JSONObject详解(com.alibaba)-fastjson2

蔚落 2023-10-08 23:03 6阅读 0赞

## 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]

[fastjson2 的github地址][fastjson2 _github]

## 一、导入fastjson2依赖 ##

maven如下：

pom(本文所有代码仅使用这一个依赖即可):

<dependencies>
            <dependency>
                <groupId>com.alibaba.fastjson2</groupId>
                <artifactId>fastjson2</artifactId>
                <version>2.0.26</version>
            </dependency>
        </dependencies>

![fd50f6dc51b14d608a226a68715bdc53.png][]

需要注意的一点是在使用 fastjson2 时导入的包名是 com.alibaba.fastjson2 ，就像下面这样：

import com.alibaba.fastjson2.JSON;

import com.alibaba.fastjson2.JSONObject;

import com.alibaba.fastjson2.JSONArray;

## 二、json对象与json数组的创建 ##

### json对象创建 ###

import com.alibaba.fastjson2.JSONObject;
    
    public class Demo {
        public static void main(String[] args) {
            JSONObject info = new JSONObject();
            info.put("name", "张三");
            info.put("age", "18");
            info.put("地理", "70");
            info.put("英语", "60");
    
            System.out.println(info);
        }
    }

![278d7af0c38f457c8b35deb6b5f24db5.png][]

### json数组创建 ###

import com.alibaba.fastjson2.JSONArray;
    
    public class Demo {
        public static void main(String[] args) {
            JSONArray array = new JSONArray();
            array.add("1班");
            array.add("2班");
            array.add("3班");
    
            System.out.println(array);
        }
    }

![8266fc98b06841829bbcd529d25be2f7.png][]

import com.alibaba.fastjson2.JSONArray;
    import com.alibaba.fastjson2.JSONObject;
    
    public class Demo {
        public static void main(String[] args) {
            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);
    
            System.out.println(array);
        }
    }

![ce8eae1580664fe192ec5fb0b3216fa0.png][]

## 三、json对象取值与json数组遍历取值 ##

### json对象取值 ###

import com.alibaba.fastjson2.JSONArray;
    import com.alibaba.fastjson2.JSONObject;
    
    public class Demo {
        public static void main(String[] args) {
            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"));//18
            System.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"}
        }
    }

![6b4e86d3e57d4c45bf43a6d00fee5c60.png][]

### json数组遍历取值 ###

import com.alibaba.fastjson2.JSONArray;
    import com.alibaba.fastjson2.JSONObject;
    
    public class Demo {
        public static void main(String[] args) {
            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"));
            }
        }
    }

![3cd7476eb307452e98584a6d1a4bfa86.png][]

## 四、json对象与字符串的转换 ##

### json对象与字符串的转换 ###

import com.alibaba.fastjson2.JSON;
    import com.alibaba.fastjson2.JSONObject;
    
    public class Demo {
        public static void main(String[] args) {
            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);
            System.out.println(str);
            //JSON字符串转JSON对象
            JSONObject json = JSONObject.parseObject(str);
            System.out.println(json);
        }
    }

![4057528381ea45cbbba7a3e8e0e9c620.png][]

### json字符串的字节数组转json对象 ###

import com.alibaba.fastjson2.JSON;
    import com.alibaba.fastjson2.JSONObject;
    
    public class Demo {
        public static void main(String[] args) {
            String str = "{\"name\":\"张三\",\"age\":\"18\",\"地理\":\"70\",\"英语\":\"60\"}";
    
            byte[] bytes = str.getBytes();
            JSONObject data = JSON.parseObject(bytes);
    
            System.out.println(data);
        }
    }

![a4e31b862e234ee5b37f88a6b08cce72.png][]

## 五、json数组与字符串的转换 ##

import com.alibaba.fastjson2.JSON;
    import com.alibaba.fastjson2.JSONArray;
    
    public class Demo {
        public static void main(String[] args) {
            String text = "[\"张三\",\"李四\",\"王五\"]";
            System.out.println(text);
    
            //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);
    
            System.out.println(data);
            System.out.println(str);
        }
    }

![ce1e58b9ac4047419f948b4c190bfbba.png][]

## 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 ###

import com.alibaba.fastjson2.JSON;
    
    public class Demo {
        public static void main(String[] args) {
            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);
    
            System.out.println(studentStr);
        }
    }

![3c3ae9d8fc0046ffbd1a7279c19b3536.png][]

### java对象转byte数组转换 ###

import com.alibaba.fastjson2.JSON;
    
    public class Demo {
        public static void main(String[] args) {
            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);
    
            System.out.println(data.getName() + data.getAge());
        }
    }

![c040247ff5fd46c985a4b9beea389744.png][]

## 七、json字符串与Map转换 ##

### json字符串转Map ###

import com.alibaba.fastjson2.JSONObject;
    import com.alibaba.fastjson2.TypeReference;
    
    import java.util.Map;
    
    public class Demo {
        public static void main(String[] args) {
            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Map
            Map<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());
    
        }
    }

![f8a895681a334988a04b8c3e2e921ee5.png][]

### Map转json字符串 ###

(注意：如果直接使用JSON.toJSONString(map)转换，因为"测试1"的值为null，转换的结果就会是 \{“测试2”:“hello”\})

import com.alibaba.fastjson2.JSON;
    import com.alibaba.fastjson2.JSONWriter;
    
    import java.util.HashMap;
    import java.util.Map;
    
    public class Demo {
        public static void main(String[] args) {
            Map<String, String> map = new HashMap<>();
            map.put("测试1", null);
            map.put("测试2", "hello");
    
            //{"测试2":"hello","测试1":null}
            String str = JSON.toJSONString(map, JSONWriter.Feature.WriteMapNullValue);
    
            System.out.println(str);
        }
    }

![fbc785e6256641d0bf86cb0810fe0345.png][]

如果你使用的是老的fastjson1(下述是简单示例，不可使用),可以像下面这样转换：

Map<String, String> map = new HashMap<>();
    map.put("测试1", null);
    map.put("测试2", "hello");
    String str = JSON.toJSONString(map, SerializerFeature.WriteMapNullValue) ;

## 八、json数组转List ##

import com.alibaba.fastjson2.JSONArray;
    import com.alibaba.fastjson2.JSONObject;
    
    import java.util.List;
    import java.util.Map;
    
    public class Demo {
        public static void main(String[] args) {
            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List
            List<Map> list = people.toJavaList(Map.class);
    
            System.out.println(str);
        }
    }

![95b59a1504714bd595215b255e77a497.png][]

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);

[fastjson2]: https://github.com/alibaba/fastjson2/wiki/fastjson_1_upgrade_cn
[fastjson2 _github]: https://github.com/alibaba/fastjson2
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