Java如何將json字符串與實(shí)體類互相轉(zhuǎn)換

更新時(shí)間：2023年11月24日 09:24:50 作者：彤彤的小跟班

在我們調(diào)用三方平臺(tái)接口時(shí),經(jīng)常需要將我們封裝的實(shí)體類轉(zhuǎn)換為json作為傳參,下面這篇文章主要給大家介紹了關(guān)于Java如何將json字符串與實(shí)體類互相轉(zhuǎn)換的相關(guān)資料,需要的朋友可以參考下

01.概述

如果我們接收到的是一個(gè)json字符串，我們?cè)撊绾螌?duì)該字符串進(jìn)行解析？

方式一：使用實(shí)體類進(jìn)行解析
方式二：使用map進(jìn)行解析

使用的依賴jar包：fastjson

compile('com.alibaba:fastjson:1.2.xx')

02.對(duì)json字符串進(jìn)行解析

使用實(shí)體類進(jìn)行解析

創(chuàng)建一個(gè)用于接收的實(shí)體類：使用json字符串中的那些字段，實(shí)體類的屬性值一定要和JSON串中的key對(duì)應(yīng)

假設(shè)JSON字符串如下：

"{\"bornTime\":\"2022-09-30 19:48:59\",\"userName\":\"AISMALL\",\"sex\":\"man\",\"age\":18}"

對(duì)應(yīng)的實(shí)體類屬性就應(yīng)該定義成如下的樣子：

public class PersonInfoDto {
    private Date bornTime;
    private String userName;
    private String sex;
    private Integer age;
   
    public Date getBornTime() {
        return bornTime;
    }
    public void setBornTime(Date bornTime) {
        this.bornTime = bornTime;
    }

    public String getUserName() {
        return userName;
    }
    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }

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

    @Override
    public String toString() {
        return "PersonInfoDto{" +
                "bornTime=" + bornTime +
                ", userName='" + userName + '\'' +
                ", sex='" + sex + '\'' +
                ", age=" + age +
                '}';
    }
}

代碼示例：

public class test01 {
    public static void main(String[] args) {
        String jsonStr = "{\"bornTime\":\"2022-09-30 19:48:59\",\"userName\":\"AISMALL\",\"sex\":\"man\",\"age\":18}";
        PersonInfoDto personInfoDto = JSONObject.parseObject(jsonStr, PersonInfoDto.class);
        System.out.println(personInfoDto.toString());
    }
}

運(yùn)行結(jié)果：

PersonInfoDto{bornTime=Fri Sep 30 19:48:59 CST 2022, userName='AISMALL', sex='man', age=18}

使用實(shí)體類解析拓展

public class test01 {
    public static void main(String[] args) {
        // json串里面的key與實(shí)體類字段匹配幾個(gè)就會(huì)賦值幾個(gè)，匹配不上的賦值為null
        String jsonStr1 ="{\"bornTime\":\"2022-09-30 19:48:59\"}";
        PersonInfoDto personInfoDto1 = JSONObject.parseObject(jsonStr1, PersonInfoDto.class);
        System.out.println("personInfoDto1: " + personInfoDto1);

        // json串中出現(xiàn)重復(fù)的字段，就會(huì)使用后者進(jìn)行覆蓋
        String jsonStr2 ="{\"bornTime\":\"2022-09-30 19:48:59\",\"userName\":\"AISMALL\",\"userName\":\"AISMALL2\"}";
        PersonInfoDto personInfoDto2 = JSONObject.parseObject(jsonStr2, PersonInfoDto.class);
        System.out.println("personInfoDto2: " + personInfoDto2);

        // json串里面的key與實(shí)體類字段匹配幾個(gè)就會(huì)賦值幾個(gè)，不管該傳有多長(zhǎng)，只取匹配到的key的value給實(shí)體類賦值
        String jsonStr3 ="{\"bornTime\":\"2022-09-30 19:48:59\",\"userName\":\"AISMALL\",\"sex\":\"man\",\"age\":18,\"age2\":18}";
        PersonInfoDto personInfoDto3 = JSONObject.parseObject(jsonStr3,PersonInfoDto.class);
        System.out.println("personInfoDto3: " + personInfoDto3);

        // 剛好對(duì)應(yīng)的情況
        String jsonStr4="{\"bornTime\":\"2022-09-30 19:48:59\",\"userName\":\"AISMALL\",\"sex\":\"man\",\"age\":18}";
        PersonInfoDto personInfoDto4 = JSONObject.parseObject(jsonStr4, PersonInfoDto.class);
        System.out.println("personInfoDto4: " + personInfoDto4);
    }
}

