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Using Chainsaw to tail your JBoss server log

Sheila — Tue, 07 Apr 2009 11:06:21 +0000

Log4j is a logging library from Apache. It consists of loggers (log events) and appenders (a destination for a log message). There’s always a rootLogger defined, plus however many other loggers you require. A logger can have several appenders attached to it which can format and write the message to the console or a file etc. The logging levels are TRACE, DEBUG, INFO, WARN, ERROR and FATAL.

A default JBoss installation uses log4j for logging. The log4j settings are configured in JBOSS_HOME\server\default\conf\jboss-log4j.xml which sends output to both the console and JBOSS_HOME\server\default\log\server.log

Chainsaw is a GUI tool for parsing and analysing log files generated by log4j. It allows you to read and filter events. It can be used to tail the server.log file allowing you to filter the messages you see rather than searching through the log file in an editor.

You can download Chainsaw from here.

Download the chainsawWebStart.jnlp file and open it up to start the Chainsaw Log viewer.

Tailing a Log file
Create a file somewhere on your system to hold configuration information for chainsaw.

chainsaw-config.xml

Edit the filename to match where the jboss server.log is on your system.

Select the ‘view-show application wide preferences’ menu.

In the automatic configuration url field, enter the URL to your config file.file:///c:/chainsaw-config.xml
Select OK and restart Chainsaw.

You'll see the file load up ina new tab 'file/c:Applications/jboss-4.2.2.GA/server/default/log/server.log.

There's a dropdown menu that lets you filter the log entries from the most verbose TRACE up to FATAL errors only.

Chainsaw basics:
The toolbar icons at the top let you pause the logging, configure what gets displayed and clear the screen of events among other things. The first thing to get accustomed to is drilling through the log events to see the information you're interested in. In the left pane you can move through the logging tree to select a particular logger. Any messages from a Logger matching the one selected are highlighted in black. You can then right click on the selected logger in the tree and choose either 'Focus on' to filter to just those events or 'Ignore' to exclude them. Selecting a specific event gives you more detailed information in the lower pane.

Loading a properties file in a java web app

Sheila — Tue, 31 Mar 2009 11:00:23 +0000

You’ll often want to configure parameters in a properties file and read this into a class.

config.properties: value.a=orange value.b=apple

If you’re simply loading a file in a java program you can use: Properties props = new Properties(); props.load(new FileInputStream("config.properties")); String value = props.getProperty("value.a");

But when loading a property file in a web application you should package the file in your deployed archive and load the file from the classpath. This avoids problems with loading files from different locations on a file system.

build.xml: gen-jar-files target

This takes any properties files in the resources.dir and copies them into the jar file. Now you can access the file within your application from the classpath: ClassLoader cl = this.getClass().getClassLoader(); InputStream is = cl.getResourceAsStream("config.properties"); Properties configProperties = new Properties(); try { configProperties.load(is); String valueA = configProperties.getProperty("value.a"); } catch (IOException e) { e.printStackTrace(); }

Automated Build – Database scripts

Sheila — Wed, 25 Mar 2009 17:42:38 +0000

When you’re developing a project, you put all your java code into source control. You should also include database scripts in source control. These scripts can be used by developers to keep their local copies of the database up to date in the same way as they get the latest code from source control.

As part of your automated build system you should run the database scripts whenever there’s a change to keep your code and database in synch. You can add the code into your existing build in a db folder or check it into source control separately.

You follow almost the same process whether adding scripts for mysql or oraclexe and can modify the scripts to cater for multiple schemas across different databases. In this example we’ll cover the configuration for setting up the testdb schema in both oraclexe and mysql before writing the scripts for each. This example assumes you already have both databases running locally on your machine.

To start with you create a PROJECT_HOME/db folder which contains: db/config db/datasources db/lib db/oraclexe/testdb db/mysql/testdb

In the lib folder add the connector jars for the databases eg. db/lib/oracle/ojdbc5.jar db/lib/mysql/mysql-connector-java-5.1.6-bin.jar

In the config folder we need some property files to configure the build. db/config/mysql.properties db/config/xe.properties db/config/schema.properties

Schema.properties is used to configure the build depending on whether you want to just use oracle xe or mysql or use both. In this example oraclexe is enabled and mysql is disabled.

schema.properties: ## ## Use this property file to enable or disable the databases and ## schemas you want to run the build scripts against. ## Comment them out with a # if you don't want to enable a ## setting. #Databases xe.db.enable xe.username=testdb xe.password=testdb #mysql.db.enable #mysql.username=testdb #mysql.password=testdb

The next two give the access details for your oracle xe and mysql databases.

mysql.properties: # MySql Database Details mysql.rootuser=root mysql.rootpass=password mysql.url=jdbc:mysql://localhost:3306 mysql.schema=testdb mysql.driver=com.mysql.jdbc.Driver mysql.user.location=localhost mysql.create.tables.script=createTables.sql mysql.drop.tables.script=dropTables.sql mysql.populate.tables.script=populateTables.sql mysql.testdata.script=testData.sql print=false

xe.properties: # Oracle XE Database Details xe.rootuser=sys xe.host=localhost xe.sid=XE xe.rootpass=password xe.port=1521 xe.driver=oracle.jdbc.OracleDriver xe.url=jdbc:oracle:thin:@${xe.host}:${xe.port}:${xe.sid} xe.create.user.script=createUser.sql xe.delete.user.script=dropUser.sql xe.create.tables.script=createTables.sql xe.drop.tables.script=dropTables.sql xe.populate.tables.script=populateTables.sql xe.testdata.script=testdata.sql print=false

We start off with a master build.xml script in PROJECT_HOME which calls oraclexe/testdb/build-xe-testdb.xml and mysql/testdb/build-mysql-testdb.xml script. The ‘ant dir’ value specifies the directory the script to be called in, ‘antfile’ gives the name of the script, and lastly you specify the target to be run in that script.

db/build.xml:

The install target is used to create the database schemas from scratch – including the users.

The recreateTables target is the default and is used when the schemas and users already exist and you just want to drop and create the tables to pick up changes.

The rest of the targets can be called separately for creating tables, populating them with default data (eg. lists of countries that would always be needed for an application) adding some test data and deleting the tables again.

The next step is to add the oraclexe-specific scripts and the mysql-specific scripts.

Serving static external content in JBoss

Sheila — Tue, 10 Mar 2009 11:47:56 +0000

To serve external static content in JBoss you need to add a Context element mapping the url eg. /application/test_data to the external folder as follows:

Edit /server/default/deploy/jbossweb-tomcat50.sar/server.xml and add a Context element just under the host tag.

Replace C:/test_data with the path to the folder on the server.

Redeploy the application to make sure that the config change has been picked up and then test that the files can be accessed.

Note: this content will be accessible without logging into the application if the url is known.

Use a different compiler with ant’s javac task

Sheila — Mon, 09 Mar 2009 14:16:14 +0000

To ignore the JAVA_HOME settings and specify the compiler to use in ant’s javac task set the following properties:

build.properties: # Set the jdk compiler properties build.javac.executable=C:/Applications/Java/jdk1.5.0_13/bin/javac.exe build.javac.compiler=javac1.5

Then in the build script use: