servletlogger.java

一个用于java web页面开发的开源包

package org.apache.velocity.tools.view.servlet;

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */

import javax.servlet.ServletContext;

import org.apache.velocity.runtime.log.LogSystem;
import org.apache.velocity.runtime.RuntimeConstants;
import org.apache.velocity.runtime.RuntimeServices;


/**
 * Simple wrapper for the servlet log.  This has Velocity log
 * messages to ServletContext.log(String).
 *
 * @author <a href="mailto:[e-mail]">Geir Magnusson Jr.</a>
 * @version $Revision: 477914 $ $Date: 2006-11-21 13:52:11 -0800 (Tue, 21 Nov 2006) $
 */
public class ServletLogger implements LogSystem
{
    protected ServletContext servletContext = null;

    public static final String PREFIX = " Velocity ";

    /**
     * Construct a simple logger for a servlet environment.
     * <br>
     * NOTE: this class expects that the ServletContext has already
     *       been placed in the runtime's application attributes
     *       under its full class name (i.e. "javax.servlet.ServletContext").
     */
    public ServletLogger()
    {
    }

    /**
     * init()
     *
     * @throws IllegalStateException if the ServletContext is not available
     *         in the application attributes under the appropriate key.
     */
    public void init( RuntimeServices rs )
        throws Exception
    {
        Object obj = rs.getApplicationAttribute(ServletContext.class.getName());
        if (obj == null)
        {
            throw new IllegalStateException("Could not retrieve ServletContext from application attributes!");
        }
        servletContext = (ServletContext)obj;
    }

    /**
     * Send a log message from Velocity.
     */
    public void logVelocityMessage(int level, String message)
    {
        switch (level)
        {
            case LogSystem.WARN_ID:
                servletContext.log( PREFIX + RuntimeConstants.WARN_PREFIX + message );
                break;
            case LogSystem.INFO_ID:
                servletContext.log( PREFIX + RuntimeConstants.INFO_PREFIX + message);
                break;
            case LogSystem.DEBUG_ID:
                servletContext.log( PREFIX + RuntimeConstants.DEBUG_PREFIX + message);
                break;
            case LogSystem.ERROR_ID:
                servletContext.log( PREFIX + RuntimeConstants.ERROR_PREFIX + message);
                break;
            default:
                servletContext.log( PREFIX + " : " + message);
                break;
        }
    }

}