java怎么使用json？

json串示例

[{"id":1,"name":"name1","password":"password1","remark":"remark1"},{"id":2,"name":"name2","password":"password2","remark":"remark2"},{"id":3,"name":"name3","password":"password3","remark":"remark3"}] 

主要分为以下几种： 

1. 直接构建json串，主要代码； 

2. json串 -> java对象； 

3. java对象 -> json串/json对象； 

4. List -> json串； 

5. 对象数组 -> json串。 

程序如下： 

TestJson.java 

Java代码  收藏代码 

import java.util.*;  

import net.sf.json.*;  

import com.hs.sig.ui.sgms.vo.User;  

public class TestJson {  

/** 

* 初始化userList大小 

*/  

public static final int USERLISTSIZE = 3;   

/** 

* 直接构建json串 

* @return 

*/  

public String toJsonString() {  

// 初始化 User 对象  

User user = null;  

ListuserList = this.initUserList(USERLISTSIZE);  

// 构建 json 串  

StringBuffer json = new StringBuffer();  

json.append("[");  

for (int i = 0; i < userList.size(); i++) {  

user = userList.get(i);  

json.append("{");  

json.append("\"id\":\"").append(user.getId()).append("\",");  

json.append("\"name\":\"").append(user.getName()).append("\",");  

json.append("\"password\":\"").append(user.getPassword()).append("\",");  

json.append("\"remark\":\"").append(user.getRemark()).append('"');  

json.append("},");  

}  

json.deleteCharAt(json.lastIndexOf(","));  

json.append("]");  

//System.out.println("直接构建 json 串结果：" + json.toString());  

return json.toString();  

}  

/** 

* json串 -> java对象 

* @return 

*/  

public String jsonToObject() {  

StringBuffer info = new StringBuffer();  

if(this.isArray(this.toJsonString())){  

JSONArray jSONArray = JSONArray.fromObject(this.toJsonString());  

JsonConfig jsonConfig = new JsonConfig();  

jsonConfig.setArrayMode(JsonConfig.MODE_LIST);  

jsonConfig.setRootClass(User.class);  

ListuserList = (List) JSONSerializer.toJava(jSONArray, jsonConfig);  

User user = null;  

for (int i = 0; i < userList.size(); i++) {  

user = userList.get(i);  

info.append("user" + (i + 1) + ".id=" + user.getId());  

info.append(",user" + (i + 1) + ".name=" + user.getName());  

info.append(",user" + (i + 1) + ".password=" + user.getPassword());  

info.append(",user" + (i + 1) + ".remark=" + user.getRemark());  

info.append("\n");  

}  

//System.out.println("json串 -> java对象：" + info.toString());  

}  

return info.toString();  

}  

/** 

* java对象 -> json串/json对象 

* @return 

*/  

public String objectToJson() {  

// 初始化一个user对象  

User user = null;  

ListuserList = this.initUserList(USERLISTSIZE);  

user = userList.get(0);  

// 转换user对象的配置  

JsonConfig jsonConfig = new JsonConfig();  

// 过滤对象中不需要转化的属性  

jsonConfig.setExcludes(new String[]{"id"});  

// 将对象user转化为json串  

JSONArray jsonArray = JSONArray.fromObject(user, jsonConfig);  

//jsonArray = JSONArray.fromObject(user);  

// 转化为json对象  

//JSONObject jsonObject = JSONObject.fromObject(user, jsonConfig);  

//jsonObject = JSONObject.fromObject(user);  

return jsonArray.toString();  

}  

/** 

* List-> json串 

* @return 

*/  

public String listToJson(){  

ListuserList = this.initUserList(USERLISTSIZE);  

// list转换为JSON串  

JSONArray jsonArray = JSONArray.fromObject(userList);

//System.out.println("List-> json串：" + jsonArray.toString());  

return jsonArray.toString();  

}  

/** 

* 对象数组 -> json串 

* @return 

*/  

public String arrayToJson() {  

ListuserList = this.initUserList(USERLISTSIZE);  

User[] userArray = new User[userList.size()];  

for(int i = 0 ; i < userList.size() ; i++){  

userArray[i] = userList.get(i);  

}  

// user数组转为json串  

JSONArray jsonArray = JSONArray.fromObject(userArray);  

//System.out.println("对象数组 -> json串：" + jsonArray.toString());  

return jsonArray.toString();  

}  

/** 

* 初始化用户 

* @param userListSize list 的大小 

* @return 

*/  

private ListinitUserList(int userListSize) {  

User user = null;  

ListuserList = new ArrayList();  

for (int i = 0; i < userListSize; i++) {  

user = new User();  

user.setId(i + 1);  

user.setName("name" + (i + 1));  

user.setPassword("password" + (i + 1));  

user.setRemark("remark" + (i + 1));  

userList.add(user);  

}  

return userList;  

}  

/** 

* 判断JSON串是否以"["开头，是则认定为jsonArray，否则认定为jsonObject 

* @param str 

* @return 

*/  

private boolean isArray(String str) {  

return str.startsWith("[") ? true : false;  

}  

public static void main(String[] args) {  

TestJson testJson = new TestJson();  

System.out.println("直接构建json串：" + testJson.toJsonString());  

System.out.println("json串 -> java对象：" + testJson.jsonToObject());  

System.out.println("java对象 -> json串：" + testJson.objectToJson());  

System.out.println("List-> json串：" + testJson.listToJson());  

System.out.println("对象数组 -> json串：" + testJson.arrayToJson());  

}  

}  

User.java 

Java代码   

public class User {  

private Integer id;  

private String name;  

private String password;  

private String remark;  

public String getName() {  

return name;  

}  

public void setName(String name) {  

this.name = name;  

}  

public String getPassword() {  

return password;  

}  

public void setPassword(String password) {  

this.password = password;  

}  

public String getRemark() {  

return remark;  

}  

public void setRemark(String remark) {  

this.remark = remark;  

}  

public Integer getId() {  

return id;  

}  

public void setId(Integer id) {  

this.id = id;  

}  

}  

直接构建json串：[{"id":"1","name":"name1","password":"password1","remark":"remark1"},{"id":"2","name":"name2","password":"password2","remark":"remark2"},{"id":"3","name":"name3","password":"password3","remark":"remark3"}] 

json串 -> java对象：user1.id=1,user1.name=name1,user1.password=password1,user1.remark=remark1 

user2.id=2,user2.name=name2,user2.password=password2,user2.remark=remark2 

user3.id=3,user3.name=name3,user3.password=password3,user3.remark=remark3 

java对象 -> json串：[{"name":"name1","password":"password1","remark":"remark1"}] 

List-> json串：[{"id":1,"name":"name1","password":"password1","remark":"remark1"},{"id":2,"name":"name2","password":"password2","remark":"remark2"},{"id":3,"name":"name3","password":"password3","remark":"remark3"}] 

对象数组 -> json串：[{"id":1,"name":"name1","password":"password1","remark":"remark1"},{"id":2,"name":"name2","password":"password2","remark":"remark2"},{"id":3,"name":"name3","password":"password3","remark":"remark3"}]