Java 进阶 & FastJson 的使用

需要包：

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.43</version>
</dependency>
1、 Json字符串转 map 对象
String jsonString1 = "{\"param5\":\"value5\",\"param3\":\"value3\",\"param4\":\"value4\",\"param1\":\"value1\",\"param2\":\"value2\"}";
System.out.println(jsonString1);
Map<String,String> stringStringMap = (Map<String,String>) JSON.parse(jsonString1);
for (String s : stringStringMap.keySet()) {
    System.out.println(s + "==>" +stringStringMap.get(s));
}

输出：

{"param5":"value5","param3":"value3","param4":"value4","param1":"value1","param2":"value2"}
param5==>value5
param3==>value3
param4==>value4
param1==>value1
param2==>value2
2、Json字符串转 List 集合
String jsonString2 = "[{\"param5\":\"value5\",\"param3\":\"value3\",\"param4\":\"value4\",\"param1\":\"value1\",\"param2\":\"value2\"},{\"p1\":\"v1\",\"p2\":\"v2\",\"p3\":\"v3\",\"p4\":\"v4\",\"p5\":\"v5\"}]";
System.out.println(jsonString2);
List<Map<String,String>> mapList = JSON.parseObject(jsonString2, new TypeReference<List<Map<String,String>>>(){});
for (Map<String, String> stringObjectMap : mapList) {
    for (String s : stringObjectMap.keySet()) {
        System.out.println(s + "==>" + stringObjectMap.get(s));
    }
}

输出：

[{"param5":"value5","param3":"value3","param4":"value4","param1":"value1","param2":"value2"},{"p1":"v1","p2":"v2","p3":"v3","p4":"v4","p5":"v5"}]
param5==>value5
param3==>value3
param4==>value4
param1==>value1
param2==>value2
p1==>v1
p2==>v2
p3==>v3
p4==>v4
p5==>v5
3、复杂JSON字符串 转 List集合
String jsonString3 = "{\"count\":2,\"list\":[{\"param5\":\"value5\",\"param3\":\"value3\",\"param4\":\"value4\",\"param1\":\"value1\",\"param2\":\"value2\"},{\"p1\":\"v1\",\"p2\":\"v2\",\"p3\":\"v3\",\"p4\":\"v4\",\"p5\":\"v5\"}]}";
System.out.println(jsonString3);
Map<String,Object> map = JSON.parseObject(jsonString3);
System.out.println(map.get("count"));
String tempjsonString3 = map.get("list").toString();
System.out.println(tempjsonString3);
List<Map<String,String>> mapList2 = JSON.parseObject(tempjsonString3, new TypeReference<List<Map<String,String>>>(){});
for (Map<String, String> stringObjectMap : mapList2) {
    for (String s : stringObjectMap.keySet()) {
        System.out.println(s + "==>" + stringObjectMap.get(s));
    }
}

输出：

{"count":2,"list":[{"param5":"value5","param3":"value3","param4":"value4","param1":"value1","param2":"value2"},{"p1":"v1","p2":"v2","p3":"v3","p4":"v4","p5":"v5"}]}
2
[{"param5":"value5","param3":"value3","param4":"value4","param1":"value1","param2":"value2"},{"p1":"v1","p2":"v2","p3":"v3","p4":"v4","p5":"v5"}]
param5==>value5
param3==>value3
param4==>value4
param1==>value1
param2==>value2
p1==>v1
p2==>v2
p3==>v3
p4==>v4
p5==>v5
4、解析JSON字符串到指定对象class

第一种方式，使用parseArray

String jsonString4 = "[{\"age\":12,\"date\":1465475917155,\"name\":\"s1\"},{\"age\":12,\"date\":1465475917175,\"name\":\"s2\"},{\"age\":12,\"date\":1465475917175,\"name\":\"s3\"},{\"age\":12,\"date\":1465475917175,\"name\":\"s4\"},{\"age\":12,\"date\":1465475917175,\"name\":\"s5\"},{\"age\":12,\"date\":1465475917175,\"name\":\"s6\"}]";
System.out.println(jsonString4);
List<Student> studentList = JSON.parseArray(jsonString4,Student.class);
for (Student student : studentList) {
    System.out.println(student);
}

第二种方式，使用parseObject

System.out.println(jsonString4);
List<Student> studentList2 = JSON.parseObject(jsonString4,new TypeReference<List<Student>>(){});
for (Student student : studentList2) {
    System.out.println(student);
}

输出：

[{"age":12,"date":1465475917155,"name":"s1"},{"age":12,"date":1465475917175,"name":"s2"},{"age":12,"date":1465475917175,"name":"s3"},{"age":12,"date":1465475917175,"name":"s4"},{"age":12,"date":1465475917175,"name":"s5"},{"age":12,"date":1465475917175,"name":"s6"}]
Student{name='s1', age=12, date=Thu Jun 09 20:38:37 CST 2016}
Student{name='s2', age=12, date=Thu Jun 09 20:38:37 CST 2016}
Student{name='s3', age=12, date=Thu Jun 09 20:38:37 CST 2016}
Student{name='s4', age=12, date=Thu Jun 09 20:38:37 CST 2016}
Student{name='s5', age=12, date=Thu Jun 09 20:38:37 CST 2016}
Student{name='s6', age=12, date=Thu Jun 09 20:38:37 CST 2016}
5、 Map对象转化成json字符串
Map<String, Object> maps = new HashMap<String,Object>();
maps.put("grant_code","XF9JKY0R");
maps.put("is_car_config",0);
maps.put("isCN",1);
maps.put("vinCode","LGBG22E22AY081092");
String jsonParam = JSON.toJSONString(maps);
System.out.println(jsonParam);

