Jackson解析Json
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JSON数据和Java对象的相互转换
* JSON解析器:
* 常见的解析器:Jsonlib,Gson,fastjson,jackson
1. JSON转为Java对象
1. 导入jackson的相关jar包
2. 创建Jackson核心对象 ObjectMapper
3. 调用ObjectMapper的相关方法进行转换
1. readValue(json字符串数据,Class)
2. Java对象转换JSON
1. 使用步骤:
1. 导入jackson的相关jar包
2. 创建Jackson核心对象 ObjectMapper
3. 调用ObjectMapper的相关方法进行转换
1. 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
2. 注解:
1. @JsonIgnore:排除属性。
2. @JsonFormat:属性值得格式化
* @JsonFormat(pattern = "yyyy-MM-dd")
3. 复杂java对象转换
1. List:数组
2. Map:对象格式一致
测试类
import com.code_g.domain.Person;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.junit.Test;
import java.io.File;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
public class TestJackSon {
//将java对象转换为javascript
@Test
public void testJack1() throws Exception {
Person person = new Person();
person.setName("code_g");
person.setAge(18);
person.setGender("male");
ObjectMapper mapper = new ObjectMapper();
// String s = mapper.writeValueAsString(person); //将对象转换为json字符串
// System.out.println(s); //{"name":"code_g","age":18,"gender":"male"}
//将对象转为json在写入文件中
mapper.writeValue(new File("E:\\\\a.txt"),person);
}
//测试注解
@Test
public void testJack2() throws Exception {
Person person = new Person();
person.setName("code_g");
person.setAge(18);
person.setGender("male");
person.setBirthday(new Date());
ObjectMapper mapper = new ObjectMapper();
String s = mapper.writeValueAsString(person);
System.out.println(s);
//{"name":"code_g","age":18,"gender":"male","birthday":1620825617349}
//加@JsonIgnore注解 {"name":"code_g","age":18,"gender":"male"}
//加@JsonFormat注解 {"name":"code_g","age":18,"gender":"male","birthday":"2021-05-12"}
}
//数组转换
@Test
public void testJack3() throws Exception {
Person person1 = new Person();
person1.setName("code_g");
person1.setAge(18);
person1.setGender("male");
person1.setBirthday(new Date());
Person person2 = new Person();
person2.setName("code_g");
person2.setAge(18);
person2.setGender("male");
person2.setBirthday(new Date());
Person person3 = new Person();
person3.setName("code_g");
person3.setAge(18);
person3.setGender("male");
person3.setBirthday(new Date());
ArrayList<Person> list = new ArrayList<>();
list.add(person1);
list.add(person2);
list.add(person3);
ObjectMapper mapper = new ObjectMapper();
String s = mapper.writeValueAsString(list);
System.out.println(s);
//[
// {"name":"code_g","age":18,"gender":"male","birthday":"2021-05-12"},
// {"name":"code_g","age":18,"gender":"male","birthday":"2021-05-12"},{
// "name":"code_g","age":18,"gender":"male","birthday":"2021-05-12"}
// ]
}
//map
@Test
public void testJack4() throws Exception {
HashMap<String, Object> map = new HashMap<>();
map.put("name","code_g");
map.put("age",18);
map.put("gender","female");
ObjectMapper mapper = new ObjectMapper();
String s = mapper.writeValueAsString(map);
System.out.println(s);
//{"gender":"female","name":"code_g","age":18}
}
//将json转换为java对象
@Test
public void testJack5() throws Exception {
String s = "{\\"gender\\":\\"female\\",\\"name\\":\\"code_g\\",\\"age\\":18}";
ObjectMapper mapper = new ObjectMapper();
Person person = mapper.readValue(s, Person.class);
System.out.println(person); //Person{name=\'code_g\', age=18, gender=\'female\', birthday=null}
}
}
Person类
import com.fasterxml.jackson.annotation.JsonFormat;
import com.fasterxml.jackson.annotation.JsonIgnore;
import java.util.Date;
public class Person {
private String name;
private int age;
private String gender;
// @JsonIgnore
@JsonFormat(pattern = "yyyy-MM-dd")
private Date birthday;
public Date getBirthday() {
return birthday;
}
@Override
public String toString() {
return "Person{" +
"name=\'" + name + \'\\\'\' +
", age=" + age +
", gender=\'" + gender + \'\\\'\' +
", birthday=" + birthday +
\'}\';
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
public Person(String name, int age, String gender, Date birthday) {
this.name = name;
this.age = age;
this.gender = gender;
this.birthday = birthday;
}
public Person() {
}
public Person(String name, int age, String gender) {
this.name = name;
this.age = age;
this.gender = gender;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
}
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