com.excilys.ebi.utils.spring.log.logback.web.LogbackWebConfigurer.java Source code

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Here is the source code for com.excilys.ebi.utils.spring.log.logback.web.LogbackWebConfigurer.java

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/**
 * Copyright 2011-2012 eBusiness Information, Groupe Excilys (www.excilys.com)
 *
 * 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 com.excilys.ebi.utils.spring.log.logback.web;

import java.io.FileNotFoundException;

import javax.servlet.ServletContext;

import org.springframework.util.ResourceUtils;
import org.springframework.util.SystemPropertyUtils;
import org.springframework.web.util.WebUtils;

import ch.qos.logback.core.joran.spi.JoranException;

import com.excilys.ebi.utils.spring.log.logback.LogbackConfigurer;

/**
 * Convenience class that performs custom Logback initialization for web
 * environments, allowing for log file paths within the web application,
 * inspired by {@link org.springframework.web.util.Log4jWebConfigurer}.
 * <p>
 * Supports an init parameter at the servlet context level (that is,
 * context-param entries in web.xml):
 * <ul>
 * <li><i>"logbackConfigLocation":</i><br>
 * Location of the Logback config file; either a "classpath:" location (e.g.
 * "classpath:myLogback.xml"), an absolute file URL (e.g.
 * "file:C:/logback.properties), or a plain path relative to the web application
 * root directory (e.g. "/WEB-INF/logback.xml"). If not specified, default
 * Logback initialization will apply ("logback.xml" or "logback-test.xml" in the
 * class path; see Logback documentation for details).
 * </ul>
 * <p>
 * Note: <code>initLogging</code> should be called before any other Spring
 * activity (when using Logback), for proper initialization before any Spring
 * logging attempts.
 * <p>
 * 
 * @author <a href="mailto:slandelle@excilys.com">Stephane LANDELLE</a>
 */
public final class LogbackWebConfigurer {

    /** Parameter specifying the location of the logback config file. */
    public static final String CONFIG_LOCATION_PARAM = "logbackConfigLocation";

    /**
     * Instantiates a new logback web configurer.
     */
    private LogbackWebConfigurer() {
    }

    /**
     * Initialize Logback, including setting the web app root system property.
     * 
     * @param servletContext
     *            the current ServletContext
     * @see org.springframework.web.util.WebUtils#setWebAppRootSystemProperty
     */
    public static void initLogging(ServletContext servletContext) {

        // Only perform custom Logback initialization in case of a config file.
        String location = getConfigLocation(servletContext);

        if (location != null) {
            // Perform actual Logback initialization; else rely on Logback's
            // default initialization.
            try {
                // Return a URL (e.g. "classpath:" or "file:") as-is;
                // consider a plain file path as relative to the web application
                // root directory.
                if (!ResourceUtils.isUrl(location)) {
                    // Resolve system property placeholders before resolving
                    // real path.
                    location = SystemPropertyUtils.resolvePlaceholders(location);
                    location = WebUtils.getRealPath(servletContext, location);
                }

                // Write log message to server log.
                servletContext.log("Initializing Logback from [" + location + "]");

                // Initialize
                LogbackConfigurer.initLogging(location);
            } catch (FileNotFoundException ex) {
                throw new IllegalArgumentException("Invalid 'logbackConfigLocation' parameter: " + ex.getMessage());
            } catch (JoranException e) {
                throw new RuntimeException("Unexpected error while configuring logback", e);
            }
        }
    }

    /**
     * Search for a specified config location, first in the servlet context and
     * then as a System property
     * 
     * @param servletContext
     *            the servletContext
     * @return the config location
     */
    private static String getConfigLocation(ServletContext servletContext) {
        String location = servletContext.getInitParameter(CONFIG_LOCATION_PARAM);
        if (location == null) {
            location = System.getProperty(CONFIG_LOCATION_PARAM);
        }
        return location;
    }

    /**
     * Shut down Logback, properly releasing all file locks and resetting the
     * web app root system property.
     * 
     * @param servletContext
     *            the current ServletContext
     * @see WebUtils#removeWebAppRootSystemProperty
     */
    public static void shutdownLogging(ServletContext servletContext) {
        servletContext.log("Shutting down Logback");
        LogbackConfigurer.shutdownLogging();
    }
}