運(yùn)行結(jié)果：

personInfoDto1: PersonInfoDto{bornTime=Fri Sep 30 19:48:59 CST 2022, userName='null', sex='null', age=null}
personInfoDto2: PersonInfoDto{bornTime=Fri Sep 30 19:48:59 CST 2022, userName='AISMALL2', sex='null', age=null}
personInfoDto3: PersonInfoDto{bornTime=Fri Sep 30 19:48:59 CST 2022, userName='AISMALL', sex='man', age=18}
personInfoDto4: PersonInfoDto{bornTime=Fri Sep 30 19:48:59 CST 2022, userName='AISMALL', sex='man', age=18}

小結(jié)

json串里面的key與實(shí)體類字段匹配幾個(gè)就會(huì)賦值幾個(gè)，不管該傳有多長(zhǎng)，只取匹配到的key的value給實(shí)體類賦值，匹配不上的賦值為null。
json串中出現(xiàn)重復(fù)的字段，就會(huì)使用后者進(jìn)行覆蓋。

使用map進(jìn)行解析

public class test01 {
    public static void main(String[] args) {
        // json字符串
        String jsonStr = "{\"age\":18,\"sex\":\"man1\",\"userName\":\"AISMALL1\"}";
        //====================方式一==============================
        Map maps = (Map)JSON.parse(jsonStr);
        for (Object map : maps.entrySet()) {
            System.out.println(((Map.Entry)map).getKey()+": " + ((Map.Entry)map).getValue());
        }

        //====================方式二==============================
        Map mapTypes =JSON.parseObject(jsonStr);
        for(Object obj :mapTypes.keySet()){
            System.out.println("key: " + obj + "  value: " + mapTypes.get(obj));
        }
        //====================方式三==============================
        Map mapType = JSON.parseObject(jsonStr, Map.class);
        System.out.println("這個(gè)是用JSON類，指定解析類型，來(lái)解析JSON字符串!!!");
        for(Object obj :mapType.keySet()){
            System.out.println("key: " + obj + "  value: " + mapType.get(obj));
        }

        //====================方式四==============================
        Map json =(Map)JSONObject.parse(jsonStr); //用Json對(duì)象解析成Map類型
        for (Object map : json.entrySet()){
            System.out.println(((Map.Entry)map).getKey() + ": "+((Map.Entry)map).getValue());
        }

        //====================方式五==============================
        JSONObject jsonobject = JSONObject.parseObject(jsonStr);
        for(Object map:jsonobject.entrySet()){
            System.out.println(((Map.Entry)map).getKey()+": "+((Map.Entry)map).getValue());
        }
    }
}

03.Map和json字符串的互相轉(zhuǎn)換

3.1.json字符串轉(zhuǎn)換為Map

參考：使用map進(jìn)行解析

3.2.Map轉(zhuǎn)換為json字符串

public class test01 {
    public static void main(String[] args) {
        // 創(chuàng)建一個(gè)Hashmap
        Map<String, Object> paraMap = new HashMap();
        paraMap.put("userName","AISMALL");
        paraMap.put("sex","man");
        paraMap.put("age",18);
        // 方式一：轉(zhuǎn)換為json字符串
        String jsonStr = JSONObject.toJSONString(paraMap);
        System.out.println("jsonStr: " + jsonStr);
        // 方式二：轉(zhuǎn)換為json字符串
        String jsonStr2 = Json.toJson(paraMap);
        System.out.println("jsonStr2: " + jsonStr2);
    }
}

運(yùn)行結(jié)果：

jsonStr: {"sex":"man","userName":"AISMALL","age":18}
jsonStr2: {"sex":"man","userName":"AISMALL","age":18}

04.json操作的一些小技巧

4.1.json字符轉(zhuǎn)換為實(shí)體類

前面已經(jīng)介紹了：

JSONObject.parseObject(jsonString, PersonInfoDto .class);

4.2.實(shí)體類轉(zhuǎn)json字符串

public class test01 {
    public static void main(String[] args) {
        Date date = new Date(); // 創(chuàng)建一個(gè)Date對(duì)象，獲取當(dāng)前時(shí)間
        SimpleDateFormat f = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); // 指定格式化格式
        f.format(date);  // 將當(dāng)前時(shí)間袼式化為指定的格式

        PersonInfoDto personInfoDto = new PersonInfoDto();
        personInfoDto.setBornTime(date);
        personInfoDto.setUserName("AISMALL");
        personInfoDto.setSex("man");
        personInfoDto.setAge(18);

        String jsonStr = JSON.toJSONString(personInfoDto);
        System.out.println(jsonStr);
    }
}

