Migrated attachment for Guice issue 635, comment 4

guice-filter.patch

Index: extensions/servlet/src/com/google/inject/servlet/GuiceFilter.java
===================================================================
--- extensions/servlet/src/com/google/inject/servlet/GuiceFilter.java	(revision 1556)
+++ extensions/servlet/src/com/google/inject/servlet/GuiceFilter.java	(working copy)
@@ -17,6 +17,7 @@
 package com.google.inject.servlet;
 
 import com.google.inject.Inject;
+import com.google.inject.Injector;
 import com.google.inject.OutOfScopeException;
 import java.io.IOException;
 import java.lang.ref.WeakReference;
@@ -57,13 +58,19 @@
  */
 public class GuiceFilter implements Filter {
   static final ThreadLocal<Context> localContext = new ThreadLocal<Context>();
-  static volatile FilterPipeline pipeline = new DefaultFilterPipeline();
+  static volatile boolean multipleStaticPipelines = false;
+  static volatile FilterPipeline staticPipeline = new DefaultFilterPipeline();
+  @Inject
+  private final FilterPipeline injectedPipeline = null;
 
   /**
-   * We allow both the static and dynamic versions of the pipeline to exist.
+   * The pipeline is set by:
+   * 
+   * 1. GuiceServletContextListener, otherwise by
+   * 2. Field injection, otherwise by
+   * 3. GuiceFilter.setPipeline()
    */
-  @Inject
-  private final FilterPipeline injectedPipeline = null;
+  private FilterPipeline pipeline = null;
 
   /** Used to inject the servlets configured via {@link ServletModule} */
   static volatile WeakReference<ServletContext> servletContext =
@@ -77,23 +84,24 @@
       + "ignore this message. If this is NOT deliberate however, "
       + "your application may not work as expected.";
 
+  private static final Logger log = Logger.getLogger(GuiceFilter.class.getName());
+  
   //VisibleForTesting
   @Inject
   static void setPipeline(FilterPipeline pipeline) {
 
     // This can happen if you create many injectors and they all have their own
     // servlet module. This is legal, caveat a small warning.
-    if (GuiceFilter.pipeline instanceof ManagedFilterPipeline) {
-        Logger.getLogger(GuiceFilter.class.getName()).warning(MULTIPLE_INJECTORS_WARNING);
-    }
+    if (GuiceFilter.staticPipeline instanceof ManagedFilterPipeline)
+      multipleStaticPipelines = true;
 
-    // We overwrite the default pipeline
-    GuiceFilter.pipeline = pipeline;
+    // We overwrite the static pipeline
+    GuiceFilter.staticPipeline = pipeline;
   }
 
   //VisibleForTesting
   static void reset() {
-    pipeline = new DefaultFilterPipeline();
+    staticPipeline = new DefaultFilterPipeline();
   }
 
   public void doFilter(ServletRequest servletRequest,
@@ -102,15 +110,12 @@
 
     Context previous = localContext.get();
 
-    // Prefer the injected pipeline, but fall back on the static one for web.xml users.
-    FilterPipeline filterPipeline = null != injectedPipeline ? injectedPipeline : pipeline;
-
     try {
       localContext.set(new Context((HttpServletRequest) servletRequest,
           (HttpServletResponse) servletResponse));
 
       //dispatch across the servlet pipeline, ensuring web.xml's filterchain is honored
-      filterPipeline.dispatch(servletRequest, servletResponse, filterChain);
+      pipeline.dispatch(servletRequest, servletResponse, filterChain);
 
     } finally {
       localContext.set(previous);
@@ -165,20 +170,28 @@
     // Store servlet context in a weakreference, for injection
     GuiceFilter.servletContext = new WeakReference<ServletContext>(servletContext);
 
-    // In the default pipeline, this is a noop. However, if replaced
-    // by a managed pipeline, a lazy init will be triggered the first time
-    // dispatch occurs.
-    FilterPipeline filterPipeline = null != injectedPipeline ? injectedPipeline : pipeline;
-    filterPipeline.initPipeline(servletContext);
+    Injector injector = (Injector) servletContext.getAttribute(Injector.class.getName());
+    if (injector != null)
+      pipeline = injector.getInstance(FilterPipeline.class);
+    else if (injectedPipeline != null)
+      pipeline = injectedPipeline;
+    else {
+      pipeline = staticPipeline;
+      if (multipleStaticPipelines) {
+        // Only issue a warning if multiple injectors are detected and
+        // the static pipeline gets used.
+        log.warning(MULTIPLE_INJECTORS_WARNING);
+      }
+    }
+    pipeline.initPipeline(servletContext);
   }
 
   public void destroy() {
 
     try {
       // Destroy all registered filters & servlets in that order
-      FilterPipeline filterPipeline = null != injectedPipeline ? injectedPipeline : pipeline;
-      filterPipeline.destroyPipeline();
-
+      if (pipeline != null)
+        pipeline.destroyPipeline();
     } finally {
       reset();
       servletContext.clear();