定制app开发将json字符串与实体类互相转换

01.概述

定制app开发如果我们接收到的是一个json，定制app开发我们该如何对该定制app开发字符串进行解析？

• 定制app开发使用实体类进行解析
• 使用map进行解析

定制app开发使用的依赖jar包：fastjson

compile('com.alibaba:fastjson:1.2.xx')
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02.对json字符串进行解析

定制app开发使用进行解析

创建一个用于接收的实体类：使用json字符串中的那些字段，实体类就创建那些属性值

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 +                '}';    }}
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使用实体类进行解析

public class test01 {    //创建一个映射关系    private static ObjectMapper objectMapper = new ObjectMapper();    //映射关系配置    static {        objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);        objectMapper.setDateFormat(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));    }    public static void main(String[] args) {        // json串里面的key与实体类字段匹配几个就会赋值几个，匹配不上的赋值为null        String jsonStr1 ="{\"bornTime\":\"2022-09-30 19:48:59\"}";        PersonInfoDto personInfoDto1 = fromJson(jsonStr1,PersonInfoDto.class);        System.out.println("personInfoDto1: " + personInfoDto1);        // json串中出现重复的字段，就会使用后者进行覆盖        String jsonStr2 ="{\"bornTime\":\"2022-09-30 19:48:59\",\"userName\":\"AISMALL\",\"userName\":\"AISMALL2\"}";        PersonInfoDto personInfoDto2 = fromJson(jsonStr2,PersonInfoDto.class);        System.out.println("personInfoDto2: " + personInfoDto2);        // json串里面的key与实体类字段匹配几个就会赋值几个，不管该传有多长，只取匹配到的key的value给实体类赋值        String jsonStr3 ="{\"bornTime\":\"2022-09-30 19:48:59\",\"userName\":\"AISMALL\",\"sex\":\"man\",\"age\":18,\"age2\":18}";        PersonInfoDto personInfoDto3 = fromJson(jsonStr3,PersonInfoDto.class);        System.out.println("personInfoDto3: " + personInfoDto3);        String jsonStr4="{\"bornTime\":\"2022-09-30 19:48:59\",\"userName\":\"AISMALL\",\"sex\":\"man\",\"age\":18}";        PersonInfoDto personInfoDto4 = fromJson(jsonStr4,PersonInfoDto.class);        System.out.println("personInfoDto4: " + personInfoDto4);    }    /*    * json字符串赋值给实体类方法    * */    public static <T> T fromJson(String s, Class<T> clazz) {        if (s == null || s.length() == 0) {            return null;        }        try {            return (T) objectMapper.readValue(s, clazz);        } catch (Exception e) {            e.printStackTrace();        }        return null;    }}
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运行结果：

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}
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小结

• json串里面的key与实体类字段匹配几个就会赋值几个，不管该传有多长，只取匹配到的key的value给实体类赋值，匹配不上的赋值为null。
• json串中出现重复的字段，就会使用后者进行覆盖。

使用map进行解析

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("这个是用JSON类，指定解析类型，来解析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对象解析成Map类型        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());        }    }}
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03.Map和json字符串的互相转换

3.1.json字符串转换为Map

参考：使用map进行解析

3.2.Map转换为json字符串

public class test01 {    public static void main(String[] args) {        // 创建一个Hashmap        Map<String, Object> paraMap = new HashMap();        paraMap.put("userName","AISMALL");        paraMap.put("sex","man");        paraMap.put("age",18);        // 转换为json字符串        String jsonStr = JSONObject.toJSONString(paraMap);        System.out.println("jsonStr: " + jsonStr);    }}
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运行结果：

jsonStr: {"sex":"man","userName":"AISMALL","age":18}
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04.json操作的一些小技巧

4.1.json字符转换为实体类

前面已经介绍了：

JSONObject.parseObject(jsonString, PersonInfoDto .class);
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4.2.实体类转json字符串

public class test01 {    public static void main(String[] args) {        Date date = new Date(); // 创建一个Date对象，获取当前时间        SimpleDateFormat f = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); // 指定格式化格式        f.format(date);  // 将当前时间袼式化为指定的格式        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);    }}
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运行结果：

{"age":18,"bornTime":1665113383685,"sex":"man","userName":"AISMALL"}
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4.3.json字符串转换为json对象

