fix(jersey): run servlet filters before Jersey resources

aws-serverless-java-container-jersey/src/main/java/com/amazonaws/serverless/proxy/jersey/JerseyHandlerFilter.java

@@ -52,10 +52,15 @@
 import static com.amazonaws.serverless.proxy.RequestReader.LAMBDA_CONTEXT_PROPERTY;
 
 /**
- * Servlet filter class that calls Jersey's ApplicationHandler. Given a Jax RS Application object, this class
- * initializes a Jersey {@link ApplicationHandler} and calls its <code>handle</code> method. Requests are transformed
- * to <code>ContainerRequest</code> objects by the {@link #servletRequestToContainerRequest(ServletRequest)} method.
+ * Calls Jersey's ApplicationHandler. Given a Jax RS Application object, this class initializes a Jersey
+ * {@link ApplicationHandler} and calls its <code>handle</code> method. Requests are transformed to
+ * <code>ContainerRequest</code> objects by the {@link #servletRequestToContainerRequest(ServletRequest)} method.
  * Jersey responses are written directly to the ServletResponse by the {@link JerseyServletResponseWriter}.
+ *
+ * {@link JerseyLambdaContainerHandler} invokes this class from the servlet at the end of the filter chain, so that
+ * application filters run before a JAX-RS resource. It is no longer registered as a servlet filter itself. The
+ * <code>Filter</code> interface is still implemented because this class is public, but {@link #doFilter} is
+ * deprecated: Jersey writes the response, so there is nothing for a filter after it to do.
  */
 public class JerseyHandlerFilter implements Filter, Container {
     public static final String JERSEY_SERVLET_REQUEST_PROPERTY = "com.amazonaws.serverless.jersey.servletRequest";
@@ -86,9 +91,28 @@ public void init(FilterConfig filterConfig) {
     }
 
 
+    /**
+     * @deprecated This class is not registered as a filter any more, and nothing in the library calls this method.
+     *     It runs Jersey and ignores the chain, because Jersey writes the response: a filter placed after it could
+     *     only run once the resource had already executed. Register filters on the servlet context instead, through
+     *     {@link com.amazonaws.serverless.proxy.internal.servlet.AwsLambdaServletContainerHandler#onStartup}, and
+     *     they will run before Jersey.
+     */
+    @Deprecated
     @Override
     public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain)
             throws IOException, ServletException {
+        handle(servletRequest, servletResponse);
+    }
+
+    /**
+     * Runs the request through Jersey and waits for the response to be written. {@link JerseyLambdaContainerHandler}
+     * calls this from the servlet at the end of the filter chain, so the resource is only reached once every filter
+     * registered with the servlet context has passed the request on.
+     * @param servletRequest The incoming servlet request
+     * @param servletResponse The response Jersey writes to
+     */
+    void handle(ServletRequest servletRequest, ServletResponse servletResponse) {
         Timer.start("JERSEY_FILTER_DOFILTER");
         // we use a latch to make the processing inside Jersey synchronous
         CountDownLatch jerseyLatch = new CountDownLatch(1);
@@ -106,7 +130,6 @@ public void doFilter(ServletRequest servletRequest, ServletResponse servletRespo
             throw new InternalServerErrorException(e);
         }
         Timer.stop("JERSEY_FILTER_DOFILTER");
-        filterChain.doFilter(servletRequest, servletResponse);
     }
 
     @Override

aws-serverless-java-container-jersey/src/main/java/com/amazonaws/serverless/proxy/jersey/JerseyLambdaContainerHandler.java

@@ -30,15 +30,16 @@
 import org.glassfish.jersey.process.internal.RequestScoped;
 import org.glassfish.jersey.server.ResourceConfig;
 
-import jakarta.servlet.DispatcherType;
-import jakarta.servlet.FilterRegistration;
 import jakarta.servlet.Servlet;
+import jakarta.servlet.ServletConfig;
 import jakarta.servlet.ServletContext;
+import jakarta.servlet.ServletRegistration;
+import jakarta.servlet.ServletRequest;
+import jakarta.servlet.ServletResponse;
 import jakarta.servlet.http.HttpServletRequest;
 import jakarta.servlet.http.HttpServletResponse;
 import jakarta.ws.rs.core.Application;
 
