edu.cornell.mannlib.oce.startup.LogFileAdjuster.java Source code

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Here is the source code for edu.cornell.mannlib.oce.startup.LogFileAdjuster.java

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/* $This file is distributed under the terms of the license in /doc/license.txt$ */

package edu.cornell.mannlib.oce.startup;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Map;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.log4j.Appender;
import org.apache.log4j.FileAppender;
import org.apache.log4j.Logger;

/**
 * TODO
 */
public class LogFileAdjuster {
    private static final Log log = LogFactory.getLog(LogFileAdjuster.class);

    private enum SpecialLog {
        SUCCESS("logfile.success", "SuccessAppender"),

        PROBLEM("logfile.problem", "ProblemAppender");

        final String settingsKey;
        final String appenderName;

        private SpecialLog(String settingsKey, String appenderName) {
            this.settingsKey = settingsKey;
            this.appenderName = appenderName;
        }
    }

    private final Map<String, String> settings;

    LogFileAdjuster(Map<String, String> settings) {
        this.settings = settings;
    }

    /**
     * If settings are provide for the SUCCESS and PROBLEM log files,
     */
    void setupLogging() {
        adjustLog(SpecialLog.SUCCESS);
        adjustLog(SpecialLog.PROBLEM);
    }

    /**
     * If they have a setting for the log file, verify that it is valid, and
     * adjust the logger to write to it.
     */
    private void adjustLog(SpecialLog specialLog) {
        try {
            String logFile = getLogFileSetting(specialLog);
            validateLogFileSetting(specialLog, logFile);

            FileAppender fileAppender = locateAppender(specialLog);

            fileAppender.setFile(logFile);
            fileAppender.activateOptions();

            log.info("Redirected " + specialLog + " logger to '" + logFile + "'");
            return;
        } catch (LogAdjustmentException e) {
            if (e.getCause() == null) {
                log.warn(e.getMessage());
            } else {
                log.warn(e.getMessage(), e.getCause());
            }
        }
    }

    /**
     * Get the log file setting, or complain if it's not there.
     */
    private String getLogFileSetting(SpecialLog specialLog) throws LogAdjustmentException {
        String setting = settings.get(specialLog.settingsKey);
        if (setting == null) {
            throw new LogAdjustmentException(
                    "No setting for the " + specialLog + " log file, '" + specialLog.settingsKey + "'");
        }
        return setting;
    }

    /**
     * Confirm that the log file will go into an existing directory, and that
     * either it does exist, or we can create it. Should also be writeable.
     */
    private void validateLogFileSetting(SpecialLog specialLog, String logFile) throws LogAdjustmentException {
        Path path = Paths.get(logFile);
        if (!Files.exists(path.getParent())) {
            throw new LogAdjustmentException("Cannot create " + specialLog + " log file '" + logFile
                    + "', parent directory does not exist.");
        }

        if (!Files.exists(path)) {
            try {
                Files.createFile(path);
            } catch (IOException e) {
                throw new LogAdjustmentException("Failed to create " + specialLog + " log file '" + path + "'", e);
            }
        }

        if (!Files.isWritable(path)) {
            throw new LogAdjustmentException(
                    "Cannot write to log file '" + logFile + "' for " + specialLog + " log.");
        }
    }

    /**
     * Locate the logger for this category and find the expected Appender. If
     * it's not there, or is not a FileAppender, complain.
     */
    private FileAppender locateAppender(SpecialLog specialLog) throws LogAdjustmentException {
        Logger logger = Logger.getLogger(specialLog.name());

        Appender appender = logger.getAppender(specialLog.appenderName);
        if (appender == null) {
            throw new LogAdjustmentException("Failed to redirect logger " + "for category  " + specialLog
                    + ". Logger does not have an appender named '" + specialLog.appenderName + "'.");
        }

        if (!(appender instanceof FileAppender)) {
            throw new LogAdjustmentException("Can't redirect logger for category  " + specialLog + ". Appender '"
                    + specialLog.appenderName + "' is not a FileAppender.");
        }

        FileAppender fileAppender = (FileAppender) appender;
        return fileAppender;
    }

    /**
     * Indicates a problem with adjusting one of the special logs.
     */
    private static class LogAdjustmentException extends Exception {
        LogAdjustmentException(String message) {
            super(message);
        }

        LogAdjustmentException(String message, Throwable cause) {
            super(message, cause);
        }
    }

}