记录：265

场景：Java对象转换为Map；Map转换为Java对象；Map转换为Json字符串。

本例环境：JDK 1.8

1.Java对象转换为Map

普通java对象的属性和属性值，转换为Map的Key和Value。

方法：

public static Map<String, Object> object2Map(Object obj) throws Exception {
 Map<String, Object> map = new HashMap<String, Object>();
 Field[] fields = obj.getClass().getDeclaredFields();
 for (Field field : fields) {
   field.setAccessible(true);
   map.put(field.getName(), field.get(obj));
 }
 return map;
}

测试：

GirlInfo girlInfo2 = new  GirlInfo("小州",Double.valueOf("165"),
    Double.valueOf("102"),"C","杭州");
Map<String,Object> map2 = MapToObjectUtils.object2Map(girlInfo2);

2.Map转换为Java对象

Map的Key和Value转换为普通java对象的属性和属性值。

方法：

public static <T> T map2Object(Map<String, Object> map, Class<T> clazz) {
  if (map == null) {
      return null; }
  T obj = null;
  try {
   obj = clazz.newInstance();
   Field[] fields = clazz.getDeclaredFields();
   for (Field field : fields) {
    int modifiers = field.getModifiers();
    //判断Static属性或者Final属性
    if (Modifier.isStatic(modifiers) || Modifier.isFinal(modifiers)) {
        continue;
    } else {
      //设置为true后,反射即可访问私有变量
      field.setAccessible(true);
      field.set(obj, map.get(field.getName()));
    }}
  } catch (Exception e) {
     e.printStackTrace();
  }
     return obj;
}

测试：

Map<String,Object> map = new HashMap<String,Object>();
map.put("name","小杭");
map.put("height",Double.valueOf("162"));
map.put("weight",Double.valueOf("100"));
map.put("cup","B");
map.put("city","杭州");
GirlInfo girlInfo = MapToObjectUtils.map2Object(map,GirlInfo.class);

3.Map转换为Json字符串

Map的Key和Value转换为JSON字符串格式。

方法：

public static String mapToJsonString(Map map){
  JSONObject json = new JSONObject();
  Iterator<Map.Entry<String, String>> entries = map.entrySet().iterator();
  while (entries.hasNext()) {
    Map.Entry<String, String> entry = entries.next();
    json.put(entry.getKey(),entry.getValue());
  }
  return json.toString();
}

测试：

Map<String,Object> map3 = new HashMap<String,Object>();
map3.put("name","小杭");
map3.put("height",Double.valueOf("162"));
map3.put("weight",Double.valueOf("100"));
map3.put("cup","B");
map3.put("city","杭州");
String result = MapToObjectUtils.mapToJsonString(map3);

数据格式：

{
  "city":"杭州",
  "name":"小杭",
  "weight":100.0,
  "height":162.0,
  "cup":"B"
}

4.实体类GirlInfo

测试中使用到的GirlInfo类

public class GirlInfo implements Serializable {

 private String name;
 private Double height;
 private Double weight;
 private String cup;
 private String city;
 public GirlInfo(){}
 public GirlInfo(String name,Double height, 
     Double weight,String cup,String city){
  this.name = name;
  this.height = height;
  this.weight = weight;
  this.cup=cup;
  this.city = city;
 }
 public String getName() {
     return name;
 }
 public void setName(String name) {
     this.name = name;
 }
 public Double getHeight() {
     return height;
 }
 public void setHeight(Double height) {
     this.height = height;
 }
 public Double getWeight() {
     return weight;
 }
 public void setWeight(Double weight) {
     this.weight = weight;
 }
 public String getCup() {
     return cup;
 }
 public void setCup(String cup) {
     this.cup = cup;
 }
 public String getCity() {
     return city;
 }
 public void setCity(String city) {
     this.city = city;
 }
}

以上，感谢。

2021年12月16日

今天真是 非常头大的一天,不过没关系,加油!!!!

先看看存入的格式

     例如:  {"第1个问题:":18,"第3个问题:":132,"第2个问题:":12,"第4个问题:":123,"第5个问题:":138,"第6个问题:":65}

                   {"goods_id":140861765,"cat_id":210,"goods_sn":171073501,"goods_sn_back":171073501,"goods_upc":11,"goods_name":45}

好了 ,进入正文

1.要有个数据库,并且有一张表(我的表是property,里面有两个字段id自增,name 类型是 text) mysql数据库,我用的大三层,在这里就不写service了,为了简单的测试

