高性能JSON框架之FastJson的简单使用

我会带着你远行 2022-05-29 09:48 129阅读 0赞

转载自:[https://segmentfault.com/a/1190000011212806][https_segmentfault.com_a_1190000011212806]  
1.前言  
1.1.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: FastJson

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

1.3.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：  
1.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  
2.JSONObject：fastJson提供的json对象  
3.JSONArray：fastJson提供json数组对象

2.FastJson的用法

import java.util.ArrayList;
    import java.util.List;
    
    import org.junit.Test;
    
    import com.alibaba.fastjson.JSONArray;
    import com.alibaba.fastjson.JSONObject;
    import com.alibaba.fastjson.TypeReference;
    
    public class TestFastJson {
    
    	// json字符串-简单对象型
    	private static final String JSON_OBJ_STR = "{\"studentName\":\"lily\",\"studentAge\":12}";
    	// private static final String JSON_OBJ_STR2 =
    	// "{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-简单对象型到JSONObject的转换 JSONObject.parseObject(Str)
    	 */
    	@Test
    	public void testJSONStrToJSONObject() {
    
    		JSONObject jsonObject = JSONObject.parseObject(JSON_OBJ_STR);
    
    		System.out.println("studentName:  " + jsonObject.getString("studentName") + ":" + "  studentAge:  "
    				+ jsonObject.getInteger("studentAge"));
    
    	}
    
    	/**
    	 * JSONObject到json字符串-简单对象型的转换 JSONObject.toJSONString(jsonObject)
    	 */
    	@Test
    	public void testJSONObjectToJSONStr() {
    
    		// 已知JSONObject,目标要转换为json字符串
    		JSONObject jsonObject = JSONObject.parseObject(JSON_OBJ_STR);
    		// 第一种方式
    		String jsonString = JSONObject.toJSONString(jsonObject);
    
    		// 第二种方式
    		// String jsonString = jsonObject.toJSONString();
    		System.out.println(jsonString);
    	}
    
    	/**
    	 * json字符串-数组类型到JSONArray的转换 JSONArray.parseArray(Str)
    	 */
    	@Test
    	public void testJSONStrToJSONArray() {
    
    		JSONArray jsonArray = JSONArray.parseArray(JSON_ARRAY_STR);
    
    		// 遍历方式1
    		int size = jsonArray.size();
    		for (int i = 0; i < size; i++) {
    
    			JSONObject jsonObject = jsonArray.getJSONObject(i);
    			System.out.println("studentName:  " + jsonObject.getString("studentName") + ":" + "  studentAge:  "
    					+ jsonObject.getInteger("studentAge"));
    		}
    
    		// 遍历方式2
    		for (Object obj : jsonArray) {
    
    			JSONObject jsonObject = (JSONObject) obj;
    			System.out.println("studentName:  " + jsonObject.getString("studentName") + ":" + "  studentAge:  "
    					+ jsonObject.getInteger("studentAge"));
    		}
    	}
    
    	/**
    	 * JSONArray到json字符串-数组类型的转换 JSONArray.toJSONString(jsonArray)
    	 */
    	@Test
    	public void testJSONArrayToJSONStr() {
    
    		// 已知JSONArray,目标要转换为json字符串
    		JSONArray jsonArray = JSONArray.parseArray(JSON_ARRAY_STR);
    		// 第一种方式
    		String jsonString = JSONArray.toJSONString(jsonArray);
    
    		// 第二种方式
    		// String jsonString = jsonArray.toJSONString(jsonArray);
    		System.out.println(jsonString);
    	}
    
    	/**
    	 * 复杂json格式字符串到JSONObject的转换
    	 */
    	@Test
    	public void testComplexJSONStrToJSONObject() {
    
    		JSONObject jsonObject = JSONObject.parseObject(COMPLEX_JSON_STR);
    
    		String teacherName = jsonObject.getString("teacherName");
    		Integer teacherAge = jsonObject.getInteger("teacherAge");
    
    		System.out.println("teacherName:  " + teacherName + "   teacherAge:  " + teacherAge);
    
    		JSONObject jsonObjectcourse = jsonObject.getJSONObject("course");
    		// 获取JSONObject中的数据
    		String courseName = jsonObjectcourse.getString("courseName");
    		Integer code = jsonObjectcourse.getInteger("code");
    
