JavaBean转json错误

Question

Document类：
public class DocBean {
private String docId;
private String docName;
private String typeId;
private String typeName;
private String content;
private String docTime;
private String views;
private String cover;
}

page类
public class Page {
private int pageNo;
private int totalItem;
private int pageSize;
private String typeId;
private List<DocBean> doc=new ArrayList<DocBean>();
}

转化代码：
JSONObject page_json=JSONObject.fromObject(page);

error：
net.sf.json.JSONException: There is a cycle in the hierarchy!

at net.sf.json.util.CycleDetectionStrategy$StrictCycleDetectionStrategy.handleRepeatedReferenceAsObject(CycleDetectionStrategy.java:97)
at net.sf.json.JSONObject._fromBean(JSONObject.java:833)
at net.sf.json.JSONObject.fromObject(JSONObject.java:168)
at net.sf.json.AbstractJSON._processValue(AbstractJSON.java:265)
at net.sf.json.JSONObject._processValue(JSONObject.java:2808)
at net.sf.json.JSONObject.processValue(JSONObject.java:2874)
at net.sf.json.JSONObject.setInternal(JSONObject.java:2889)
at net.sf.json.JSONObject.setValue(JSONObject.java:1577)
at net.sf.json.JSONObject._fromBean(JSONObject.java:934)
at net.sf.json.JSONObject.fromObject(JSONObject.java:168)
at net.sf.json.JSONObject.fromObject(JSONObject.java:130)
at hyit.dataBind.DocBind.initDocList(DocBind.java:124)
at hyit.dataBind.DocBind.test01(DocBind.java:132)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)

Answer 1

这个问题，我之前也遇到过：对象嵌套对象的情况，不能直接用 JSONObject.fromObject(page) 这方法。我当时处理的办法很low。代码仅供参考： public static void fromJson(String jsonStr) throws Exception{ JSONArray jsonArray = JSONArray.fromObject(jsonStr); Object[] objs = jsonArray.toArray(); for (Object object : objs) { JSONObject jsonObject = JSONObject.fromObject(object); if(jsonObject.has("images")){ // 嵌套的对象 String imgString = jsonObject.getString("images"); JSONArray imgArray = JSONArray.fromObject(imgString); Object[] imgObjs = imgArray.toArray(); for (Object object2 : imgObjs) { JSONObject jsonObject2 = JSONObject.fromObject(object2); System.out.println(jsonObject2.getString("height")+"\t"+jsonObject2.getString("url")); } } if(jsonObject.has("countrys")){ // 嵌套的对象 String countrysString = jsonObject.getString("countrys"); List<String> stringList = binder.getMapper().readValue(countrysString, List.class); System.out.println("String List:"); for (String element : stringList) { System.out.print(element+"\t"); } } System.out.println(jsonObject.getString("offerId")+"\t"+jsonObject.getString("name")); } } 你也可以选择百度：java 对象嵌套 转json

Answer 2

你可以考虑给每个变量生成默认的get和set方法。

Answer 3

谢邀。net.sf.json印象中是比较老的一个包，建议使用jackson和gson。关键字可以搜索google: jackson object to json gson object to json

Answer 4

net.sf.json.JSONObject jsonObject = net.sf.json.JSONObject.fromObject(JsonStr); Map<String, Class> classMap = new HashMap<String, Class>(); classMap.put("selectInfo", SelectPropsDto.class); classMap.put("checkBoxInfo", CheckPropsDto.class); classMap.put("radioInfo", RadioPropsDto.class); GoodsDto goods = (GoodsDto) net.sf.json.JSONObject.toBean(jsonObject, GoodsDto .class,classMap); 多看看文档！希望能帮到你