com.google.inject.servlet.ServletDefinition Maven / Gradle / Ivy
/**
* Copyright (C) 2010 Mycila ([email protected])
*
* 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.common.collect.Iterators;
import com.google.inject.Injector;
import com.google.inject.Key;
import com.google.inject.Scopes;
import com.google.inject.spi.BindingTargetVisitor;
import com.google.inject.spi.ProviderInstanceBinding;
import com.google.inject.spi.ProviderWithExtensionVisitor;
import javax.servlet.*;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import java.io.IOException;
import java.util.*;
import java.util.concurrent.atomic.AtomicReference;
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 [email protected] (Dhanji R. Prasanna)
*/
class ServletDefinition implements ProviderWithExtensionVisitor {
private final String pattern;
private final Key servletKey;
private final UriPatternMatcher patternMatcher;
private final Map 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 = new AtomicReference();
public ServletDefinition(String pattern, Key servletKey,
UriPatternMatcher patternMatcher, Map initParams, HttpServlet servletInstance) {
this.pattern = pattern;
this.servletKey = servletKey;
this.patternMatcher = patternMatcher;
this.initParams = Collections.unmodifiableMap(new HashMap(initParams));
this.servletInstance = servletInstance;
}
public ServletDefinition get() {
return this;
}
public V acceptExtensionVisitor(BindingTargetVisitor visitor,
ProviderInstanceBinding binding) {
if (visitor instanceof ServletModuleTargetVisitor) {
if (servletInstance != null) {
return ((ServletModuleTargetVisitor) visitor).visit(
new InstanceServletBindingImpl(initParams,
pattern,
servletInstance,
patternMatcher));
} else {
return ((ServletModuleTargetVisitor) visitor).visit(
new LinkedServletBindingImpl(initParams,
pattern,
servletKey,
patternMatcher));
}
} else {
return visitor.visit(binding);
}
}
boolean shouldServe(String uri) {
return patternMatcher.matches(uri);
}
public void init(final ServletContext servletContext, Injector injector,
Set 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 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 HttpServletRequest request = (HttpServletRequest) servletRequest;
final String path = request.getRequestURI().substring(request.getContextPath().length());
final boolean serve = shouldServe(path);
//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.
*/
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;
}
}
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