Lift Framework example source code file (Logging.scala)

This example Lift Framework source code file (Logging.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Lift Framework tags/keywords

anyref, anyref, box, failure, failure, full, logger, marker, marker, string, throwable, throwable, unit, utf-8

The Lift Framework Logging.scala source code

/*
 * Copyright 2010-2011 WorldWide Conferencing, LLC
 *
 * 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 net.liftweb
package common
  
import org.slf4j.{MDC => SLF4JMDC, Marker, Logger => SLF4JLogger, LoggerFactory}

object Logger {
  private[common] lazy val checkConfig: Boolean = {
    setup.foreach {_()}; 
    true
  }
  
  /**
   * This function, if set, will be called before any loggers are created
   * 
   * Useful for initializing the logging backend with a non-default configuration
   * 
   * Helpers exists for log4j & logback:
   * 
   *   Logger.setup = Full(Log4j.withFile(url)
   * 
   * or
   * 
   *   Logger.setup = Full(Logback.withFile(url))
   * 
   */
  var setup: Box[() => Unit] = Empty
  
  def loggerNameFor(cls: Class[_]) = {
    val className = cls.getName
    if (className endsWith "$") 
      className.substring(0, className.length - 1)
    else 
      className
  }

  def apply(cls: Class[_]): Logger = if (checkConfig) new WrappedLogger(LoggerFactory.getLogger(loggerNameFor(cls))) else null
  def apply(name: String): Logger = if (checkConfig) new WrappedLogger(LoggerFactory.getLogger(name)) else null
  
 /**
   * Set the Mapped Diagnostic Context for the thread and execute
   * the function f
   *
   * Upon return, the MDC is cleared of the values passed (any
   * MDC values that existed prior to this call remains)
   */
  def logWith[F](mdcValues: (String,Any)*)(f: => F): F = {
    val old = SLF4JMDC.getCopyOfContextMap
    MDC.put(mdcValues:_*)
    try {
      f
    } finally {
      if (old eq null) 
        MDC.clear
      else  
        SLF4JMDC.setContextMap(old)
    }
  }
}

/**
 * The Mapped Diagnostics Context can hold values per thread and output them
 * with each logged output.
 * 
 * The logging backend needs to be configured to log these values
 */
object MDC {
  /**
   * Put a (key,value) pair into the Mapped Diagnostic Context
   */
  def put(kvs: (String,Any)*) = {
    kvs foreach {v => SLF4JMDC.put(v._1, v._2.toString)}
  }

  /**
   * Clear key from the Mapped Diagnostic Context
   */
  def remove(keys: String*) = {
    keys foreach {k => SLF4JMDC.remove(k)}
  }

  /**
   * Clear all entries from the Mapped Diagnostic Context
   */
  def clear() = org.slf4j.MDC.clear
}

/**
 * Logger is a thin wrapper on top of an SLF4J Logger
 *
 * The main purpose is to utilize Scala features for logging
 * 
 * Note that the dynamic type of "this" is used when this trait is
 * mixed in. 
 * 
 * This may not always be what you want. If you need the static type, you have to declare your
 * own Logger:
 * 
 * class MyClass {
 *   val logger = Logger(classOf[MyClass])
 * }
 * 
 */
trait Logger  {
  private lazy val logger: SLF4JLogger = _logger // removed @transient 'cause there's no reason for transient on val
  // changed to lazy val so it only gets initialized on use rather than on instantiation
  protected def _logger = if (Logger.checkConfig) LoggerFactory.getLogger(Logger.loggerNameFor(this.getClass)) else null
  
  def assertLog(assertion: Boolean, msg: => String) = if (assertion) info(msg)

  /**
   * Log the value of v with trace and return v. Useful for tracing values in expressions
   */
  def trace[T](msg: String, v: T): T = {
    logger.trace(msg+": "+v.toString)
    v
  }
 
