Allow application filters on smart HTTP operations

Permit applications embedding GitServlet to wrap the
info/refs?service=$name and /$name operations with a
servlet Filter.

To help applications inspect state of the operation,
expose the UploadPack or ReceivePack object into a
request attribute.  This can be useful for logging,
or to implement throttling of requests like Gerrit
Code Review uses to prevent server overload.

Change-Id: Ib8773c14e2b7a650769bd578aad745e6651210cb
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/GitServlet.java

@@ -45,7 +45,10 @@ package org.eclipse.jgit.http.server;
 
 import java.io.File;
 import java.text.MessageFormat;
+import java.util.LinkedList;
+import java.util.List;
 
+import javax.servlet.Filter;
 import javax.servlet.ServletConfig;
 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServletRequest;
@@ -55,9 +58,9 @@ import org.eclipse.jgit.http.server.glue.ErrorServlet;
 import org.eclipse.jgit.http.server.glue.MetaServlet;
 import org.eclipse.jgit.http.server.glue.RegexGroupFilter;
 import org.eclipse.jgit.http.server.glue.ServletBinder;
+import org.eclipse.jgit.http.server.resolver.AsIsFileService;
 import org.eclipse.jgit.http.server.resolver.DefaultReceivePackFactory;
 import org.eclipse.jgit.http.server.resolver.DefaultUploadPackFactory;
-import org.eclipse.jgit.http.server.resolver.AsIsFileService;
 import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.transport.ReceivePack;
 import org.eclipse.jgit.transport.UploadPack;
@@ -114,6 +117,10 @@ public class GitServlet extends MetaServlet {
 
 	private ReceivePackFactory<HttpServletRequest> receivePackFactory = new DefaultReceivePackFactory();
 
+	private final List<Filter> uploadPackFilters = new LinkedList<Filter>();
+
+	private final List<Filter> receivePackFilters = new LinkedList<Filter>();
+
 	/**
 	 * New servlet that will load its base directory from {@code web.xml}.
 	 * <p>
@@ -160,6 +167,17 @@ public class GitServlet extends MetaServlet {
 		this.uploadPackFactory = f != null ? f : (UploadPackFactory<HttpServletRequest>)UploadPackFactory.DISABLED;
 	}
 
+	/**
+	 * @param filter
+	 *            filter to apply before any of the UploadPack operations. The
+	 *            UploadPack instance is available in the request attribute
+	 *            {@link ServletUtils#ATTRIBUTE_HANDLER}.
+	 */
+	public void addUploadPackFilter(Filter filter) {
+		assertNotInitialized();
+		uploadPackFilters.add(filter);
+	}
+
 	/**
 	 * @param f
 	 *            the factory to construct and configure a {@link ReceivePack}
@@ -171,6 +189,17 @@ public class GitServlet extends MetaServlet {
 		this.receivePackFactory = f != null ? f : (ReceivePackFactory<HttpServletRequest>)ReceivePackFactory.DISABLED;
 	}
 
+	/**
+	 * @param filter
+	 *            filter to apply before any of the ReceivePack operations. The
+	 *            ReceivePack instance is available in the request attribute
+	 *            {@link ServletUtils#ATTRIBUTE_HANDLER}.
+	 */
+	public void addReceivePackFilter(Filter filter) {
+		assertNotInitialized();
+		receivePackFilters.add(filter);
+	}
+
 	private void assertNotInitialized() {
 		if (initialized)
 			throw new IllegalStateException(HttpServerText.get().alreadyInitializedByContainer);
@@ -189,23 +218,29 @@ public class GitServlet extends MetaServlet {
 		initialized = true;
 
 		if (uploadPackFactory != UploadPackFactory.DISABLED) {
-			serve("*/git-upload-pack")//
-					.with(new UploadPackServlet(uploadPackFactory));
+			ServletBinder b = serve("*/git-upload-pack");
+			b = b.through(new UploadPackServlet.Factory(uploadPackFactory));
+			for (Filter f : uploadPackFilters)
+				b = b.through(f);
+			b.with(new UploadPackServlet());
 		}
 
 		if (receivePackFactory != ReceivePackFactory.DISABLED) {
-			serve("*/git-receive-pack")//
-					.with(new ReceivePackServlet(receivePackFactory));
+			ServletBinder b = serve("*/git-receive-pack");
+			b = b.through(new ReceivePackServlet.Factory(receivePackFactory));
+			for (Filter f : receivePackFilters)
+				b = b.through(f);
+			b.with(new ReceivePackServlet());
 		}
 
