在Jersey调用之前，如何获取与URI匹配的资源方法？

Question

我正在尝试实现一个ContainerRequestFilter对请求参数进行自定义验证的方法。我需要查找将与URI匹配的资源方法，以便可以从方法的参数中抓取自定义注释。

基于此答案，我应该能够注入ExtendedUriInfo然后使用它来匹配方法：

public final class MyRequestFilter implements ContainerRequestFilter {

    @Context private ExtendedUriInfo uriInfo;

    @Override
    public ContainerRequest filter(ContainerRequest containerRequest) {

        System.out.println(uriInfo.getMatchedMethod());

        return containerRequest;
    }
}

但是getMatchedMethod显然返回null，一直到实际调用该方法为止（这时我进行验证为时已晚）。

Method在调用资源方法之前，如何检索将与给定URI匹配的？

对于那些感兴趣的人，我正在尝试进行自己所需的参数验证，如JERSEY-351中所述。

Answer 1

我想出了如何仅使用Jersey来解决问题的方法。显然，没有办法将请求的URI与将在调用该方法之前匹配的方法进行匹配，至少在Jersey1.x中。但是，我可以使用a为每个单独的资源方法ResourceFilterFactory创建一个ResourceFilter-这样，这些过滤器就可以提前知道目标方法。

这是我的解决方案，包括验证所需的查询参数（使用Guava和JSR 305）：

public final class ValidationFilterFactory implements ResourceFilterFactory {

    @Override
    public List<ResourceFilter> create(AbstractMethod abstractMethod) {

        //keep track of required query param names
        final ImmutableSet.Builder<String> requiredQueryParamsBuilder =
                ImmutableSet.builder();

        //get the list of params from the resource method
        final ImmutableList<Parameter> params =
                Invokable.from(abstractMethod.getMethod()).getParameters();

        for (Parameter param : params) {
            //if the param isn't marked as @Nullable,
            if (!param.isAnnotationPresent(Nullable.class)) {
                //try getting the @QueryParam value
                @Nullable final QueryParam queryParam =
                        param.getAnnotation(QueryParam.class);
                //if it's present, add its value to the set
                if (queryParam != null) {
                    requiredQueryParamsBuilder.add(queryParam.value());
                }
            }
        }

        //return the new validation filter for this resource method
        return Collections.<ResourceFilter>singletonList(
                new ValidationFilter(requiredQueryParamsBuilder.build())
        );
    }

    private static final class ValidationFilter implements ResourceFilter {

        final ImmutableSet<String> requiredQueryParams;

        private ValidationFilter(ImmutableSet<String> requiredQueryParams) {
            this.requiredQueryParams = requiredQueryParams;
        }

        @Override
        public ContainerRequestFilter getRequestFilter() {
            return new ContainerRequestFilter() {
                @Override
                public ContainerRequest filter(ContainerRequest request) {

                    final Collection<String> missingRequiredParams =
                            Sets.difference(
                                    requiredQueryParams,
                                    request.getQueryParameters().keySet()
                            );

                    if (!missingRequiredParams.isEmpty()) {

                        final String message =
                                "Required query params missing: " +
                                Joiner.on(", ").join(missingRequiredParams);

                        final Response response = Response
                                .status(Status.BAD_REQUEST)
                                .entity(message)
                                .build();

                        throw new WebApplicationException(response);
                    }

                    return request;
                }
            };
        }

        @Override
        public ContainerResponseFilter getResponseFilter() {
            return null;
        }
    }
}

并在ResourceFilterFactoryJersey中注册为servlet的init参数web.xml：

<init-param>
    <param-name>com.sun.jersey.spi.container.ResourceFilters</param-name>
    <param-value>my.package.name.ValidationFilterFactory</param-value>
</init-param>

在启动时，ValidationFilterFactory.create为Jersey所检测到的每个资源方法调用。