提供几个Jackson Mixin的功能示例

好的，以下是几个 Jackson Mixin 的功能示例：

1. 为某个类添加序列化和反序列化规则：

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "type")
@JsonSubTypes({
    @JsonSubTypes.Type(value = Dog.class, name = "dog"),
    @JsonSubTypes.Type(value = Cat.class, name = "cat")
})
public abstract class AnimalMixin {
    @JsonCreator
    public AnimalMixin(@JsonProperty("name") String name) {}
    @JsonProperty("name")
    abstract String getName();
}

2. 为某个属性添加序列化和反序列化规则：

public class Person {
    private String name;
    private int age;
    // getters and setters
}

public interface PersonMixin {
    @JsonProperty("fullName")
    String getName();
    @JsonIgnore
    int getAge();
}

ObjectMapper mapper = new ObjectMapper();
mapper.addMixIn(Person.class, PersonMixin.class);

3. 为某个类添加自定义序列化和反序列化规则：

public class User {
    private String username;
    private String password;
    // getters and setters
}

public abstract class UserMixin {
    @JsonCreator
    public UserMixin(@JsonProperty("username") String username, @JsonProperty("password") String password) {}
    @JsonProperty("username")
    abstract String getUsername();
    @JsonProperty("password")
    abstract String getPassword();
}

public class UserDeserializer extends StdDeserializer<User> {
    public UserDeserializer() {
        super(User.class);
    }
    @Override
    public User deserialize(JsonParser p, DeserializationContext ctxt) throws IOException, JsonProcessingException {
        JsonNode node = p.getCodec().readTree(p);
        String username = node.get("username").asText();
        String password = node.get("password").asText();
        return new User(username.toUpperCase(), password);
    }
}

ObjectMapper mapper = new ObjectMapper();
SimpleModule module = new SimpleModule();
module.setMixInAnnotation(User.class, UserMixin.class);
module.addDeserializer(User.class, new UserDeserializer());
mapper.registerModule(module);