 		ServletBinder refs = serve("*/" + Constants.INFO_REFS);
 		if (uploadPackFactory != UploadPackFactory.DISABLED) {
-			refs = refs.through(//
-					new UploadPackServlet.InfoRefs(uploadPackFactory));
+			refs = refs.through(new UploadPackServlet.InfoRefs(
+					uploadPackFactory, uploadPackFilters));
 		}
 		if (receivePackFactory != ReceivePackFactory.DISABLED) {
-			refs = refs.through(//
-					new ReceivePackServlet.InfoRefs(receivePackFactory));
+			refs = refs.through(new ReceivePackServlet.InfoRefs(
+					receivePackFactory, receivePackFilters));
 		}
 		if (asIs != AsIsFileService.DISABLED) {
 			refs = refs.through(new IsLocalFilter());

org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/ReceivePackServlet.java

@@ -47,11 +47,19 @@ import static javax.servlet.http.HttpServletResponse.SC_FORBIDDEN;
 import static javax.servlet.http.HttpServletResponse.SC_INTERNAL_SERVER_ERROR;
 import static javax.servlet.http.HttpServletResponse.SC_UNAUTHORIZED;
 import static javax.servlet.http.HttpServletResponse.SC_UNSUPPORTED_MEDIA_TYPE;
+import static org.eclipse.jgit.http.server.ServletUtils.ATTRIBUTE_HANDLER;
 import static org.eclipse.jgit.http.server.ServletUtils.getInputStream;
 import static org.eclipse.jgit.http.server.ServletUtils.getRepository;
 
 import java.io.IOException;
-
+import java.util.List;
+
+import javax.servlet.Filter;
+import javax.servlet.FilterChain;
+import javax.servlet.FilterConfig;
+import javax.servlet.ServletException;
+import javax.servlet.ServletRequest;
+import javax.servlet.ServletResponse;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
@@ -72,18 +80,27 @@ class ReceivePackServlet extends HttpServlet {
 	private static final long serialVersionUID = 1L;
 
 	static class InfoRefs extends SmartServiceInfoRefs {
-		private final ReceivePackFactory receivePackFactory;
+		private final ReceivePackFactory<HttpServletRequest> receivePackFactory;
 
-		InfoRefs(final ReceivePackFactory receivePackFactory) {
-			super("git-receive-pack");
+		InfoRefs(ReceivePackFactory<HttpServletRequest> receivePackFactory,
+				List<Filter> filters) {
+			super("git-receive-pack", filters);
 			this.receivePackFactory = receivePackFactory;
 		}
 
 		@Override
-		protected void advertise(HttpServletRequest req, Repository db,
+		protected void begin(HttpServletRequest req, Repository db)
+				throws IOException, ServiceNotEnabledException,
+				ServiceNotAuthorizedException {
+			ReceivePack rp = receivePackFactory.create(req, db);
+			req.setAttribute(ATTRIBUTE_HANDLER, rp);
+		}
+
+		@Override
+		protected void advertise(HttpServletRequest req,
 				PacketLineOutRefAdvertiser pck) throws IOException,
 				ServiceNotEnabledException, ServiceNotAuthorizedException {
-			ReceivePack rp = receivePackFactory.create(req, db);
+			ReceivePack rp = (ReceivePack) req.getAttribute(ATTRIBUTE_HANDLER);
 			try {
 				rp.sendAdvertisedRefs(pck);
 			} finally {
@@ -92,10 +109,44 @@ class ReceivePackServlet extends HttpServlet {
 		}
 	}
 
-	private final ReceivePackFactory receivePackFactory;
+	static class Factory implements Filter {
+		private final ReceivePackFactory<HttpServletRequest> receivePackFactory;
 
