genericportlet.java

GridSphere 门户 提供一个基于 portlet 的高级开放源代码门户。GridSphere 是在欧盟提供基金的 GridLab 项目下开发的

/**
 * Copyright 2003 IBM Corporation and Sun Microsystems, Inc.
 * All rights reserved.
 * Use is subject to license terms.
 */

package javax.portlet;


/**
 * The <CODE>GenericPortlet</CODE> class provides a default implementation
 * for the <CODE>Portlet</CODE> interface.
 * <p/>
 * It provides an abstract class to be subclassed to create portlets. A
 * subclass of <CODE>GenericPortlet</CODE> should override at least
 * one method, usually one of the following:
 * <ul>
 * <li>processAction, to handle action requests</li>
 * <li>doView, to handle render requests when in VIEW mode</li>
 * <li>doEdit, to handle render requests when in EDIT mode</li>
 * <li>doHelp, to handle render request when in HELP mode</li>
 * <li>init and destroy, to manage resources that are held for the life of
 * the servlet</li>
 * </ul>
 * <p/>
 * Normally there is no need to override the render or the doDispatch
 * methods. Render handles render requests setting the title of the
 * portlet in the response and invoking doDispatch. doDispatch dispatches
 * the request to one of the doView, doEdit or doHelp method depending on
 * the portlet mode indicated in the request.
 * <p/>
 * Portlets typically run on multithreaded servers, so please note that a
 * portlet must handle concurrent requests and be careful to synchronize
 * access to shared resources.  Shared resources include in-memory data
 * such as  instance or class variables and external objects  such as
 * files, database connections, and network  connections.
 */
public abstract class GenericPortlet implements Portlet, PortletConfig {

    private transient PortletConfig config;

    /**
     * Does nothing.
     */

    public GenericPortlet() {
    }


    /**
     * Called by the portlet container to indicate to a portlet that the
     * portlet is being placed into service.
     * <p/>
     * The default implementation just stores the <code>PortletConfig</code>
     * object.
     * <p>The portlet container calls the <code>init</code>
     * method exactly once after instantiating the portlet.
     * The <code>init</code> method must complete successfully
     * before the portlet can receive any requests.
     * <p/>
     * <p>The portlet container cannot place the portlet into service
     * if the <code>init</code> method does one of the following:
     * <ol>
     * <li>it throws a <code>PortletException</code>
     * <li>it does not return within a time period defined by the Web server
     * </ol>
     *
     * @param config a <code>PortletConfig</code> object
     *               containing the portlet
     *               configuration and initialization parameters
     * @throws PortletException     if an exception has occurred that
     *                              interferes with the portlet normal
     *                              operation.
     * @throws UnavailableException if the portlet cannot perform the initialization at this time.
     */

    public void init(PortletConfig config) throws PortletException {
        this.config = config;
        this.init();
    }


    /**
     * A convenience method which can be overridden so that there's no need
     * to call <code>super.init(config)</code>.
     * <p/>
     * <p>Instead of overriding {@link #init(PortletConfig)}, simply override
     * this method and it will be called by
     * <code>GenericPortlet.init(PortletConfig config)</code>.
     * The <code>PortletConfig</code> object can still be retrieved via {@link
     * #getPortletConfig}.
     *
     * @throws PortletException     if an exception has occurred that
     *                              interferes with the portlet normal
     *                              operation.
     * @throws UnavailableException if the portlet is unavailable to perform init
     */

    public void init() throws PortletException {
    }


    /**
     * Called by the portlet container to allow the portlet to process
     * an action request. This method is called if the client request was
     * originated by a URL created (by the portlet) with the
     * <code>RenderResponse.createActionURL()</code> method.
     * <p/>
     * The default implementation throws an exception.
     *
     * @param request  the action request
     * @param response the action response
     * @throws PortletException         if the portlet cannot fulfilling the request
     * @throws UnavailableException     if the portlet is unavailable to process the action at this time
     * @throws PortletSecurityException if the portlet cannot fullfill this request because of security reasons
     * @throws java.io.IOException      if the streaming causes an I/O problem
     */
    public void processAction(ActionRequest request, ActionResponse response)
            throws PortletException, java.io.IOException {
        throw new PortletException("processAction method not implemented");
    }


