JSON数据-jackson的使用

1.使用jackson需要先导包

    com.fasterxml.jackson.core
    jackson-databind
    2.13.0

2.web.xml

<?xml version="1.0" encoding="UTF-8"?>

    
    
    
        springmvc
        org.springframework.web.servlet.DispatcherServlet
        
            contextConfigLocation
            classpath:springmvc-servlet.xml
        
    
    
        springmvc
        /
    
    
    
    
        encoding
        org.springframework.web.filter.CharacterEncodingFilter
    
    
        encoding
        /*
    
    

3.springmvc-servlet.xml

<?xml version="1.0" encoding="UTF-8"?>


    
    


    
    
        
        
    

4.UserController:

package com.kakafa.controller;


import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.kakafa.pojo.User;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller //增加了这个注解会走视图解析器
public class UserController {

    //produces = "application/json;charset=utf-8"解决json中文乱码问题
    @RequestMapping(value="/j1",produces = "application/json;charset=utf-8")
    @ResponseBody //增加了这个注解，则这个方法就不会走视图解析器，会直接返回一个字符串
    public String jason1() throws JsonProcessingException {

        //jackson ObjectMapper
        ObjectMapper mapper = new ObjectMapper();

        User user=new User(1,"卡卡","123456");

        String s = mapper.writeValueAsString(user);

        return s;
    }
}

5.利用springmvc统一解决乱码

在springmvc-servlet.xml中添加如下代码：

<?xml version="1.0" encoding="UTF-8"?>


    
    

    
    
        
            
                
            
            
                
                    
                        
                    
                
            
        
    


    
    
        
        
    

6.@RestController

用@RestController来代替@Controller和@ResponseBody

@RestController //增加了这个注解这个类里面的所有方法都不会走视图解析器，而是返回一个字符串
public class UserController {


    @RequestMapping("/j1")
    public String jason1() throws JsonProcessingException {

        //jackson ObjectMapper
        ObjectMapper mapper = new ObjectMapper();
        User user=new User(1,"卡卡","123456");
        String s = mapper.writeValueAsString(user);
        return s;
    }
}

7.创建一个JSON工具类

当多个controller里面多个方法需要用到JSON时，可以提取出公共代码，创建一个JSON工具类

• JsonUtil:

package com.kakafa.utils;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import java.text.SimpleDateFormat;

public class JsonUtil {

    public static String getJson(Object o){
        ObjectMapper mapper = new ObjectMapper();
        try {
            return mapper.writeValueAsString(o);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
        return null;
    }

    public static String getJson(Object o, String dataFormat) {
        ObjectMapper mapper = new ObjectMapper();

        //不使用时间戳的方式,JSON输出日期类型的字符串，默认是时间戳的形式，因此这里设置为false
        mapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
        //自定义时间的格式
        SimpleDateFormat sdf = new SimpleDateFormat(dataFormat);
        mapper.setDateFormat(sdf);

        try {
            return mapper.writeValueAsString(o);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
        return null;
    }
}

• UserController

import com.fasterxml.jackson.core.JsonProcessingException;
import com.kakafa.pojo.User;
import com.kakafa.utils.JsonUtil;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import java.util.Date;

@RestController //增加了这个注解这个类里面的所有方法都不会走视图解析器，而是返回一个字符串
public class UserController {


    @RequestMapping("/j1")
    public String jason1() throws JsonProcessingException {

        User user=new User(1,"卡卡","123456");
        return JsonUtil.getJson(user);
    }

    @RequestMapping("/j2")
    public String jason2() throws JsonProcessingException {

        Date date=new Date();
        return JsonUtil.getJson(date,"yyyy-MM-dd HH:mm:ss");
    }

}