-	ReceivePackServlet(final ReceivePackFactory receivePackFactory) {
-		this.receivePackFactory = receivePackFactory;
+		Factory(ReceivePackFactory<HttpServletRequest> receivePackFactory) {
+			this.receivePackFactory = receivePackFactory;
+		}
+
+		public void doFilter(ServletRequest request, ServletResponse response,
+				FilterChain chain) throws IOException, ServletException {
+			HttpServletRequest req = (HttpServletRequest) request;
+			HttpServletResponse rsp = (HttpServletResponse) response;
+			ReceivePack rp;
+			try {
+				rp = receivePackFactory.create(req, getRepository(req));
+			} catch (ServiceNotAuthorizedException e) {
+				rsp.sendError(SC_UNAUTHORIZED);
+				return;
+
+			} catch (ServiceNotEnabledException e) {
+				rsp.sendError(SC_FORBIDDEN);
+				return;
+			}
+
+			try {
+				req.setAttribute(ATTRIBUTE_HANDLER, rp);
+				chain.doFilter(req, rsp);
+			} finally {
+				req.removeAttribute(ATTRIBUTE_HANDLER);
+			}
+		}
+
+		public void init(FilterConfig filterConfig) throws ServletException {
+			// Nothing.
+		}
+
+		public void destroy() {
+			// Nothing.
+		}
 	}
 
 	@Override
@@ -106,9 +157,8 @@ class ReceivePackServlet extends HttpServlet {
 			return;
 		}
 
-		final Repository db = getRepository(req);
+		ReceivePack rp = (ReceivePack) req.getAttribute(ATTRIBUTE_HANDLER);
 		try {
-			final ReceivePack rp = receivePackFactory.create(req, db);
 			rp.setBiDirectionalPipe(false);
 			rsp.setContentType(RSP_TYPE);
 
@@ -120,15 +170,6 @@ class ReceivePackServlet extends HttpServlet {
 			};
 			rp.receive(getInputStream(req), out, null);
 			out.close();
-
-		} catch (ServiceNotAuthorizedException e) {
-			rsp.sendError(SC_UNAUTHORIZED);
-			return;
-
-		} catch (ServiceNotEnabledException e) {
-			rsp.sendError(SC_FORBIDDEN);
-			return;
-
 		} catch (IOException e) {
 			getServletContext().log(HttpServerText.get().internalErrorDuringReceivePack, e);
 			rsp.sendError(SC_INTERNAL_SERVER_ERROR);

org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/ServletUtils.java

@@ -71,6 +71,9 @@ public final class ServletUtils {
 	/** Request attribute which stores the {@link Repository} instance. */
 	public static final String ATTRIBUTE_REPOSITORY = "org.eclipse.jgit.Repository";
 
+	/** Request attribute storing either UploadPack or ReceivePack. */
+	public static final String ATTRIBUTE_HANDLER = "org.eclipse.jgit.transport.UploadPackOrReceivePack";
+
 	/**
 	 * Get the selected repository from the request.
 	 *

org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/SmartServiceInfoRefs.java

@@ -45,9 +45,11 @@ package org.eclipse.jgit.http.server;
 
 import static javax.servlet.http.HttpServletResponse.SC_FORBIDDEN;
 import static javax.servlet.http.HttpServletResponse.SC_UNAUTHORIZED;
+import static org.eclipse.jgit.http.server.ServletUtils.ATTRIBUTE_HANDLER;
 import static org.eclipse.jgit.http.server.ServletUtils.getRepository;
 
 import java.io.IOException;
+import java.util.List;
 
 import javax.servlet.Filter;
 import javax.servlet.FilterChain;
@@ -68,8 +70,11 @@ import org.eclipse.jgit.transport.resolver.ServiceNotEnabledException;
 abstract class SmartServiceInfoRefs implements Filter {
 	private final String svc;
 
-	SmartServiceInfoRefs(final String service) {
+	private final Filter[] filters;
+
+	SmartServiceInfoRefs(final String service, final List<Filter> filters) {
 		this.svc = service;
+		this.filters = filters.toArray(new Filter[filters.size()]);
 	}
 
 	public void init(FilterConfig config) throws ServletException {
@@ -83,31 +88,71 @@ abstract class SmartServiceInfoRefs implements Filter {
 	public void doFilter(ServletRequest request, ServletResponse response,
 			FilterChain chain) throws IOException, ServletException {
 		final HttpServletRequest req = (HttpServletRequest) request;
+		final HttpServletResponse rsp = (HttpServletResponse) response;
 