    		System.out.println("courseName:  " + courseName + "   code:  " + code);
    
    		JSONArray jsonArraystudents = jsonObject.getJSONArray("students");
    
    		// 遍历JSONArray
    		for (Object object : jsonArraystudents) {
    
    			JSONObject jsonObjectone = (JSONObject) object;
    			String studentName = jsonObjectone.getString("studentName");
    			Integer studentAge = jsonObjectone.getInteger("studentAge");
    
    			System.out.println("studentName:  " + studentName + "   studentAge:  " + studentAge);
    		}
    	}
    
    	/**
    	 * 复杂JSONObject到json格式字符串的转换
    	 */
    	@Test
    	public void testJSONObjectToComplexJSONStr() {
    
    		// 复杂JSONObject,目标要转换为json字符串
    		JSONObject jsonObject = JSONObject.parseObject(COMPLEX_JSON_STR);
    
    		// 第一种方式
    		// String jsonString = JSONObject.toJSONString(jsonObject);
    
    		// 第二种方式
    		String jsonString = jsonObject.toJSONString();
    		System.out.println(jsonString);
    
    	}
    
    	/**
    	 * json字符串-简单对象到JavaBean之间的转换 JSONObject.parseObject(JSON_OBJ_STR,
    	 * Student.class)
    	 */
    	@Test
    	public void testJSONStrToJavaBeanObj() {
    
    		// 第一种方式
    		JSONObject jsonObject = JSONObject.parseObject(JSON_OBJ_STR);
    
    		String studentName = jsonObject.getString("studentName");
    		Integer studentAge = jsonObject.getInteger("studentAge");
    
    		// Student student = new Student(studentName, studentAge);
    
    		// 第二种方式,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 student = JSONObject.parseObject(JSON_OBJ_STR, new
    		// TypeReference<Student>() {});
    
    		// 第三种方式,使用Gson的思想 need default constructor
    		Student student = JSONObject.parseObject(JSON_OBJ_STR, Student.class);
    
    		System.out.println(student.toString());
    	}
    
    	/**
    	 * JavaBean到json字符串-简单对象的转换
    	 */
    	@Test
    	public void testJavaBeanObjToJSONStr() {
    
    		Student student = new Student("lily", 12);
    		String jsonString = JSONObject.toJSONString(student);
    		System.out.println(jsonString);
    	}
    
    	/**
    	 * json字符串-数组类型到JavaBean_List的转换
    	 */
    	@Test
    	public void testJSONStrToJavaBeanList() {
    
    		// 第一种方式
    		JSONArray jsonArray = JSONArray.parseArray(JSON_ARRAY_STR);
    
    		// 遍历JSONArray
    		List<Student> students = new ArrayList<Student>();
    		Student student = null;
    		for (Object object : jsonArray) {
    
    			JSONObject jsonObjectone = (JSONObject) object;
    			String studentName = jsonObjectone.getString("studentName");
    			Integer studentAge = jsonObjectone.getInteger("studentAge");
    
    			student = new Student(studentName, studentAge);
    			students.add(student);
    		}
    
    		System.out.println("students:  " + students);
    
    		// 第二种方式,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> studentList = JSONArray.parseObject(JSON_ARRAY_STR, new TypeReference<ArrayList<Student>>() {
    		});
    		System.out.println("studentList:  " + studentList);
    
    		// 第三种方式,使用Gson的思想
    		List<Student> studentList1 = JSONArray.parseArray(JSON_ARRAY_STR, Student.class);
    		System.out.println("studentList1:  " + studentList1);
    
    	}
    
    	/**
    	 * JavaBean_List到json字符串-数组类型的转换
    	 */
    	@Test
    	public void testJavaBeanListToJSONStr() {
    
    		Student student = new Student("lily", 12);
    		Student studenttwo = new Student("lucy", 15);
    
    		List<Student> students = new ArrayList<Student>();
    		students.add(student);
    		students.add(studenttwo);
    
    		String jsonString = JSONArray.toJSONString(students);
    		System.out.println(jsonString);
    
    	}
    
    	/**
    	 * 复杂json格式字符串到JavaBean_obj的转换
    	 */
    	@Test
    	public void testComplexJSONStrToJavaBean() {
    
