我可以在ConstraintValidator中为Method参数更改属性路径吗？

Question

如果您熟悉Bean验证框架,则您知道无法获取方法参数的名称.因此,如果对方法的第一个参数执行@NotNull约束并且验证失败,则getPropertyPath将类似于"arg1".

我想创建我自己的@NotNull版本,它可以取一个值,例如@NamedNotNull("emailAddress").但我无法弄清楚如何覆盖我的Validator中的#getPropertyPath？有没有办法做到这一点,或者我坚持使用"arg1"或"arg2"等.

编辑

根据我收到的答案,我能够提出以下实现,允许我从@QueryParam或@PathParam注释中获取值,并将其用作Bean验证注释(如@NotNull)的属性路径.

对于Jersey,您需要创建以下类.请注意DefaultParameterNameProvider的实现:

public class ValidationConfigurationContextResolver implements ContextResolver<ValidationConfig> {
    @Override
    public ValidationConfig getContext( final Class<?> type ) {
        final ValidationConfig config = new ValidationConfig();
        config.parameterNameProvider( new RestAnnotationParameterNameProvider() );
        return config;
    }

    static class RestAnnotationParameterNameProvider extends DefaultParameterNameProvider {

        @Override
        public List<String> getParameterNames( Method method ) {
            Annotation[][] annotationsByParam = method.getParameterAnnotations();
            List<String> names = new ArrayList<>( annotationsByParam.length );
            for ( Annotation[] annotations : annotationsByParam ) {
                String name = getParamName( annotations );
                if ( name == null )
                    name = "arg" + ( names.size() + 1 );

                names.add( name );
            }

            return names;
        }

        private static String getParamName( Annotation[] annotations ) {
            for ( Annotation annotation : annotations ) {
                if ( annotation.annotationType() == QueryParam.class ) {
                    return QueryParam.class.cast( annotation ).value();
                }
                else if ( annotation.annotationType() == PathParam.class ) {
                    return PathParam.class.cast( annotation ).value();
                }
            }

            return null;
        }
    }
}

然后在RestConfig中,您需要添加以下行:

register( ValidationConfigurationContextResolver.class );

而已.现在,您的ConstraintValidationExceptions将包含它们带有注释的QueryParam或PathParam的名称.例如:

 public void getUser( 
     @NotNull @QueryParam( "emailAddress" ) String emailAddress,
     @NotNull @QueryParam( "password" ) String password ) 
 { ... }

Answer 1

如果您熟悉Bean验证框架,则您知道无法获取方法参数的名称

这不太正确.Bean Validation指定ParameterNameProvider的概念,它允许您提供自己的实现.Hibernate Validator与ParaNamer集成以提供参数名称.有关更多信息,请参阅Validator 在线文档.一旦Validator支持Java 8,它还将支持Java 8参数命名工具.

IMO,你应该给ParaNamer一个去吧.

Answer 2

Bean Validation 1.1引入了ParameterNameProvider在创建约束违规对象时为方法和构造函数参数提供名称的接口.

Hibernate Validator 5.2引入了这个ReflectionParameterNameProvider类,一个ParameterNameProvider使用反射来获取实际参数名的实现(为了正常工作,它需要使用-parameters编译器参数编译类):

/**
 * Uses Java 8 reflection to get the parameter names.
 * <p>
 * <p>For this provider to return the actual parameter names, classes must be compiled with the '-parameters' compiler
 * argument. Otherwise, the JDK will return synthetic names in the form {@code arg0}, {@code arg1}, etc.</p>
 * <p>
 * <p>See also <a href="http://openjdk.java.net/jeps/118">JEP 118</a></p>
 *
 * @author Khalid Alqinyah
 * @since 5.2
 */
public class ReflectionParameterNameProvider implements ParameterNameProvider {

    @Override
    public List<String> getParameterNames(Constructor<?> constructor) {
        return getParameterNames(constructor.getParameters());
    }

    @Override
    public List<String> getParameterNames(Method method) {
        return getParameterNames(method.getParameters());
    }

    private List<String> getParameterNames(Parameter[] parameters) {

        List<String> parameterNames = newArrayList();
        for (Parameter parameter : parameters) {
            // If '-parameters' is used at compile time, actual names will be returned. Otherwise, it will be arg0, arg1...
            parameterNames.add(parameter.getName());
        }

        return parameterNames;
    }
}

Dropwizard扩展了它并添加了对JAX-RS @XxxParam注释的支持,JerseyParameterNameProvider它也可以与其他JAX-RS实现一起使用:

/**
 * Adds jersey support to parameter name discovery in hibernate validator.
 * <p>
 * <p>This provider will behave like the hibernate-provided {@link ReflectionParameterNameProvider} except when a
 * method parameter is annotated with a jersey parameter annotation, like {@link QueryParam}. If a jersey parameter
 * annotation is present the value of the annotation is used as the parameter name.</p>
 */
public class JerseyParameterNameProvider extends ReflectionParameterNameProvider {

    @Override
    public List<String> getParameterNames(Method method) {
        Parameter[] parameters = method.getParameters();
        Annotation[][] parameterAnnotations = method.getParameterAnnotations();
        List<String> names = new ArrayList<>(parameterAnnotations.length);
        for (int i = 0; i < parameterAnnotations.length; i++) {
            Annotation[] annotations = parameterAnnotations[i];
            String name = getParameterNameFromAnnotations(annotations).orElse(parameters[i].getName());
            names.add(name);
        }
        return names;
    }

    /**
     * Derives member's name and type from it's annotations
     */
    public static Optional<String> getParameterNameFromAnnotations(Annotation[] memberAnnotations) {

        for (Annotation a : memberAnnotations) {
            if (a instanceof QueryParam) {
                return Optional.of("query param " + ((QueryParam) a).value());
            } else if (a instanceof PathParam) {
                return Optional.of("path param " + ((PathParam) a).value());
            } else if (a instanceof HeaderParam) {
                return Optional.of("header " + ((HeaderParam) a).value());
            } else if (a instanceof CookieParam) {
                return Optional.of("cookie " + ((CookieParam) a).value());
            } else if (a instanceof FormParam) {
                return Optional.of("form field " + ((FormParam) a).value());
            } else if (a instanceof Context) {
                return Optional.of("context");
            } else if (a instanceof MatrixParam) {
                return Optional.of("matrix param " + ((MatrixParam) a).value());
            }
        }

        return Optional.empty();
    }
}

如果您不使用Dropwizard,则可以使用上面的代码创建自己的实现.

Validator用于验证Jersey资源类/方法的定制可以使用ValidationConfig类完成并通过ContextResolver<T>机制公开它:

public class ValidationConfigurationContextResolver 
        implements ContextResolver<ValidationConfig> {

    @Override
    public ValidationConfig getContext(final Class<?> type) {
        ValidationConfig config = new ValidationConfig();
        config.parameterNameProvider(new CustomParameterNameProvider());
        return config;
    }
}

然后登记ValidationConfigurationContextResolver在ResourceConfig.

有关更多详细信息,请参阅有关Bean验证支持的Jersey文档.