高性能JSON框架之FastJson的简单使用

转载自: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();
}