    		// 第一种方式,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
    		Teacher teacher = JSONObject.parseObject(COMPLEX_JSON_STR, new TypeReference<Teacher>() {
    		});
    		System.out.println(teacher);
    
    		// 第二种方式,使用Gson思想
    		Teacher teacher1 = JSONObject.parseObject(COMPLEX_JSON_STR, Teacher.class);
    		System.out.println(teacher1);
    	}
    
    	/**
    	 * 复杂JavaBean_obj到json格式字符串的转换
    	 */
    	@Test
    	public void testJavaBeanToComplexJSONStr() {
    
    		// 已知复杂JavaBean_obj
    		Teacher teacher = JSONObject.parseObject(COMPLEX_JSON_STR, new TypeReference<Teacher>() {
    		});
    		String jsonString = JSONObject.toJSONString(teacher);
    		System.out.println(jsonString);
    	}
    
    	/**
    	 * 简单JavaBean_obj到json对象的转换
    	 */
    	@Test
    	public void testJavaBeanToJSONObject() {
    
    		// 已知简单JavaBean_obj
    		Student student = new Student("lily", 12);
    
    		// 方式一
    		String jsonString = JSONObject.toJSONString(student);
    		JSONObject jsonObject = JSONObject.parseObject(jsonString);
    		System.out.println(jsonObject);
    
    		// 方式二
    		JSONObject jsonObject1 = (JSONObject) JSONObject.toJSON(student);
    		System.out.println(jsonObject1);
    	}
    
    	/**
    	 * 简单json对象到JavaBean_obj的转换
    	 */
    	@Test
    	public void testJSONObjectToJavaBean() {
    
    		// 已知简单json对象
    		JSONObject jsonObject = JSONObject.parseObject(JSON_OBJ_STR);
    
    		// 第一种方式,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 student = JSONObject.parseObject(jsonObject.toJSONString(), new TypeReference<Student>() {
    		});
    		System.out.println(student);
    
    		// 第二种方式,使用Gson的思想
    		Student student1 = JSONObject.parseObject(jsonObject.toJSONString(), Student.class);
    		System.out.println(student1);
    	}
    
    	/**
    	 * JavaList到JsonArray的转换
    	 */
    	@Test
    	public void testJavaListToJsonArray() {
    
    		// 已知JavaList
    		Student student = new Student("lily", 12);
    		Student studenttwo = new Student("lucy", 15);
    
    		List<Student> students = new ArrayList<Student>();
    		students.add(student);
    		students.add(studenttwo);
    
    		// 方式一
    		String jsonString = JSONArray.toJSONString(students);
    		JSONArray jsonArray = JSONArray.parseArray(jsonString);
    		System.out.println(jsonArray);
    
    		// 方式二
    		JSONArray jsonArray1 = (JSONArray) JSONArray.toJSON(students);
    		System.out.println(jsonArray1);
    	}
    
    	/**
    	 * JsonArray到JavaList的转换
    	 */
    	@Test
    	public void testJsonArrayToJavaList() {
    
    		// 已知JsonArray
    		JSONArray jsonArray = JSONArray.parseArray(JSON_ARRAY_STR);
    
    		// 第一种方式,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
    		ArrayList<Student> students = JSONArray.parseObject(jsonArray.toJSONString(),
    				new TypeReference<ArrayList<Student>>() {
    				});
    
    		System.out.println(students);
    
    		// 第二种方式,使用Gson的思想
    		List<Student> students1 = JSONArray.parseArray(jsonArray.toJSONString(), Student.class);
    		System.out.println(students1);
    	}
    
    	/**
    	 * 复杂JavaBean_obj到json对象的转换
    	 */
    	@Test
    	public void testComplexJavaBeanToJSONObject() {
    
    		// 已知复杂JavaBean_obj
    		Student student = new Student("lily", 12);
    		Student studenttwo = new Student("lucy", 15);
    
    		List<Student> students = new ArrayList<Student>();
    		students.add(student);
    		students.add(studenttwo);
    		Course course = new Course("english", 1270);
    
    		Teacher teacher = new Teacher("crystall", 27, course, students);
    
