jackson是一款非常好用的json转换工具，总结一下具体用法

一：导入依赖

<dependency>
	<groupId>com.fasterxml.jackson.core</groupId>
	<artifactId>jackson-databind</artifactId>
	<version>2.7.3</version>
</dependency>

二：User

package com.mote.jackson;

public class User {
	
	private String name;
	private Integer age;
	private String city;
	
	public User() {
		super();
	}
	public User(String name, Integer age, String city) {
		super();
		this.name = name;
		this.age = age;
		this.city = city;
	}
	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 String getCity() {
		return city;
	}
	public void setCity(String city) {
		this.city = city;
	}
	@Override
	public String toString() {
		return "User [name=" + name + ", age=" + age + ", city=" + city + "]";
	}

}

三：jackson操作

package com.mote.jackson;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.ObjectMapper;
public class JackSonDemo {
	
	private static ObjectMapper MAPPER = new ObjectMapper();
	
	public static void main(String[] args) throws Exception {
		//对象转json
		User user = new User("tom",23,"上海");
		String json = MAPPER.writeValueAsString(user);
		System.out.println(json);
		//json转对象
		User uuser = MAPPER.readValue(json, User.class);
		System.out.println(uuser);
		
		//map<String,String>转json
		HashMap<String, String> map = new HashMap<String,String>();
		map.put("name", "jack");map.put("city", "beijin");
		String mjson = MAPPER.writeValueAsString(map);
		System.out.println(mjson);
		//json转map<String,String>
		HashMap<String,String> mmap = MAPPER.readValue(mjson, HashMap.class);
		System.out.println(mmap);
		
		//map<String,User>转json
		HashMap<String, User> umap = new HashMap<String, User>();
		umap.put(user.getName(), user);
		String mmjson = MAPPER.writeValueAsString(umap);
		System.out.println(mmjson);
		//json转map<String,User>
		JavaType jvt = MAPPER.getTypeFactory().constructParametricType(HashMap.class,String.class,User.class);
        Map<String,User> urMap = MAPPER.readValue(mmjson, jvt);
        System.out.println(urMap);
		
		
		//list<String>转json
		ArrayList<String> list = new ArrayList<String>();
		list.add("jack");
		list.add("tom");
		String ljson = MAPPER.writeValueAsString(list);
		System.out.println(ljson);
		//json转list<String>
		ArrayList<String> sList = MAPPER.readValue(ljson, ArrayList.class);
		System.out.println(sList);
		
		//list<User>转json
        List<User> ulist = new ArrayList<User>();
        ulist.add(user);
        String ujson = MAPPER.writeValueAsString(ulist);
        System.out.println(ujson);
        //json转list<User>
        JavaType jt = MAPPER.getTypeFactory().constructParametricType(ArrayList.class, User.class);
        List<User> urlist = MAPPER.readValue(ujson, jt);
        System.out.println(urlist);
		
	}

}