Java中使用Jackson進行JSON解析和序列化

1.新增依賴，在Maven的pom.xml檔案中新增以下依賴

<dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.5.3</version>
</dependency>

2.封裝JSON解析和序列化工具類

import java.io.IOException;
import java.util.List;

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

// JSON/物件轉換類
public class JsonUtils {

    // 定義jackson物件
    private static ObjectMapper MAPPER=new ObjectMapper();

    // 將物件轉換成json字串
    public static String objectToJson(Object obj){
        try {
            String str=MAPPER.writeValueAsString(obj);
            return str;
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
        return null;
    }

    // 將json資料轉換成pojo物件
    public static <T> T jsonToObject(String json,Class<T> beanType){
        try {
            T t=MAPPER.readValue(json, beanType);
            return t;
        } catch (JsonParseException e) {
            e.printStackTrace();
        } catch (JsonMappingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    // 將json資料轉換成pojo物件list
    public static <T> List<T> jsonToList(String json,Class<T> beanType){
        JavaType javaType=MAPPER.getTypeFactory().constructParametricType(List.class, beanType);
        try{
            List<T> list=MAPPER.readValue(json, javaType);
            return list;
        }catch(Exception e){
            e.printStackTrace();
        }
        return null;
    }
}
 

3.使用
（1）自定義物件：User

import java.util.Date;

public class User {
    private String name;
    private Integer age;
    private Date birthday;
    private String email;
    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 [name=" + name + ", age=" + age + ", birthday=" + birthday + ", email=" + email + "]";
    }

}
 

（2）工具類的使用

I.序列化物件
List<User> users=new ArrayList<User>();
        for(int i=0;i<20;i++){
            User user=new User();
            user.setName("Apple"+i);
            user.setAge(20+i);
            SimpleDateFormat dateformat = new SimpleDateFormat("yyyy-MM-dd");
            user.setBirthday(dateformat.parse("1991-10-01"));
            user.setEmail("12345678"+i+"@qq.com");

          //  序列化單個物件
            // String json=JsonUtils.objectToJson(user);

            users.add(user);

            // 序列化物件列表
            String json=JsonUtils.objectToJson(users);
       System.out.println(json);
    }
 

II.反序列化物件
// 反序列化單個物件

User u=JsonUtils.jsonToObject(record.value(), User.class);
System.out.println(u.toString());

// 序列化物件列表
List<User> list=JsonUtils.jsonToList(record.value(), User.class);
System.out.println(list);