edu.vt.middleware.gator.log4j.Log4jConfigUtils.java Source code

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Here is the source code for edu.vt.middleware.gator.log4j.Log4jConfigUtils.java

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/*
  $Id: Log4jConfigUtils.java 1421 2010-06-25 16:43:59Z dfisher $
    
  Copyright (C) 2009-2010 Virginia Tech.
  All rights reserved.
    
  SEE LICENSE FOR MORE INFORMATION
    
  Author:  Middleware Services
  Email:   middleware@vt.edu
  Version: $Revision: 1421 $
  Updated: $Date: 2010-06-25 12:43:59 -0400 (Fri, 25 Jun 2010) $
*/
package edu.vt.middleware.gator.log4j;

import edu.vt.middleware.gator.AppenderConfig;
import edu.vt.middleware.gator.ParamConfig;
import edu.vt.middleware.gator.ProjectConfig;
import edu.vt.middleware.gator.server.ConfigurationException;
import edu.vt.middleware.gator.util.FileHelper;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.log4j.Appender;
import org.apache.log4j.Layout;
import org.apache.log4j.config.PropertySetter;
import org.apache.log4j.spi.ErrorHandler;
import org.apache.log4j.spi.OptionHandler;

/**
 * Utility class with static methods to create and configure log4j configuration
 * objects.
 *
 * @author  Middleware Services
 * @version  $Revision: 1421 $
 */
public final class Log4jConfigUtils {

    /** Logger instance. */
    private static final Log LOGGER = LogFactory.getLog(Log4jConfigUtils.class);

    /** Default protected constructor of utility class. */
    protected Log4jConfigUtils() {
    }

    /**
     * Creates a Log4j appender from an {@link AppenderConfig} domain object.
     *
     * @param  project  Project configuration to which appender belongs.
     * @param  appenderCfg  Source of appender configuration.
     * @param  rootDirectory  Full path to appender root directory.
     *
     * @return  Log4j appender that is semantically simlar to given appender
     * configuration.
     *
     * @throws  ConfigurationException  On configuration errors.
     */
    public static Appender toLog4jAppender(final ProjectConfig project, final AppenderConfig appenderCfg,
            final String rootDirectory) throws ConfigurationException {
        if (appenderCfg.getAppenderClassName() == null) {
            throw new ConfigurationException("Appender class name required.");
        }
        if (appenderCfg.getName() == null) {
            throw new ConfigurationException("Appender name required.");
        }

        final Appender appender = instantiate(Appender.class, appenderCfg.getAppenderClassName());
        appender.setName(appenderCfg.getName());
        if (appenderCfg.getErrorHandlerClassName() != null) {
            final ErrorHandler errHandler = instantiate(ErrorHandler.class, appenderCfg.getErrorHandlerClassName());
            activate(errHandler);
            appender.setErrorHandler(errHandler);
        }
        if (appenderCfg.getLayoutClassName() != null) {
            final Layout layout = instantiate(Layout.class, appenderCfg.getLayoutClassName());
            for (ParamConfig param : appenderCfg.getLayoutParams()) {
                setProperty(layout, param.getName(), param.getValue());
            }
            activate(layout);
            appender.setLayout(layout);
        }
        for (ParamConfig param : appenderCfg.getAppenderParams()) {
            // Check for the "file" property of FileAppender and subclasses
            // and prefix path with clientRootLogDirectory
            String value = param.getValue();
            if (param.getName().equalsIgnoreCase("file")) {
                value = FileHelper.pathCat(rootDirectory, project.getName(), value);
            }
            setProperty(appender, param.getName(), value);
        }
        activate(appender);
        return appender;
    }

    /**
     * Instantiate a new instance of the given class name.
     *
     * @param  <T>  Type of class to instantiate.
     * @param  clazz  Class of type to instantiate.
     * @param  name  Fully-qualified class name.
     *
     * @return  New instance of specified class.
     *
     * @throws  ConfigurationException  On configuration errors.
     */
    public static <T> T instantiate(final Class<T> clazz, final String name) throws ConfigurationException {
        Class<?> c;
        try {
            LOGGER.trace("Instantiating new instance of " + name);
            c = Class.forName(name);
        } catch (ClassNotFoundException e) {
            throw new ConfigurationException(String.format("Class %s not found.", name));
        }
        try {
            return clazz.cast(c.newInstance());
        } catch (InstantiationException e) {
            throw new ConfigurationException(String.format("Cannot instantiate %s.", name), e);
        } catch (IllegalAccessException e) {
            throw new ConfigurationException(
                    String.format("Cannot instantiate %s -- constructor not accessible.", name), e);
        } catch (ClassCastException e) {
            throw new ConfigurationException(String.format("%s is not an instance of %s", name, clazz), e);
        }
    }

    /**
     * Sets the value of a property on a target object. Property setter is
     * expected to follow JavaBean naming convention.
     *
     * @param  target  Target of setter invocation.
     * @param  property  Name of property to set. Without "set" prefix.
     * @param  value  Property value.
     *
     * @throws  ConfigurationException  On configuration errors.
     */
    public static void setProperty(final Object target, final String property, final String value)
            throws ConfigurationException {
        final PropertySetter ps = new PropertySetter(target);
        LOGGER.trace(String.format("Setting property %s on instance of %s", property, target.getClass()));
        ps.setProperty(property, value);
    }

    /**
     * Activates any log4j object that implements {@link OptionHandler} by calling
     * the {@link OptionHandler#activateOptions()} method.
     *
     * @param  o  Object that possibly implements {@link OptionHandler}.
     */
    public static void activate(final Object o) {
        if (o instanceof OptionHandler) {
            ((OptionHandler) o).activateOptions();
        }
    }
}