Apache TomEE

Logging for Users

All logging in OpenEJB is done using the openejb.base/conf/logging.properties file. When you download and extract OpenEJB, you will not find this file under the openejb.base/conf directory. However, when you start the server, this file magically appears. So what does this give you as a user of OpenEJB? Here are some of the benefits:

You do not have to author a logging.properties from scratch. You get one with sensible defaults.
If you did modify the default file, and you wanted to revert back to the default file generated by OpenEJB, all you have to do is
= Delete or rename the file e.g. rename it to logging.properties.BAK .
= Restart the server

OpenEJB will find that the logging.properties file is missing from the openejb.base/conf directory and it will automatically create a new one with the default configuration. The good thing is that if you modify the logging.properties file, OpenEJB will NOT over-write it.

The default logging configuration created by OpenEJB uses RollingFileAppender’s. The log files are located under the openejb.base/logs directory. By default it writes to just two files , openejb.log and transaction.log {info:title=Embedded Testing} When running tests using embedded OpenEJB, the logging.properties will be ignored. You need to use a file named embedded.logging.properties instead. Place this file under src/test/resources {info}

Logging for contributors/committers

The org.apache.openejb.util.Logger class is the one which is used for logging. This class is a wrapper around log4.

LogCategory

Each Logger instance belongs to a category represented by a org.apache.openejb.util.LogCategory instance. Here is what the LogCategory class looks like

public final class LogCategory {
  private final String name;
  public static final LogCategory OPENEJB = new LogCategory( "OpenEJB");
  public static final LogCategory OPENEJB_ADMIN = OPENEJB.createChild("admin");
  public static final LogCategory OPENEJB_STARTUP = OPENEJB.createChild("startup");
  public static final LogCategory OPENEJB_STARTUP_CONFIG = OPENEJB_STARTUP.createChild("config");
  public static final LogCategory OPENEJB_STARTUP_VALIDATION = OPENEJB_STARTUP.createChild("validation");
       // other categories removed for code brevity
  private LogCategory(String name){
    this.name = name;
  }
  public String getName() {
    return name;
  }
  /**
   * Creates a child category of this category. <B>Use this method sparingly</B>. This method is to be used in only those circumstances where the name of the
   * category is not known upfront and is a derived name. If you know the name of the category, it is highly recommended to add a static final field
   * of type LogCategory in this class
   * @param child
   * @return - LogCategory
   */
  public LogCategory createChild(String child){
    return new LogCategory(this.name+"."+child);
  }

}

Notice carefully how each LogCategory instance is created. The objective here is that each LogCategory should be a child of the OPENEJB category. If you need to add a new category and you know the name of the category upfront, simply open the LogCategory class and add another category. For example, if you needed to add a category named SHUTDOWN, here is the recommended way to add it

public static final LogCategory OPENEJB_SHUTDOWN = LogCategory.OPENEJB.createChild("shutdown");

Sometimes you may want to create a category whose name is "generated" at runtime. In that case you can use the "createChild" method of the LogCategory class to create this new category. For example, if you wanted to create a category of Logger for every deployed module, then assuming you have the moduleId information you could do something as follows to create a category:

String moduleId = "mymodule";
LogCategory generatedCategory = LogCategory.OPENEJB.createChild(moduleId);

Logger

The preference is to externalize all logging messages in properties file. Typically each package should have a file called Messages.properties. This file should have all the keys and the corresponding messages. Here are the steps you would follow to log a message:

For each message you need to log, you would open the Messages.properties file in the corresponding package and add a key-value pair for the message. For example, if you were authoring a class called org.apache.openejb.util.Connect, then you would add a key-value pair to the Messages.properties file located in the org.apache.openejb.util package.
Obtain a Logger instance in one of the following ways:

Using the package name

Logger logger = Logger.getInstance (LogCategory.OPENEJB, "org.apache.openejb.util");

Using the Class

Logger logger = Logger.getInsance(LogCategory.OPENEJB, Connect.class);

Get a child Logger for an existing Logger instance

Logger logger = Logger.getInsance(LogCategory.OPENEJB, Connect.class);
Logger child = logger.getChildLogger("shutdown");

Get a child Logger of an existing Logger using a LogCategory

LogCategory childCategory = LogCategory.OPENEJB.createChild("shutdown");
Logger logger = Logger.getInstance(childCategory,Connect.class);

Call one of the following methods passing in the key as an argument debug error fatal info ** warning

Logger logger = Logger.getInstance(LogCategory.OPENEJB,Connect.class); logger.info("error.file");

The Messages.properties file under org.apache.openejb.util must have the "error.file" key in it with the corresponding message.

Logger Inheritance

Another interesting feature of the Logging framework is inheritance. Here is how it works:

Say you have the following Messages.properties files in the classpath.

org/apache/openejb/Messages.properties
org/apache/openejb/core/Messages.properties
org/apache/openejb/core/stateless/Messages.properties

Then you have a class such as org.apache.openejb.core.stateless.StatelessContainer (note the package) If that class referenced a message key "classNotFound" for example, the Logger would look for the message first in Messages.properties 3, then 2, then 1 and so on until it found the required message. This would allow better reuse of messages, more flexibility in where we put the Message.properties files, as well as the added bonus in that we no longer need to pass in the location of where our Message.properties file is

Logging for integrators

If you want to embed OpenEJB in your application and need to control the logging configuration of OpenEJB, simple set the openejb.logger.external system property to true. Now, its your applications' responsibility to configure logging, OpenEJB will simply use your configuration.

Origination of the Logging Idea

There has been a long discussion for this logging idea. Its going to be worth it to read the discussion at i18n and logging

Here is a extract from an email from David Blevins which talks about the existing logging framework. The current framework is more or less the same as this one, just some added features and a rewrite of the API

Each module has a file called default.logging.conf. This file contains the definition of all Loggers, their appenders and warning levels. However, we do not use default.logging.conf first. The basic idea is that first we look for say conf/logging.conf in the openejb.base directory. If we don’t find it there, we look for default.logging.conf in the classpath. If we did find default.logging.conf (which we should) and there is an openejb.base/conf/ directory then expand the default.logging.conf to openejb.base/conf/logging.conf where we expected to find the file in the first place. If there was no openejb.base/conf/ directory, then it’s safe to assume we’re running embedded (in a test case perhaps) and just use the default.logging.conf and do no extra work.

We have default.logging.conf which we use this way as well as default.openejb.conf and now more recently users.properties and groups.properties. We search on disk for the resource in openejb.base/conf/ if we don’t find them we unpack the default one we stuffed in openejb-core jar and extract it to disk in the openejb.base/conf directory if there is one — if there isn’t one we just use the default file.

The basic ideas behind the pattern are that: 1. If you’ve messed up your configuration, just delete or rename the respective files in your conf/ directory and new (working) ones will magically appear. 2. When upgrading its nice that our zip file won’t overwrite any existing files in conf/ 3. If you’re running embedded you don’t have to setup any directories or have any config files, we can run on defaults.

The ConfUtils.getConfResource utility to do that pattern generically , but so far we’re only using it for the users.properties and groups.properties files. We should be using it everywhere. Having the code in multiple places has lead to some inconsistencies such as we expand the default.openejb.conf file to conf/openejb.xml (not even the same file extension). We really don’t need the "default" part in our file names and the lingering usage of the "conf" file extension is something that needs to go bye-bye — we should use properties for properties files and xml for xml files, etc.