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spring framework 3.0.0 » org » springframework » web » servlet » mvc » ServletWrappingController.java
/*
 * Copyright 2002-2007 the original author or authors.
 *
 * 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 org.springframework.web.servlet.mvc;

import java.util.Enumeration;
import java.util.Properties;

import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.beans.factory.BeanNameAware;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.web.servlet.ModelAndView;

/**
 * Spring Controller implementation that wraps a servlet instance which it manages
 * internally. Such a wrapped servlet is not known outside of this controller;
 * its entire lifecycle is covered here (in contrast to {@link ServletForwardingController}).
 *
 * <p>Useful to invoke an existing servlet via Spring's dispatching infrastructure,
 * for example to apply Spring HandlerInterceptors to its requests.
 *
 * <p>Note that Struts has a special requirement in that it parses <code>web.xml</code>
 * to find its servlet mapping. Therefore, you need to specify the DispatcherServlet's
 * servlet name as "servletName" on this controller, so that Struts finds the
 * DispatcherServlet's mapping (thinking that it refers to the ActionServlet).
 *
 * <p><b>Example:</b> a DispatcherServlet XML context, forwarding "*.do" to the Struts
 * ActionServlet wrapped by a ServletWrappingController. All such requests will go
 * through the configured HandlerInterceptor chain (e.g. an OpenSessionInViewInterceptor).
 * From the Struts point of view, everything will work as usual.
 *
 * <pre>
 * &lt;bean id="urlMapping" class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping"&gt;
 *   &lt;property name="interceptors"&gt;
 *     &lt;list&gt;
 *       &lt;ref bean="openSessionInViewInterceptor"/&gt;
 *     &lt;/list&gt;
 *   &lt;/property&gt;
 *   &lt;property name="mappings"&gt;
 *     &lt;props&gt;
 *       &lt;prop key="*.do"&gt;strutsWrappingController&lt;/prop&gt;
 *     &lt;/props&gt;
 *   &lt;/property&gt;
 * &lt;/bean&gt;
 *
 * &lt;bean id="strutsWrappingController" class="org.springframework.web.servlet.mvc.ServletWrappingController"&gt;
 *   &lt;property name="servletClass"&gt;
 *     &lt;value&gt;org.apache.struts.action.ActionServlet&lt;/value&gt;
 *   &lt;/property&gt;
 *   &lt;property name="servletName"&gt;
 *     &lt;value&gt;action&lt;/value&gt;
 *   &lt;/property&gt;
 *   &lt;property name="initParameters"&gt;
 *     &lt;props&gt;
 *       &lt;prop key="config"&gt;/WEB-INF/struts-config.xml&lt;/prop&gt;
 *     &lt;/props&gt;
 *   &lt;/property&gt;
 * &lt;/bean&gt;</pre>
 *
 * @author Juergen Hoeller
 * @since 1.1.1
 * @see ServletForwardingController
 * @see org.springframework.orm.hibernate3.support.OpenSessionInViewInterceptor
 * @see org.springframework.orm.hibernate3.support.OpenSessionInViewFilter
 * @see org.springframework.orm.jdo.support.OpenPersistenceManagerInViewInterceptor
 * @see org.springframework.orm.jdo.support.OpenPersistenceManagerInViewFilter
 */
public class ServletWrappingController extends AbstractController
  implements BeanNameAware, InitializingBean, DisposableBean {

  private Class servletClass;

  private String servletName;

  private Properties initParameters = new Properties();

  private String beanName;

  private Servlet servletInstance;


  /**
   * Set the class of the servlet to wrap.
   * Needs to implement <code>javax.servlet.Servlet</code>.
   * @see javax.servlet.Servlet
   */
  public void setServletClass(Class servletClass) {
    this.servletClass = servletClass;
  }

  /**
   * Set the name of the servlet to wrap.
   * Default is the bean name of this controller.
   */
  public void setServletName(String servletName) {
    this.servletName = servletName;
  }

  /**
   * Specify init parameters for the servlet to wrap,
   * as name-value pairs.
   */
  public void setInitParameters(Properties initParameters) {
    this.initParameters = initParameters;
  }

  public void setBeanName(String name) {
    this.beanName = name;
  }


  /**
   * Initialize the wrapped Servlet instance.
   * @see javax.servlet.Servlet#init(javax.servlet.ServletConfig)
   */
  public void afterPropertiesSet() throws Exception {
    if (this.servletClass == null) {
      throw new IllegalArgumentException("servletClass is required");
    }
    if (!Servlet.class.isAssignableFrom(this.servletClass)) {
      throw new IllegalArgumentException("servletClass [" + this.servletClass.getName() +
        "] needs to implement interface [javax.servlet.Servlet]");
    }
    if (this.servletName == null) {
      this.servletName = this.beanName;
    }
    this.servletInstance = (Servlet) this.servletClass.newInstance();
    this.servletInstance.init(new DelegatingServletConfig());
  }


  /**
   * Invoke the the wrapped Servlet instance.
   * @see javax.servlet.Servlet#service(javax.servlet.ServletRequest, javax.servlet.ServletResponse)
   */
  @Override
  protected ModelAndView handleRequestInternal(HttpServletRequest request, HttpServletResponse response)
    throws Exception {

    this.servletInstance.service(request, response);
    return null;
  }


  /**
   * Destroy the wrapped Servlet instance.
   * @see javax.servlet.Servlet#destroy()
   */
  public void destroy() {
    this.servletInstance.destroy();
  }


  /**
   * Internal implementation of the ServletConfig interface, to be passed
   * to the wrapped servlet. Delegates to ServletWrappingController fields
   * and methods to provide init parameters and other environment info.
   */
  private class DelegatingServletConfig implements ServletConfig {

    public String getServletName() {
      return servletName;
    }

    public ServletContext getServletContext() {
      return ServletWrappingController.this.getServletContext();
    }

    public String getInitParameter(String paramName) {
      return initParameters.getProperty(paramName);
    }

    public Enumeration getInitParameterNames() {
      return initParameters.keys();
    }
  }

}
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