Jackson serialization and deserialization

　　1, Download Jackson Tool Package (jackson-core-2.2.3.jar jackson-annotations-2.2.3.jar jackson-databind-2.2.3.jar)

jackson-core-2.2.3.jar core package
http://repo1.maven.org/maven2/com/fasterxml/jackson/core/jackson-core/2.2.3/jackson-core-2.2.3.jar

jackson-annotations-2.2.3.jar provides Json annotation support
http://repo1.maven.org/maven2/com/fasterxml/jackson/core/jackson-annotations/2.2.3/jackson-annotations-2.2.3.jar

jackson-databind-2.2.3.jar
http://repo1.maven.org/maven2/com/fasterxml/jackson/core/jackson-databind/2.2.3/jackson-databind-2.2.3.jar

　　2. User class used for JSON serialization and deserialization

package com.st.json;

import java.util.Date;

/**
 * @Description: User class used for JSON serialization and deserialization
 * @author Mr.Li
 *@date April 21, 2018 at 10:55:34 PM
 */
public class User {

    /**
     * JSON annotation Jackson provides a series of annotations to facilitate the control of JSON serialization and deserialization. Some commonly used annotations are described below.
     *
     * @JsonIgnore This annotation is used on properties to ignore this property when performing JSON operations.
     * @JsonFormat This annotation is used on properties to directly convert the Date type to the desired format, such as @JsonFormat(pattern = "yyyy-MM-dd
     *             HH-mm-ss")。
     * @JsonProperty This annotation is used on properties to serialize the name of the property to another name, such as serializing the trueName property to name, @JsonProperty("name").
     */

    private Integer id;
    private String name;
    private Integer age;
    private Date birthday;
    private String email;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    @Override
    public String toString() {
        return "User [id=" + id + ", name=" + name + ", age=" + age + ", birthday=" + birthday + ", email=" + email
                + "]";
    }

    public User(Integer id, String name, Integer age, Date birthday, String email) {
        super();
        this.id = id;
        this.name = name;
        this.age = age;
        this.birthday = birthday;
        this.email = email;
    }

    public User() {
        super();
        // TODO Auto-generated constructor stub
    }

}

　　3. The use of Jackson serialization and deserialization

package com.st.json;

import java.io.IOException;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;

import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;


/** 
 * @Description: Jackson's use of JSON [serialize] and [deserialize]
 * @author Mr.Li
 *@date April 21, 2018 11:05:31 PM
 */ 
public  class JacksonDemo {
    
    public static void main(String[] args) throws ParseException, IOException {
        jsonTest();
    }
    
    /**
     * Use of jackson serialization
     * @throws ParseException
     * @throws JsonProcessingException
     */
    public static void jackTest() throws ParseException, JsonProcessingException {
        User u = new User();
        u.setId ( 1 );
        u.setName("curry");
        u.setAge(30);
        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
        u.setBirthday(dateFormat.parse("1988-9-21"));
        u.setEmail("[email protected]");
        
        
        /** 
         * ObjectMapper is the core of JSON operations, all JSON operations of Jackson are implemented in ObjectMapper.
         * ObjectMapper has multiple JSON serialization methods, which can save JSON strings in different media such as File and OutputStream.
         * writeValue(File arg0, Object arg1) convert arg1 to json sequence and save it to arg0 file.
         * writeValue(OutputStream arg0, Object arg1) converts arg1 into a json sequence and saves it to the arg0 output stream.
         * writeValueAsBytes(Object arg0) converts arg0 into a json sequence and outputs the result as a byte array.
         * writeValueAsString(Object arg0) converts arg0 into a json sequence and outputs the result as a string.
         */
        ObjectMapper mapper = new ObjectMapper();
        
        //User对象转Json,
        //输出{"id":1,"name":"curry","age":30,"birthday":590774400000,"email":"[email protected]"}
        String jsonValue = mapper.writeValueAsString(u);
        System.out.println(jsonValue);
        
        User u2 = new User();
        u2.setId( 2 );
        u2.setName("KD");
        u2.setAge(29);
        u2.setBirthday(dateFormat.parse("1989-9-21"));
        u2.setEmail("[email protected]");
        
        
        List<User> users = new ArrayList<>();
        users.add(u);
        users.add(u2);
        String jsonList = mapper.writeValueAsString(users);
        System.out.println(jsonList);
        
    }
    
    /**
     * JSON to Java object [JSON deserialization]
     * @throws IOException 
     * @throws JsonMappingException 
     * @throws JsonParseException 
     */

    public static void jsonTest() throws JsonParseException, JsonMappingException, IOException {
        String json = " {\"id\":3, \"name\":\"小明\", \"age\":18, \"birthday\":590774400000, \"email\":\"[email protected]\"} ";  
        
        /** 
         * ObjectMapper supports JSON deserialization from byte[], File, InputStream, String, etc. data.
         */  
        ObjectMapper mapper = new ObjectMapper();
        User user = mapper.readValue(json, User.class);
        System.out.println(user);
    }
}