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JacksonTest.java
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116 lines (96 loc) · 3.63 KB
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package test;
import com.fasterxml.jackson.databind.ObjectMapper;
import domain.Person;
import org.junit.Test;
import java.io.FileWriter;
import java.util.*;
/**
* @author ： CodeWater
* @create ：2022-03-22-16:56
* @Function Description ：
* java转成json
*/
public class JacksonTest {
@Test
public void test1() throws Exception {
//1.创建person对象
Person p = new Person();
p.setName("张三");
p.setAge(23);
p.setGender("男");
//2.创建Jackson的核心对象 ObjectMapper
ObjectMapper mapper = new ObjectMapper();
//转换
/* 转换方法：
writeValue(参数1，obj):
参数1：
File：将obj对象转换为JSON字符串，并保存到指定的文件中
Writer：将obj对象转换为JSON字符串，并将json数据填充到字符输出流中
OutputStream：将obj对象转换为JSON字符串，并将json数据填充到字节输出流中
writeValueAsString(obj):将对象转为json字符串
*/
String json = mapper.writeValueAsString(p);
//{"name":"张三","age":23,"gender":"男"}
// System.out.println( json );
//writeValue，将数据写到d://a.txt文件中
// mapper.writeValue( new File( "E://JavaCode//JQuery//src//test//a.txt" ) , p );
//writeValue.将数据关联到Writer中
mapper.writeValue(new FileWriter("E://JavaCode//JQuery//src//test//b.txt"), p);
}
// 注解： 属性设置成固定格式
@Test
public void test2() throws Exception {
Person p = new Person();
p.setName("zhansgan");
p.setAge(23);
p.setGender("nan");
p.setBirthday(new Date());
ObjectMapper mapper = new ObjectMapper();
String json = mapper.writeValueAsString(p);
// 默认格式：{"name":"张三","age":23,"gender":"男","birthday":1530958029263}
// System.out.println( json );
//加了注解@JsonFormat:{"name":"zhansgan","age":23,"gender":"nan","birthday":"2022-03-22"}
System.out.println(json);
}
// 复杂对象转换，list、map
@Test
public void test3() throws Exception {
Person p = new Person();
p.setName("张三");
p.setAge(23);
p.setGender("男");
p.setBirthday(new Date());
Person p1 = new Person();
p1.setName("张三");
p1.setAge(23);
p1.setGender("男");
p1.setBirthday(new Date());
List<Person> ps = new ArrayList<Person>();
ps.add(p);
ps.add(p1);
ObjectMapper mapper = new ObjectMapper();
String json = mapper.writeValueAsString(ps);
//[{"name":"张三","age":23,"gender":"男","birthday":"2022-03-22"},{"name":"张三","age":23,"gender":"男","birthday":"2022-03-22"}]
System.out.println(json);
}
@Test
public void test4() throws Exception {
Map<String, Object> map = new HashMap<String, Object>();
map.put("name", "zhangsan");
map.put("age", 23);
map.put("gender", "nan");
ObjectMapper mapper = new ObjectMapper();
String json = mapper.writeValueAsString(map);
// {"gender":"nan","name":"zhangsan","age":23}
System.out.println(json);
}
//演示 JSON字符串转为Java对象
@Test
public void test5() throws Exception {
//1.初始化JSON字符串
String json = "{\"gender\":\"男\",\"name\":\"张三\",\"age\":23}";
ObjectMapper mapper = new ObjectMapper();
Person p = mapper.readValue(json, Person.class);
System.out.println(p);
}
}