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字符串转换为jsonObject        JSONObject jSONObject = JSONObject.parseObject(jsonStr);        System.out.println(jSONObject);    }}
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运行结果：

{"test":"test","Result":[{"Detail1":"Detail1","Result1":"Result1"},{"Detail2":"Detail2","Result2":"Result2"},{"Detail3":"Detail3","Result3":"Result3"}]}
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4.4.json对象转换为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字符串转换为jsonObject        JSONObject jSONObject = JSONObject.parseObject(jsonStr);        // json对象转换为json字符串        String jsonObjectConv = JSON.toJSONString(jSONObject);        System.out.println(jsonObjectConv);    }}
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运行结果：

{"test":"test","Result":[{"Detail1":"Detail1","Result1":"Result1"},{"Detail2":"Detail2","Result2":"Result2"},{"Detail3":"Detail3","Result3":"Result3"}]}
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4.5.json字符串数组转换json数组

注意：json字符串数组，即String是JSONArray格式的字符串

public class test01 {    public static void main(String[] args) {        // json字符串数组        String jsonArr = "[{\"Detail1\":\"Detail1\",\"Result1\":\"Result1\"},{\"Detail2\":\"Detail2\",\"Result2\":\"Result2\"},{\"Detail3\":\"Detail3\",\"Result3\":\"Result3\"}]";        JSONArray jsonArray= JSONArray.parseArray(jsonArr);        // 转换成Json字符串数组之后，就可以遍历了，字符串是无法遍历的        for (Object jsonStr:jsonArray) {            System.out.println(jsonStr);        }    }}
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运行结果：

{"Detail1":"Detail1","Result1":"Result1"}{"Detail2":"Detail2","Result2":"Result2"}{"Detail3":"Detail3","Result3":"Result3"}
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4.6.List<实体类>转json数组

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);        // 转换为json字符串        String jsonStr = JSONObject.toJSONString(list);        System.out.println("jsonStr: " + jsonStr);        // json字符串转换为json数组        JSONArray jsonArray= JSONArray.parseArray(jsonStr);        // 转换成Json字符串数组之后，就可以遍历了，字符串是无法遍历的        for (Object jsonStr1:jsonArray) {            System.out.println(jsonStr1);        }    }}
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运行结果：

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}
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4.7.json数组转List<实体类>

public class test01 {    public static void main(String[] args) {        // json字符串数组        String jsonStr = "[{\"age\":18,\"sex\":\"man1\",\"userName\":\"AISMALL1\"},{\"age\":19,\"sex\":\"man2\",\"userName\":\"AISMALL2\"}]";        System.out.println("jsonStr: " + jsonStr);        // json字符串转换为json数组        JSONArray jsonArray= JSONArray.parseArray(jsonStr);        List<PersonInfoDto> personInfoDtoList = jsonArray.toJavaList(PersonInfoDto.class);        for (PersonInfoDto personInfoDto:personInfoDtoList) {            System.out.println("personInfoDto: " + personInfoDto);        }    }}
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运行结果：

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}
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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"	  }  ]}
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5.1.JSONObject中的数组提取为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字符串转换为jsonObject        JSONObject jSONObject = JSONObject.parseObject(jsonStr);        // 获取里面的Json字符串数组        JSONArray jsonArray = jSONObject.getJSONArray("Result");        // 转换成Json字符串数组之后，就可以遍历了，字符串是无法遍历的        for (Object jsonStr2:jsonArray) {            System.out.println(jsonStr2);        }    }}
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运行结果

[{"Detail1":"Detail1","Result1":"Result1"},{"Detail2":"Detail2","Result2":"Result2"},{"Detail3":"Detail3","Result3":"Result3"}]
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5.2.JSONObject获取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字符串转换为jsonObject        JSONObject jSONObject = JSONObject.parseObject(jsonStr);        // 返回值为String类型        String testStr = jSONObject.getString("test");        System.out.println("testStr: " + testStr);                // 返回值为Object类型        Object testObject = jSONObject.get("Result");        System.out.println("testObject: " + testObject);    }}
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运行结果：

testStr: testtestObject: [{"Detail1":"Detail1","Result1":"Result1"},{"Detail2":"Detail2","Result2":"Result2"},{"Detail3":"Detail3","Result3":"Result3"}]
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06.总结

更多方法可以去查看JSONArray，JSONObject的源码。