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java 中关于json的使用方法
json在数据传输起了很大的作用，下面说说java中json的使用方法。
文章参考：http://www.codes51.com/article/detail_99574.html
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;
List<User> userList = 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);
List<User> userList = (List<User>) 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;
List<User> userList = 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<User> -> json串
* @return
*/
public String listToJson(){
List<User> userList = this.initUserList(USERLISTSIZE);
// list转换为JSON串
JSONArray jsonArray = JSONArray.fromObject(userList);
//System.out.println("List<User> -> json串：" + jsonArray.toString());
return jsonArray.toString();
}
/**
* 对象数组 -> json串
* @return
*/
public String arrayToJson() {
List<User> userList = 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 List<User> initUserList(int userListSize) {
User user = null;
List<User> userList = new ArrayList<User>();
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<User> -> 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<User> -> 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"}]
java 中关于json的使用方法