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;

@Overridepublic 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;

@Overridepublic 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);