運(yùn)行結(jié)果：

{"age":18,"bornTime":1665113383685,"sex":"man","userName":"AISMALL"}

4.3.json字符串轉(zhuǎn)換為json對(duì)象

public class test01 {
    public static void main(String[] args) {
        // json字符串
        String jsonStr = "{\"test\":\"test\",\"Result\":[{\"Result1\":\"Result1\",\"Detail1\":\"Detail1\"},{\"Result2\":\"Result2\",\"Detail2\":\"Detail2\"},{\"Result3\":\"Result3\",\"Detail3\":\"Detail3\"}]}";
        // json字符串轉(zhuǎn)換為jsonObject
        JSONObject jSONObject = JSONObject.parseObject(jsonStr);
        System.out.println(jSONObject);
        // 根據(jù)Key取出Json對(duì)象中的值
        String testStr = jSONObject.getString("test");
        System.out.println("testStr: " + testStr);
    }
}

運(yùn)行結(jié)果：

{"test":"test","Result":[{"Detail1":"Detail1","Result1":"Result1"},{"Detail2":"Detail2","Result2":"Result2"},{"Detail3":"Detail3","Result3":"Result3"}]}
testStr: test

注意：

Json對(duì)象和Json字符串的區(qū)別在于，Json對(duì)象（JSONObject）里面有很多定義好的方法可以幫助我們根據(jù)Key取出Json對(duì)象中的值，后面我們也會(huì)演示幾個(gè)JSONObject提供的方法。

4.4.json對(duì)象轉(zhuǎn)換為json字符串

public class test01 {
    public static void main(String[] args) {
        // json字符串
        String jsonStr = "{\"test\":\"test\",\"Result\":[{\"Detail1\":\"Detail1\",\"Result1\":\"Result1\"},{\"Detail2\":\"Detail2\",\"Result2\":\"Result2\"},{\"Detail3\":\"Detail3\",\"Result3\":\"Result3\"}]}";
        // json字符串轉(zhuǎn)換為jsonObject
        JSONObject jSONObject = JSONObject.parseObject(jsonStr);
        // json對(duì)象轉(zhuǎn)換為json字符串
        String jsonObjectConv = JSON.toJSONString(jSONObject);
        System.out.println(jsonObjectConv);
    }
}

運(yùn)行結(jié)果：

{"test":"test","Result":[{"Detail1":"Detail1","Result1":"Result1"},{"Detail2":"Detail2","Result2":"Result2"},{"Detail3":"Detail3","Result3":"Result3"}]}

4.5.json字符串?dāng)?shù)組轉(zhuǎn)換json數(shù)組

注意：json字符串?dāng)?shù)組，即String是JSONArray格式的字符串

public class test01 {
    public static void main(String[] args) {
        // json字符串?dāng)?shù)組
        String jsonArr = "[{\"Detail1\":\"Detail1\",\"Result1\":\"Result1\"},{\"Detail2\":\"Detail2\",\"Result2\":\"Result2\"},{\"Detail3\":\"Detail3\",\"Result3\":\"Result3\"}]";
        JSONArray jsonArray= JSONArray.parseArray(jsonArr);
        // 轉(zhuǎn)換成Json字符串?dāng)?shù)組之后，就可以遍歷了，字符串是無(wú)法遍歷的
        for (Object jsonStr:jsonArray) {
            System.out.println(jsonStr);
        }
    }
}

運(yùn)行結(jié)果：

{"Detail1":"Detail1","Result1":"Result1"}
{"Detail2":"Detail2","Result2":"Result2"}
{"Detail3":"Detail3","Result3":"Result3"}

4.6.List<實(shí)體類>轉(zhuǎn)json數(shù)組

public class test01 {
    public static void main(String[] args) {
        PersonInfoDto personInfoDto1 = new PersonInfoDto();
        personInfoDto1.setUserName("AISMALL1");
        personInfoDto1.setSex("man1");
        personInfoDto1.setAge(18);

        PersonInfoDto personInfoDto2 = new PersonInfoDto();
        personInfoDto2.setUserName("AISMALL2");
        personInfoDto2.setSex("man2");
        personInfoDto2.setAge(19);

        List<PersonInfoDto> list = new ArrayList<>();
        list.add(personInfoDto1);
        list.add(personInfoDto2);

        // 轉(zhuǎn)換為json字符串
        String jsonStr = JSONObject.toJSONString(list);
        System.out.println("jsonStr: " + jsonStr);
        // json字符串轉(zhuǎn)換為json數(shù)組
        JSONArray jsonArray= JSONArray.parseArray(jsonStr);
        // 轉(zhuǎn)換成Json字符串?dāng)?shù)組之后，就可以遍歷了，字符串是無(wú)法遍歷的
        for (Object jsonStr1:jsonArray) {
            System.out.println(jsonStr1);
        }
    }
}

