java中JSON的相关应用

1，先引用maven

<dependency>  
    <groupId>com.alibaba</groupId>  
    <artifactId>fastjson</artifactId>  
    <version>1.2.41</version>  
</dependency>  

2，解析JSON数组

import java.util.Map;
import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONArray;
import com.alibaba.fastjson.JSONObject;
import com.alibaba.fastjson.TypeReference;
import com.example.demo.common.Person;


public class JsonLib {
    //json字符串-简单对象型
    private static final String  JSON_OBJ_STR = "{"studentName":"lily","studentAge":12}";
    //json字符串-数组类型
    private static final String  JSON_ARRAY_STR = "[{"studentName":"lily","studentAge":12},{"studentName":"lucy","studentAge":15}]";
    //复杂格式json字符串
    private static final String  COMPLEX_JSON_STR = "{"teacherName":"crystall","teacherAge":27,"course":{"courseName":"english","code":1270},"students":[{"studentName":"lily","studentAge":12},{"studentName":"lucy","studentAge":15}]}";
    @SuppressWarnings("unchecked")
   public static void main(String[] args) {
       //demoJson();

        //testJSONStrToJSONObject();//json字符串转化对象
        //testJSONStrToJSONArray();//json数组转化json对象
        testComplexJSONStrToJSONObject();//json对象嵌套json对象
   }

    /**
     * 复杂json格式字符串与JSONObject之间的转换
     */
    public static void testComplexJSONStrToJSONObject(){
        System.out.println(COMPLEX_JSON_STR);
        JSONObject jsonObject = JSON.parseObject(COMPLEX_JSON_STR);
        //JSONObject jsonObject1 = JSONObject.parseObject(COMPLEX_JSON_STR);//因为JSONObject继承了JSON，所以这样也是可以的
        System.out.println(jsonObject);
        String teacherName = jsonObject.getString("teacherName");
        Integer teacherAge = jsonObject.getInteger("teacherAge");
        JSONObject course = jsonObject.getJSONObject("course");
        JSONArray students = jsonObject.getJSONArray("students");
        System.out.println(teacherName+"------"+teacherAge+"===json对象===="+course+"----json数组----"+students);
        JSONArray jsonArray = JSON.parseArray(students.toString());
        System.out.println(jsonArray);
    }

    /**
     * json字符串-数组类型与JSONArray之间的转换
     */
    public static void testJSONStrToJSONArray(){

        JSONArray jsonArray = JSON.parseArray(JSON_ARRAY_STR);
        //JSONArray jsonArray1 = JSONArray.parseArray(JSON_ARRAY_STR);//因为JSONArray继承了JSON，所以这样也是可以的

        //遍历方式1
        int size = jsonArray.size();
        for (int i = 0; i < size; i++){
            JSONObject jsonObject = jsonArray.getJSONObject(i);
            System.out.println(jsonObject.getString("studentName")+":"+jsonObject.getInteger("studentAge"));
        }

        //遍历方式2
        for (Object obj : jsonArray) {
            JSONObject jsonObject = (JSONObject) obj;
            System.out.println(jsonObject.getString("studentName")+":"+jsonObject.getInteger("studentAge"));
        }
    }

    /**
     * json字符串-简单对象型与JSONObject之间的转换
     */
    public static void testJSONStrToJSONObject(){

        JSONObject jsonObject = JSON.parseObject(JSON_OBJ_STR);
        //JSONObject jsonObject1 = JSONObject.parseObject(JSON_OBJ_STR); //因为JSONObject继承了JSON，所以这样也是可以的

        System.out.println(jsonObject.getString("studentName")+":"+jsonObject.getInteger("studentAge"));

    }
    public static void demoJson() {
        /**
            * 将 Json 形式的字符串转换为 Map
            */
           String str = "{"name":"Tom","age":90}";
           JSONObject jsonObject = JSONObject.parseObject(str);
           Map<String, String> params = JSONObject.parseObject(jsonObject.toString(), new TypeReference<Map<String, String>>(){});
           System.out.println(params);

           /**
            * 将 Json 形式的字符串转换为 JavaBean
            */
             str = "{"id":"A001","name":"Jack"}";
             jsonObject = JSONObject.parseObject(str);
             System.out.println(jsonObject);
             Person person = JSON.parseObject(str, new TypeReference<Person>() {});
             System.out.println(person.toString());
    }
}

