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Java example source code file (InternalServletModule.java)

This example Java source code file (InternalServletModule.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

api, backwardscompatibleservletcontextprovider, guicefilter, http, httpservletresponse, inject, internalservletmodule, jvm, logging, override, please, provides, request, requestscoped, response, servlet, servletcontext, singleton, util, you

The InternalServletModule.java Java example source code

/**
 * Copyright (C) 2009 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 static com.google.inject.servlet.ServletScopes.REQUEST;
import static com.google.inject.servlet.ServletScopes.SESSION;

import com.google.inject.AbstractModule;
import com.google.inject.Inject;
import com.google.inject.Key;
import com.google.inject.Provider;
import com.google.inject.Provides;
import com.google.inject.Singleton;

import java.util.Map;
import java.util.logging.Logger;

import javax.servlet.ServletContext;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

/**
 * This is a left-factoring of all ServletModules installed in the system.
 * In other words, this module contains the bindings common to all ServletModules,
 * and is bound exactly once per injector.
 *
 * @author dhanji@gmail.com (Dhanji R. Prasanna)
 */
final class InternalServletModule extends AbstractModule {

  /**
   * Special Provider that tries to obtain an injected servlet context, specific
   * to the current injector, failing which, it falls back to the static singleton
   * instance that is available in the legacy Guice Servlet.
   */
  @Singleton
  static class BackwardsCompatibleServletContextProvider implements Provider<ServletContext> {
    private ServletContext injectedServletContext;

    @Inject BackwardsCompatibleServletContextProvider() {}

    // This setter is called by the GuiceServletContextListener
    void set(ServletContext injectedServletContext) {
      this.injectedServletContext = injectedServletContext;
    }

    public ServletContext get() {
      if (null != injectedServletContext) {
        return injectedServletContext;
      }

      Logger.getLogger(InternalServletModule.class.getName())
          .warning("You are attempting to use a deprecated API (specifically,"
          + " attempting to @Inject ServletContext inside an eagerly created"
          + " singleton. While we allow this for backwards compatibility, be"
          + " warned that this MAY have unexpected behavior if you have more"
          + " than one injector (with ServletModule) running in the same JVM."
          + " Please consult the Guice documentation at"
          + " https://github.com/google/guice/wiki/Servlets for more"
          + " information.");
      return GuiceFilter.getServletContext();
    }
  }

  @Override
  protected void configure() {
    bindScope(RequestScoped.class, REQUEST);
    bindScope(SessionScoped.class, SESSION);
    bind(ServletRequest.class).to(HttpServletRequest.class);
    bind(ServletResponse.class).to(HttpServletResponse.class);

    // inject the pipeline into GuiceFilter so it can route requests correctly
    // Unfortunate staticness... =(
    // NOTE(dhanji): This is maintained for legacy purposes.
    requestStaticInjection(GuiceFilter.class);

    bind(ManagedFilterPipeline.class);
    bind(ManagedServletPipeline.class);
    bind(FilterPipeline.class).to(ManagedFilterPipeline.class).asEagerSingleton();

    bind(ServletContext.class).toProvider(BackwardsCompatibleServletContextProvider.class);
    bind(BackwardsCompatibleServletContextProvider.class);
  }

  @Provides @Singleton @ScopingOnly GuiceFilter provideScopingOnlyGuiceFilter() {
    return new GuiceFilter(new DefaultFilterPipeline());
  }

  @Provides @RequestScoped HttpServletRequest provideHttpServletRequest() {
    return GuiceFilter.getRequest(Key.get(HttpServletRequest.class));
  }

  @Provides @RequestScoped HttpServletResponse provideHttpServletResponse() {
    return GuiceFilter.getResponse(Key.get(HttpServletResponse.class));
  }

  @Provides HttpSession provideHttpSession() {
    return GuiceFilter.getRequest(Key.get(HttpSession.class)).getSession();
  }

  @SuppressWarnings("unchecked") // defined by getParameterMap()
  @Provides @RequestScoped @RequestParameters Map<String, String[]> provideRequestParameters(
      ServletRequest req) {
    return req.getParameterMap();
  }

  @Override
  public boolean equals(Object o) {
    // Is only ever installed internally, so we don't need to check state.
    return o instanceof InternalServletModule;
  }

  @Override
  public int hashCode() {
    return InternalServletModule.class.hashCode();
  }
}

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