運(yùn)行結(jié)果：

jsonStr: [{"age":18,"sex":"man1","userName":"AISMALL1"},{"age":19,"sex":"man2","userName":"AISMALL2"}]

{"sex":"man1","userName":"AISMALL1","age":18}
{"sex":"man2","userName":"AISMALL2","age":19}

4.7.json數(shù)組轉(zhuǎn)List<實(shí)體類>

public class test01 {
    public static void main(String[] args) {
        // json字符串?dāng)?shù)組
        String jsonStr = "[{\"age\":18,\"sex\":\"man1\",\"userName\":\"AISMALL1\"},{\"age\":19,\"sex\":\"man2\",\"userName\":\"AISMALL2\"}]";
        System.out.println("jsonStr: " + jsonStr);
        // json字符串轉(zhuǎn)換為json數(shù)組
        JSONArray jsonArray= JSONArray.parseArray(jsonStr);
        List<PersonInfoDto> personInfoDtoList = jsonArray.toJavaList(PersonInfoDto.class);
        for (PersonInfoDto personInfoDto:personInfoDtoList) {
            System.out.println("personInfoDto: " + personInfoDto);
        }
    }
}

運(yùn)行結(jié)果：

jsonStr: [{"age":18,"sex":"man1","userName":"AISMALL1"},{"age":19,"sex":"man2","userName":"AISMALL2"}]
personInfoDto: PersonInfoDto{bornTime=null, userName='AISMALL1', sex='man1', age=18}
personInfoDto: PersonInfoDto{bornTime=null, userName='AISMALL2', sex='man2', age=19}

05.josnObject操作的一些小技巧

JSONObject如下：

{
  "test": "test",
  "Result": [
	  {
	  "Result1": "Result1",
	  "Detail1": "Detail1"
	  },
	  {
	  "Result2": "Result2",
	  "Detail2": "Detail2"
	  },
	  {
	  "Result3": "Result3",
	  "Detail3": "Detail3"
	  }
  ]
}

5.1.JSONObject中的數(shù)組提取為JSONArray

public class test01 {
    public static void main(String[] args) {
        // json字符串
        String jsonStr = "{\"test\":\"test\",\"Result\":[{\"Result1\":\"Result1\",\"Detail1\":\"Detail1\"},{\"Result2\":\"Result2\",\"Detail2\":\"Detail2\"},{\"Result3\":\"Result3\",\"Detail3\":\"Detail3\"}]}";
        // json字符串轉(zhuǎn)換為jsonObject
        JSONObject jSONObject = JSONObject.parseObject(jsonStr);
        // 獲取里面的Json字符串?dāng)?shù)組
        JSONArray jsonArray = jSONObject.getJSONArray("Result");
        // 轉(zhuǎn)換成Json字符串?dāng)?shù)組之后，就可以遍歷了，字符串是無(wú)法遍歷的
        for (Object jsonStr2:jsonArray) {
            System.out.println(jsonStr2);
        }
    }
}

運(yùn)行結(jié)果

[{"Detail1":"Detail1","Result1":"Result1"},{"Detail2":"Detail2","Result2":"Result2"},{"Detail3":"Detail3","Result3":"Result3"}]

5.2.JSONObject獲取value

public class test01 {
    public static void main(String[] args) {
        // json字符串
        String jsonStr = "{\"test\":\"test\",\"Result\":[{\"Result1\":\"Result1\",\"Detail1\":\"Detail1\"},{\"Result2\":\"Result2\",\"Detail2\":\"Detail2\"},{\"Result3\":\"Result3\",\"Detail3\":\"Detail3\"}]}";
        // json字符串轉(zhuǎn)換為jsonObject
        JSONObject jSONObject = JSONObject.parseObject(jsonStr);
        // 返回值為String類型
        String testStr = jSONObject.getString("test");
        System.out.println("testStr: " + testStr);
        
        // 返回值為Object類型
        Object testObject = jSONObject.get("Result");
        System.out.println("testObject: " + testObject);
    }
}

運(yùn)行結(jié)果：

testStr: test
testObject: [{"Detail1":"Detail1","Result1":"Result1"},{"Detail2":"Detail2","Result2":"Result2"},{"Detail3":"Detail3","Result3":"Result3"}]

06.總結(jié)

更多方法可以去查看JSONArray，JSONObject的源碼。

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