Jackson 是一个 Java 用来处理 JSON 格式数据的类库，性能非常好。

首先创建一个User对象类 (User.java)

package com.sivalabs.json;



import java.util.Date;



public class User {



private String userId;



private UserName userName;



private Date dob;



@Override



public String toString(){



return "User [dob=" + dob + ", userId=" + userId + ", userName="+ userName + "]";


}



//setters and getters



}

UserName.java

package com.sivalabs.json;



public class UserName {



private String firstname;



private String middlename;



private String lastname;



@Override



public String toString()



{



return "UserName [firstname=" + firstname + 



", lastname=" + lastname+ 



", middlename=" + middlename + "]";



}



//setters and getters



}

[Java]代码

//接下来创建User实例，并生成JSON数据

ObjectMapper mapper = new ObjectMapper();



UserName userName = new UserName();



userName.setFirstname("Katamreddy");



userName.setMiddlename("Siva");



userName.setLastname("PrasadReddy");



User user = new User();



user.setUserId("1");



user.setUserName(userName);



user.setDob(new Date());



Writer strWriter = new StringWriter();



mapper.writeValue(strWriter, user);



String userDataJSON = strWriter.toString();



System.out.println(userDataJSON);

执行结果

{


"userId":"1",


"userName":


{


"firstname":"Katamreddy",


"middlename":"Siva",


"lastname":"PrasadReddy"


},


"dob":1300878089906


}

接下来进行JSON到Java对象的转换

String userDataJSON = 


"{\"userId\":\"100\",\"userName\":{\"firstname\":\"K\""+


",\"middlename\":\"Siva\",\"lastname\":\"Prasad\"},\"dob\":1300878089906}";


User userFromJSON = mapper.readValue(userDataJSON, User.class);


System.out.println(userFromJSON);

时间的格式化处理

DateFormat dateFormat = new SimpleDateFormat("MM-dd-yyyy");


SerializationConfig serConfig = mapper.getSerializationConfig();


serConfig.setDateFormat(dateFormat);


DeserializationConfig deserializationConfig = mapper.getDeserializationConfig();


deserializationConfig.setDateFormat(dateFormat);


mapper.configure(SerializationConfig.Feature.WRITE_DATES_AS_TIMESTAMPS, false);

[Java]代码

//从文件中读取JSON数据


User user = mapper.readValue(new File("user.json"), User.class);

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