如何使用javax.validation验证路径id与请求体对象id的一致性？

当然可以用javax.validation框架实现这个需求，核心思路是自定义方法级别的约束注解，用来校验方法中路径参数id和请求体QdCFPresenter的id是否相等。以下是具体实现步骤：

1. 自定义约束注解 #

创建一个方法级的约束注解，用于标记需要校验的方法，并指定要对比的参数/字段名称：

import javax.validation.Constraint;
import javax.validation.Payload;
import java.lang.annotation.*;

@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy = PathIdMatchesBodyIdValidator.class)
public @interface PathIdMatchesBodyId {
    String message() default "路径ID与请求体ID不匹配";

    Class<?>[] groups() default {};

    Class<? extends Payload>[] payload() default {};

    String pathIdParam() default "id";

    String bodyParam() default "qdcf";

    String bodyIdField() default "id";
}

2. 实现约束校验器 #

编写对应的校验器类，实现ConstraintValidator接口，通过反射获取参数值并完成对比：

import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;
import org.springframework.core.DefaultParameterNameDiscoverer;
import org.springframework.core.ParameterNameDiscoverer;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;

public class PathIdMatchesBodyIdValidator implements ConstraintValidator<PathIdMatchesBodyId, Object> {

    private String pathIdParam;
    private String bodyParam;
    private String bodyIdField;
    private final ParameterNameDiscoverer parameterNameDiscoverer = new DefaultParameterNameDiscoverer();

    @Override
    public void initialize(PathIdMatchesBodyId constraintAnnotation) {
        this.pathIdParam = constraintAnnotation.pathIdParam();
        this.bodyParam = constraintAnnotation.bodyParam();
        this.bodyIdField = constraintAnnotation.bodyIdField();
    }

    @Override
    public boolean isValid(Object target, ConstraintValidatorContext context) {
        // 从Spring的方法验证上下文获取当前方法和参数
        org.springframework.validation.beanvalidation.SpringValidatorAdapter.MethodValidationContext validationContext =
                (org.springframework.validation.beanvalidation.SpringValidatorAdapter.MethodValidationContext) target;
        Method method = validationContext.getMethod();
        Object[] args = validationContext.getArgs();

        // 构建参数名与参数值的映射
        String[] paramNames = parameterNameDiscoverer.getParameterNames(method);
        Map<String, Object> paramMap = new HashMap<>();
        for (int i = 0; i < paramNames.length; i++) {
            paramMap.put(paramNames[i], args[i]);
        }

        // 获取路径ID和请求体对象
        Long pathId = (Long) paramMap.get(pathIdParam);
        Object bodyObj = paramMap.get(bodyParam);

        // 若任一参数为空，直接返回true（非空校验由@NotNull单独处理）
        if (pathId == null || bodyObj == null) {
            return true;
        }

        // 反射获取请求体中的ID字段值并对比
        try {
            Field idField = bodyObj.getClass().getDeclaredField(bodyIdField);
            idField.setAccessible(true);
            Long bodyId = (Long) idField.get(bodyObj);
            return pathId.equals(bodyId);
        } catch (NoSuchFieldException | IllegalAccessException e) {
            throw new IllegalArgumentException("请求体中不存在指定的ID字段", e);
        }
    }
}

3. 在控制器中应用校验 #

给控制器类添加@Validated注解开启方法级验证，再在目标方法上添加自定义的@PathIdMatchesBodyId注解：

import org.springframework.validation.annotation.Validated;
import org.springframework.web.bind.annotation.*;
import javax.validation.Valid;
import javax.validation.constraints.NotNull;
import reactor.core.publisher.Mono;

@RestController
@Validated // 开启方法级javax.validation验证
public class QdCFController {

    private final QdCFService qdcfService;

    public QdCFController(QdCFService qdcfService) {
        this.qdcfService = qdcfService;
    }

    @PutMapping("{id}")
    @PathIdMatchesBodyId // 应用自定义校验规则
    public Mono<QdCFPresenter> save(
            @PathVariable Long id,
            @RequestBody @Valid @NotNull QdCFPresenter qdcf
    ) {
        return this.qdcfService.store(qdcf);
    }
}

4. 全局处理校验异常 #

Spring WebFlux中方法级验证失败会抛出ConstraintViolationException，可以全局捕获并返回统一错误响应：

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;
import javax.validation.ConstraintViolation;
import javax.validation.ConstraintViolationException;
import java.util.stream.Collectors;

@RestControllerAdvice
public class GlobalExceptionHandler {

    @ExceptionHandler(ConstraintViolationException.class)
    public ResponseEntity<String> handleConstraintViolation(ConstraintViolationException e) {
        String errorMsg = e.getConstraintViolations().stream()
                .map(ConstraintViolation::getMessage)
                .collect(Collectors.joining("; "));
        return new ResponseEntity<>(errorMsg, HttpStatus.BAD_REQUEST);
    }
}

补充说明 #

• 自定义注解的参数可灵活调整，若参数名或字段名不同，只需在注解上指定对应值即可。
• 校验器默认忽略参数为空的情况，因为@NotNull已单独处理非空校验，若路径参数id必填，也可给其添加@NotNull注解。

内容的提问来源于stack exchange，提问作者Jordi