genericfilterbean.java

spring的源代码

/*
 * Copyright 2002-2004 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.filter;

import java.util.ArrayList;
import java.util.List;

import javax.servlet.Filter;
import javax.servlet.FilterConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.beans.BeanWrapper;
import org.springframework.beans.BeanWrapperImpl;
import org.springframework.beans.BeansException;
import org.springframework.beans.PropertyValues;

/**
 * Simple base implementation of javax.servlet.Filter that treats its config
 * parameters as bean properties. A very handy superclass for any type of filter.
 * Type conversion is automatic. It is also possible for subclasses to specify
 * required properties.
 *
 * <p>This filter leaves actual filtering to subclasses.
 *
 * @author Juergen Hoeller
 * @since 06.12.2003
 * @see #initFilterBean
 */
public abstract class GenericFilterBean implements Filter {

	protected final Log logger = LogFactory.getLog(getClass());

	/**
	 * May be null. List of required properties (Strings) that must
	 * be supplied as config parameters to this servlet.
	 */
	private List requiredProperties = new ArrayList();

	/* The FilterConfig of this filter */
	private FilterConfig filterConfig;

	/**
	 * Subclasses can invoke this method to specify that this property
	 * (which must match a JavaBean property they expose) is mandatory,
	 * and must be supplied as a config parameter.
	 * @param property name of the required property
	 */
	protected final void addRequiredProperty(String property) {
		requiredProperties.add(property);
	}

	/**
	 * Map config parameters onto bean properties of this filter, and
	 * invoke subclass initialization.
	 * @throws ServletException if bean properties are invalid (or required
	 * properties are missing), or if subclass initialization fails.
	 * @see #initFilterBean
	 */
	public final void init(FilterConfig filterConfig) throws ServletException {
		logger.info("Initializing filter '" + filterConfig.getFilterName() + "'");
		this.filterConfig = filterConfig;

		// set bean properties
		try {
			PropertyValues pvs = new FilterConfigPropertyValues(filterConfig, this.requiredProperties);
			BeanWrapper bw = new BeanWrapperImpl(this);
			bw.setPropertyValues(pvs);
		}
		catch (BeansException ex) {
			String msg = "Failed to set bean properties on filter '" + filterConfig.getFilterName() + "': " + ex.getMessage();
			logger.error(msg, ex);
			throw new ServletException(msg, ex);
		}

		// let subclasses do whatever initialization they like
		initFilterBean();
		logger.info("Filter '" + filterConfig.getFilterName() + "' configured successfully");
	}

	/**
	 * Make the FilterConfig of this filter available to subclasses.
	 * Analogous to GenericServlet's getServletConfig.
	 * @see javax.servlet.GenericServlet#getServletConfig
	 */
	protected final FilterConfig getFilterConfig() {
		return this.filterConfig;
	}

	/**
	 * Make the name of this filter available to subclasses.
	 * Analogous to GenericServlet's getServletName.
	 * @see javax.servlet.GenericServlet#getServletName
	 */
	protected final String getFilterName() {
		return this.filterConfig.getFilterName();
	}

	/**
	 * Make the ServletContext of this filter available to subclasses.
	 * Analogous to GenericServlet's getServletContext.
	 * @see javax.servlet.GenericServlet#getServletContext
	 */
	protected final ServletContext getServletContext() {
		return this.filterConfig.getServletContext();
	}

	/**
	 * Subclasses may override this to perform custom initialization.
	 * All bean properties of this servlet will have been set before this
	 * method is invoked. This default implementation does nothing.
	 * @throws ServletException if subclass initialization fails
	 */
	protected void initFilterBean() throws ServletException {
	}

	/**
	 * Subclasses may override this to perform custom filter shutdown.
	 * This default implementation does nothing.
	 */
	public void destroy() {
	}

}