重构。

src/main/java/xyz/zhouxy/plusone/commons/exception/BaseException.java

@@ -0,0 +1,33 @@
+package xyz.zhouxy.plusone.commons.exception;
+
+/**
+ * 带错误码的异常。
+ *
+ * @author <a href="https://gitee.com/zhouxy108">ZhouXY</a>
+ */
+public abstract class BaseException extends RuntimeException implements IWithCode {
+
+    private static final long serialVersionUID = -2546365325001947203L;
+
+    private final int code;
+
+    protected BaseException(int code, String msg) {
+        super(msg);
+        this.code = code;
+    }
+
+    protected BaseException(int code, Throwable cause) {
+        super(cause);
+        this.code = code;
+    }
+
+    protected BaseException(int code, String msg, Throwable cause) {
+        super(msg, cause);
+        this.code = code;
+    }
+
+    @Override
+    public int getCode() {
+        return this.code;
+    }
+}

src/main/java/xyz/zhouxy/plusone/commons/exception/IWithCode.java

@@ -0,0 +1,13 @@
+package xyz.zhouxy.plusone.commons.exception;
+
+/**
+ * 规定实现类带有 {@code getCode} 方法。
+ * 用于像自定义异常等需要带有 {@code code} 字段的类，
+ * 方便其它地方的程序判断该类的是否实现了此接口，以此获取其实例的 {@code code} 字段的值。
+ *
+ * @author <a href="https://gitee.com/zhouxy108">ZhouXY</a>
+ * @see BaseException
+ */
+public interface IWithCode {
+    int getCode();
+}