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Jackson自定义注解

电脑变wifi•2022-12-16•随笔•阅读8

Jackson自定义注解,第1张

Jackson自定义注解

目录
  • 用三种方案实现
  • 共用类
    • 适配实体类 CcyAmt.class
    • 序列化实现类 CcySerializer.class
    • 反序列化实现类 CcyDeserializer.class
  • 1、最简单的实现
    • Ccy注解 直接指定策略
    • 在 Person.class 字段上直接添加Cyy注解
    • 简单使用 XmlMapper
    • 打印结果
  • 2、使用 MixIn 功能
    • 仍然是Ccy注解 直接指定策略
    • 未添加注解的 Person.class
    • CcyMixIn.class 给指定字段混入注解
    • 使用 XmlMapper 添加混入策略
    • 打印结果
  • 3、使用 AnnotationIntrospector 功能
    • 仍然是未添加注解的 Person.class
    • 简单的Ccy注解
    • 创建 CcyAnnotationIntrospector 类 指定Ccy注解的策略
    • 使用 XmlMapper 设置自定义的 CcyAnnotationIntrospector
    • 打印结果

用三种方案实现 
private String salary; 与 20000.00 的序列化和反序列化
共用类 适配实体类 CcyAmt.class 
import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlProperty;
import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlText;

public class CcyAmt {
	
	@JacksonXmlProperty(isAttribute = true)
	private String ccy;
	
	@JacksonXmlText
	private Object value;

	public CcyAmt() {}

	public CcyAmt(String ccy, Object value) {
		this.ccy = ccy;
		this.value = value;
	}

	public String getCcy() {
		return ccy;
	}

	public void setCcy(String ccy) {
		this.ccy = ccy;
	}

	public Object getValue() {
		return value;
	}

	public void setValue(Object value) {
		this.value = value;
	}
}
序列化实现类 CcySerializer.class 
import java.io.IOException;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.SerializerProvider;

public class CcySerializer extends JsonSerializer {

	@Override
	public void serialize(Object value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
		CcyAmt ccyAmt = new CcyAmt("CNY", value);
		gen.writeObject(ccyAmt);
	}

}
 
反序列化实现类 CcyDeserializer.class 

import java.io.IOException;

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;

public class CcyDeserializer extends JsonDeserializer {

	@Override
	public Object deserialize(JsonParser p, DeserializationContext ctxt) throws IOException, JsonProcessingException {
		CcyAmt ccyAmt = p.readValueAs(CcyAmt.class);
		return ccyAmt.getValue();
	}

}
 
1、最简单的实现 
Ccy注解 直接指定策略 

import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

import java.lang.annotation.Retention;
import java.lang.annotation.Target;

import com.fasterxml.jackson.annotation.JacksonAnnotationsInside;
import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
import com.fasterxml.jackson.databind.annotation.JsonSerialize;

@Retention(RUNTIME)
@Target(FIELD)
@JacksonAnnotationsInside
@JsonSerialize(using = CcySerializer.class)
@JsonDeserialize(using = CcyDeserializer.class)
public @interface Ccy {

}

 
在 Person.class 字段上直接添加Cyy注解 

public class Person {

	private String name;
	
	private String age;
	
	private String sex;
	
	private String testName;
	
	@Ccy
	private String salary;

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getAge() {
		return age;
	}

	public void setAge(String age) {
		this.age = age;
	}

	public String getSex() {
		return sex;
	}

	public void setSex(String sex) {
		this.sex = sex;
	}

	public String getSalary() {
		return salary;
	}

	public void setSalary(String salary) {
		this.salary = salary;
	}

	public String getTestName() {
		return testName;
	}

	public void setTestName(String testName) {
		this.testName = testName;
	}

	@Override
	public String toString() {
		return "Person [name=" + name + ", age=" + age + ", sex=" + sex + ", testName=" + testName + ", salary="
				+ salary + "]";
	}
	
}

 
简单使用 XmlMapper 

import java.io.IOException;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.PropertyNamingStrategies;
import com.fasterxml.jackson.dataformat.xml.XmlMapper;

public class Test {

	public static void main(String[] args) throws IOException {
		Person person = new Person();
		person.setName("一个人");
		person.setAge("18");
		person.setSex("1");
		person.setSalary("20000.00");
		person.setTestName("测试人");
		
		ObjectMapper mapper = new XmlMapper();
		mapper.setPropertyNamingStrategy(PropertyNamingStrategies.UPPER_CAMEL_CASE);
		String value = mapper.writevalueAsString(person);
		System.out.println(value);
		
		Person readValue = mapper.readValue(value, Person.class);
		System.out.println(readValue);
	}
}

 
打印结果 

一个人181测试人20000.00
Person [name=一个人, age=18, sex=1, testName=测试人, salary=20000.00]

 
2、使用 MixIn 功能 
仍然是Ccy注解 直接指定策略 

import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

import java.lang.annotation.Retention;
import java.lang.annotation.Target;

import com.fasterxml.jackson.annotation.JacksonAnnotationsInside;
import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
import com.fasterxml.jackson.databind.annotation.JsonSerialize;

@Retention(RUNTIME)
@Target(FIELD)
@JacksonAnnotationsInside
@JsonSerialize(using = CcySerializer.class)
@JsonDeserialize(using = CcyDeserializer.class)
public @interface Ccy {

}

 
未添加注解的 Person.class 

public class Person {

	private String name;
	
	private String age;
	
	private String sex;
	
	private String testName;
	
	private String salary;