2.添加主要的依赖

<!-- https://mvnrepository.com/artifact/com.google.code.gson/gson -->
        <!--主要的-->
        <dependency>
            <groupId>com.google.code.gson</groupId>
            <artifactId>gson</artifactId>
            <version>2.8.2</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.codehaus.jackson/jackson-mapper-asl -->
        <!--主要的-->
        <dependency>
            <groupId>org.codehaus.jackson</groupId>
            <artifactId>jackson-mapper-asl</artifactId>
            <version>1.9.13</version>
        </dependency>

3.创建实体类

package com.example.entity;
/*project实体类*/
public class Project {
    private Integer id;
    private String name;

    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;
    }
}

4.创建mapper接口

package com.example.mapper;

import org.apache.ibatis.annotations.Mapper;

@Mapper
public interface ProjectMapper {
    //增加json串
    public Integer addproject(String name);
    //获取json字符串
    public String getname();
}

5.对mapper接口的sql编写

<!DOCTYPE mapper  PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"  "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.example.mapper.ProjectMapper">
    <insert id="addproject" parameterType="String">
        INSERT INTO school.project
        (
        NAME
        )
        VALUES
        (
        #{name}
        );
    </insert>

    <!--我数据库里六条数据,我固定接受 第六条做测试-->
    <select id="getname"  resultType="string">
        SELECT
        NAME

        FROM
        school.project
        WHERE id=6
    </select>
</mapper>

6.controller控制层

package com.example.controller;

import com.example.mapper.ProjectMapper;
import org.codehaus.jackson.JsonGenerationException;
import org.codehaus.jackson.map.JsonMappingException;
import org.codehaus.jackson.map.ObjectMapper;
import com.google.gson.Gson;
import com.google.gson.JsonSyntaxException;
import com.google.gson.reflect.TypeToken;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

@Controller
public class ProjectController {
    @Autowired
    private ProjectMapper projectMapper;

    /*将map转换为json字符串并且存入数据库的字段中*/
    @RequestMapping("add")
    public String addProject(){
        Map<String,Integer> map=new HashMap<String,Integer>();
        map.put("第1个问题:",18);
        map.put("第2个问题:",12);
        map.put("第3个问题:",132);
        map.put("第4个问题:",123);
        map.put("第5个问题:",138);
        map.put("第6个问题:",65);

        ObjectMapper json = new ObjectMapper();
        String names=null;
        try {
            names = json.writeValueAsString(map);
            System.out.println("++++++++++++++++++转成的json格式字符串："+names);
        } catch (JsonGenerationException e) {
            e.printStackTrace();
        } catch (JsonMappingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        /*将json加入数据库中*/
        projectMapper.addproject(names);
        return "";
    }

    /*获取json字符串并转换为map */
    @RequestMapping("get")
    public String getProject(){
        //查询出json字符串
        String name=projectMapper.getname();

        Map<String, Integer> res = null;
        try {
            Gson gson = new Gson();
            /*将json格式的字符串,转换为map*/
            res = gson.fromJson(name, new TypeToken<Map<String, Integer>>() {
            }.getType());
        } catch (JsonSyntaxException e) {
        }

        System.out.println(res);
        /*这里不需要进入页面,只是做测试*/
        return "";
    }
}

一、前言

我们在开发中难免和JSON打交道，这不小编最近遇到了。需要把一些信息转成JSON字符串，然后保存到数据库中。想到两种方式，一是新建实体类，然后转化为JSON，小编比较懒，直接Map多香呀！我们直接只有阿里巴巴的fastjson来进行转化即可，很方便！

二、理想转化展示

{"gender":"男","name":"小明","age":"18"}
// 为空显示
{}

三、导入maven依赖

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.69</version>
</dependency>

四、Map转化JSON字符串

private static String mapToJson() {
    Map<String,String> map = new HashMap<>();
    map.put("age","18");
    map.put("name","小明");
    map.put("gender","男");
    String string = JSON.toJSONString(map);
    System.out.println(string);
    map.clear();
    String stringNull = JSON.toJSONString(map);
    System.out.println(stringNull);
    return string;
}

五、对象转JSON字符串

1. Pojo类

import lombok.Data;

@Data
public class UserPojo {

    private String name;
    private String gender;
    private String age;
    
}

2. 方法

private static String pojoToJson() {

    UserPojo userPojo = new UserPojo();
    String stringNull = JSON.toJSONString(userPojo);
    System.out.println(stringNull);
    userPojo.setAge("19");
    userPojo.setGender("女");
    userPojo.setName("小红");
    String string = JSON.toJSONString(userPojo);
    System.out.println(string);
    return string;
    
}

六、总结

这样就实现了哦，总体来说fastjson还是挺好用的，不过都说fastjson不安全，没有jackson安全。但是小编还是觉得fastjson用的比较多，也习惯了里面的方法了哈！！对你有帮助，点个赞呗！！