3，json数组转map

public static void main(String[] args){  
  
        String strArr = "[{"0":"zhangsan","1":"lisi","2":"wangwu","3":"maliu"}," +  
                "{"00":"zhangsan","11":"lisi","22":"wangwu","33":"maliu"}]";  
        //第一种方式  
        List<Map<String,String>> listObjectFir = (List<Map<String,String>>) JSONArray.parse(strArr);  
        System.out.println("利用JSONArray中的parse方法来解析json数组字符串");  
        for(Map<String,String> mapList : listObjectFir){  
            for (Map.Entry entry : mapList.entrySet()){  
               System.out.println( entry.getKey()  + "  " +entry.getValue());  
            }  
        }  
        //第二种方式  
        List<Map<String,String>> listObjectSec = JSONArray.parseObject(strArr,List.class);  
        System.out.println("利用JSONArray中的parseObject方法并指定返回类型来解析json数组字符串");  
        for(Map<String,String> mapList : listObjectSec){  
            for (Map.Entry entry : mapList.entrySet()){  
                System.out.println( entry.getKey()  + "  " +entry.getValue());  
            }  
        }  
        //第三种方式  
        JSONArray listObjectThir = JSONArray.parseArray(strArr);  
        System.out.println("利用JSONArray中的parseArray方法来解析json数组字符串");  
        for(Object mapList : listObjectThir){  
            for (Object entry : ((Map)mapList).entrySet()){  
                System.out.println(((Map.Entry)entry).getKey()  + "  " +((Map.Entry)entry).getValue());  
            }  
        }  
        //第四种方式  
        List listObjectFour = JSONArray.parseArray(strArr,Map.class);  
        System.out.println("利用JSONArray中的parseArray方法并指定返回类型来解析json数组字符串");  
        for(Object mapList : listObjectFour){  
            for (Object entry : ((Map)mapList).entrySet()){  
                System.out.println(((Map.Entry)entry).getKey()  + "  " +((Map.Entry)entry).getValue());  
            }  
        }  
        //第五种方式  
        JSONArray listObjectFifth = JSONObject.parseArray(strArr);  
        System.out.println("利用JSONObject中的parseArray方法来解析json数组字符串");  
        for(Object mapList : listObjectFifth){  
            for (Object entry : ((Map)mapList).entrySet()){  
                System.out.println(((Map.Entry)entry).getKey()  + "  " +((Map.Entry)entry).getValue());  
            }  
        }  
        //第六种方式  
        List listObjectSix = JSONObject.parseArray(strArr,Map.class);  
        System.out.println("利用JSONObject中的parseArray方法并指定返回类型来解析json数组字符串");  
        for(Object mapList : listObjectSix){  
            for (Object entry : ((Map)mapList).entrySet()){  
                System.out.println(((Map.Entry)entry).getKey()  + "  " +((Map.Entry)entry).getValue());  
            }  
        }  
        //第七种方式  
        JSONArray listObjectSeven = JSON.parseArray(strArr);  
        System.out.println("利用JSON中的parseArray方法来解析json数组字符串");  
        for(Object mapList : listObjectSeven){  
            for (Object entry : ((Map)mapList).entrySet()){  
                System.out.println(((Map.Entry)entry).getKey()  + "  " +((Map.Entry)entry).getValue());  
            }  
        }  
        //第八种方式  
        List listObjectEigh = JSONObject.parseArray(strArr,Map.class);  
        System.out.println("利用JSON中的parseArray方法并指定返回类型来解析json数组字符串");  
        for(Object mapList : listObjectEigh){  
            for (Object entry : ((Map)mapList).entrySet()){  
                System.out.println(((Map.Entry)entry).getKey()  + "  " +((Map.Entry)entry).getValue());  
            }  
        }  
    }

4、map转json字符串

public static void main(String[] args) {
        Map map = new HashMap();
        map.put("msg", "yes");//map里面装有yes
        JSONObject jsonObject = JSONObject.fromObject(map);
        System.out.println("输出的结果是：" + jsonObject);
        //3、将json对象转化为json字符串
        String result = jsonObject.toString();
        System.out.println(result);
    }