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>2.0.26</version>
</dependency>
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
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"));//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"}
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字符串与Map转换
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());
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”})
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);
如果你使用的是老的fastjson1,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
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);
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);
九、json字符串格式化
有时候我们想把 json 字符串格式化输出，也就是该缩进的缩进该换行的换行，让它更美观的输出，可以像下面这样：
String str = "[{\"isSendPhone\":\"true\",\"id\":\"22258352\",\"phoneMessgge\":\"为避免影响您的正常使用请及时续费，若已续费请忽略此信息。\",\"readsendtime\":\"9\",\"countdown\":\"7\",\"count\":\"5\",\"serviceName\":\"流程助手\",\"startdate\":\"2022-02-09 00:00:00.0\",\"insertTime\":\"2023-02-02 07:00:38.0\",\"enddate\":\"2023-02-08 23:59:59.0\",\"emailMessage\":\"为避免影响您的正常使用请及时续费，若已续费请忽略此信息。\",\"phone\":\"\",\"companyname\":\"顾问有限责任公司\",\"serviceId\":\"21\",\"isSendeMail\":\"true\",\"email\":\"\"},{\"isSendPhone\":\"true\",\"eid\":\"7682130\",\"phoneMessgge\":\"为避免影响您的正常使用请及时续费，若已续费请忽略此信息。\",\"readsendtime\":\"9\",\"countdown\":\"15\",\"count\":\"50\",\"serviceName\":\"经理人自助服务\",\"startdate\":\"2022-02-17 00:00:00.0\",\"insertTime\":\"2023-02-02 07:00:38.0\",\"enddate\":\"2023-02-16 23:59:59.0\",\"emailMessage\":\"为避免影响您的正常使用请及时续费，若已续费请忽略此信息。\",\"phone\":\"\",\"companyname\":\"生物科技股份有限公司\",\"serviceId\":\"2\",\"isSendeMail\":\"true\",\"email\":\"\"}]";
str = str.trim();
String formatStr = null;
if (str.startsWith("[")) {
JSONArray data = JSON.parseArray(str);
formatStr = JSONArray.toJSONString(data, JSONWriter.Feature.PrettyFormat, JSONWriter.Feature.WriteMapNullValue, JSONWriter.Feature.WriteNullListAsEmpty);
} else {
JSONObject strJson = JSONObject.parseObject(str);
formatStr = JSON.toJSONString(strJson, JSONWriter.Feature.PrettyFormat, JSONWriter.Feature.WriteMapNullValue, JSONWriter.Feature.WriteNullListAsEmpty);
}
System.out.println(formatStr);
输出结果：文章来源：https://www.toymoban.com/news/detail-418889.html
[
{
"isSendPhone":"true",
"id":"22258352",
"phoneMessgge":"为避免影响您的正常使用请及时续费，若已续费请忽略此信息。",
"readsendtime":"9",
"countdown":"7",
"count":"5",
"serviceName":"流程助手",
"startdate":"2022-02-09 00:00:00.0",
"insertTime":"2023-02-02 07:00:38.0",
"enddate":"2023-02-08 23:59:59.0",
"emailMessage":"为避免影响您的正常使用请及时续费，若已续费请忽略此信息。",
"phone":"",
"companyname":"XX顾问有限责任公司",
"serviceId":"21",
"isSendeMail":"true",
"email":""
},
{
"isSendPhone":"true",
"eid":"7682130",
"phoneMessgge":"为避免影响您的正常使用请及时续费，若已续费请忽略此信息。",
"readsendtime":"9",
"countdown":"15",
"count":"50",
"serviceName":"经理人自助服务",
"startdate":"2022-02-17 00:00:00.0",
"insertTime":"2023-02-02 07:00:38.0",
"enddate":"2023-02-16 23:59:59.0",
"emailMessage":"为避免影响您的正常使用请及时续费，若已续费请忽略此信息。",
"phone":"",
"companyname":"XX科技股份有限公司",
"serviceId":"2",
"isSendeMail":"true",
"email":""
}
]
参考：
fastjson2文章来源地址https://www.toymoban.com/news/detail-418889.html
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