slf4j-ext/src/main/java/org/slf4j/ext/XLogger.java

package org.slf4j.ext;

import org.slf4j.Logger;
import org.slf4j.Marker;
import org.slf4j.MarkerFactory;
import org.slf4j.helpers.MessageFormatter;
import org.slf4j.spi.LocationAwareLogger;

/**
 * A utility that provides standard mechanisms for logging certain kinds of
 * activities.
 * 
 * @author Ralph Goers
 * @author Ceki Gülcü
 */
public class XLogger extends LoggerWrapper implements Logger {

  private static final String FQCN = XLogger.class.getName();
  static Marker FLOW_MARKER = MarkerFactory.getMarker("FLOW");
  static Marker ENTRY_MARKER = MarkerFactory.getMarker("ENTRY");
  static Marker EXIT_MARKER = MarkerFactory.getMarker("EXIT");

  static Marker EXCEPTION_MARKER = MarkerFactory.getMarker("EXCEPTION");
  static Marker THROWING_MARKER = MarkerFactory.getMarker("THROWING");
  static Marker CATCHING_MARKER = MarkerFactory.getMarker("CATCHING");

  static String EXIT_MESSAGE_0 = "exit";
  static String EXIT_MESSAGE_1 = "exit with ({})";

  static String ENTRY_MESSAGE_0 = "entry";
  static String ENTRY_MESSAGE_1 = "entry with ({})";
  static String ENTRY_MESSAGE_2 = "entry with ({}, {})";
  static String ENTRY_MESSAGE_3 = "entry with ({}, {}, {})";
  static String ENTRY_MESSAGE_4 = "entry with ({}, {}, {}, {})";
  static int ENTRY_MESSAGE_ARRAY_LEN = 5;
  static String[] ENTRY_MESSAGE_ARRAY = new String[ENTRY_MESSAGE_ARRAY_LEN];
  static {
    ENTRY_MARKER.add(FLOW_MARKER);
    EXIT_MARKER.add(FLOW_MARKER);
    THROWING_MARKER.add(EXCEPTION_MARKER);
    CATCHING_MARKER.add(EXCEPTION_MARKER);

    ENTRY_MESSAGE_ARRAY[0] = ENTRY_MESSAGE_0;
    ENTRY_MESSAGE_ARRAY[1] = ENTRY_MESSAGE_1;
    ENTRY_MESSAGE_ARRAY[2] = ENTRY_MESSAGE_2;
    ENTRY_MESSAGE_ARRAY[3] = ENTRY_MESSAGE_3;
    ENTRY_MESSAGE_ARRAY[4] = ENTRY_MESSAGE_4;
  }

  public enum Level {
    TRACE("TRACE", LocationAwareLogger.TRACE_INT),
    DEBUG("DEBUG", LocationAwareLogger.DEBUG_INT),
    INFO("INFO", LocationAwareLogger.INFO_INT),
    WARN("WARN", LocationAwareLogger.WARN_INT),
    ERROR("ERROR", LocationAwareLogger.ERROR_INT);

    private final String name;
    private final int level;

    public String toString() {
      return this.name;
    }

    public int intValue() {
      return this.level;
    }

    private Level(String name, int level) {
      this.name = name;
      this.level = level;
    }
  }

  /**
   * Given an underlying logger, construct an XLogger
   * 
   * @param logger
   *                underlying logger
   */
  public XLogger(Logger logger) {
    // If class B extends A, assuming B does not override method x(), the caller
    // of new B().x() is A and not B, see also
    // http://bugzilla.slf4j.org/show_bug.cgi?id=114
    super(logger, LoggerWrapper.class.getName());
  }

  /**
   * Log method entry.
   * 
   * @param argArray
   *                supplied parameters
   */
  public void entry(Object... argArray) {
    if (instanceofLAL && logger.isTraceEnabled(ENTRY_MARKER)) {
      String messagePattern = null;
      if (argArray.length <= ENTRY_MESSAGE_ARRAY_LEN) {
        messagePattern = ENTRY_MESSAGE_ARRAY[argArray.length];
      } else {
        messagePattern = buildMessagePattern(argArray.length);
      }
      String formattedMessage = MessageFormatter.arrayFormat(messagePattern,
          argArray);
      ((LocationAwareLogger) logger).log(ENTRY_MARKER, FQCN,
          LocationAwareLogger.TRACE_INT, formattedMessage, null);
    }
  }

  /**
   * Log method exit
   */
  public void exit() {
    if (instanceofLAL && logger.isTraceEnabled(ENTRY_MARKER)) {
      ((LocationAwareLogger) logger).log(EXIT_MARKER, FQCN,
          LocationAwareLogger.TRACE_INT, EXIT_MESSAGE_0, null);
    }
  }

  /**
   * Log method exit
   * 
   * @param result
   *                The result of the method being exited
   */
  public void exit(Object result) {
    if (instanceofLAL && logger.isTraceEnabled(ENTRY_MARKER)) {
      String formattedMessage = MessageFormatter.format(EXIT_MESSAGE_1, result);
      ((LocationAwareLogger) logger).log(EXIT_MARKER, FQCN,
          LocationAwareLogger.TRACE_INT, formattedMessage, null);
    }
  }

  /**
   * Log an exception being thrown. The generated log event uses Level ERROR.
   * 
   * @param throwable
   *                the exception being caught.
   */
  public void throwing(Throwable throwable) {
    if (instanceofLAL) {
      ((LocationAwareLogger) logger).log(THROWING_MARKER, FQCN,
          LocationAwareLogger.ERROR_INT, "throwing", throwable);
    }
  }

  /**
   * Log an exception being thrown allowing the log level to be specified.
   *
   * @param level the logging level to use.
   * @param throwable
   *                the exception being caught.
   */
  public void throwing(Level level, Throwable throwable) {
    if (instanceofLAL) {
      ((LocationAwareLogger) logger).log(THROWING_MARKER, FQCN,
          level.level, "throwing", throwable);
    }
  }

  /**
   * Log an exception being caught. The generated log event uses Level ERROR.
   * 
   * @param throwable
   *                the exception being caught.
   */
  public void catching(Throwable throwable) {
    if (instanceofLAL) {
      ((LocationAwareLogger) logger).log(CATCHING_MARKER, FQCN,
          LocationAwareLogger.ERROR_INT, "catching", throwable);
    }
  }

  /**
   * Log an exception being caught allowing the log level to be specified.
   *
   * @param level the logging level to use.
   * @param throwable
   *                the exception being caught.
   */
  public void catching(Level level, Throwable throwable) {
    if (instanceofLAL) {
      ((LocationAwareLogger) logger).log(CATCHING_MARKER, FQCN,
          level.level, "catching", throwable);
    }
  }

  private static String buildMessagePattern(int len) {
    StringBuilder sb = new StringBuilder();
    sb.append(" entry with (");
    for (int i = 0; i < len; i++) {
      sb.append("{}");
      if (i != len - 1)
        sb.append(", ");
    }
    sb.append(')');
    return sb.toString();
  }
}