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]
<dependency>
<groupId>com.noveogroup.android</groupId>
<artifactId>android-logger</artifactId>
<version>1.3.4</version>
</dependency>'com.noveogroup.android:android-logger:1.3.4'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-UIThe 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");
}
}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.
Escapes special sign. Prints just one '%' instead.
Prints a new line character '\n'.
Prints date/time of a message. Date format should be supported by SimpleDateFormat. Default date format is "yyyy-MM-dd HH:mm:ss.SSS".
Prints logging level of a message.
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 |
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 |
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) |
Prints a name of the thread which causes the logging event.
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 ] |
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
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.
- Noveo Group
- Pavel Stepanov - pstepanov@noveogroup.com
- Margarita Kurushina - mkurushina@noveogroup.com
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