  /**
   * Trace a Failure.  If the log level is trace and the Box is
   * a Failure, trace the message concatenated with the Failure's message.
   * If the Failure contains an Exception, trace that as well.
   */
  def trace(msg: => AnyRef, box: Box[_]): Unit = {
    if (logger.isTraceEnabled) {
      box match {
        case Failure(fmsg, Full(e), _) => trace(String.valueOf(msg)+": "+
                                                fmsg: AnyRef, e: Throwable)
        case Failure(fmsg, _, _) => trace(String.valueOf(msg)+": "+fmsg)
        case _ =>
      }
    }
  }


  def trace(msg: => AnyRef) = if (logger.isTraceEnabled) logger.trace(String.valueOf(msg))
  def trace(msg: => AnyRef, t: Throwable) = if (logger.isTraceEnabled) logger.trace(String.valueOf(msg), t)
  def trace(msg: => AnyRef, marker:  Marker) = if (logger.isTraceEnabled) logger.trace(marker,String.valueOf(msg))
  def trace(msg: => AnyRef, t: Throwable, marker: => Marker) = if (logger.isTraceEnabled) logger.trace(marker,String.valueOf(msg), t)
  def isTraceEnabled = logger.isTraceEnabled

  /**
   * Debug a Failure.  If the log level is debug and the Box is
   * a Failure, debug the message concatenated with the Failure's message.
   * If the Failure contains an Exception, debug that as well.
   */
  def debug(msg: => AnyRef, box: Box[_]): Unit = {
    if (logger.isDebugEnabled) {
      box match {
        case Failure(fmsg, Full(e), _) => debug(String.valueOf(msg)+": "+
                                                fmsg, e)
        case Failure(fmsg, _, _) => debug(String.valueOf(msg)+": "+fmsg)
        case _ =>
      }
    }
  }
 
  
  def debug(msg: => AnyRef) = if (logger.isDebugEnabled) logger.debug(String.valueOf(msg))
  def debug(msg: => AnyRef, t:  Throwable) = if (logger.isDebugEnabled) logger.debug(String.valueOf(msg), t)
  def debug(msg: => AnyRef, marker: Marker) = if (logger.isDebugEnabled) logger.debug(marker, String.valueOf(msg))
  def debug(msg: => AnyRef, t: Throwable, marker: Marker) = if (logger.isDebugEnabled) logger.debug(marker, String.valueOf(msg), t)
  def isDebugEnabled = logger.isDebugEnabled
  
  /**
   * Info a Failure.  If the log level is info and the Box is
   * a Failure, info the message concatenated with the Failure's message.
   * If the Failure contains an Exception, info that as well.
   */
  def info(msg: => AnyRef, box: Box[_]): Unit = {
    if (logger.isInfoEnabled) {
      box match {
        case Failure(fmsg, Full(e), _) => info(String.valueOf(msg)+": "+
                                                fmsg, e)
        case Failure(fmsg, _, _) => info(String.valueOf(msg)+": "+fmsg)
        case _ =>
      }
    }
  }
  def info(msg: => AnyRef) = if (logger.isInfoEnabled) logger.info(String.valueOf(msg))
  def info(msg: => AnyRef, t: => Throwable) = if (logger.isInfoEnabled) logger.info(String.valueOf(msg), t)
  def info(msg: => AnyRef, marker: Marker) = if (logger.isInfoEnabled) logger.info(marker,String.valueOf(msg))
  def info(msg: => AnyRef, t: Throwable, marker: Marker) = if (logger.isInfoEnabled) logger.info(marker,String.valueOf(msg), t)
  def isInfoEnabled = logger.isInfoEnabled
  
  /**
   * Warn a Failure.  If the log level is warn and the Box is
   * a Failure, warn the message concatenated with the Failure's message.
   * If the Failure contains an Exception, warn that as well.
   */
  def warn(msg: => AnyRef, box: Box[_]): Unit = {
    if (logger.isWarnEnabled) {
      box match {
        case Failure(fmsg, Full(e), _) => warn(String.valueOf(msg)+": "+
                                                fmsg, e)
        case Failure(fmsg, _, _) => warn(String.valueOf(msg)+": "+fmsg)
        case _ =>
      }
    }
  }
  def warn(msg: => AnyRef) = if (logger.isWarnEnabled) logger.warn(String.valueOf(msg))
  def warn(msg: => AnyRef, t: Throwable) = if (logger.isWarnEnabled) logger.warn(String.valueOf(msg), t)
  def warn(msg: => AnyRef, marker: Marker) = if (logger.isWarnEnabled) logger.warn(marker,String.valueOf(msg))
  def warn(msg: => AnyRef, t: Throwable, marker: Marker) = if (logger.isWarnEnabled) logger.warn(marker,String.valueOf(msg), t)
  def isWarnEnabled = logger.isWarnEnabled
  