    		// 方式一
    		String jsonString = JSONObject.toJSONString(teacher);
    		JSONObject jsonObject = JSONObject.parseObject(jsonString);
    		System.out.println(jsonObject);
    
    		// 方式二
    		JSONObject jsonObject1 = (JSONObject) JSONObject.toJSON(teacher);
    		System.out.println(jsonObject1);
    
    	}
    
    	/**
    	 * 复杂json对象到JavaBean_obj的转换
    	 */
    	@Test
    	public void testComplexJSONObjectToJavaBean() {
    
    		// 已知复杂json对象
    		JSONObject jsonObject = JSONObject.parseObject(COMPLEX_JSON_STR);
    
    		// 第一种方式,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
    		Teacher teacher = JSONObject.parseObject(jsonObject.toJSONString(), new TypeReference<Teacher>() {
    		});
    		System.out.println(teacher);
    
    		// 第二种方式,使用Gson的思想
    		Teacher teacher1 = JSONObject.parseObject(jsonObject.toJSONString(), Teacher.class);
    		System.out.println(teacher1);
    	}
    }
    
    /**
     * @author Zhangdi class Student
     */
    class Student {
    	private String studentName;
    	private Integer studentAge;
    
    	protected Student() {
    		super();
    	}
    
    	protected Student(String studentName, Integer studentAge) {
    		super();
    		this.studentName = studentName;
    		this.studentAge = studentAge;
    	}
    
    	public String getStudentName() {
    		return studentName;
    	}
    
    	public void setStudentName(String studentName) {
    		this.studentName = studentName;
    	}
    
    	public Integer getStudentAge() {
    		return studentAge;
    	}
    
    	public void setStudentAge(Integer studentAge) {
    		this.studentAge = studentAge;
    	}
    
    	@Override
    	public String toString() {
    		return "Student [studentName=" + studentName + ", studentAge=" + studentAge + "]";
    	}
    
    }
    
    /**
     * @author Zhangdi Teacher
     */
    class Teacher {
    	private String teacherName;
    	private Integer teacherAge;
    	private Course course;
    	private List<Student> students;
    
    	protected Teacher() {
    		super();
    		// TODO Auto-generated constructor stub
    	}
    
    	protected Teacher(String teacherName, Integer teacherAge) {
    		super();
    		this.teacherName = teacherName;
    		this.teacherAge = teacherAge;
    	}
    
    	public Teacher(String teacherName, int teacherAge, Course course, List<Student> students) {
    		this.teacherName = teacherName;
    		this.teacherAge = teacherAge;
    		this.course = course;
    		this.students = students; 
    	}
    
    	public String getTeacherName() {
    		return teacherName;
    	}
    
    	public void setTeacherName(String teacherName) {
    		this.teacherName = teacherName;
    	}
    
    	public Integer getTeacherAge() {
    		return teacherAge;
    	}
    
    	public void setTeacherAge(Integer teacherAge) {
    		this.teacherAge = teacherAge;
    	}
    
    	@Override
    	public String toString() {
    		return "Teacher [teacherName=" + teacherName + ", teacherAge=" + teacherAge + "]";
    	}
    
    }
    
    class Course{
    	private String courseName;
    	private Integer code;
    	
    	
    	protected Course() {
    		super();
    	}
    	
    	protected Course(String courseName, Integer code) {
    		super();
    		this.courseName = courseName;
    		this.code = code;
    	}
    
    	public String getCourseName() {
    		return courseName;
    	}
    	public void setCourseName(String courseName) {
    		this.courseName = courseName;
    	}
    	public Integer getCode() {
    		return code;
    	}
    	public void setCode(Integer code) {
    		this.code = code;
    	}
    	
    	
    }

## 20190625 update: ##

public static String getArrJson() { 
        JSONObject jsonObject = new JSONObject();
        List<Map<String, Object>> list = new ArrayList<>();
        Map<String, Object> map = null;
        for (int i = 1; i < 5; i++) { 
            map = new HashMap<>();
            map.put("name", "name" + i);
            map.put("age", "age" + i);
            list.add(map);
        }
        jsonObject.put("result_data", list);
        return jsonObject.toJSONString();
    }

[https_segmentfault.com_a_1190000011212806]: https://segmentfault.com/a/1190000011212806