【转】JSON字符串与Java对象的相互转换

╰半夏微凉° 2023-01-16 14:22 147阅读 0赞

注意：本文中代码使用时所有的“《”需转换为左括号，“》”需转换为右括号  
所用Java包：json-lib  
Maven代码：  
 《dependency》  
  《groupId》net.sf.json-lib《/groupId》  
  《artifactId》json-lib《/artifactId》  
  《version》2.4《/version》  
  《classifier》jdk15《/classifier》  
 《/dependency》  
如果有类定义为：  
public class CollectionCircleMessage \{  
   
 private Integer messageId;  
   
 private String userId;  
   
 private String nickname;  
   
 private String portrait;  
   
 private RudderMessage rudderMessage;  
   
 private List《CollectionUserComment》 rudderCircleComments;  
   
 private List《CollectionUserAttention》 rudderAttention;  
\}

**1.将Java对象(JSONObject)转换为Json字符串**  
JSONObject.fromObject(collectionCircleMessage).toString();

**2.将Java对象列表(JSONArray)转换为Json字符串**  
JSONArray.fromObject(collectionCircleMessage).toString();

**3.将Json字符串转换为Java对象**  
JSONObject jSONObject = JSONObject.fromObject(jsonString);  
CollectionCircleMessage collectionCircleMessagesList = (CollectionCircleMessage)JSONObject.toBean(jSONObject, CollectionCircleMessage.class);  
如果有复杂对象：  
JSONObject jSONObject = JSONObject.fromObject(jsonString);  
Map《String, Class》 classMap = new HashMap《String, Class》();  
classMap.put("rudderCircleComments", CollectionUserComment.class);  
classMap.put("rudderAttention", CollectionUserAttention.class);  
CollectionCircleMessage collectionCircleMessages = (CollectionCircleMessage)JSONObject.toBean(jSONObject, CollectionCircleMessage.class,classMap);  
否则会出现  
 net.sf.ezmorph.bean.MorphDynaBean cannot be cast to XXX的错误

**4.将Json字符串转换为Java对象列表**  
JSONArray jsonArray = JSONArray.fromObject(jsonString);  
List《CollectionCircleMessage》 collectionCircleMessagesList = (List《CollectionCircleMessage》)JSONArray.toCollection(jsonArray, CollectionCircleMessage.class);  
如果有复杂对象：  
JSONArray jsonArray = JSONArray.fromObject(jsonString);  
Map《String, Class》 classMap = new HashMap《String, Class》();  
classMap.put("rudderCircleComments", CollectionUserComment.class);  
classMap.put("rudderAttention", CollectionUserAttention.class);  
List《CollectionCircleMessage》 collectionCircleMessagesList = (List《CollectionCircleMessage》)JSONArray.toList(jsonArray, CollectionCircleMessage.class,classMap);  
否则会出现  
 net.sf.ezmorph.bean.MorphDynaBean cannot be cast to XXX的错误