    /**
     * The default implementation of this method sets the title
     * using the <code>getTitle</code> method and invokes the
     * <code>doDispatch</code> method.
     *
     * @param request  the render request
     * @param response the render response
     * @throws PortletException         if the portlet cannot fulfilling the request
     * @throws UnavailableException     if the portlet is unavailable to perform render at this time
     * @throws PortletSecurityException if the portlet cannot fullfill this request because of security reasons
     * @throws java.io.IOException      if the streaming causes an I/O problem
     */
    public void render(RenderRequest request,
                       RenderResponse response)
            throws PortletException, java.io.IOException {
        response.setTitle(getTitle(request));
        doDispatch(request, response);
    }


    /**
     * Used by the render method to get the title.
     * <p/>
     * The default implementation gets the title from the ResourceBundle
     * of the PortletConfig of the portlet. The title is retrieved
     * using the 'javax.portlet.title' resource name.
     * <p/>
     * Portlets can overwrite this method to provide dynamic
     * titles (e.g. based on locale, client, and session information).
     * Examples are:
     * <UL>
     * <LI>language-dependant titles for multi-lingual portals
     * <LI>shorter titles for WAP phones
     * <LI>the number of messages in a mailbox portlet
     * </UL>
     *
     * @return the portlet title for this window
     */
    protected java.lang.String getTitle(RenderRequest request) {
        return config.getResourceBundle(request.getLocale()).getString("javax.portlet.title");
    }


    /**
     * The default implementation of this method routes the render request
     * to a set of helper methods depending on the current portlet mode the
     * portlet is currently in.
     * These methods are:
     * <ul>
     * <li><code>doView</code> for handling <code>view</code> requests
     * <li><code>doEdit</code> for handling <code>edit</code> requests
     * <li><code>doHelp</code> for handling <code>help</code> requests
     * </ul>
     * <P>
     * If the window state of this portlet is <code>minimized</code>, this
     * method does not invoke any of the portlet mode rendering methods.
     * <p/>
     * For handling custom portlet modes the portlet should override this
     * method.
     *
     * @param request  the render request
     * @param response the render response
     * @throws PortletException         if the portlet cannot fulfilling the request
     * @throws UnavailableException     if the portlet is unavailable to perform render at this time
     * @throws PortletSecurityException if the portlet cannot fullfill this request because of security reasons
     * @throws java.io.IOException      if the streaming causes an I/O problem
     * @see #doView(RenderRequest, RenderResponse)
     * @see #doEdit(RenderRequest, RenderResponse)
     * @see #doHelp(RenderRequest, RenderResponse)
     */
    protected void doDispatch(RenderRequest request,
                              RenderResponse response) throws PortletException, java.io.IOException {
        WindowState state = request.getWindowState();

        if (!state.equals(WindowState.MINIMIZED)) {
            PortletMode mode = request.getPortletMode();
            if (mode.equals(PortletMode.VIEW)) {
                doView(request, response);
            } else if (mode.equals(PortletMode.EDIT)) {
                doEdit(request, response);
            } else if (mode.equals(PortletMode.HELP)) {
                doHelp(request, response);
            } else {
                throw new PortletException("unknown portlet mode: " + mode);
            }
        }

