Merged fix for GRAILS-5892 "SecurtyFilter Example of chapter 11.3 Authentication in the doc causes Exception in Grails 1.2.1"

Author: graemerocher

src/java/org/codehaus/groovy/grails/web/sitemesh/GrailsContentBufferingResponse.java

@@ -18,6 +18,7 @@ public class GrailsContentBufferingResponse extends HttpServletResponseWrapper {
     private final GrailsPageResponseWrapper pageResponseWrapper;
     private final ContentProcessor contentProcessor;
     private final SiteMeshWebAppContext webAppContext;
+    private boolean redirectCalled;
 
     public GrailsContentBufferingResponse(HttpServletResponse response, final ContentProcessor contentProcessor, final SiteMeshWebAppContext webAppContext) {
         super(new GrailsPageResponseWrapper(webAppContext.getRequest(), response, new PageParserSelector() {
@@ -65,19 +66,30 @@ public Content getContent() throws IOException {
 
     public void sendError(int sc) throws IOException {
         GrailsWebRequest webRequest = WebUtils.retrieveGrailsWebRequest();
+
         try {
-            super.sendError(sc);
-        } finally {
+            if(!redirectCalled && !isCommitted())
+                super.sendError(sc);
+        }
+        finally {
             WebUtils.storeGrailsWebRequest(webRequest);
         }
     }
 
     public void sendError(int sc, String msg) throws IOException {
         GrailsWebRequest webRequest = WebUtils.retrieveGrailsWebRequest();
         try {
-            super.sendError(sc, msg);
-        } finally {
+            if(!redirectCalled && !isCommitted())
+                super.sendError(sc, msg);
+        }
+        finally {
             WebUtils.storeGrailsWebRequest(webRequest);
         }
     }
+
+    @Override
+    public void sendRedirect(String location) throws IOException {
+        this.redirectCalled = true;
+        super.sendRedirect(location);
+    }
 }