Package org.jboss.weld.extensions.log

Provides injectable typed loggers and injectable typed message bundles suitable for internationalization and localization which can use any logging backend.

See:
Description

Class Summary

LoggerExtension	Adds Producers to the deployment, and detects and installs beans for any typed loggers defined.
MessageBundleLiteral

Annotation Types Summary

Category	Specifies a Category for the injected logger.
Locale	Specifies a Locale for a typed logger.
MessageBundle	Signify that a MessageBundle should be injected.
Suffix	A suffix to use on the specified category (or fully qualified name of the injection point type if no category is specified).

Package org.jboss.weld.extensions.log Description

Provides injectable typed loggers and injectable typed message bundles suitable for internationalization and localization which can use any logging backend.

Weld Extensions integrates JBoss Logging 3 as it's logging framework of choice. JBoss Logging 3 is a modern logging framework offering:

A number of the features of JBoss Logging 3 are still under development - at the moment only runtime generation of typed is supported, and these loggers only support the default message placed on the typed logger, and will not look up a localized message.

• Abstracts away from common logging backends and frameworks (such as JDK Logging, log4j and slf4j)
• Provides a innovative, typed logger (see below for examples)
• Full support for internationalization and localization
  • Developers can work with interfaces and annotations only
  • Translators can work with message bundles in properties files
• Build time tooling to generate typed loggers for production, and runtime generation of typed loggers for development
• Access to MDC and NDC (if underlying logger supports it)
• Loggers are serializable

To use a typed logger, first create the logger definition:

 @MessageLogger
 interface TrainSpotterLog {

    // Define log call with message, using printf-style interpolation of parameters
    @LogMessage @Message("Spotted %s diesel trains") 
    void dieselTrainsSpotted(int number);

 }
 

You can then inject the typed logger with no further configuration:

    // Use the train spotter log, with the log category "trains"
    @Inject @Category("trains") TrainSpotterLog log;
 

and use it:

    log.dieselTrainsSpotted(7);
 

JBoss Logging will use the default locale unless overridden:

    // Use the train spotter log, with the log category "trains", and select the UK locale
    @Inject @Category("trains") @Locale("en_GB") TrainSpotterLog log;
 

You can also log exceptions:

 @MessageLogger
 interface TrainSpotterLog {

    // Define log call with message, using printf-style interpolation of parameters
    // The exception parameter will be logged as an exception
    @LogMessage @Message("Failed to spot train %s") 
    void missedTrain(String trainNumber, @Cause Exception exception);

 }
 

You can then log a message with exception:

    log.missedTrain("RH1", cause);
 

You can also inject a "plain old" Logger:

    @Inject Logger log;
 

Typed loggers also provide internationalization support, simply add the @MessageBundle annotation to the logger interface (not currently supported).

Sometimes you need to access the message directly (for example to localize an exception message). Weld Extensions let's you inject a typed message bundle. First, declare the message bundle:

 @MessageBundle
 interface TrainMessages {

    // Define a message using printf-style interpolation of parameters
    @Message("No trains spotted due to %s") 
    String noTrainsSpotted(String cause);

 }
 

Inject it:

    @Inject @MessageBundle TrainMessages messages;
 

And use it:

   throw new BadDayException(messages.noTrainsSpotted("leaves on the line"));
 

See Also:

Category, Suffix, Locale, MessageBundle