问题
I'm trying to implement a ContainerRequestFilter that does custom validation of a request's parameters. I need to look up the resource method that will be matched to the URI so that I can scrape custom annotations from the method's parameters.
Based on this answer I should be able to inject ExtendedUriInfo and then use it to match the method:
public final class MyRequestFilter implements ContainerRequestFilter {
@Context private ExtendedUriInfo uriInfo;
@Override
public ContainerRequest filter(ContainerRequest containerRequest) {
System.out.println(uriInfo.getMatchedMethod());
return containerRequest;
}
}
But getMatchedMethod apparently returns null, all the way up until the method is actually invoked (at which point it's too late for me to do validation).
How can I retrieve the Method that will be matched to a given URI, before the resource method is invoked?
For those interested, I'm trying to roll my own required parameter validation, as described in JERSEY-351.
回答1:
Actually, you should try to inject ResourceInfo into your custom request filter. I have tried it with RESTEasy and it works there. The advantage is that you code against the JSR interfaces and not the Jersey implementation.
public class MyFilter implements ContainerRequestFilter
{
@Context
private ResourceInfo resourceInfo;
@Override
public void filter(ContainerRequestContext requestContext)
throws IOException
{
Method theMethod = resourceInfo.getResourceMethod();
return;
}
}
回答2:
I figured out how to solve my problem using only Jersey. There's apparently no way to match a request's URI to the method that will be matched before that method is invoked, at least in Jersey 1.x. However, I was able to use a ResourceFilterFactory to create a ResourceFilter for each individual resource method - that way these filters can know about the destination method ahead of time.
Here's my solution, including the validation for required query params (uses Guava and 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;
}
}
}
And the ResourceFilterFactory is registered with Jersey as an init param of the servlet in web.xml:
<init-param>
<param-name>com.sun.jersey.spi.container.ResourceFilters</param-name>
<param-value>my.package.name.ValidationFilterFactory</param-value>
</init-param>
At startup, ValidationFilterFactory.create gets called for each resource method detected by Jersey.
Credit goes to this post for getting me on the right track: How can I get resource annotations in a Jersey ContainerResponseFilter
回答3:
I know you're looking for a Jersey only solution but here's a Guice approach that should get things working:
public class Config extends GuiceServletContextListener {
@Override
protected Injector getInjector() {
return Guice.createInjector(
new JerseyServletModule() {
@Override
protected void configureServlets() {
bindInterceptor(Matchers.inSubpackage("org.example"), Matchers.any(), new ValidationInterceptor());
bind(Service.class);
Map<String, String> params = Maps.newHashMap();
params.put(PackagesResourceConfig.PROPERTY_PACKAGES, "org.example");
serve("/*").with(GuiceContainer.class, params);
}
});
}
public static class ValidationInterceptor implements MethodInterceptor {
public Object invoke(MethodInvocation method) throws Throwable {
System.out.println("Validating: " + method.getMethod());
return method.proceed();
}
}
}
@Path("/")
public class Service {
@GET
@Path("service")
@Produces({MediaType.TEXT_PLAIN})
public String service(@QueryParam("name") String name) {
return "Service " + name;
}
}
EDIT: A performance comparison:
public class AopPerformanceTest {
@Test
public void testAopPerformance() {
Service service = Guice.createInjector(
new AbstractModule() {
@Override
protected void configure() { bindInterceptor(Matchers.inSubpackage("org.example"), Matchers.any(), new ValidationInterceptor()); }
}).getInstance(Service.class);
System.out.println("Total time with AOP: " + timeService(service) + "ns");
}
@Test
public void testNonAopPerformance() {
System.out.println("Total time without AOP: " + timeService(new Service()) + "ns");
}
public long timeService(Service service) {
long sum = 0L;
long iterations = 1000000L;
for (int i = 0; i < iterations; i++) {
long start = System.nanoTime();
service.service(null);
sum += (System.nanoTime() - start);
}
return sum / iterations;
}
}
回答4:
In resteasy-jaxrs-3.0.5, you can retrieve a ResourceMethodInvoker representing the matched resource method from ContainerRequestContext.getProperty() inside a ContainerRequestFilter:
import org.jboss.resteasy.core.ResourceMethodInvoker;
public class MyRequestFilter implements ContainerRequestFilter
{
public void filter(ContainerRequestContext request) throws IOException
{
String propName = "org.jboss.resteasy.core.ResourceMethodInvoker";
ResourceMethodInvoker invoker = (ResourceMethodInvoker)request.getProperty();
invoker.getMethod().getParameterTypes()....
}
}
来源：https://stackoverflow.com/questions/16303694/how-to-get-resource-method-matched-to-uri-before-jersey-invokes-it