[JSON] 2 FastJson 的用法

FastJson 的用法

Posted by Mr.Vincent on 2020-03-24
Estimated Reading Time 5 Minutes
Words 1k In Total
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前言

FastJson的介绍

JSON 协议使用方便,越来越流行,JSON 的处理器有很多,这里我介绍一下 FastJson,FastJson 是阿里的开源框架,被不少企业使用,是一个极其优秀的Json 框架,Github 地址: https://github.com/alibaba/fastjson

FastJson 的特点

  • FastJson 速度快,无论序列化和反序列化,都是当之无愧的 fast
  • 功能强大(支持普通 JDK 类包括任意Java Bean Class、Collection、Map、Date 或 enum)
  • 零依赖(没有依赖其它任何类库)

FastJson 的简单说明

FastJson 对于 JSON 格式字符串的解析主要用到了下面三个类:

  • JSON:fastJson 的解析器,用于 JSON 格式字符串与 JSON 对象及 javaBean 之间的转换
  • JSONObject:fastJson 提供的 json 对象
  • JSONArray:fastJson 提供 json 数组对象

FastJson 的用法

引入 maven 依赖:

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<!-- fastjson -->
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>1.2.62</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.13</version>
</dependency>
<!-- lombok -->
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.10</version>
<scope>provided</scope>
</dependency>

先写几个类:

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@Data
public class Student {
private String studentName;
private Integer studentAge;

public Student(String studentName, Integer studentAge) {
this.studentName = studentName;
this.studentAge = studentAge;
}
}
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@Data
public class Course {
private String courseName;
private Integer code;
}
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@Data
public class Teacher {
private String teacherName;
private Integer teacherAge;
private Course course;
private List<Student> students;
}

再定义三个 json 格式的字符串:

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//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}]}";

json 字符串与 JSONObject 之间的转换

案例:

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/**
* json Str <-> JSONObject 之间的转换
*/
@Test
public void testJSONStrTransformJSONObject() {
//例1:
//json Str -> JSONObject 的转换
JSONObject jsonObject = JSON.parseObject(JSON_OBJ_STR);
String studentName = jsonObject.getString("studentName");
Integer studentAge = jsonObject.getInteger("studentAge");
System.out.println(String.format("studentName:%s,studentAge:%s", studentName, studentAge));

//JSONObject -> json Str 的转换
String jsonString = JSON.toJSONString(jsonObject);
System.out.println(jsonString);


//例2:
//复杂 json StrComplex -> JSONObject 的转换
JSONObject jsonObjCom = JSON.parseObject(COMPLEX_JSON_STR);
String teacherNameCom = jsonObjCom.getString("teacherName");
Integer teacherAgeCom = jsonObjCom.getInteger("teacherAge");
System.out.println("teacherName: " + teacherNameCom + " teacherAge: " + teacherAgeCom);

JSONObject jsonObjCourseCom = jsonObjCom.getJSONObject("course");
String courseNameCom = jsonObjCourseCom.getString("courseName");
Integer codeCom = jsonObjCourseCom.getInteger("code");
System.out.println("courseName: " + courseNameCom + " code: " + codeCom);

JSONArray jsonArrayStudentCom = jsonObjCom.getJSONArray("students");
for (Object object : jsonArrayStudentCom) {
JSONObject jsonObjectOne = (JSONObject) object;
String studentNameCom = jsonObjectOne.getString("studentName");
Integer studentAgeCom = jsonObjectOne.getInteger("studentAge");
System.out.println("studentName: " + studentNameCom + " studentAge: " + studentAgeCom);
}

//JSONObject -> 复杂 json StrComplex 的转换
String jsonStringCom = JSON.toJSONString(jsonObjCom);
System.out.println(jsonStringCom);
}

json 字符串与 JavaBean 之间的转换

案例:

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/**
* json Str <-> JavaBean 之间的转换
*/
@Test
public void testJSONStrTransformJavaBean() {
//例1:
//json Str -> JavaBean 的转换
//方法一:
Student student = JSON.parseObject(JSON_OBJ_STR, Student.class);
System.out.println(student);

//方法二:
//或者使用 TypeReference<T> 类,由于其构造方法使用 protected 进行修饰,故创建其子类
Student studentTR = JSON.parseObject(JSON_OBJ_STR, new TypeReference<Student>() {
});
System.out.println(studentTR);

//JavaBean -> json Str 的转换
String jsonStrStu = JSON.toJSONString(student);
System.out.println(jsonStrStu);


//例2:
//复杂 json StrComplex -> JavaBean 的转换
//方法一:
Teacher teacher = JSON.parseObject(COMPLEX_JSON_STR, Teacher.class);
System.out.println(teacher);

//方法二:
Teacher teacherTR = JSON.parseObject(COMPLEX_JSON_STR, new TypeReference<Teacher>() {
});
System.out.println(teacherTR);

//复杂 json StrComplex -> json Str 的转换
String jsonStrTea = JSON.toJSONString(teacher);
System.out.println(jsonStrTea);
}

json 字符串(数组类型)与 JavaBean_List 之间的转换

案例:

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/**
* json StrArray <-> JavaBean_List 之间的转换
*/
@Test
public void testJSONStrArrayTransformJavaBeanList() {
//json StrArray -> JavaBean_List 的转换
//方法一:遍历(硬编码,不推荐)
JSONArray jsonArray = JSON.parseArray(JSON_ARRAY_STR);
List<Student> students = new ArrayList<>();
Student student;
for (Object object : jsonArray) {
JSONObject jsonObject = (JSONObject) object;
String studentName = jsonObject.getString("studentName");
Integer studentAge = jsonObject.getInteger("studentAge");
student = new Student(studentName, studentAge);
students.add(student);
}
System.out.println(students);

//方法二:或者使用 parseArray(推荐)
List<Student> studentsArr = JSON.parseArray(JSON_ARRAY_STR, Student.class);
System.out.println(studentsArr);

//方法三:或者使用 TypeReference<T> 类,由于其构造方法使用 protected 进行修饰,故创建其子类
List<Student> studentsTR = JSON.parseObject(JSON_ARRAY_STR, new TypeReference<ArrayList<Student>>() {
});
System.out.println(studentsTR);


//JavaBean_List -> json StrArray 的转换
String jsonString = JSON.toJSONString(studentsArr);
System.out.println(jsonString);
}

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