  /**
   * Error a Failure.  If the log level is error and the Box is
   * a Failure, error the message concatenated with the Failure's message.
   * If the Failure contains an Exception, error that as well.
   */
  def error(msg: => AnyRef, box: Box[_]): Unit = {
    if (logger.isErrorEnabled) {
      box match {
        case Failure(fmsg, Full(e), _) => error(String.valueOf(msg)+": "+
                                                fmsg, e)
        case Failure(fmsg, _, _) => error(String.valueOf(msg)+": "+fmsg)
        case _ =>
      }
    }
  }

  def error(msg: => AnyRef) = if (logger.isErrorEnabled) logger.error(String.valueOf(msg))
  def error(msg: => AnyRef, t: Throwable) = if (logger.isErrorEnabled) logger.error(String.valueOf(msg), t)
  def error(msg: => AnyRef, marker: Marker) = if (logger.isErrorEnabled) logger.error(marker,String.valueOf(msg))
  def error(msg: => AnyRef, t: Throwable, marker: Marker) = if (logger.isErrorEnabled) logger.error(marker,String.valueOf(msg), t)
  def isErrorEnabled = logger.isErrorEnabled
  
}

class WrappedLogger(l: SLF4JLogger) extends Logger {
  override def _logger = l
}

/**
 * Mixin with a nested Logger
 */
trait Loggable {
  @transient protected val logger = Logger(this.getClass)
}

/**
 * Mixin with a nested lazy Logger
 * 
 * Useful for mixin to objects that are created before Lift has booted (and thus Logging is not yet configured)
 */
trait LazyLoggable {
  @transient protected lazy val logger = Logger(this.getClass)
}

/**
 * Configuration helpers for the log4j logging backend
 */
object Log4j {
  import org.apache.log4j.{LogManager,PropertyConfigurator}
  import org.apache.log4j.xml.DOMConfigurator
  
  val defaultProps =
    """<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
    <log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
    <appender name="appender" class="org.apache.log4j.ConsoleAppender">
    <layout class="org.apache.log4j.SimpleLayout"/>
    </appender>
    <root>
    <priority value ="INFO"/>
    <appender-ref ref="appender"/>
    </root>
    </log4j:configuration>
    """
  
  /**
   * Configure with contents of the specified filed (either .xml or .properties)
   */
  def withFile(url: java.net.URL)() = {
    if (url.getPath.endsWith(".xml")) {
      val domConf = new DOMConfigurator
      domConf.doConfigure(url, LogManager.getLoggerRepository())
    } else 
      PropertyConfigurator.configure(url)
  }
  /**
   * Configure with the specified configuration. config must contain a valid XML document
   */
  def withConfig(config: String)() = {
    val domConf = new DOMConfigurator
    val is = new java.io.ByteArrayInputStream(config.getBytes("UTF-8"))
    domConf.doConfigure(is, LogManager.getLoggerRepository())
  }
  
  /**
   * Configure with simple defaults
   */
  def withDefault() = withConfig(defaultProps)
}

/**
 * Configuration helpers for the Logback logging backend
 */
object Logback  {
  import ch.qos.logback.classic.LoggerContext;
  import ch.qos.logback.core.util.StatusPrinter;
  import ch.qos.logback.classic.joran.JoranConfigurator;

  /**
   * Configure with contents of the specified XML filed 
   */
  def withFile(url: java.net.URL)() = {
    val lc = LoggerFactory.getILoggerFactory().asInstanceOf[LoggerContext];
    val configurator = new JoranConfigurator();
    configurator.setContext(lc);
    // the context was probably already configured by default configuration rules
    lc.reset(); 
    configurator.doConfigure(url);
  }
}