用 Jackson 来处理 JSON

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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