@JsonDeserialize注解用于在将JSON反序列化为Java对象时声明自定义反序列化器。我们可以通过使用泛型类型Employee继承 StdDeserializer类来实现自定义反序列化器，并且需要重写StdDeserializer类的deserialize()方法。
语法@Target(value={ANNOTATION_TYPE,METHOD,FIELD,TYPE,PARAMETER})
@Retention(value=RUNTIME)
public @interface JsonDeserialize
在下面的程序中，我们可以使用@JsonDeserialize注释实现自定义反序列化器
示例import java.io.*;
import com.fasterxml.jackson.core.*;
import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.annotation.*;
import com.fasterxml.jackson.databind.deser.std.*;
public class JsonDeSerializeAnnotationTest {
public static void main (String[] args) throws JsonProcessingException, IOException {
Employee emp = new Employee(115, "Adithya");
ObjectMapper mapper = new ObjectMapper();
String jsonString = mapper.writeValueAsString(emp);
emp = mapper.readValue(jsonString, Employee.class);
System.out.println(emp);
}
}
// CustomDeserializer 类
class CustomDeserializer extends StdDeserializer {
public CustomDeserializer(Class t) {
super(t);
}
public CustomDeserializer() {
this(Employee.class);
}
@Override
public Employee deserialize(JsonParser jp, DeserializationContext dc) throws IOException, JsonProcessingException
{
int id = 0;
String name = null;
JsonToken currentToken = null;
while((currentToken = jp.nextValue()) != null) {
switch(currentToken) {
case VALUE_NUMBER_INT:
if(jp.getCurrentName().equals("id")) {
id = jp.getIntValue();
}
break;
case VALUE_STRING:
switch(jp.getCurrentName()) {
case "name":
name = jp.getText();
break;
default:
break;
}
break;
default:
break;
}
}
return new Employee(id, name);
}
}
// Employee 类
@JsonDeserialize(using=CustomDeserializer.class)
class Employee {
private int id;
private String name;
public Employee(int id, String name) {
this.id = id;
this.name = name;
}
public int getId() {
return id;
}
public String getName() {
return name;
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder("ID: ").append(this.id).append("\nName: ").append(this.name);
return sb.toString();
}
}
输出结果ID: 115
Name: Adithya