 		if (svc.equals(req.getParameter("service"))) {
-			final HttpServletResponse rsp = (HttpServletResponse) response;
+			final Repository db = getRepository(req);
 			try {
-				final Repository db = getRepository(req);
-				rsp.setContentType("application/x-" + svc + "-advertisement");
-
-				final SmartOutputStream buf = new SmartOutputStream(req, rsp);
-				final PacketLineOut out = new PacketLineOut(buf);
-				out.writeString("# service=" + svc + "\n");
-				out.end();
-				advertise(req, db, new PacketLineOutRefAdvertiser(out));
-				buf.close();
+				begin(req, db);
 			} catch (ServiceNotAuthorizedException e) {
 				rsp.sendError(SC_UNAUTHORIZED);
-
+				return;
 			} catch (ServiceNotEnabledException e) {
 				rsp.sendError(SC_FORBIDDEN);
+				return;
+			}
+
+			try {
+				if (filters.length == 0)
+					service(req, response);
+				else
+					new Chain().doFilter(request, response);
+			} finally {
+				req.removeAttribute(ATTRIBUTE_HANDLER);
 			}
 		} else {
 			chain.doFilter(request, response);
 		}
 	}
 
-	protected abstract void advertise(HttpServletRequest req, Repository db,
+	private void service(ServletRequest request, ServletResponse response)
+			throws IOException {
+		final HttpServletRequest req = (HttpServletRequest) request;
+		final HttpServletResponse rsp = (HttpServletResponse) response;
+		try {
+			rsp.setContentType("application/x-" + svc + "-advertisement");
+
+			final SmartOutputStream buf = new SmartOutputStream(req, rsp);
+			final PacketLineOut out = new PacketLineOut(buf);
+			out.writeString("# service=" + svc + "\n");
+			out.end();
+			advertise(req, new PacketLineOutRefAdvertiser(out));
+			buf.close();
+		} catch (ServiceNotAuthorizedException e) {
+			rsp.sendError(SC_UNAUTHORIZED);
+
+		} catch (ServiceNotEnabledException e) {
+			rsp.sendError(SC_FORBIDDEN);
+		}
+	}
+
+	protected abstract void begin(HttpServletRequest req, Repository db)
+			throws IOException, ServiceNotEnabledException,
+			ServiceNotAuthorizedException;
+
+	protected abstract void advertise(HttpServletRequest req,
 			PacketLineOutRefAdvertiser pck) throws IOException,
 			ServiceNotEnabledException, ServiceNotAuthorizedException;
+
+	private class Chain implements FilterChain {
+		private int filterIdx;
+
+		public void doFilter(ServletRequest req, ServletResponse rsp)
+				throws IOException, ServletException {
+			if (filterIdx < filters.length)
+				filters[filterIdx++].doFilter(req, rsp, this);
+			else
+				service(req, rsp);
+		}
+	}
 }

org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/UploadPackServlet.java

@@ -47,18 +47,26 @@ import static javax.servlet.http.HttpServletResponse.SC_FORBIDDEN;
 import static javax.servlet.http.HttpServletResponse.SC_INTERNAL_SERVER_ERROR;
 import static javax.servlet.http.HttpServletResponse.SC_UNAUTHORIZED;
 import static javax.servlet.http.HttpServletResponse.SC_UNSUPPORTED_MEDIA_TYPE;
+import static org.eclipse.jgit.http.server.ServletUtils.ATTRIBUTE_HANDLER;
 import static org.eclipse.jgit.http.server.ServletUtils.getInputStream;
 import static org.eclipse.jgit.http.server.ServletUtils.getRepository;
 
 import java.io.IOException;
-
+import java.util.List;
+
+import javax.servlet.Filter;
+import javax.servlet.FilterChain;
+import javax.servlet.FilterConfig;
+import javax.servlet.ServletException;
+import javax.servlet.ServletRequest;
+import javax.servlet.ServletResponse;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
 import org.eclipse.jgit.lib.Repository;
-import org.eclipse.jgit.transport.UploadPack;
 import org.eclipse.jgit.transport.RefAdvertiser.PacketLineOutRefAdvertiser;
+import org.eclipse.jgit.transport.UploadPack;
 import org.eclipse.jgit.transport.resolver.ServiceNotAuthorizedException;
 import org.eclipse.jgit.transport.resolver.ServiceNotEnabledException;
 import org.eclipse.jgit.transport.resolver.UploadPackFactory;
@@ -72,18 +80,27 @@ class UploadPackServlet extends HttpServlet {
 	private static final long serialVersionUID = 1L;
 
 	static class InfoRefs extends SmartServiceInfoRefs {
-		private final UploadPackFactory uploadPackFactory;
+		private final UploadPackFactory<HttpServletRequest> uploadPackFactory;
 
