extensions/servlet/src/com/google/inject/servlet/ServletDefinition.java - platform/external/guice - Git at Google

 /**
  * Copyright (C) 2008 Google Inc.
  *
  * 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.
  */
 package com.google.inject.servlet;

 import com.google.inject.Injector;
 import com.google.inject.Key;
 import com.google.inject.Scopes;
 import com.google.inject.internal.util.Iterators;
 import com.google.inject.spi.BindingTargetVisitor;
 import com.google.inject.spi.ProviderInstanceBinding;
 import com.google.inject.spi.ProviderWithExtensionVisitor;

 import java.io.IOException;
 import java.util.Collections;
 import java.util.Enumeration;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicReference;
 import javax.servlet.ServletConfig;
 import javax.servlet.ServletContext;
 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.HttpServletRequestWrapper;

 import static com.google.inject.servlet.ManagedServletPipeline.REQUEST_DISPATCHER_REQUEST;

 /**
  * An internal representation of a servlet definition mapped to a particular URI pattern. Also
  * performs the request dispatch to that servlet. How nice and OO =)
  *
  * @author dhanji@gmail.com (Dhanji R. Prasanna)
  */
 class ServletDefinition implements ProviderWithExtensionVisitor<ServletDefinition> {
   private final String pattern;
   private final Key<? extends HttpServlet> servletKey;
   private final UriPatternMatcher patternMatcher;
   private final Map<String, String> initParams;
   // set only if this was bound using a servlet instance.
   private final HttpServlet servletInstance;

   //always set in init, our servlet is always presumed to be a singleton
   private final AtomicReference<HttpServlet> httpServlet = new AtomicReference<HttpServlet>();

   public ServletDefinition(String pattern, Key<? extends HttpServlet> servletKey,
       UriPatternMatcher patternMatcher, Map<String, String> initParams, HttpServlet servletInstance) {
     this.pattern = pattern;
     this.servletKey = servletKey;
     this.patternMatcher = patternMatcher;
     this.initParams = Collections.unmodifiableMap(new HashMap<String, String>(initParams));
     this.servletInstance = servletInstance;
   }

   public ServletDefinition get() {
     return this;
   }

   public <B, V> V acceptExtensionVisitor(BindingTargetVisitor<B, V> visitor,
       ProviderInstanceBinding<? extends B> binding) {
     if(visitor instanceof ServletModuleTargetVisitor) {
       if(servletInstance != null) {
         return ((ServletModuleTargetVisitor<B, V>)visitor).visit(
             new InstanceServletBindingImpl(initParams,
                 pattern,
                 servletInstance,
                 patternMatcher.getPatternType()));
       } else {
         return ((ServletModuleTargetVisitor<B, V>)visitor).visit(
             new LinkedServletBindingImpl(initParams,
                 pattern,
                 servletKey,
                 patternMatcher.getPatternType()));
       }
     } else {
       return visitor.visit(binding);
     }
   }

   boolean shouldServe(String uri) {
     return patternMatcher.matches(uri);
   }

   public void init(final ServletContext servletContext, Injector injector,
       Set<HttpServlet> initializedSoFar) throws ServletException {

     // This absolutely must be a singleton, and so is only initialized once.
     if (!Scopes.isSingleton(injector.getBinding(servletKey))) {
       throw new ServletException("Servlets must be bound as singletons. "
         + servletKey + " was not bound in singleton scope.");
     }

     HttpServlet httpServlet = injector.getInstance(servletKey);
     this.httpServlet.set(httpServlet);

     // Only fire init() if we have not appeared before in the filter chain.
     if (initializedSoFar.contains(httpServlet)) {
       return;
     }

     //initialize our servlet with the configured context params and servlet context
     httpServlet.init(new ServletConfig() {
       public String getServletName() {
         return servletKey.toString();
       }

       public ServletContext getServletContext() {
         return servletContext;
       }

       public String getInitParameter(String s) {
         return initParams.get(s);
       }

       public Enumeration getInitParameterNames() {
         return Iterators.asEnumeration(initParams.keySet().iterator());
       }
     });