输出：

{"grant_code":"XF9JKY0R","is_car_config":0,"vinCode":"LGBG22E22AY081092","isCN":1}
6、综合运用
package com.sc.fastjson;

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONArray;
import com.alibaba.fastjson.JSONObject;
import com.alibaba.fastjson.TypeReference;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class FastJsonDemo {
    public static void main(String[] args) {
//        ObjectToJson();
        JsonToString();
    }

    public static void  ObjectToJson(){
        Map<String,Object> map = new HashMap<String,Object>();
        map.put("id","123");
        map.put("name","张三");
        map.put("sex","男");
        map.put("age","15");
        /**
         * 1、先将map 进行json格式化，JSON.toJSONString(map) 返回json字符串
         * 2、然后将json字符串转换成对象
         */
        JSONObject jsonObject = JSON.parseObject(JSON.toJSONString(map));
        String age = jsonObject.get("age").toString();
        System.out.println(age);//15


        List<String> list = new ArrayList<String>();
        list.add("{a,b,c}");
        list.add("{a1,b1,c1}");
        list.add("{a2,b2,c2}");
        list.add("{a3,b3,c3}");
        JSONArray jsonArray = JSON.parseArray(JSON.toJSONString(list));
        System.out.println(jsonArray.get(2));//{a2,b2,c2}


        map.put("list",list);
        JSONObject jsonObject1 = JSON.parseObject(JSON.toJSONString(map));
        JSONArray jsonArray1 = jsonObject1.getJSONArray("list");
        System.out.println(jsonArray1.get(3));//{a3,b3,c3}

    }


    public static void JsonToString(){
        String jsonStr1 = "{\"param5\":\"value5\",\"param3\":\"value3\",\"param4\":\"value4\",\"param1\":\"value1\",\"param2\":\"value2\"}";
        Object object = JSON.parse(jsonStr1);
        System.out.println(object.toString());

        Map<String,Object> map = (Map<String, Object>) JSON.parse(jsonStr1);
        System.out.println(map.get("param4").toString());
        System.out.println("---------第一种写法----------");
        //复杂json转换成List
        //第一种写法
        String jsonStr2 = "{\"count\":2,\"list\":[{\"param5\":\"value5\",\"param3\":\"value3\",\"param4\":\"value4\",\"param1\":\"value1\",\"param2\":\"value2\"},{\"p1\":\"v1\",\"p2\":\"v2\",\"p3\":\"v3\",\"p4\":\"v4\",\"p5\":\"v5\"}]}";
        JSONObject jsonObject = (JSONObject) JSON.parse(jsonStr2);
        JSONArray array = (JSONArray) jsonObject.get("list");
        for (Object o : array){
            System.out.println(o.toString());
        }
        System.out.println("---------第二种写法----------");
        //第二种写法
        String jsonStr3 = "{\"count\":2,\"list\":[{\"param5\":\"value5\",\"param3\":\"value3\",\"param4\":\"value4\",\"param1\":\"value1\",\"param2\":\"value2\"},{\"p1\":\"v1\",\"p2\":\"v2\",\"p3\":\"v3\",\"p4\":\"v4\",\"p5\":\"v5\"}]}";
        Map<String,Object> map2 = (Map<String, Object>) JSON.parse(jsonStr3);
        List<Object> list2 = (List<Object>) map2.get("list");
        for(Object o:list2){
            System.out.println(o.toString());
        }
        System.out.println("---------第三种写法-------------");
        //第三种写法
        String jsonStr4 = "{\"count\":2,\"list\":[{\"param5\":\"value5\",\"param3\":\"value3\",\"param4\":\"value4\",\"param1\":\"value1\",\"param2\":\"value2\"},{\"p1\":\"v1\",\"p2\":\"v2\",\"p3\":\"v3\",\"p4\":\"v4\",\"p5\":\"v5\"}]}";
        Map<String,Object> map4 = JSON.parseObject(jsonStr4,new TypeReference<Map<String,Object>>(){});
        String jsonList = map4.get("list").toString();
        List<Object> list4 =JSON.parseObject(jsonList,new TypeReference<List<Object>>(){});
        for(Object o : list4){
            System.out.println(o.toString());
        }
        System.out.println("---------第四种写法-------------");
        String jsonStr5 = "{\"count\":2,\"list\":[{\"param5\":\"value5\",\"param3\":\"value3\",\"param4\":\"value4\",\"param1\":\"value1\",\"param2\":\"value2\"},{\"p1\":\"v1\",\"p2\":\"v2\",\"p3\":\"v3\",\"p4\":\"v4\",\"p5\":\"v5\"}]}";
        JSONObject jsonEntry = JSON.parseObject(jsonStr5);
        for(Map.Entry<String,Object> entry:jsonEntry.entrySet()){
            if(entry.getKey().equals("list")){
                JSONArray  jsonArray = JSON.parseArray(entry.getValue().toString());
                for(Object o: jsonArray){
                    System.out.println(o.toString());
                }
            }
        }
 
    }
}

以上输出结果为：
{"param5":"value5","param3":"value3","param4":"value4","param1":"value1","param2":"value2"}
{"p1":"v1","p2":"v2","p3":"v3","p4":"v4","p5":"v5"}

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