Micronaut中基于类型动态类字段的灵活验证机制

// src/main/java/com/example/A.java
package com.example;

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

// 通过 @JsonDeserialize 注解指定自定义反序列化器
@JsonDeserialize(using = ADeserializer.class)
public interface A {
    String getType();
    // 可以添加其他所有具体类型共有的方法
}

// src/main/java/com/example/Type1.java
package com.example;

import io.micronaut.core.annotation.Introspected;
import javax.validation.constraints.NotBlank;

@Introspected // 推荐在Micronaut中使用，以便AOT编译时生成反射元数据
public class Type1 implements A {

    private String type = "type1"; // 固定为该类型标识符

    @NotBlank(message = "Type1的值不能为空")
    private String value;

    @Override
    public String getType() {
        return this.type;
    }

    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }
}

// src/main/java/com/example/Type2.java
package com.example;

import io.micronaut.core.annotation.Introspected;
import javax.validation.constraints.Pattern;
import javax.validation.constraints.Size;

@Introspected
public class Type2 implements A {

    private String type = "type2"; // 固定为该类型标识符

    @Size(min = 5, max = 10, message = "Type2的值长度必须在5到10之间")
    @Pattern(regexp = "^[a-zA-Z0-9]*$", message = "Type2的值只能包含字母和数字")
    private String value;

    @Override
    public String getType() {
        return this.type;
    }

    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }
}

// 示例：自定义验证注解和对应的验证器
// @YourCustomValidator
// public @interface YourCustomValidator { ... }
// public class YourCustomValidatorImpl implements ConstraintValidator<YourCustomValidator, String> { ... }

// src/main/java/com/example/ADeserializer.java
package com.example;

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

public class ADeserializer extends JsonDeserializer<A> {

    // 映射类型字符串到对应的具体类
    private static final Map<String, Class<? extends A>> typeRegistry = new HashMap<>();

    static {
        typeRegistry.put("type1", Type1.class);
        typeRegistry.put("type2", Type2.class);
        // 注册更多类型...
    }

    @Override
    public A deserialize(JsonParser p, DeserializationContext ctxt) throws IOException {
        ObjectMapper mapper = (ObjectMapper) p.getCodec();
        JsonNode node = mapper.readTree(p); // 读取整个JSON节点

        // 从JSON节点中获取'type'字段的值
        JsonNode typeNode = node.get("type");
        if (typeNode == null || !typeNode.isTextual()) {
            // 处理没有'type'字段或'type'字段不是文本的情况
            throw new IOException("Missing or invalid 'type' field for A object.");
        }

        String type = typeNode.asText();
        Class<? extends A> targetClass = typeRegistry.get(type);

        if (targetClass == null) {
            throw new IOException("Unknown type: " + type);
        }

        // 将当前JSON节点反序列化为目标具体类的一个实例
        return mapper.treeToValue(node, targetClass);
    }
}

// src/main/java/com/example/AController.java
package com.example;

import io.micronaut.http.annotation.Body;
import io.micronaut.http.annotation.Controller;
import io.micronaut.http.annotation.Post;
import io.micronaut.validation.Validated;
import javax.validation.Valid;

@Controller("/api/a")
@Validated // 启用控制器级别的验证
public class AController {

    @Post
    public String processA(@Body @Valid A aObject) {
        // 如果aObject是Type1或Type2的实例，并且通过了各自的验证，
        // 则会执行到这里。
        // Micronaut会自动根据@Valid注解对传入的A对象进行验证。
        System.out.println("Received and validated A object: " + aObject.getType());
        return "Processed " + aObject.getType() + " with value: " + 
               (aObject instanceof Type1 ? ((Type1) aObject).getValue() : 
                aObject instanceof Type2 ? ((Type2) aObject).getValue() : "N/A");
    }
}