddress[] tracker_servers) {
-    this.tracker_servers = tracker_servers;
-    this.lock = new Integer(0);
-    this.tracker_server_index = 0;
-  }
-
-  /**
-   * return connected tracker server
-   *
-   * @return connected tracker server, null for fail
-   */
-  public TrackerServer getTrackerServer(int serverIndex) throws IOException {
-    return new TrackerServer(this.tracker_servers[serverIndex]);
-  }
-
-  /**
-   * return connected tracker server
-   *
-   * @return connected tracker server, null for fail
-   */
-  public TrackerServer getTrackerServer() throws IOException {
-    int current_index;
-
-    synchronized (this.lock) {
-      this.tracker_server_index++;
-      if (this.tracker_server_index >= this.tracker_servers.length) {
+    /**
+     * Constructor
+     *
+     * @param tracker_servers tracker servers
+     */
+    public TrackerGroup(InetSocketAddress[] tracker_servers) {
+        this.tracker_servers = tracker_servers;
+        this.lock = new Integer(0);
         this.tracker_server_index = 0;
-      }
-
-      current_index = this.tracker_server_index;
     }
 
-    try {
-      return this.getTrackerServer(current_index);
-    } catch (IOException ex) {
-      System.err.println("connect to server " + this.tracker_servers[current_index].getAddress().getHostAddress() + ":" + this.tracker_servers[current_index].getPort() + " fail");
-      ex.printStackTrace(System.err);
+    /**
+     * return connected tracker server
+     *
+     * @return connected tracker server, null for fail
+     */
+    public TrackerServer getTrackerServer(int serverIndex) throws IOException {
+        return new TrackerServer(this.tracker_servers[serverIndex], serverIndex);
     }
-
-    for (int i = 0; i < this.tracker_servers.length; i++) {
-      if (i == current_index) {
-        continue;
-      }
-
-      try {
-        TrackerServer trackerServer = this.getTrackerServer(i);
+    /**
+     * return connected tracker server
+     *
+     * @return connected tracker server, null for fail
+     */
+    public TrackerServer getTrackerServer() throws IOException {
+        int current_index;
 
         synchronized (this.lock) {
-          if (this.tracker_server_index == current_index) {
-            this.tracker_server_index = i;
-          }
+            this.tracker_server_index++;
+            if (this.tracker_server_index >= this.tracker_servers.length) {
+                this.tracker_server_index = 0;
+            }
+
+            current_index = this.tracker_server_index;
         }
 
-        return trackerServer;
-      } catch (IOException ex) {
-        System.err.println("connect to server " + this.tracker_servers[i].getAddress().getHostAddress() + ":" + this.tracker_servers[i].getPort() + " fail");
-        ex.printStackTrace(System.err);
-      }
+        try {
+            return this.getTrackerServer(current_index);
+        } catch (IOException ex) {
+            System.err.println("connect to server " + this.tracker_servers[current_index].getAddress().getHostAddress() + ":" + this.tracker_servers[current_index].getPort() + " fail");
+            ex.printStackTrace(System.err);
+        }
+
+        for (int i = 0; i < this.tracker_servers.length; i++) {
+            if (i == current_index) {
+                continue;
+            }
+
+            try {
+                TrackerServer trackerServer = this.getTrackerServer(i);
+
+                synchronized (this.lock) {
+                    if (this.tracker_server_index == current_index) {
+                        this.tracker_server_index = i;
+                    }
+                }
+
+                return trackerServer;
+            } catch (IOException ex) {
+                System.err.println("connect to server " + this.tracker_servers[i].getAddress().getHostAddress() + ":" + this.tracker_servers[i].getPort() + " fail");
+                ex.printStackTrace(System.err);
+            }
+        }
+
+        return null;
     }
 
-    return null;
-  }
+    public Object clone() {
+        InetSocketAddress[] trackerServers = new InetSocketAddress[this.tracker_servers.length];
+        for (int i = 0; i < trackerServers.length; i++) {
+            trackerServers[i] = new InetSocketAddress(this.tracker_servers[i].getAddress().getHostAddress(), this.tracker_servers[i].getPort());
+        }
 
-  public Object clone() {
-    InetSocketAddress[] trackerServers = new InetSocketAddress[this.tracker_servers.length];
-    for (int i = 0; i < trackerServers.length; i++) {
-      trackerServers[i] = new InetSocketAddress(this.tracker_servers[i].getAddress().getHostAddress(), this.tracker_servers[i].getPort());
+        return new TrackerGroup(trackerServers);
     }
-
-    return new TrackerGroup(trackerServers);
-  }
 }

src/main/java/org/csource/fastdfs/TrackerServer.java

@@ -25,11 +25,18 @@ import java.net.InetSocketAddress;
 public class TrackerServer {
     protected InetSocketAddress inetSockAddr;
 
+    protected int index;
+
 
     public TrackerServer(InetSocketAddress inetSockAddr) throws IOException {
         this.inetSockAddr = inetSockAddr;
     }
 
+    public TrackerServer(InetSocketAddress inetSockAddr, int index) {
+        this.inetSockAddr = inetSockAddr;
+        this.index = index;
+    }
+
     public Connection getConnection() throws MyException, IOException {
         Connection connection;
         if (ClientGlobal.g_connection_pool_enabled) {
@@ -48,4 +55,11 @@ public class TrackerServer {
         return this.inetSockAddr;
     }
 
+    public int getIndex() {
+        return index;
+    }
+
+    public void setIndex(int index) {
+        this.index = index;
+    }
 }

src/test/java/org/csource/fastdfs/FdfsTest.java

@@ -87,9 +87,9 @@ public class FdfsTest {
 
     @Test
     public void download() throws Exception {
-        String[] uploadresult = {"group1", "M00/00/00/wKgBZV0phl2ASV1nAACk1tFxwrM3814331"};
+        String[] uploadresult = {"group1", "M00/00/00/J2fL12PVypeAWiGcAAM_gDeWVyw5817085"};
         byte[] result = storageClient.download_file(uploadresult[0], uploadresult[1]);
-        String local_filename = "build.PNG";
+        String local_filename = "commitment.d2f57e10.jpg";
         writeByteToFile(result, local_filename);
         File file = new File(local_filename);
         Assert.assertTrue(file.isFile());
@@ -98,17 +98,17 @@ public class FdfsTest {
     @Test
     public void testUploadDownload() throws Exception {
         NameValuePair[] metaList = new NameValuePair[1];
-        String local_filename = "build.PNG";
+        String local_filename = "commitment.d2f57e10 (2).jpg";
         metaList[0] = new NameValuePair("fileName", local_filename);
-        File file = new File("C:/Users/chengdu/Desktop/build.PNG");
+        File file = new File("/Users/iyw/Downloads/commitment.d2f57e10 (2).jpg");
         InputStream inputStream = new FileInputStream(file);
         int length = inputStream.available();
         byte[] bytes = new byte[length];
         inputStream.read(bytes);
         String[] result = storageClient.upload_file(bytes, null, metaList);
-        Assert.assertTrue(storageClient.isConnected());
+        //Assert.assertTrue(storageClient.isConnected());
         // pool testOnborrow  isAvaliable
-        Assert.assertTrue(storageClient.isAvaliable());
+       // Assert.assertTrue(storageClient.isAvaliable());
         LOGGER.info("result {}", Arrays.asList(result));
         byte[] resultbytes = storageClient.download_file(result[0], result[1]);
         writeByteToFile(resultbytes, local_filename);