Logging levels - meanings and use

All popular logging frameworks follow a similar severity convention for log levels. There are five primary levels used in production code, with two additional special‑purpose levels.

Order (high priority to low):

• FATAL · ERROR · WARN · INFO · DEBUG · TRACE

Meaning and use:

1. DEBUG for fine‑grained diagnostic messages that help you trace flow and variable values. These should never appear in production – set your root logger to INFO or higher to silence them. In your code: logger.debug("Processing request id={}", id);
2. INFO for normal, informative messages that mark significant application events (startup, shutdown, important state changes). Think of it as a “verbose” mode. Example: logger.info("Connection pool initialised with {} threads", poolSize);
3. WARN for potential issues that do not stop the application from functioning. Use it when you fall back to a default, or when a deprecated API is called. The system carries on without a problem. logger.warn("Configuration key 'max.retries' missing – defaulting to 3");
4. ERROR for application errors that still allow the application to hobble along. These indicate a real problem – an exception caught, a service call failed, but the operation can be retried or the user can continue. Like a missing admin‑supplied config value that falls back to a hard‑coded default. logger.error("Unable to reach inventory service, using cached prices", ex);
5. FATAL for critical failures, after which the application quits abnormally. After logging a fatal message, the system is considered dead. For example, in Log4j2: logger.fatal("Database connection pool exhausted, aborting.");

Additionally, two special levels exist with obvious meanings:

1. ALL – enables every log statement, regardless of its level. Handy for temporarily debugging a specific component, but never for production.
2. OFF – disables all logging output. Use it to silence a noisy logger completely.

grails detecting environment - groovy & gsp code

Grails/Groovy working code snippet to detect the current environment (development, test, production, or your  custom). Custom environment are defined in config.groovy file.

Detecting Environment in GSP code :

Following checks if current environment is other than production.

    <g:if test="${env != "production"}">
        //your logic 

    </g:if>

Detecting environment in Groovy Code ( in Controller, Service, etc..), using switch-case comparison

        switch(Environment.current.getName()){
            case "development":
                //do your stuff 1
                break;
            case "test":
                //do your stuff 2
                break;
            case "production":
                //do your stuff 3
                break;
            case "my_environment":  // for custom environment : my_environment
                //todo:
                break;
        }

Simple comparison in groovy

if(Environment.current.getName()=="development") {
    //do your stuff
}

Grails - auto login in spring security

Consider a typical web application where you have multiple user roles (like SUPER_ADMIN, OPERATOR, VISITOR etc ) and you need to do login and switch between them frequently. It certainly consumes a lot of time if you do this manually. One simple solution would be to use the browser's password remember feature. But this would not be useful if you need to switch between different role.

Here, I am going to do show how we can setup this mechanism in Grails applications which uses Spring Security plugin.

If you are using Spring Security plugin then, by default you will have following names for html textbox for username and password : j_username and j_password. and you have login request url as http://localhost:8080/YOUR_APP/j_spring_security_check .

The required login script :

Groovy Grails - Dynamic Method n Variable name and invoking them

Groovy allows to use dynamic method name and variable name and invoke/use them.

Dynamic Variable Names

Groovy allows to use variable name dynamically. To test this lets introduce a variable  "dogname" to Dog class

class Dog {

def dogname

...

}

//Testing dynamic variable name

        def aDog= new Dog()

aDog.name="Hachi"

def prop="dogname"

println aDog."$prop" // prints Hachi

git- saving username password - credential.helper cache - how to

Isn't is interesting if there is an option in GIT to save your credentials for short time so that you don't enter your username/password repeatedly each time when you do pull/push? Yes! there is an option introduced in GIT since 1.7.9 (released on January 2012). This method is more secure than permanently saving your username/password in   .git  file of your git clone directory.

So, run the following command at the GIT console (git bash) :

git config --global credential.helper cache

This caches the credentials for 15 minutes ( 900 seconds) by default. If you want a longer timeout period (say3600 seconds), you can do the following :

git config --global credential.helper 'cache --timeout=3600'

Grails - beginners video tutorial

From the Grails site: "Grails aims to bring the 'coding by convention' paradigm to Groovy. It's an open-source web application framework that leverages the Groovy language and complements Java Web development. You can use Grails as a standalone development environment that hides all configuration details or integrate your Java business logic. Grails aims to make development as simple as possible and hence should appeal to a wide range of developers not just those from the Java community."

grails- add jar to lib folder - not working - solution

In grails application you can add jar dependencies by just pasting the .jar file to lib folder. If your code doesn't find the jar dependency at runtime then you can do following :

Run the following grail command (s):

• clean
• compile --refresh-dependencies 

In eclipse you can open the Grails Command Prompt by :
Right Click on project -> Grail Tools -> Open Grails Command Prompt

Hope this helps.

nepali english date conversion logic - working java code

My friend Manoj has written about Nepali-English date conversion in this post. Take a look :

http://forjavaprogrammers.blogspot.com/2012/06/how-to-convert-english-date-to-nepali.html

He has explained the algorithm in detail about how to convert English dates into Nepali dates with java code.

android media player - play file http rtsp streams

MediaPlayer class (android.media.MediaPlayer ) can be used to control playback of audio/video files and streams.  

Code:

String url = "http://........"; // your media URL here
//String url = "rtsp://........"; 
//String url = "file:///sdcard/intro.3gp"; //local file

MediaPlayer mediaPlayer = new MediaPlayer();
mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
mediaPlayer.setDataSource(url); //Sets the data source (file-path or http/rtsp URL) to use

To play audio file, you can simply call mediaPlayer.start();

mediaPlayer.prepare()
mediaPlayer.start();

For the Audio Stream (http, rtsp)

After setting the datasource and the display surface, you need to either call prepare() or prepareAsync().
For streams, you should call prepareAsync(), which returns immediately, rather than blocking until enough data has been buffered.

A MediaPlayer object must first enter the Prepared state before playback can be started. MediaPlayer.OnPreparedListener defines Interfaces  for a callback to be invoked when the media source is ready for playback.

mediaPlayer.prepareAsync();
//You can show progress dialog here untill it prepared to play

mediaPlayer.setOnPreparedListener(new OnPreparedListener() {
        @Override
        public void onPrepared(MediaPlayer mp) {
            //Called when the media file is ready for playback.
            mp.start();
        }
    });
    mediaPlayer.setOnErrorListener(new OnErrorListener() {
        @Override
        public boolean onError(MediaPlayer mp, int what, int extra) {
            return false;
        }
    });

java spring - read properties file variable from xml -PropertyPlaceholderConfigurer

Java springframework xml configuration file - how to read properties file variables from spring xml :
We have to use PropertyPlaceholderConfigurer bean for this.

1).properties file location -

• src/main/resource @ maven managed project
• OR at classpath

2)The xml code to initialize/read properties file,