前言

fastjson2 是 FASTJSON 项目的重要升级，目标是为下一个十年提供一个高性能的JSON库， fastjson2 性能相比原先旧的 fastjson 有了很大提升,并且 fastjson2 更安全，完全删除autoType白名单，提升了安全性。

关于fastjson2升级指南
fastjson2 的github地址

一、导入fastjson2依赖

maven如下：

        <dependency><groupId>com.alibaba.fastjson2</groupId><artifactId>fastjson2</artifactId><version>2.0.20</version></dependency>

二、json对象与json数组的创建

json对象创建：

        JSONObject info = new JSONObject();info.put("name", "张三");info.put("age", "18");info.put("地理", "70");info.put("英语", "60");

json数组创建：

		JSONObject info1 = new JSONObject();info1.put("name", "张三");info1.put("age", "18");JSONObject info2 = new JSONObject();info2.put("name", "李四");info2.put("age", "19");//把上面创建的两个json对象加入到json数组里JSONArray array = new JSONArray();array.add(info1);array.add(info2);

        JSONArray array = new JSONArray();array.add("1班");array.add("2班");array.add("3班");

三、json对象取值与json数组遍历取值

json对象取值：

        JSONArray array = new JSONArray();array.add("1班");array.add("2班");array.add("3班");JSONObject school = new JSONObject();school.put("schoolName", "第一中学");school.put("teacher", "刘梅");JSONObject info = new JSONObject();info.put("name", "张三");info.put("age", "18");info.put("gradle",array);info.put("schoolInfo",school);//从info中取值System.out.println(info.getString("name")); //张三System.out.println(info.getIntValue("age"));//18System.out.println(info.getJSONArray("gradle"));//["1班","2班","3班"]System.out.println(info.getJSONObject("schoolInfo"));//{"schoolName":"第一中学","teacher":"刘梅"}

json数组遍历取值：

        JSONObject info1 = new JSONObject();info1.put("name", "张三");info1.put("age", "18");JSONObject info2 = new JSONObject();info2.put("name", "李四");info2.put("age", "19");JSONArray array = new JSONArray();array.add(info1);array.add(info2);//遍历获取json数组中对象的值for (int i = 0; i < array.size(); i++) {JSONObject json = array.getJSONObject(i);System.out.println(json.getString("name"));System.out.println(json.getString("age"));}

四、json对象与字符串的转换

json对象与字符串的转换

		JSONObject info = new JSONObject();info.put("name", "张三");info.put("age", "18");info.put("地理", "70");info.put("英语", "60");//JSON对象转字符串String str = JSON.toJSONString(info);//JSON字符串转JSON对象JSONObject json = JSONObject.parseObject(str);

json字符串的字节数组转json对象

        String str = "{\"name\":\"张三\",\"age\":\"18\",\"地理\":\"70\",\"英语\":\"60\"}";byte[] bytes = str.getBytes();JSONObject data = JSON.parseObject(bytes);

五、json数组与字符串的转换

        String text = "[\"张三\",\"李四\",\"王五\"]";//json字符串转json数组JSONArray data = JSON.parseArray(text);//json数组转json字符串String str = JSONArray.toJSONString(data);

六、json字符串转java对象的转换

Student类如下：

public class Student {public String name;public int age;public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public Student(String name, int age) {this.name = name;this.age = age;}
}

json字符串转java对象的转换

        Student student = new Student("张三", 18);//Student对象转JSON字符串String studentStr = JSON.toJSONString(student);//JSON字符串转Student对象Student data = JSON.parseObject(studentStr, Student.class);

java对象转byte数组转换

        Student student = new Student("张三", 18);//Student对象转字节数组byte[] text = JSON.toJSONBytes(student);//字节数组转Student对象Student data = JSON.parseObject(text, Student.class);

七、json字符串转Map

        String str="{\n" +"\"gradle\":\"高一\",\n" +"\"number\":\"2\",\n" +"\"people\":[{\"name\":\"张三\",\"age\":\"15\",\"phone\":\"123456\"},\n" +"         {\"name\":\"李四\",\"age\":\"16\",\"phone\":\"78945\"}]\n" +"}";//json字符串转MapMap<String, Object> map = JSONObject.parseObject(str, new TypeReference<Map<String, Object>>() {});System.out.println(map.get("gradle").toString());System.out.println(map.get("number").toString());System.out.println(map.get("people").toString());

八、json数组转List

        String str="{\n" +"\"gradle\":\"高一\",\n" +"\"number\":\"2\",\n" +"\"people\":[{\"name\":\"张三\",\"age\":\"15\",\"phone\":\"123456\"},\n" +"         {\"name\":\"李四\",\"age\":\"16\",\"phone\":\"78945\"}]\n" +"}";JSONObject strJson = JSONObject.parseObject(str);//获取people数组JSONArray people = strJson.getJSONArray("people");//json数组转ListList<Map> list = people.toJavaList(Map.class);

如果你使用的是老的fastjson1,可以像下面这样转换：

        String str="{\n" +"\"gradle\":\"高一\",\n" +"\"number\":\"2\",\n" +"\"people\":[{\"name\":\"张三\",\"age\":\"15\",\"phone\":\"123456\"},\n" +"         {\"name\":\"李四\",\"age\":\"16\",\"phone\":\"78945\"}]\n" +"}";JSONObject strJson=JSONObject.parseObject(str);//字符串转json对象String people = String.valueOf(strJson.getJSONArray("people"));List<Map<String,String>> list = (List<Map<String,String>>) JSONArray.parse(people);

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参考：
fastjson2