    }


    /**
     * Helper method to serve up the mandatory <code>view</code> mode.
     * <p/>
     * The default implementation throws an exception.
     *
     * @param request  the portlet request
     * @param response the render response
     * @throws PortletException         if the portlet cannot fulfilling the request
     * @throws UnavailableException     if the portlet is unavailable to perform render at this time
     * @throws PortletSecurityException if the portlet cannot fullfill this request because of security reasons
     * @throws java.io.IOException      if the streaming causes an I/O problem
     */

    protected void doView(RenderRequest request,
                          RenderResponse response)
            throws PortletException, java.io.IOException {
        throw new PortletException("doView method not implemented");
    }


    /**
     * Helper method to serve up the <code>edit</code> mode.
     * <p/>
     * The default implementation throws an exception.
     *
     * @param request  the portlet request
     * @param response the render response
     * @throws PortletException         if the portlet cannot fulfilling the request
     * @throws UnavailableException     if the portlet is unavailable to perform render at this time
     * @throws PortletSecurityException if the portlet cannot fullfill this request because of security reasons
     * @throws java.io.IOException      if the streaming causes an I/O problem
     */

    protected void doEdit(RenderRequest request,
                          RenderResponse response)
            throws PortletException, java.io.IOException {
        throw new PortletException("doEdit method not implemented");
    }

    /**
     * Helper method to serve up the <code>help</code> mode.
     * <p/>
     * The default implementation throws an exception.
     *
     * @param request  the portlet request
     * @param response the render response
     * @throws PortletException         if the portlet cannot fulfilling the request
     * @throws UnavailableException     if the portlet is unavailable to perform render at this time
     * @throws PortletSecurityException if the portlet cannot fullfill this request because of security reasons
     * @throws java.io.IOException      if the streaming causes an I/O problem
     */

    protected void doHelp(RenderRequest request,
                          RenderResponse response)
            throws PortletException, java.io.IOException {
        throw new PortletException("doHelp method not implemented");

    }


    /**
     * Returns the PortletConfig object of this portlet.
     *
     * @return the PortletConfig object of this portlet
     */

    public PortletConfig getPortletConfig() {
        return config;
    }


    /**
     * Called by the portlet container to indicate to a portlet that the portlet
     * is being taken out of service.
     * <p/>
     * The default implementation does nothing.
     */

    public void destroy() {
        // do nothing
    }

    //-------------------------------------------------------------------------
    // implement PortletConfig
    //-------------------------------------------------------------------------


    /**
     * Returns the name of this portlet.
     *
     * @return the portlet name
     * @see PortletConfig#getPortletName()
     */

    public String getPortletName() {
        return config.getPortletName();
    }


    /**
     * Returns the <code>PortletContext</code> of the portlet application
     * the portlet is in.
     *
     * @return the portlet application context
     */

    public PortletContext getPortletContext() {
        return config.getPortletContext();
    }


    /**
     * Gets the resource bundle for the given locale based on the
     * resource bundle defined in the deployment descriptor
     * with <code>resource-bundle</code> tag or the inlined resources
     * defined in the deployment descriptor.
     *
     * @return the resource bundle for the given locale
     */

    public java.util.ResourceBundle getResourceBundle(java.util.Locale locale) {
        return config.getResourceBundle(locale);
    }


    /**
     * Returns a String containing the value of the named initialization parameter,
     * or null if the parameter does not exist.
     *
     * @param name a <code>String</code> specifying the name
     *             of the initialization parameter
     * @return		a <code>String</code> containing the value
     * of the initialization parameter
     * @exception	java.lang.IllegalArgumentException if name is <code>null</code>.
     */

    public String getInitParameter(java.lang.String name) {
        return config.getInitParameter(name);
    }


    /**
     * Returns the names of the portlet initialization parameters as an
     * Enumeration of String objects, or an empty Enumeration if the
     * portlet has no initialization parameters.
     *
     * @return		an <code>Enumeration</code> of <code>String</code>
     * objects containing the names of the portlet
     * initialization parameters, or an empty Enumeration if the
     * portlet has no initialization parameters.
     */

    public java.util.Enumeration getInitParameterNames() {
        return config.getInitParameterNames();
    }
}