正如所承诺的,我正在举例说明如何使用注释来序列化/反序列化多态对象,我在您正在阅读的教程中的Animal类中使用此示例.
首先,你的Animal类带有子类的Json Annotations.
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonSubTypes;
import com.fasterxml.jackson.annotation.JsonTypeInfo;
@JsonIgnoreProperties(ignoreUnknown = true)
@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY)
@JsonSubTypes({
@JsonSubTypes.Type(value = Dog.class, name = "Dog"),
@JsonSubTypes.Type(value = Cat.class, name = "Cat") }
)
public abstract class Animal {
private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
然后你的子类,狗和猫.
public class Dog extends Animal {
private String breed;
public Dog() {
}
public Dog(String name, String breed) {
setName(name);
setBreed(breed);
}
public String getBreed() {
return breed;
}
public void setBreed(String breed) {
this.breed = breed;
}
}
public class Cat extends Animal {
public String getFavoriteToy() {
return favoriteToy;
}
public Cat() {}
public Cat(String name, String favoriteToy) {
setName(name);
setFavoriteToy(favoriteToy);
}
public void setFavoriteToy(String favoriteToy) {
this.favoriteToy = favoriteToy;
}
private String favoriteToy;
}
正如您所看到的,Cat和Dog没有什么特别之处,唯一了解它们的是抽象类Animal,因此在反序列化时,您将定位到Animal,而ObjectMapper将返回实际的实例,如您所见以下测试：
public class Test {
public static void main(String[] args) {
ObjectMapper objectMapper = new ObjectMapper();
Animal myDog = new Dog("ruffus","english shepherd");
Animal myCat = new Cat("goya", "mice");
try {
String dogJson = objectMapper.writeValueAsString(myDog);
System.out.println(dogJson);
Animal deserializedDog = objectMapper.readValue(dogJson, Animal.class);
System.out.println("Deserialized dogJson Class: " + deserializedDog.getClass().getSimpleName());
String catJson = objectMapper.writeValueAsString(myCat);
Animal deseriliazedCat = objectMapper.readValue(catJson, Animal.class);
System.out.println("Deserialized catJson Class: " + deseriliazedCat.getClass().getSimpleName());
} catch (Exception e) {
e.printStackTrace();
}
}
}
运行Test类后输出：
{“@ type”：“狗”,“名字”：“ruffus”,“品种”：“英国牧羊犬”}
反序列化的dogJson类：狗
{ “@type”： “猫”, “名”： “戈雅”, “favoriteToy”： “老鼠”}
反序列化的catJson类：Cat
希望这可以帮助,
何塞路易斯