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getAge() {
		return age;
	}

	public void setAge(String age) {
		this.age = age;
	}

	public String getSex() {
		return sex;
	}

	public void setSex(String sex) {
		this.sex = sex;
	}

	public String getSalary() {
		return salary;
	}

	public void setSalary(String salary) {
		this.salary = salary;
	}

	public String getTestName() {
		return testName;
	}

	public void setTestName(String testName) {
		this.testName = testName;
	}

	@Override
	public String toString() {
		return "Person [name=" + name + ", age=" + age + ", sex=" + sex + ", testName=" + testName + ", salary="
				+ salary + "]";
	}
	
}

 
CcyMixIn.class 给指定字段混入注解 

import com.fasterxml.jackson.annotation.JsonProperty;

public class CcyMixIn {

	@Ccy
	private String salary;
	
	@JsonProperty("xingbie")
	private String sex;

}

 
使用 XmlMapper 添加混入策略 

import java.io.IOException;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.PropertyNamingStrategies;
import com.fasterxml.jackson.dataformat.xml.XmlMapper;

public class Test {

	public static void main(String[] args) throws IOException {
		Person person = new Person();
		person.setName("一个人");
		person.setAge("18");
		person.setSex("1");
		person.setSalary("20000.00");
		person.setTestName("测试人");
		
		ObjectMapper mapper = new XmlMapper();
		mapper.setPropertyNamingStrategy(PropertyNamingStrategies.UPPER_CAMEL_CASE);
		//给Person混入CcyMixIn
		mapper.addMixIn(Person.class, CcyMixIn.class);
		String value = mapper.writevalueAsString(person);
		System.out.println(value);
		
		Person readValue = mapper.readValue(value, Person.class);
		System.out.println(readValue);
	}
}

 
打印结果 

一个人18测试人20000.001
Person [name=一个人, age=18, sex=1, testName=测试人, salary=20000.00]

 
3、使用 AnnotationIntrospector 功能 
仍然是未添加注解的 Person.class 

public class Person {

	private String name;
	
	private String age;
	
	private String sex;
	
	private String testName;
	
	private String salary;

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getAge() {
		return age;
	}

	public void setAge(String age) {
		this.age = age;
	}

	public String getSex() {
		return sex;
	}

	public void setSex(String sex) {
		this.sex = sex;
	}

	public String getSalary() {
		return salary;
	}

	public void setSalary(String salary) {
		this.salary = salary;
	}

	public String getTestName() {
		return testName;
	}

	public void setTestName(String testName) {
		this.testName = testName;
	}

	@Override
	public String toString() {
		return "Person [name=" + name + ", age=" + age + ", sex=" + sex + ", testName=" + testName + ", salary="
				+ salary + "]";
	}
	
}

 
简单的Ccy注解 

import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

import java.lang.annotation.Retention;
import java.lang.annotation.Target;

@Retention(RUNTIME)
@Target(FIELD)
public @interface Ccy {

}

 
创建 CcyAnnotationIntrospector 类 指定Ccy注解的策略 

import com.fasterxml.jackson.databind.introspect.Annotated;
import com.fasterxml.jackson.databind.introspect.NopAnnotationIntrospector;

public class CcyAnnotationIntrospector extends NopAnnotationIntrospector {

	private static final long serialVersionUID = -1495356687014456822L;

	@Override
	public Object findSerializer(Annotated am) {
		Ccy annotation = am.getAnnotation(Ccy.class);
		if (annotation != null) {
			return CcySerializer.class;
		}
		return null;
	}

	@Override
	public Object findDeserializer(Annotated am) {
		Ccy annotation = am.getAnnotation(Ccy.class);
		if (annotation != null) {
			return CcyDeserializer.class;
		}
		return null;
	}

}

 
使用 XmlMapper 设置自定义的 CcyAnnotationIntrospector 

import java.io.IOException;

import com.fasterxml.jackson.databind.AnnotationIntrospector;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.PropertyNamingStrategies;
import com.fasterxml.jackson.databind.introspect.AnnotationIntrospectorPair;
import com.fasterxml.jackson.dataformat.xml.XmlMapper;

public class Test {

	public static void main(String[] args) throws IOException {
		Person person = new Person();
		person.setName("一个人");
		person.setAge("18");
		person.setSex("1");
		person.setSalary("20000.00");
		person.setTestName("测试人");
		
		ObjectMapper mapper = new XmlMapper();
		mapper.setPropertyNamingStrategy(PropertyNamingStrategies.UPPER_CAMEL_CASE);
		//必须在原有的AnnotationIntrospector中追加，否则其他Jackson注解将不可用
		AnnotationIntrospector sis = mapper.getSerializationConfig().getAnnotationIntrospector();
        AnnotationIntrospector dis = mapper.getDeserializationConfig().getAnnotationIntrospector();
        AnnotationIntrospector is1 = AnnotationIntrospectorPair.pair(sis, new CcyAnnotationIntrospector());
        AnnotationIntrospector is2 = AnnotationIntrospectorPair.pair(dis, new CcyAnnotationIntrospector());
        mapper.setAnnotationIntrospectors(is1, is2);
		String value = mapper.writevalueAsString(person);
		System.out.println(value);
		
		Person readValue = mapper.readValue(value, Person.class);
		System.out.println(readValue);
	}
}

 
打印结果 

一个人181测试人20000.00
Person [name=一个人, age=18, sex=1, testName=测试人, salary=20000.00]

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