-import java.util.EnumSet;
 import java.util.concurrent.CountDownLatch;
 
 
@@ -72,7 +73,10 @@ public class JerseyLambdaContainerHandler<RequestType, ResponseType> extends Aws
     // Variables - Private
     //-------------------------------------------------------------
 
+    private static final String JERSEY_SERVLET_NAME = "JerseyServlet";
+
     private JerseyHandlerFilter jerseyFilter;
+    private JerseyServlet jerseyServlet;
     private boolean initialized;
 
     //-------------------------------------------------------------
@@ -174,6 +178,7 @@ protected void configure() {
         }
 
         this.jerseyFilter = new JerseyHandlerFilter(jaxRsApplication);
+        this.jerseyServlet = new JerseyServlet(jerseyFilter);
         Timer.stop("JERSEY_CONTAINER_CONSTRUCTOR");
     }
 
@@ -194,7 +199,7 @@ protected void handleRequest(HttpServletRequest httpServletRequest, AwsHttpServl
             ((AwsHttpServletRequest)httpServletRequest).setServletContext(getServletContext());
         }
 
-        doFilter(httpServletRequest, httpServletResponse, null);
+        doFilter(httpServletRequest, httpServletResponse, jerseyServlet);
         Timer.stop("JERSEY_HANDLE_REQUEST");
     }
 
@@ -207,12 +212,13 @@ protected AwsHttpServletResponse getContainerResponse(HttpServletRequest request
     public void initialize() {
         Timer.start("JERSEY_COLD_START_INIT");
 
-        // manually add the filter to the chain. This should the last one and match all uris
-        FilterRegistration.Dynamic jerseyFilterReg = getServletContext().addFilter("JerseyFilter", jerseyFilter);
-        jerseyFilterReg.addMappingForUrlPatterns(
-                EnumSet.of(DispatcherType.REQUEST, DispatcherType.ASYNC, DispatcherType.INCLUDE, DispatcherType.FORWARD),
-                true, "/*"
-        );
+        // Jersey runs as the servlet at the end of the filter chain, the way DispatcherServlet does for Spring. Every
+        // filter registered with the servlet context, before or after this method, runs first and can stop the
+        // request before it reaches a resource.
+        ServletRegistration.Dynamic jerseyServletReg = getServletContext().addServlet(JERSEY_SERVLET_NAME, jerseyServlet);
+        jerseyServletReg.addMapping("/*");
+        // the filter chain reads the servlet name from its config, so the servlet has to be initialized up front
+        jerseyServlet.init(((AwsServletRegistration) jerseyServletReg).getServletConfig());
 
         Timer.stop("JERSEY_COLD_START_INIT");
         initialized = true;
@@ -226,7 +232,53 @@ public InjectionManager getInjectionManager() {
         return jerseyFilter.getApplicationHandler().getInjectionManager();
     }
 
+    /**
+     * The servlet Jersey runs as, which is the terminal step of the filter chain for every request this handler
+     * routes. This returned null while Jersey ran as a filter and there was no servlet to hand back.
+     * @return The Jersey servlet
+     */
     public Servlet getServlet() {
-        return null;
+        return jerseyServlet;
+    }
+
+    //-------------------------------------------------------------
+    // Inner Class -
+    //-------------------------------------------------------------
+
+    /**
+     * The servlet at the end of the filter chain. It hands the request to Jersey, which writes the response.
+     */
+    private static final class JerseyServlet implements Servlet {
+        private final JerseyHandlerFilter jerseyFilter;
+        private ServletConfig config;
+
+        JerseyServlet(JerseyHandlerFilter jerseyFilter) {
+            this.jerseyFilter = jerseyFilter;
+        }
+
+        @Override
+        public void init(ServletConfig servletConfig) {
+            config = servletConfig;
+        }
+
+        @Override
+        public ServletConfig getServletConfig() {
+            return config;
+        }
+
+        @Override
+        public void service(ServletRequest servletRequest, ServletResponse servletResponse) {
+            jerseyFilter.handle(servletRequest, servletResponse);
+        }
+
+        @Override
+        public String getServletInfo() {
+            return "";
+        }
+
+        @Override
+        public void destroy() {
+
+        }
     }
 }