provide workaround for Apache adding a "-gzip" to every outgoing etag #…

…68

impl/src/main/java/org/dukecon/DukeConServerApplication.groovy

@@ -2,6 +2,7 @@ package org.dukecon
 
 import flex.messaging.MessageBroker
 import flex.messaging.io.SerializationContext
+import org.dukecon.server.core.MyShallowEtagHeaderFilter
 import org.dukecon.server.repositories.DataProviderLoader
 import org.dukecon.server.conference.ConferencesConfigurationServiceImpl
 import org.flywaydb.core.Flyway
@@ -43,7 +44,7 @@ class DukeConServerApplication {
 
     @Bean
     Filter shallowEtagHeaderFilter() {
-        return new ShallowEtagHeaderFilter()
+        return new MyShallowEtagHeaderFilter()
     }
 
     @Bean

impl/src/main/java/org/dukecon/server/core/MyShallowEtagHeaderFilter.java

@@ -0,0 +1,33 @@
+package org.dukecon.server.core;
+
+import org.springframework.web.filter.ShallowEtagHeaderFilter;
+
+import javax.servlet.FilterChain;
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletRequestWrapper;
+import javax.servlet.http.HttpServletResponse;
+import java.io.IOException;
+
+/**
+ * The Apache web server we run in front of this application compresses the responses with gzip. It also modifies the etag.
+ * This is a workaround to strip the additional etag from the header when the clients sends a request for this resource.
+ *
+ * @author Alexander Schwartz 2017
+ */
+public class MyShallowEtagHeaderFilter extends ShallowEtagHeaderFilter {
+    @Override
+    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
+        HttpServletRequestWrapper wrapper = new HttpServletRequestWrapper(request) {
+            @Override
+            public String getHeader(String name) {
+                String value = super.getHeader(name);
+                if (name.equalsIgnoreCase("If-None-Match") && value != null) {
+                    value = value.replaceAll("-gzip", "");
+                }
+                return value;
+            }
+        };
+        super.doFilterInternal(wrapper, response, filterChain);
+    }
+}