FastJson快速学习

1 JSON,JSONArray，JSONObject，必须掌握三者的关系，因为后面的方法中我们经常使用JSONObject中的方法，其实调用的是JSON

2 JSON类之parseObject()方法，实现json字符串转换为json对象或javabean对象

23JSON类之toJSONString()方法，实现json对象转化为json字符串和javabean对象转化为json 字符串,

总结：

1 这两个方法我们经常使用，因为我们往往会从前端得到一段字符串，然后使用parseObject转换为我们后端的javabean，

使用toJSONString，把我们的json对象转换为json字符串。

2 这里面我们一定要清楚，我们传输的json字符串还是json对象，使用RestController，采用的是json字符串。

最后贴出自己的例子，供参考：

package com.ying.test;

import java.util.ArrayList;

import org.junit.Test;

import com.alibaba.fastjson.JSONArray;
import com.alibaba.fastjson.JSONObject;
import com.alibaba.fastjson.serializer.SerializerFeature;
import com.ying.pojo.Course;
import com.ying.pojo.Student;

public class TestJson {

	//json字符串-简单对象型
	private static final String  JSON_OBJ_STR = "{\"STUDENTNAM\":\"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}]}"; 
	
    private static final SerializerFeature[] features =
        {

                SerializerFeature.WriteMapNullValue, // 输出空置字段
                //SerializerFeature.WriteNullListAsEmpty, // list字段如果为null，输出为[]，而不是null
                //SerializerFeature.WriteNullNumberAsZero, // 数值字段如果为null，输出为0，而不是null
                //SerializerFeature.WriteNullBooleanAsFalse, // Boolean字段如果为null，输出为false，而不是null
                SerializerFeature.WriteNullStringAsEmpty // 字符类型字段如果为null，输出为""，而不是null
        }; 
	
    
	@Test
	public void testJson2JavaBean() {
		
		Student student = JSONObject.parseObject(JSON_OBJ_STR,Student.class);
		System.out.println("name:" + student.getStudentName() + " age:" + student.getStudentAge());
	}
	
	//测试是否能正常映射
	@Test
	public void testToString() {
		Student stu = new Student();
		stu.setStudentAge(11);
		stu.setStudentName("lily");
		String stuString = JSONObject.toJSONString(stu,features);
		System.out.println(stuString);
	}
	
	//测试filed是否有效果
	@Test
	public void testToString2() {
		Student stu = new Student();
		stu.setStudentAge(11);
		String stuString = JSONObject.toJSONString(stu,features);
		System.out.println(stuString);
	}
	
	
	@Test
	public void testJsonArray2JavaBean() {
		
		JSONArray jsonArray = JSONObject.parseArray(JSON_ARRAY_STR);
		for(Object object : jsonArray) {
			JSONObject jsonObject = (JSONObject)object;
			Student student = JSONObject.toJavaObject(jsonObject, Student.class);
			System.out.println("name:" + student.getStudentName() + " age:" + student.getStudentAge());
		}
	}
	
	
	@Test
	public void testJsonArrayToString2() {
		
		ArrayList<Student > arrayList = new ArrayList<>();
		Student  student1 = new Student();
		student1.setStudentAge(11);
		
		Student  student2 = new Student();
		student2.setStudentAge(12);
		arrayList.add(student1);
		arrayList.add(student2);

		JSONArray jArray = (JSONArray)JSONArray.toJSON(arrayList);
		String stuString = JSONObject.toJSONString(jArray,features);
		System.out.println(stuString);
	}
	
	@Test
	public void testFixJson2JavaBean() {
		
		JSONObject jsonObject = JSONObject.parseObject(COMPLEX_JSON_STR);
		
		String teacherName = jsonObject.getString("teacherName");
		String teacherAge = jsonObject.getString("teacherAge");
		System.out.println("teacherName"+teacherName + "teacherAge" + teacherAge);
		JSONObject jsonObject1 = jsonObject.getJSONObject("course");
		Course course = JSONObject.toJavaObject(jsonObject1,Course.class);
		System.out.println("Course:" +course.toString());
		
		JSONArray jsonArray = jsonObject.getJSONArray("students");
		
		for(Object object : jsonArray) {
			JSONObject jsonObject2 = (JSONObject)object;
			Student student = JSONObject.toJavaObject(jsonObject2, Student.class);
			System.out.println("name:" + student.getStudentName() + " age:" + student.getStudentAge());
		}
	}
	
	
}

参考https://blog.csdn.net/srj1095530512/article/details/82529759

https://segmentfault.com/a/1190000011212806