filedecoratormapper.java

OS(OpenSymphony)的SiteMesh是一个用来在JSP中实现页面布局和装饰（layout and decoration）的框架组件

/*
 * Title:        FileDecoratorMapper
 * Description:
 *
 * This software is published under the terms of the OpenSymphony Software
 * License version 1.1, of which a copy has been included with this
 * distribution in the LICENSE.txt file.
 */

package com.opensymphony.module.sitemesh.mapper;

import com.opensymphony.module.sitemesh.Decorator;

import java.io.File;
import java.net.MalformedURLException;
import java.net.URL;
import javax.servlet.http.HttpServletRequest;

/**
 * The FileDecoratorMapper will treat the name of the decorator as a file-name to use
 * (in the context of the web-app).
 *
 * @author <a href="[e-mail]">Joe Walnes</a>
 * @author <a href="[e-mail]">Mike Cannon-Brookes</a>
 * @version $Revision: 1.3 $
 *
 * @see com.opensymphony.module.sitemesh.DecoratorMapper
 * @see com.opensymphony.module.sitemesh.mapper.DefaultDecorator
 */
public class FileDecoratorMapper extends AbstractDecoratorMapper {
    private boolean pathNotAvailable = false;

    public Decorator getNamedDecorator(HttpServletRequest req, String name) {
        if (pathNotAvailable || name == null) {
            return super.getNamedDecorator(req, name);
        }

        URL resourcePath;

        // try to locate the resource (might be an unexpanded WAR)
        try  {
            resourcePath = config.getServletContext().getResource('/' + name);
        }
        catch (MalformedURLException e) {
            return super.getNamedDecorator(req, name);
        }

        String filePath = config.getServletContext().getRealPath(name);

        if (filePath == null && resourcePath == null) {
            pathNotAvailable = true;
            return super.getNamedDecorator(req, name);
        }
        else if (filePath != null) { // do we really need this disk file check?!
            File file = new File(filePath);

            if (file.exists() && file.canRead() && file.isFile()) {
                // if filename exists with name of supplied decorator, return Decorator
                return new DefaultDecorator(name, name, null);
            }
            else {
                // otherwise delegate to parent mapper.
                return super.getNamedDecorator(req, name);
            }
        }
        else {
            // file path is null and resource path is not null - can't check file on disk
            return new DefaultDecorator(name, name, null);
        }
    }
}