修复JSON转XML时，用户指定的contentKeys只对最外面一层的元素生效

hutool-json/src/test/java/cn/hutool/json/IssueI676IT.java

@@ -0,0 +1,20 @@
+package cn.hutool.json;
+
+import cn.hutool.core.io.resource.ResourceUtil;
+import cn.hutool.core.util.XmlUtil;
+import cn.hutool.json.xml.JSONXMLSerializer;
+import org.junit.Assert;
+import org.junit.Test;
+
+import static javax.xml.xpath.XPathConstants.STRING;
+
+public class IssueI676IT {
+
+	@Test
+	public void parseXMLTest() {
+		final JSONObject jsonObject = JSONUtil.parseObj(ResourceUtil.readUtf8Str("issueI676IT.json"));
+		String xmlStr = JSONXMLSerializer.toXml(jsonObject, null, (String) null);
+		String content = String.valueOf(XmlUtil.getByXPath("/page/orderItems[1]/content", XmlUtil.readXML(xmlStr), STRING));
+		Assert.assertEquals(content, "bar1");
+	}
+}

hutool-json/src/test/resources/issueI676IT.json

@@ -0,0 +1,19 @@
+{
+  "page": {
+    "pageSize": 33,
+    "currentPage": 81,
+    "totalSize": 49,
+    "orderItems": [
+      {
+        "asc": true,
+        "columnName": "foo",
+        "content": "bar1"
+      },
+      {
+        "asc": false,
+        "columnName": "foo",
+        "content": "bar2"
+      }
+    ]
+  }
+}