java/src/main/com/google/appengine/tools/development/LocalApiProxyServletFilter.java

   1 // Copyright 2008 Google Inc. All Rights Reserved.
   2
   3 package com.google.appengine.tools.development;
   4
   5 import com.google.apphosting.api.ApiProxy;
   6 import com.google.apphosting.utils.config.AppEngineWebXml;
   7 import com.google.apphosting.utils.config.AppEngineWebXmlReader;
   8 import com.google.apphosting.utils.config.WebModule;
   9
  10 import java.io.File;
  11 import java.io.IOException;
  12 import java.io.InputStream;
  13 import java.util.logging.Logger;
  14
  15 import javax.servlet.Filter;
  16 import javax.servlet.FilterChain;
  17 import javax.servlet.FilterConfig;
  18 import javax.servlet.ServletContext;
  19 import javax.servlet.ServletException;
  20 import javax.servlet.ServletRequest;
  21 import javax.servlet.ServletResponse;
  22 import javax.servlet.http.HttpServletRequest;
  23
  24 /**
  25  * This filter is not currently used.  It was originally written for
  26  * IBM so they could see how to use our API's from their own webserver.
  27  * We kept it around because we'd ultimately like to use this ourselves but
  28  * we don't currently have a way to ensure that this filter runs before any
  29  * other filters get initialized.
  30  *
  31  * {@code LocalApiProxyServletFilter} is a servlet {@link Filter} that
  32  * sets up {@link ApiProxy} for use with the stub API implementations.
  33  *
  34  * <p>There are two parts to this:<ul>
  35
  36  * <li>At initialization, this filter installs a {@link
  37  * ApiProxy.Delegate} instance that locates any API stub
  38  * implementations on the classpath and registers them for use by
  39  * future requests.  It also looks for an App Engine-specific
  40  * deployment descriptor ({@code WEB-INF/appengine-web.xml}) and
  41  * parses it to obtain some metadata about the application
  42  * (e.g. application identifier).</li>
  43  *
  44  * <li>Around each request, a {@link ApiProxy.Environment} instance is
  45  * installed into a {@link ThreadLocal} managed by {@link ApiProxy}.
  46  * This environment instance contains the application metadata that
  47  * was extracted earlier, and also provides access to the
  48  * authentication data maintained by the stub implementation of the
  49  * Users API.</li> </ul>
  50  *
  51  */
  52 public class LocalApiProxyServletFilter implements Filter {
  53   private static final Logger logger = Logger.getLogger(LocalApiProxyServletFilter.class.getName());
  54   private static final String AE_WEB_XML = "/WEB-INF/appengine-web.xml";
  55
  56   private AppEngineWebXml appEngineWebXml;
  57
  58   /**
  59    * Register a custom {@link ApiProxy.Delegate instance}.
  60    */
  61   @Override
  62   public void init(FilterConfig config) {
  63     logger.info("Filter initialization invoked -- registering ApiProxy delegate.");
  64     ApiProxyLocalFactory factory = new ApiProxyLocalFactory();
  65     ApiProxy.setDelegate(factory.create(getLocalServerEnvironment(config)));
  66
  67     logger.info("Parsing custom deployment descriptor (" + AE_WEB_XML + ").");
  68     ServletAppEngineWebXmlReader reader =
  69         new ServletAppEngineWebXmlReader(config.getServletContext());
  70     appEngineWebXml = reader.readAppEngineWebXml();
  71     logger.info("Application identifier is: " + appEngineWebXml.getAppId());
  72   }
  73
  74   private LocalServerEnvironment getLocalServerEnvironment(final FilterConfig config) {
  75     return new LocalServerEnvironment() {
  76
  77       @Override
  78       public File getAppDir() {
  79         return new File(".");
  80       }
  81
  82       @Override
  83       public String getAddress() {
  84         throw new UnsupportedOperationException();
  85       }
  86
  87       @Override
  88       public int getPort() {
  89         throw new UnsupportedOperationException();
  90       }
  91
  92       @Override
  93       public String getHostName() {
  94         throw new UnsupportedOperationException();
  95       }
  96
  97       @Override
  98       public void waitForServerToStart() { }
  99
 100       @Override
 101       public boolean simulateProductionLatencies() {
 102         return true;
 103       }
 104
 105       @Override
 106       public boolean enforceApiDeadlines() {
 107         return false;
 108       }
 109     };
 110   }
 111
 112   /**
 113    * Remove the custom {@link ApiProxy.Delegate} instance.
 114    */
 115   @Override
 116   public void destroy() {
 117     logger.info("Filter destruction invoked -- removing delegate.");
 118     ApiProxy.setDelegate(null);
 119   }
 120
 121   /**
 122    * Wrap the request with calls to the environment-management method
 123    * on {@link ApiProxy}.
 124    */
 125   @Override
 126   public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
 127       throws IOException, ServletException {
 128     HttpServletRequest httpRequest = (HttpServletRequest) request;
 129
 130     logger.fine("Filter received a request, setting environment ThreadLocal.");
 131     ApiProxy.setEnvironmentForCurrentThread(new LocalHttpRequestEnvironment(
 132         appEngineWebXml.getAppId(), WebModule.getServerName(appEngineWebXml),
 133         appEngineWebXml.getMajorVersionId(), LocalEnvironment.MAIN_INSTANCE,
 134         httpRequest, null, null));
 135     try {
 136       chain.doFilter(request, response);
 137     } finally {
 138       logger.fine("Request has completed.  Removing environment ThreadLocal.");
 139       ApiProxy.clearEnvironmentForCurrentThread();
 140     }
 141   }
 142
 143   /**
 144    * {@code ServletAppEngineWebXmlReader} is a specialization of
 145    * {@link AppEngineWebXmlReader} that reads the custom deployment
 146    * descriptor ({@code WEB-INF/appengine-web.xml}) from a {@link
 147    * ServletContext} rather than looking for an actual file on the
 148    * filesystem.
 149    */
 150   private static class ServletAppEngineWebXmlReader extends AppEngineWebXmlReader {
 151     private final ServletContext context;
 152
 153     public ServletAppEngineWebXmlReader(ServletContext context) {
 154       super("");
 155       this.context = context;
 156     }
 157
 158     @Override
 159     protected InputStream getInputStream() {
 160       return context.getResourceAsStream(AE_WEB_XML);
 161     }
 162   }
 163 }