     // Mark as initialized.
     initializedSoFar.add(httpServlet);
   }

   public void destroy(Set<HttpServlet> destroyedSoFar) {
     HttpServlet reference = httpServlet.get();

     // Do nothing if this Servlet was invalid (usually due to not being scoped
     // properly). According to Servlet Spec: it is "out of service", and does not
     // need to be destroyed.
     // Also prevent duplicate destroys to the same singleton that may appear
     // more than once on the filter chain.
     if (null == reference || destroyedSoFar.contains(reference)) {
       return;
     }

     try {
       reference.destroy();
     } finally {
       destroyedSoFar.add(reference);
     }
   }

   /**
    * Wrapper around the service chain to ensure a servlet is servicing what it must and provides it
    * with a wrapped request.
    *
    * @return Returns true if this servlet triggered for the given request. Or false if
    *          guice-servlet should continue dispatching down the servlet pipeline.
    *
    * @throws IOException If thrown by underlying servlet
    * @throws ServletException If thrown by underlying servlet
    */
   public boolean service(ServletRequest servletRequest,
       ServletResponse servletResponse) throws IOException, ServletException {

     final boolean serve = shouldServe(((HttpServletRequest) servletRequest).getServletPath());

     //invocations of the chain end at the first matched servlet
     if (serve) {
       doService(servletRequest, servletResponse);
     }

     //return false if no servlet matched (so we can proceed down to the web.xml servlets)
     return serve;
   }

   /**
    * Utility that delegates to the actual service method of the servlet wrapped with a contextual
    * request (i.e. with correctly computed path info).
    *
    * We need to suppress deprecation coz we use HttpServletRequestWrapper, which implements
    * deprecated API for backwards compatibility.
    */
   @SuppressWarnings({ "JavaDoc", "deprecation" })
   void doService(final ServletRequest servletRequest, ServletResponse servletResponse)
       throws ServletException, IOException {

     HttpServletRequest request = new HttpServletRequestWrapper(
         (HttpServletRequest) servletRequest) {
       private String path;
       private boolean pathComputed = false;
       //must use a boolean on the memo field, because null is a legal value (TODO no, it's not)

       private boolean pathInfoComputed = false;
       private String pathInfo;

       @Override
       public String getPathInfo() {
         if (!isPathInfoComputed()) {
           int servletPathLength = getServletPath().length();
           pathInfo = getRequestURI().substring(getContextPath().length()).replaceAll("[/]{2,}", "/");
           pathInfo = pathInfo.length() > servletPathLength ? pathInfo.substring(servletPathLength) : null;

           // Corner case: when servlet path and request path match exactly (without trailing '/'),
           // then pathinfo is null
           if ("".equals(pathInfo) && servletPathLength != 0) {
             pathInfo = null;
           }

           pathInfoComputed = true;
         }

         return pathInfo;
       }

       // NOTE(dhanji): These two are a bit of a hack to help ensure that request dipatcher-sent
       // requests don't use the same path info that was memoized for the original request.
       private boolean isPathInfoComputed() {
         return pathInfoComputed
             && !(null != servletRequest.getAttribute(REQUEST_DISPATCHER_REQUEST));
       }

       private boolean isPathComputed() {
         return pathComputed
             && !(null != servletRequest.getAttribute(REQUEST_DISPATCHER_REQUEST));
       }

       @Override
       public String getServletPath() {
         return computePath();
       }

       @Override
       public String getPathTranslated() {
         final String info = getPathInfo();

         return (null == info) ? null : getRealPath(info);
       }

       // Memoizer pattern.
       private String computePath() {
         if (!isPathComputed()) {
           String servletPath = super.getServletPath();
           path = patternMatcher.extractPath(servletPath);
           pathComputed = true;

           if (null == path) {
             path = servletPath;
           }
         }

         return path;
       }
     };

     httpServlet.get().service(request, servletResponse);
   }

   String getKey() {
     return servletKey.toString();
   }

   String getPattern() {
     return pattern;
   }
 }
	/**
	* Copyright (C) 2008 Google Inc.
	*
	* 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.
	*/
	package com.google.inject.servlet;

