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Java example source code file (Struts2Factory.java)

This example Java source code file (Struts2Factory.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

annotation, class, classnotfoundexception, configurationexception, guice, guiceservletcontextlistener, injector, interceptor, log, logging, map, object, override, please, providedinterceptor, runtimeexception, string, util

The Struts2Factory.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.struts2;

import com.google.inject.AbstractModule;
import com.google.inject.Binder;
import com.google.inject.Injector;
import com.google.inject.internal.Annotations;

import com.opensymphony.xwork2.ActionInvocation;
import com.opensymphony.xwork2.ObjectFactory;
import com.opensymphony.xwork2.config.ConfigurationException;
import com.opensymphony.xwork2.config.entities.InterceptorConfig;
import com.opensymphony.xwork2.inject.Inject;
import com.opensymphony.xwork2.interceptor.Interceptor;

import java.lang.annotation.Annotation;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.logging.Logger;

/**
 * Cleanup up version from Bob's GuiceObjectFactory. Now works properly with
 * GS2 and fixes several bugs.
 *
 * @author dhanji@gmail.com
 * @author benmccann.com
 */
public class Struts2Factory extends ObjectFactory {

  private static final long serialVersionUID = 1L;
  private static final Logger logger = Logger.getLogger(Struts2Factory.class.getName());
  private static final String ERROR_NO_INJECTOR =
      "Cannot find a Guice injector.  Are you sure you registered a GuiceServletContextListener "
    + "that uses the Struts2GuicePluginModule in your application's web.xml?";

  private static @com.google.inject.Inject Injector injector;

  private final List<ProvidedInterceptor> interceptors = new ArrayList();
  private volatile Injector strutsInjector;

  @Override
  public boolean isNoArgConstructorRequired() {
    return false;
  }

  @Inject(value = "guice.module", required = false)
  void setModule(String moduleClassName) {
    throw new RuntimeException("The struts2 plugin no longer supports"
        + " specifying a module via the 'guice.module' property in XML."
        + " Please install your module via a GuiceServletContextListener instead.");
  }

  Set<Class boundClasses = new HashSet>();

  public Class<?> getClassInstance(String name) throws ClassNotFoundException {
    Class<?> clazz = super.getClassInstance(name);

    synchronized (this) {
      if (strutsInjector == null) {
        // We can only bind each class once.
        if (!boundClasses.contains(clazz)) {
          try {
            // Calling these methods now helps us detect ClassNotFoundErrors
            // early.
            clazz.getDeclaredFields();
            clazz.getDeclaredMethods();

            boundClasses.add(clazz);
          } catch (Throwable t) {
            // Struts should still work even though some classes aren't in the
            // classpath. It appears we always get the exception here when
            // this is the case.
            return clazz;
          }
        }
      }
    }

    return clazz;
  }

  @Override @SuppressWarnings("unchecked")
  public Object buildBean(Class clazz, Map<String, Object> extraContext) {
    if (strutsInjector == null) {
      synchronized (this) {
        if (strutsInjector == null) {
          createInjector();
        }
      }
    }
    return strutsInjector.getInstance(clazz);
  }

  private void createInjector() {
    logger.info("Loading struts2 Guice support...");

    // Something is wrong, since this should be there if GuiceServletContextListener
    // was present.
    if (injector == null) {
      logger.severe(ERROR_NO_INJECTOR);
      throw new RuntimeException(ERROR_NO_INJECTOR);
    }

    this.strutsInjector = injector.createChildInjector(new AbstractModule() {
      protected void configure() {

        // Tell the injector about all the action classes, etc., so it
        // can validate them at startup.
        for (Class<?> boundClass : boundClasses) {
          // TODO: Set source from Struts XML.
          bind(boundClass);
        }

        // Validate the interceptor class.
        for (ProvidedInterceptor interceptor : interceptors) {
          interceptor.validate(binder());
        }
      }
    });

    // Inject interceptors.
    for (ProvidedInterceptor interceptor : interceptors) {
      interceptor.inject();
    }

    logger.info("Injector created successfully.");
  }

  @SuppressWarnings("unchecked")
  public Interceptor buildInterceptor(InterceptorConfig interceptorConfig,
      Map interceptorRefParams) throws ConfigurationException {
    // Ensure the interceptor class is present.
    Class<? extends Interceptor> interceptorClass;
    try {
      interceptorClass = (Class<? extends Interceptor>)
          getClassInstance(interceptorConfig.getClassName());
    } catch (ClassNotFoundException e) {
      throw new RuntimeException(e);
    }

    ProvidedInterceptor providedInterceptor = new ProvidedInterceptor(
        interceptorConfig, interceptorRefParams, interceptorClass);
    interceptors.add(providedInterceptor);
    return providedInterceptor;
  }

  private Interceptor superBuildInterceptor(InterceptorConfig interceptorConfig,
      Map<String, String> interceptorRefParams) throws ConfigurationException {
    return super.buildInterceptor(interceptorConfig, interceptorRefParams);
  }

  private class ProvidedInterceptor implements Interceptor {

    private static final long serialVersionUID = 1L;

    private final InterceptorConfig config;
    private final Map<String, String> params;
    private final Class<? extends Interceptor> interceptorClass;
    private Interceptor delegate;

    ProvidedInterceptor(InterceptorConfig config, Map<String, String> params,
        Class<? extends Interceptor> interceptorClass) {
      this.config = config;
      this.params = params;
      this.interceptorClass = interceptorClass;
    }

    void validate(Binder binder) {
      // TODO: Set source from Struts XML.
      if (hasScope(interceptorClass)) {
        binder.addError("Scoping interceptors is not currently supported."
            + " Please remove the scope annotation from "
            + interceptorClass.getName() + ".");
      }

      // Make sure it implements Interceptor.
      if (!Interceptor.class.isAssignableFrom(interceptorClass)) {
        binder.addError(interceptorClass.getName() + " must implement "
          + Interceptor.class.getName() + ".");
      }
    }

    void inject() {
      delegate = superBuildInterceptor(config, params);
    }

    public void destroy() {
      if (null != delegate) {
        delegate.destroy();
      }
    }

    public void init() {
      throw new AssertionError();
    }

    public String intercept(ActionInvocation invocation) throws Exception {
      return delegate.intercept(invocation);
    }
  }

  /**
   * Returns true if the given class has a scope annotation.
   */
  private static boolean hasScope(Class<? extends Interceptor> interceptorClass) {
    for (Annotation annotation : interceptorClass.getAnnotations()) {
      if (Annotations.isScopeAnnotation(annotation.annotationType())) {
        return true;
      }
    }
    return false;
  }
}

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