basefactory.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:        BaseFactory
 * 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.factory;

import com.opensymphony.module.sitemesh.Config;
import com.opensymphony.module.sitemesh.DecoratorMapper;
import com.opensymphony.module.sitemesh.Factory;
import com.opensymphony.module.sitemesh.PageParser;
import com.opensymphony.module.sitemesh.util.ClassLoaderUtil;
import com.opensymphony.module.sitemesh.mapper.PathMapper;

import java.util.HashMap;
import java.util.Map;
import java.util.Properties;

/**
 * Base Factory implementation. Provides utility methods for implementation.
 *
 * @author <a href="mailto:[e-mail]">Joe Walnes</a>
 * @version $Revision: 1.9 $
 */
public abstract class BaseFactory extends Factory {
    /** ServletConfig or FilterConfig. */
    protected Config config = null;

    /**
     * Instance of {@link com.opensymphony.module.sitemesh.DecoratorMapper}.
     * Because it is thread-safe, it can be shared by multiple clients. This
     * is only the last DecoratorMapper in the chain, and all parents will be
     * automatically delegated to it.
     */
    protected DecoratorMapper decoratorMapper = null;

    /** Map that associates content-types with PageParser instances. */
    protected Map pageParsers = null;

    /** A map of paths that are excluded from decoration */
    protected PathMapper excludeUrls = null;

    /**
     * Constructor for default implementation of Factory.
     * Should never be called by client. Singleton instance should be
     * obtained instead.
     *
     * @see #getInstance(com.opensymphony.module.sitemesh.Config config)
     */
    protected BaseFactory(Config config) {
        this.config = config;
        clearDecoratorMappers();
        clearParserMappings();
        clearExcludeUrls();
    }

    /** Return instance of DecoratorMapper. */
    public DecoratorMapper getDecoratorMapper() {
        return decoratorMapper;
    }

    /**
     * Create a PageParser suitable for the given content-type.
     *
     * <p>For example, if the supplied parameter is <code>text/html</code>
     * a parser shall be returned that can parse HTML accordingly. Returns
     * null if no parser can be found for the supplied content type.</p>
     *
     * @param contentType The MIME content-type of the data to be parsed
     * @return Appropriate <code>PageParser</code> for reading data, or
     * <code>null</code> if no suitable parser was found.
     */
    public PageParser getPageParser(String contentType) {
        return (PageParser) pageParsers.get(contentType);
    }

    /**
     * Determine whether a Page of given content-type should be parsed or not.
     */
    public boolean shouldParsePage(String contentType) {
        return pageParsers.containsKey(contentType);
    }

    /**
     * Returns <code>true</code> if the supplied path matches one of the exclude
     * URLs specified in sitemesh.xml, otherwise returns <code>false</code>.
     * @param path
     * @return whether the path is excluded
     */
    public boolean isPathExcluded(String path) {
        return excludeUrls.get(path) != null;
    }

    /**
     * Clear all current DecoratorMappers.
     */
    protected void clearDecoratorMappers() {
        decoratorMapper = null;
    }

    /** Push new DecoratorMapper onto end of chain. */
    protected void pushDecoratorMapper(String className, Properties properties) {
        try {
            Class decoratorMapperClass = ClassLoaderUtil.loadClass(className, getClass());
            DecoratorMapper newMapper = getDecoratorMapper(decoratorMapperClass);
            newMapper.init(config, properties, decoratorMapper);
            decoratorMapper = newMapper;
        }
        catch (ClassNotFoundException e) {
            throw new FactoryException("Could not load DecoratorMapper class : " + className, e);
        }
        catch (Exception e) {
            throw new FactoryException("Could not initialize DecoratorMapper : " + className, e);
        }
    }

	protected DecoratorMapper getDecoratorMapper(Class decoratorMapperClass) throws InstantiationException, IllegalAccessException {
		return (DecoratorMapper) decoratorMapperClass.newInstance();
	}

	/** Clear all PageParser mappings. */
    protected void clearParserMappings() {
        pageParsers = new HashMap();
    }

    /**
     * Map new PageParser to given content-type. contentType = null signifies default
     * PageParser for unknown content-types.
     */
    protected void mapParser(String contentType, String className) {
        if (className.endsWith(".DefaultPageParser")) {
            return; // Backwards compatability - this can safely be ignored.
        }
        try {
            PageParser pp = (PageParser) ClassLoaderUtil.loadClass(className, getClass()).newInstance();
            // Store the parser even if the content type is NULL. [This
            // is most probably the legacy default page parser which
            // we no longer have a use for]
            pageParsers.put(contentType, pp);
        }
        catch (ClassNotFoundException e) {
            throw new FactoryException("Could not load PageParser class : " + className, e);
        }
        catch (Exception e) {
            throw new FactoryException("Could not instantiate PageParser : " + className, e);
        }
    }

    protected void addExcludeUrl(String path) {
        excludeUrls.put("", path);
    }

    /**
     * Clears all exclude URLs.
     */
    protected void clearExcludeUrls() {
        excludeUrls = new PathMapper();
    }

}