LogRedirector.java

/*
 * Copyright (c) 2014-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */

package com.facebook.stetho.common;

import java.io.PrintWriter;
import java.io.StringWriter;

import android.util.Log;

/**
 * Logging interface which allows third party code to replace Android's {@link Log} API with
 * their own implementation.  Useful in public libraries so that callers can more finely control
 * how log messages are produced.
 * <p>
 * Note that the API and implementation of this class are designed to match the semantics of
 * the default system {@link Log} API.
 */
public class LogRedirector {
  private static volatile Logger sLogger;

  /**
   * Override Android's default {@link Log} API with a custom logger interface.  This affects
   * all subsequent calls to {@link LogRedirector} APIs.
   */
  public static void setLogger(Logger logger) {
    Util.throwIfNull(logger);
    Util.throwIfNotNull(sLogger);
    sLogger = logger;
  }

  public static void e(String tag, String message, Throwable t) {
    e(tag, message + "\n" + formatThrowable(t));
  }

  public static void e(String tag, String message) {
    log(Log.ERROR, tag, message);
  }

  public static void w(String tag, String message, Throwable t) {
    w(tag, message + "\n" + formatThrowable(t));
  }

  public static void w(String tag, String message) {
    log(Log.WARN, tag, message);
  }

  public static void i(String tag, String message, Throwable t) {
    i(tag, message + "\n" + formatThrowable(t));
  }

  public static void i(String tag, String message) {
    log(Log.INFO, tag, message);
  }

  public static void d(String tag, String message, Throwable t) {
    d(tag, message + "\n" + formatThrowable(t));
  }

  public static void d(String tag, String message) {
    log(Log.DEBUG, tag, message);
  }

  public static void v(String tag, String message, Throwable t) {
    v(tag, message + "\n" + formatThrowable(t));
  }

  public static void v(String tag, String message) {
    log(Log.VERBOSE, tag, message);
  }

  private static String formatThrowable(Throwable t) {
    StringWriter buf = new StringWriter();
    PrintWriter writer = new PrintWriter(buf);
    t.printStackTrace();
    writer.flush();
    return buf.toString();
  }

  private static void log(int priority, String tag, String message) {
    Logger logger = sLogger;
    if (logger != null) {
      logger.log(priority, tag, message);
    } else {
      Log.println(priority, tag, message);
    }
  }

  public static boolean isLoggable(String tag, int priority) {
    Logger logger = sLogger;
    if (logger != null) {
      return logger.isLoggable(tag, priority);
    } else {
      return Log.isLoggable(tag, priority);
    }
  }

  /**
   * Custom logger implementation that can forward logs to something other than Android's
   * {@link Log} API.
   */
  public interface Logger {
    /**
     * Allows the caller to query if a particular tag and priority will be logged.  Note that just
     * like with {@link Log#isLoggable}, callers are required to consult this manually if the
     * result is to be considered.
     */
    boolean isLoggable(String tag, int priority);

    /**
     * Submit a log message.
     */
    void log(int priority, String tag, String message);
  }
}