	import com.google.inject.Injector;
	import com.google.inject.Key;
	import com.google.inject.Scopes;
	import com.google.inject.internal.util.Iterators;
	import com.google.inject.spi.BindingTargetVisitor;
	import com.google.inject.spi.ProviderInstanceBinding;
	import com.google.inject.spi.ProviderWithExtensionVisitor;

	import java.io.IOException;
	import java.util.Collections;
	import java.util.Enumeration;
	import java.util.HashMap;
	import java.util.Map;
	import java.util.Set;
	import java.util.concurrent.atomic.AtomicReference;
	import javax.servlet.ServletConfig;
	import javax.servlet.ServletContext;
	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.HttpServletRequestWrapper;

	import static com.google.inject.servlet.ManagedServletPipeline.REQUEST_DISPATCHER_REQUEST;

	/**
	* An internal representation of a servlet definition mapped to a particular URI pattern. Also
	* performs the request dispatch to that servlet. How nice and OO =)
	*
	* @author dhanji@gmail.com (Dhanji R. Prasanna)
	*/
	class ServletDefinition implements ProviderWithExtensionVisitor<ServletDefinition> {
	private final String pattern;
	private final Key<? extends HttpServlet> servletKey;
	private final UriPatternMatcher patternMatcher;
	private final Map<String, String> initParams;
	// set only if this was bound using a servlet instance.
	private final HttpServlet servletInstance;

	//always set in init, our servlet is always presumed to be a singleton
	private final AtomicReference<HttpServlet> httpServlet = new AtomicReference<HttpServlet>();

	public ServletDefinition(String pattern, Key<? extends HttpServlet> servletKey,
	UriPatternMatcher patternMatcher, Map<String, String> initParams, HttpServlet servletInstance) {
	this.pattern = pattern;
	this.servletKey = servletKey;
	this.patternMatcher = patternMatcher;
	this.initParams = Collections.unmodifiableMap(new HashMap<String, String>(initParams));
	this.servletInstance = servletInstance;
	}

	public ServletDefinition get() {
	return this;
	}

	public <B, V> V acceptExtensionVisitor(BindingTargetVisitor<B, V> visitor,
	ProviderInstanceBinding<? extends B> binding) {
	if(visitor instanceof ServletModuleTargetVisitor) {
	if(servletInstance != null) {
	return ((ServletModuleTargetVisitor<B, V>)visitor).visit(
	new InstanceServletBindingImpl(initParams,
	pattern,
	servletInstance,
	patternMatcher.getPatternType()));
	} else {
	return ((ServletModuleTargetVisitor<B, V>)visitor).visit(
	new LinkedServletBindingImpl(initParams,
	pattern,
	servletKey,
	patternMatcher.getPatternType()));
	}
	} else {
	return visitor.visit(binding);
	}
	}

	boolean shouldServe(String uri) {
	return patternMatcher.matches(uri);
	}

	public void init(final ServletContext servletContext, Injector injector,
	Set<HttpServlet> initializedSoFar) throws ServletException {

	// This absolutely must be a singleton, and so is only initialized once.
	if (!Scopes.isSingleton(injector.getBinding(servletKey))) {
	throw new ServletException("Servlets must be bound as singletons. "
	+ servletKey + " was not bound in singleton scope.");
	}

	HttpServlet httpServlet = injector.getInstance(servletKey);
	this.httpServlet.set(httpServlet);

	// Only fire init() if we have not appeared before in the filter chain.
	if (initializedSoFar.contains(httpServlet)) {
	return;
	}

	//initialize our servlet with the configured context params and servlet context
	httpServlet.init(new ServletConfig() {
	public String getServletName() {
	return servletKey.toString();
	}

	public ServletContext getServletContext() {
	return servletContext;
	}

	public String getInitParameter(String s) {
	return initParams.get(s);
	}

	public Enumeration getInitParameterNames() {
	return Iterators.asEnumeration(initParams.keySet().iterator());
	}
	});

	// Mark as initialized.
	initializedSoFar.add(httpServlet);
	}

	public void destroy(Set<HttpServlet> destroyedSoFar) {
	HttpServlet reference = httpServlet.get();

	// Do nothing if this Servlet was invalid (usually due to not being scoped
	// properly). According to Servlet Spec: it is "out of service", and does not
	// need to be destroyed.
	// Also prevent duplicate destroys to the same singleton that may appear
	// more than once on the filter chain.
	if (null == reference \|\| destroyedSoFar.contains(reference)) {
	return;
	}

	try {
	reference.destroy();
	} finally {
	destroyedSoFar.add(reference);
	}
	}

	/**
	* Wrapper around the service chain to ensure a servlet is servicing what it must and provides it
	* with a wrapped request.
	*
	* @return Returns true if this servlet triggered for the given request. Or false if
	* guice-servlet should continue dispatching down the servlet pipeline.
	*
	* @throws IOException If thrown by underlying servlet
	* @throws ServletException If thrown by underlying servlet
	*/
	public boolean service(ServletRequest servletRequest,
	ServletResponse servletResponse) throws IOException, ServletException {

	final boolean serve = shouldServe(((HttpServletRequest) servletRequest).getServletPath());

	//invocations of the chain end at the first matched servlet
	if (serve) {
	doService(servletRequest, servletResponse);
	}

	//return false if no servlet matched (so we can proceed down to the web.xml servlets)
	return serve;
	}

	/**
	* Utility that delegates to the actual service method of the servlet wrapped with a contextual
	* request (i.e. with correctly computed path info).
	*
	* We need to suppress deprecation coz we use HttpServletRequestWrapper, which implements
	* deprecated API for backwards compatibility.
	*/
	@SuppressWarnings({ "JavaDoc", "deprecation" })
	void doService(final ServletRequest servletRequest, ServletResponse servletResponse)
	throws ServletException, IOException {

	HttpServletRequest request = new HttpServletRequestWrapper(
	(HttpServletRequest) servletRequest) {
	private String path;
	private boolean pathComputed = false;
	//must use a boolean on the memo field, because null is a legal value (TODO no, it's not)

	private boolean pathInfoComputed = false;
	private String pathInfo;

	@Override
	public String getPathInfo() {
	if (!isPathInfoComputed()) {
	int servletPathLength = getServletPath().length();
	pathInfo = getRequestURI().substring(getContextPath().length()).replaceAll("[/]{2,}", "/");
	pathInfo = pathInfo.length() > servletPathLength ? pathInfo.substring(servletPathLength) : null;

	// Corner case: when servlet path and request path match exactly (without trailing '/'),
	// then pathinfo is null
	if ("".equals(pathInfo) && servletPathLength != 0) {
	pathInfo = null;
	}

	pathInfoComputed = true;
	}

	return pathInfo;
	}

	// NOTE(dhanji): These two are a bit of a hack to help ensure that request dipatcher-sent
	// requests don't use the same path info that was memoized for the original request.
	private boolean isPathInfoComputed() {
	return pathInfoComputed
	&& !(null != servletRequest.getAttribute(REQUEST_DISPATCHER_REQUEST));
	}

	private boolean isPathComputed() {
	return pathComputed
	&& !(null != servletRequest.getAttribute(REQUEST_DISPATCHER_REQUEST));
	}

	@Override
	public String getServletPath() {
	return computePath();
	}

	@Override
	public String getPathTranslated() {
	final String info = getPathInfo();

	return (null == info) ? null : getRealPath(info);
	}

	// Memoizer pattern.
	private String computePath() {
	if (!isPathComputed()) {
	String servletPath = super.getServletPath();
	path = patternMatcher.extractPath(servletPath);
	pathComputed = true;

	if (null == path) {
	path = servletPath;
	}
	}

	return path;
	}
	};

	httpServlet.get().service(request, servletResponse);
	}

	String getKey() {
	return servletKey.toString();
	}

	String getPattern() {
	return pattern;
	}
	}