#138 - AddressStrategy that can cope with addresses proxied by Apache http server

hapi-fhir-base/src/main/java/ca/uhn/fhir/rest/server/ApacheProxyAddressStrategy.java

@@ -0,0 +1,77 @@
+package ca.uhn.fhir.rest.server;
+
+/*
+ * #%L
+ * HAPI FHIR - Core Library
+ * %%
+ * Copyright (C) 2014 - 2015 University Health Network
+ * %%
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * #L%
+ */
+
+import ca.uhn.fhir.rest.server.IncomingRequestAddressStrategy;
+import org.apache.commons.lang3.StringUtils;
+
+import javax.servlet.ServletContext;
+import javax.servlet.http.HttpServletRequest;
+
+/**
+ * Works like the normal {@link ca.uhn.fhir.rest.server.IncomingRequestAddressStrategy} unless there's an
+ * x-forwarded-host present, in which case that's used in place of the server's address.
+ *
+ * Because Apache Http Server's mod_proxy doesn't supply <i>x-forwarded-proto</i>, you have to tell it whether to use http or https
+ * by using the appropriate factory method.
+ *
+ * If you want to make that determination based on something other than the constructor argument, you should be able to do so
+ * by overriding <i>prefix</i>.
+ *
+ * Note that while this strategy was designed to work with Apache Http Server, and has been tested against it, it should work with
+ * any proxy server that sets <i>x-forwarded-host</i>
+ *
+ * Created by Bill de Beaubien on 3/30/2015.
+ */
+public class ApacheProxyAddressStrategy extends IncomingRequestAddressStrategy {
+    private boolean myUseHttps = false;
+
+    protected ApacheProxyAddressStrategy(boolean theUseHttps) {
+        myUseHttps = theUseHttps;
+    }
+
+    public static ApacheProxyAddressStrategy forHttp() {
+        return new ApacheProxyAddressStrategy(false);
+    }
+
+    public static ApacheProxyAddressStrategy forHttps() {
+        return new ApacheProxyAddressStrategy(true);
+    }
+
+    @Override
+    public String determineServerBase(ServletContext theServletContext, HttpServletRequest theRequest) {
+        String forwardedHost = theRequest.getHeader("x-forwarded-host");
+        if (forwardedHost != null) {
+            int commaPos = forwardedHost.indexOf(',');
+            if (commaPos >= 0) {
+                forwardedHost = forwardedHost.substring(0, commaPos - 1);
+            }
+            String requestFullPath = StringUtils.defaultString(theRequest.getRequestURI());
+            String serverBase = prefix(theRequest) + forwardedHost + requestFullPath;
+            return serverBase;
+        }
+        return super.determineServerBase(theServletContext, theRequest);
+    }
+
+    protected String prefix(HttpServletRequest theRequest) {
+        return myUseHttps ? "https://" : "http://";
+    }
+}