-		InfoRefs(final UploadPackFactory uploadPackFactory) {
-			super("git-upload-pack");
+		InfoRefs(UploadPackFactory<HttpServletRequest> uploadPackFactory,
+				List<Filter> filters) {
+			super("git-upload-pack", filters);
 			this.uploadPackFactory = uploadPackFactory;
 		}
 
 		@Override
-		protected void advertise(HttpServletRequest req, Repository db,
+		protected void begin(HttpServletRequest req, Repository db)
+				throws IOException, ServiceNotEnabledException,
+				ServiceNotAuthorizedException {
+			UploadPack up = uploadPackFactory.create(req, db);
+			req.setAttribute(ATTRIBUTE_HANDLER, up);
+		}
+
+		@Override
+		protected void advertise(HttpServletRequest req,
 				PacketLineOutRefAdvertiser pck) throws IOException,
 				ServiceNotEnabledException, ServiceNotAuthorizedException {
-			UploadPack up = uploadPackFactory.create(req, db);
+			UploadPack up = (UploadPack) req.getAttribute(ATTRIBUTE_HANDLER);
 			try {
 				up.sendAdvertisedRefs(pck);
 			} finally {
@@ -92,10 +109,44 @@ class UploadPackServlet extends HttpServlet {
 		}
 	}
 
-	private final UploadPackFactory uploadPackFactory;
+	static class Factory implements Filter {
+		private final UploadPackFactory<HttpServletRequest> uploadPackFactory;
+
+		Factory(UploadPackFactory<HttpServletRequest> uploadPackFactory) {
+			this.uploadPackFactory = uploadPackFactory;
+		}
+
+		public void doFilter(ServletRequest request, ServletResponse response,
+				FilterChain chain) throws IOException, ServletException {
+			HttpServletRequest req = (HttpServletRequest) request;
+			HttpServletResponse rsp = (HttpServletResponse) response;
+			UploadPack rp;
+			try {
+				rp = uploadPackFactory.create(req, getRepository(req));
+			} catch (ServiceNotAuthorizedException e) {
+				rsp.sendError(SC_UNAUTHORIZED);
+				return;
+
+			} catch (ServiceNotEnabledException e) {
+				rsp.sendError(SC_FORBIDDEN);
+				return;
+			}
+
+			try {
+				req.setAttribute(ATTRIBUTE_HANDLER, rp);
+				chain.doFilter(req, rsp);
+			} finally {
+				req.removeAttribute(ATTRIBUTE_HANDLER);
+			}
+		}
+
+		public void init(FilterConfig filterConfig) throws ServletException {
+			// Nothing.
+		}
 
-	UploadPackServlet(final UploadPackFactory uploadPackFactory) {
-		this.uploadPackFactory = uploadPackFactory;
+		public void destroy() {
+			// Nothing.
+		}
 	}
 
 	@Override
@@ -106,9 +157,8 @@ class UploadPackServlet extends HttpServlet {
 			return;
 		}
 
-		final Repository db = getRepository(req);
+		UploadPack up = (UploadPack) req.getAttribute(ATTRIBUTE_HANDLER);
 		try {
-			final UploadPack up = uploadPackFactory.create(req, db);
 			up.setBiDirectionalPipe(false);
 			rsp.setContentType(RSP_TYPE);
 
@@ -121,16 +171,6 @@ class UploadPackServlet extends HttpServlet {
 			up.upload(getInputStream(req), out, null);
 			out.close();
 
-		} catch (ServiceNotAuthorizedException e) {
-			rsp.reset();
-			rsp.sendError(SC_UNAUTHORIZED);
-			return;
-
-		} catch (ServiceNotEnabledException e) {
-			rsp.reset();
-			rsp.sendError(SC_FORBIDDEN);
-			return;
-
 		} catch (IOException e) {
 			getServletContext().log(HttpServerText.get().internalErrorDuringUploadPack, e);
 			rsp.reset();