Useful logger for Android based on standard android.util.Log class. Simple lightweight (< 50 Kb) implementation of SLF4J API. Easy but powerful configuration via properties file and some additional helpful logging methods. Easy analogue of popular log4j library.
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README.md

Android Logger

Useful logger for Android based on standard android.util.Log class. Simple lightweight (< 50 Kb) implementation of SLF4J API. Easy but powerful configuration via properties file and some additional helpful logging methods. Easy analogue of popular log4j library.

Android SDK Version: API 7 [ Android 2.1 ]

Code Samples: [here]

Android Arsenal

Downloads

Maven Dependency

<dependency>
    <groupId>com.noveogroup.android</groupId>
    <artifactId>android-logger</artifactId>
    <version>1.3.5</version>
</dependency>

Gradle Dependency

'com.noveogroup.android:android-logger:1.3.5'

Getting Started

If you want to use Android Logger in your Android application you need to do just the following simple steps:

  • Add Android Logger as a library OR add it as Maven or Gradle dependency.

  • Configure Android Logger.

Place the following android-logger.properties file to your source directory (src/main/resources/android-logger.properties):

# Android Logger configuration example

# By default logger will print only ERROR (and higher) messages
# with "MyApplication" tag
root=ERROR:MyApplication

# DEBUG (and higher) messages from classes of com.example.database
# will be logged with "MyApplication-Database" tag
logger.com.example.database=DEBUG:MyApplication-Database

# All messages from classes of com.example.ui will be logged with
# "MyApplication-UI" tag
logger.com.example.ui=MyApplication-UI

The configuration manages which log tag will be used to print messages and which logging level filter will be applied.

logger.<package/classname>=<level>:<tag>:<message head>
# or
logger.<package/classname>=<level>:<tag>
# or
logger.<package/classname>=<tag>

The rest of messages will be managed by root logger:

root=<level>:<tag>:<message head>
# or
root=<level>:<tag>
# or
root=<tag>

You can use VERBOSE, DEBUG, INFO, WARN, ERROR, ASSERT as level in configuration files.

Format of and is desribed below in Patterns section.

  • You need to get logger instance to print messages

You can use LoggerManager to get a logger instance to print messages.

package com.example.ui;

import com.noveogroup.android.log.Logger;
import com.noveogroup.android.log.LoggerManager;

public class MainActivity extends Activity {

  // get a logger instance by name
  private static final Logger logger = LoggerManager.getLogger("com.example.ui.MyActivity");
  // get a logger instance by class
  private static final Logger logger = LoggerManager.getLogger(MainActivity.class);
  // just to use current class
  private static final Logger logger = LoggerManager.getLogger();

  private void foo(int value) {
    logger.i("entered MainActivity::foo value=%d", value);

    try {
      // some code
    } catch(IOException e) {
      logger.e("I/O error occurred", e);
    }
  }

}
  • You can use Log class to make logging calls shorter.

Any call like Log.someMethod() is equal to LoggerManager.getLogger().someMethod(). So, there will be some additional overhead to get a logger each time.

import com.noveogroup.android.log.Log;

public class Bar {

  public void foo() {
    Log.i("some log message");
  }

}

Patterns

You can configure format of tags and messages headers in your configuration file.

For example, the following configuration file:

logger.ROOT=INFO:MyApplication:%caller{-2}

will generate the following output:

PatternTest#<init>:15 your message

So, the logger insert inforation about caller before the message.

The patterns are format strings written according to a special rules described below. Log messages will be formatted and printed as it is specified in the tag and the message pattern. The tag pattern configures log tag used to print messages. The message pattern configures a head of the message but not whole message printed to log.

The tag pattern The message pattern Resulting tag Resulting message
TAG %d{yyyy-MM-dd}: TAG %d{yyyy-MM-dd}:

The tag and the message patterns are wrote according to similar rules. So we will show only one pattern in further examples.

The patterns is strings that contains a set of placeholders and other special marks. Each special mark should start with '%' sign. To escape this sign you can double it.

Conversion marks

Mark %%

Escapes special sign. Prints just one '%' instead.

Mark %n

Prints a new line character '\n'.

Marks %d{date format} and %date{date format}

Prints date/time of a message. Date format should be supported by SimpleDateFormat. Default date format is "yyyy-MM-dd HH:mm:ss.SSS".

Marks %p and %level

Prints logging level of a message.

Marks %c{count.length} and %logger{count.length}

Prints a name of the logger. The algorithm will shorten some part of full logger name to the specified length. You can find examples below.

Conversion specifier Logger name Result
%logger com.example.android.MainActivity com.example.android.MainActivity
%logger{0} com.example.android.MainActivity com.example.android.MainActivity
%logger{3} com.example.android.MainActivity com.example.android
%logger{-1} com.example.android.MainActivity example.android.MainActivity
%logger{.0} com.example.android.MainActivity com.example.android.MainActivity
%logger{.30} com.example.android.MainActivity com.example.android.*
%logger{.15} com.example.android.MainActivity com.example.*
%logger{.-25} com.example.android.MainActivity *.android.MainActivity
%logger{3.-18} com.example.android.MainActivity *.example.android
%logger{-3.-10} com.example.android.MainActivity$SubClass MainActivity$SubClass
Marks %C{count.length} and %caller{count.length}

Prints information about a caller class which causes the logging event. Additional parameters 'count' and 'length' means the same as the parameters of %logger.

Examples:

Conversion specifier Caller Result
%caller Class com.example.android.MainActivity at line 154 com.example.android.MainActivity:154
%caller{-3.-15} Class com.example.android.MainActivity at line 154 MainActivity:154
Marks %s and %source

Prints source of class which causes the logging event.

Examples:

Conversion specifier Caller Result
%source or %s Class com.example.android.MainActivity at line 154 (MainActivity.java:154)
%source or %s Native (native)
%source or %s Unknown (unknown)
Marks %t and %thread

Prints a name of the thread which causes the logging event.

Mark %(...)

Special mark used to grouping parts of message. Format modifiers (if specified) are applied on whole group.

Examples:

Example Result
[%50(%d %caller{-3.-15})] [ 2013-07-12 19:45:26.315 MainActivity:154]
[%-50(%d %caller{-3.-15})] [2013-07-12 19:45:26.315 MainActivity:154 ]

Format modifiers

After special sign '%' user can add format modifiers. The modifiers is similar to standard modifiers of Formatter conversions.

Example Result
%6(text) ' text'
%-6(text) 'text '
%.3(text) 'tex'
%.-3(text) 'ext'

For an additional information see sources of com.noveogroup.android.log.PatternHandler class

SLF4J compatibility

Android Logger is SLF4J compatible. For example, you can write such code in your library:

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class Bar {

  private static final Logger logger = LoggerFactory.getLogger(Bar.class);

  public void foo(int value) {
    logger.info("entered Bar::foo value={}", value);

    try {
      // some code
    } catch(IOException e) {
      logger.error("I/O error occurred", e);
    }
  }

}

Suppose you compiled your library as JAR-file and publish it. After that anyone who uses your JAR library will be able to add any SLF4J implementation to change the way how the library logs messages. The most powerful implementation of SLF4J is LOGBack available for Android. Unfortunately, it has about 1 Mb size and it may be critical for some Android applications. Android Logger is SLF4J compatible too. So you can just add its JAR as a library to get all your log messages in Android LogCat.

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License

Copyright (c) 2013 Noveo Group

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

Except as contained in this notice, the name(s) of the above copyright holders
shall not be used in advertising or otherwise to promote the sale, use or
other dealings in this Software without prior written authorization.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.