@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 扩展 StdDeserializer 类来实现自定义反序列化器,并且需要重写 的 deserialize() 方法StdDeserializer 类。
@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 注解实现自定义反序列化器
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 class class CustomDeserializer extends StdDeserializer<Employee> { public CustomDeserializer(Class<Employee> 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 class @JsonDeserialize(using=CustomDeserializer.class)<strong> </strong>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(); } }
ID: 115 Name: Adithya
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