org.directwebremoting.spring.DwrSpringServlet Maven / Gradle / Ivy

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DWR is easy Ajax for Java. It makes it simple to call Java code directly from Javascript. It gets rid of almost all the boiler plate code between the web browser and your Java code.
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/*
 * Copyright 2005 Joe Walker
 *
 * 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.directwebremoting.spring;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.directwebremoting.WebContextFactory.WebContextBuilder;
import org.directwebremoting.impl.ContainerUtil;
import org.directwebremoting.impl.StartupUtil;
import org.directwebremoting.servlet.UrlProcessor;
import org.directwebremoting.util.Logger;
import org.springframework.beans.factory.BeanCreationException;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;

/**
 * The servlet that handles all calls to DWR. 

 * It retrieves its configuration from the Spring IoC container. This is done in two ways:
 * 
 *   Use the Spring namespace. When using the Spring namespace for DWR, the confgiuration for DWR is
 *       automatically picked up by this servlet.
 *   Explicitly specify which configurations to pick up. When explicitly defining the DWR configuration in
 *       Spring yourself, you can explicitely specify them in the init parameters.
 * 
 * Same as with the DwrServlet, you can specify a debug init parameter on this servlet
 * to put DWR in debug mode (allowing access to the very handy debug pages).
 *
 * @see org.directwebremoting.servlet.DwrServlet
 *
 * @author Bram Smeets
 * @author Joe Walker [joe at getahead dot ltd dot uk]
 */
public class DwrSpringServlet extends HttpServlet
{
    /**
     * Setter for use by the Spring IoC container to tell us what Configurators
     * exist for us to configure ourselves.
     * @param configurators
     */
    public void setConfigurators(List configurators)
    {
        this.configurators = configurators;
    }

    /**
     * Do we prefix the list of Configurators with a default to read the system
     * dwr.xml file?
     * @param includeDefaultConfig the includeDefaultConfig to set
     */
    public void setIncludeDefaultConfig(boolean includeDefaultConfig)
    {
        this.includeDefaultConfig = includeDefaultConfig;
    }

    /* (non-Javadoc)
     * @see javax.servlet.GenericServlet#init(javax.servlet.ServletConfig)
     */
    public void init(ServletConfig servletConfig) throws ServletException
    {
        super.init(servletConfig);
        ServletContext servletContext = servletConfig.getServletContext();

        try
        {
            WebApplicationContext webappContext = WebApplicationContextUtils.getRequiredWebApplicationContext(servletContext);

            container = new SpringContainer();
            container.setBeanFactory(webappContext);
            ContainerUtil.setupDefaults(container, servletConfig);
            ContainerUtil.setupFromServletConfig(container, servletConfig);

            container.setupFinished();

            webContextBuilder = StartupUtil.initWebContext(servletConfig, servletContext, container);
            StartupUtil.initServerContext(servletConfig, servletContext, container);

            ContainerUtil.prepareForWebContextFilter(servletContext, servletConfig, container, webContextBuilder, this);
            // retrieve the configurators from Spring (loaded by the ContextLoaderListener)
            try
            {
                configurators.add(webappContext.getBean(DwrNamespaceHandler.DEFAULT_SPRING_CONFIGURATOR_ID));
            }
            catch (NoSuchBeanDefinitionException ex)
            {
                throw new ServletException("No DWR configuration was found in your application context, make sure to define one", ex);
            }

            if (includeDefaultConfig)
            {
                ContainerUtil.configureFromSystemDwrXml(container);
            }

            ContainerUtil.configureFromInitParams(container, servletConfig);
            ContainerUtil.configure(container, configurators);

            ContainerUtil.publishContainer(container, servletConfig);
        }
        catch (InstantiationException ex)
        {
            throw new BeanCreationException("Failed to instansiate", ex);
        }
        catch (IllegalAccessException ex)
        {
            throw new BeanCreationException("Access error", ex);
        }
        catch (Exception ex)
        {
            log.fatal("init failed", ex);
            throw new ServletException(ex);
        }
        finally
        {
            webContextBuilder.unset();
        }
    }

    /* (non-Javadoc)
     * @see javax.servlet.http.HttpServlet#doGet(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
     */
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException
    {
        doPost(req, resp);
    }

    /* (non-Javadoc)
     * @see javax.servlet.http.HttpServlet#doPost(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException
    {
        try
        {
            webContextBuilder.set(request, response, getServletConfig(), getServletContext(), container);

            UrlProcessor processor = (UrlProcessor) container.getBean(UrlProcessor.class.getName());
            processor.handle(request, response);
        }
        finally
        {
            webContextBuilder.unset();
        }
    }

    /**
     * DWRs IoC container (that passes stuff to Spring in this case)
     */
    private SpringContainer container;

    /**
     * The WebContext that keeps http objects local to a thread
     */
    protected WebContextBuilder webContextBuilder;

    /**
     * Do we prefix the list of Configurators with a default to read the system
     * dwr.xml file?
     */
    private boolean includeDefaultConfig = true;

    /**
     * What Configurators exist for us to configure ourselves.
     */
    private List configurators = new ArrayList();

    /**
     * The log stream
     */
    private static final Logger log = Logger.getLogger(DwrSpringServlet.class);
}