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30 day Evaluation Version distributed via the Maven Jar Repository. Clover is not free. You have 30 days to evaluate it. Please visit http://www.thecortex.net/clover to obtain a licensed version of Clover | |||||||||||||||||||
Source file | Conditionals | Statements | Methods | TOTAL | |||||||||||||||
HiveMindFilter.java | 100% | 100% | 100% | 100% |
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// Copyright 2004 The Apache Software Foundation
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package org.apache.hivemind.servlet;
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import java.io.IOException;
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import java.util.Locale;
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import javax.servlet.Filter;
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import javax.servlet.FilterChain;
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import javax.servlet.FilterConfig;
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import javax.servlet.ServletException;
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import javax.servlet.ServletRequest;
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import javax.servlet.ServletResponse;
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import javax.servlet.http.HttpServletRequest;
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import org.apache.commons.logging.Log;
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import org.apache.commons.logging.LogFactory;
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import org.apache.hivemind.ClassResolver;
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import org.apache.hivemind.Registry;
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import org.apache.hivemind.impl.DefaultClassResolver;
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import org.apache.hivemind.impl.RegistryBuilder;
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/**
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* Servlet filter that constructs the Registry at startup. It ensures that each request is
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* properly terminated with a call to
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* {@link org.apache.hivemind.service.ThreadEventNotifier#fireThreadCleanup()}.
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* It also makes the Registry available during the request by
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* storing it as a request attribute.
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*
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* @author Howard Lewis Ship
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*/
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public class HiveMindFilter implements Filter |
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{ |
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private static final Log LOG = LogFactory.getLog(HiveMindFilter.class); |
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/**
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* Request attribute key that stores the Registry.
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*/
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static final String REQUEST_KEY = "org.apache.hivemind.RequestRegistry"; |
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static final String REBUILD_REQUEST_KEY = "org.apache.hivemind.RebuildRegistry"; |
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private FilterConfig _filterConfig;
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private Registry _registry;
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/**
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* Package private method used for testing.
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*/
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Registry getRegistry() |
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{ |
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return _registry;
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} |
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/**
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* Constructs a {@link Registry} and stores it into the
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* <code>ServletContext</code>. Any exception throws is logged.
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*/
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public void init(FilterConfig config) throws ServletException |
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{ |
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_filterConfig = config; |
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initializeRegistry(); |
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} |
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private void initializeRegistry() |
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{ |
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long startTime = System.currentTimeMillis();
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LOG.info(ServletMessages.filterInit()); |
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try
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{ |
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_registry = constructRegistry(_filterConfig); |
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LOG.info( |
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ServletMessages.constructedRegistry( |
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_registry, |
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System.currentTimeMillis() - startTime)); |
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} |
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catch (Exception ex)
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{ |
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LOG.error(ex.getMessage(), ex); |
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} |
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} |
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/**
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* Invoked from {@link #init(FilterConfig)} to actually
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* construct the Registry. Subclasses may override if
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* they have specific initialization needs, or have nonstandard
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* rules for finding HiveMind module deployment descriptors.
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*/
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protected Registry constructRegistry(FilterConfig config)
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{ |
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ClassResolver resolver = new DefaultClassResolver();
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RegistryBuilder builder = new RegistryBuilder();
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builder.processModules(resolver); |
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return builder.constructRegistry(getRegistryLocale());
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} |
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/**
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* Returns the default Locale. Subclasses may override to select a particular
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* locale for the Registry.
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*/
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protected Locale getRegistryLocale()
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{ |
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return Locale.getDefault();
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} |
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/**
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* Passes the request to the filter chain, but then invokes
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* {@link ThreadEventNotifier#fireThreadCleanup()} (from a finally block).
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*/
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public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) |
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throws IOException, ServletException
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{ |
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try
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{ |
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request.setAttribute(REQUEST_KEY, _registry); |
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chain.doFilter(request, response); |
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} |
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finally
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{ |
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cleanupThread(); |
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checkRegistryRebuild(request); |
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} |
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} |
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private synchronized void checkRegistryRebuild(ServletRequest request) |
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{ |
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if (request.getAttribute(REBUILD_REQUEST_KEY) == null) |
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return;
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// This is so not threadsafe, but you don't do this very often.
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// This method is synchronized, but other threads may be actively using
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// the Registry we're shutting down.
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// What we really need is some good concurrence support to track the number
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// of threads that may be using the old registry, set a write lock, and wait
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// for that number to drop to one (this thread). Instead, we'll just swap in the
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// new Registry and hope for the best.
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Registry oldRegistry = _registry; |
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// Replace the old Registry with a new one. All other threads, but this
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// one, will begin using the new Registry. Hopefully, we didn't get
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// rebuild requests on multiple threads.
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initializeRegistry(); |
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// Shutdown the old Registry. Perhaps we should sleep for a moment, first,
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// to help ensure that other threads have "cleared out". If not, we'll see some
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// instability at the instant we shutdown (i.e., all the proxies will get disabled).
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oldRegistry.shutdown(); |
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} |
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/**
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* Cleanup the thread, ignoring any exceptions that may be thrown.
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*/
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private void cleanupThread() |
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{ |
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try
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{ |
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_registry.cleanupThread(); |
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} |
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catch (Exception ex)
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{ |
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LOG.error(ServletMessages.filterCleanupError(ex), ex); |
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} |
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} |
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/**
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* Invokes {@link Registry#shutdown()}.
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*/
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public void destroy() |
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{ |
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if (_registry != null) |
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_registry.shutdown(); |
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_filterConfig = null;
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} |
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/**
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* Returns the {@link Registry} that was stored as a request attribute
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* inside method {@link #doFilter(ServletRequest, ServletResponse, FilterChain)}.
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*/
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public static Registry getRegistry(HttpServletRequest request) |
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{ |
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return (Registry) request.getAttribute(REQUEST_KEY);
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} |
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/**
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* Sets a flag in the request that will cause the current Registry to be shutdown
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* and replaced with a new Registry (at the end of the current request).
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*/
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public static void rebuildRegistry(HttpServletRequest request) |
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{ |
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request.setAttribute(REBUILD_REQUEST_KEY, Boolean.TRUE); |
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} |
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} |
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