14 May 2010

Java XML Binding with Property Change Support

In an earlier post, I was talking about generating Java classes with xjc with property change support which is not enabled by default. This post explains the details, an in fact the Maven build explained below is a lot a easier than my original approch with Ant which required some downloads to set things up.

The general idea is same as described by Kohsuke Kawaguchi in a post of 2007, but his POM is broken with the current stage of the Maven repositories. In addition, there is a tweak with the PropertyListener customization.

So here is a little example schema:

<?xml version="1.0" encoding="UTF-8"?>
<schema xmlns="http://www.w3.org/2001/XMLSchema" xmlns:tns="http://www.example.org/person/" targetNamespace="http://www.example.org/person/">
    <complexType name="Person">
        <element name="firstName" type="string"></element>
        <element name="lastName" type="string"></element>
        <element name="address" type="tns:Address"></element>

    <complexType name="Address">
        <element name="street" type="string"></element>
        <element name="houseNumber" type="string"></element>
        <element name="city" type="string"></element>
        <element name="postalCode" type="string"></element>
        <element name="country" type="string"></element>

We use the following file bindings.xjb to customize the Java classes generated by xjc. We make all classes serializable and include support for PropertyChangeListeners.

<?xml version="1.0" encoding ="UTF-8"?>

  <jaxb:bindings node="/xs:schema">
      <jaxb:serializable uid="1" />

The following POM takes care of the code generation:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <name>JAXB PropertyListener Demo</name>



You do need to use the 1.1-SNAPSHOT version of the property-listener-injector, as the 1.0 release only supports VetoableChangeListeners and not the PropertyChangeListeners we want to use. The <li:listener> element in the bindings file is used to define the listener class.

It is important to exclude the jaxb-xjc dependency from the property-listener-injector, or else it will try to download an non-existing snapshot version. Looks like something is broken in the java.net repository, but then again, working with snapshot releases is always dangerous....

13 May 2010

Glassfish Logging with slf4j

Update 18 Dec 2010: There is an extended version of this article.

It can be annoying to have each third-party library or framework in your application logging to a different logfile. slf4j with its various adapters enables you to collect logging events from various APIs (org.slf4j.api, java.util.logging, org.apache.commons.logging) and redirect them to a logging backend of your choice.

I've always preferred log4j or, more recently, logback over java.util.logging, so after working with Glassfish v3 for a while, I tried to tweak it to use logback over slf4j and the jul-to-slf4j bridge.

To redirect java.util.logging used by Glassfish v3, you put the following libs on your classpath:
  • jul-to-slf4j.jar
  • slf4j-api.jar
  • logback-classic.jar
  • logback-core.jar
(You can replace the logback libs by any other supported backend like log4j, see the slf4j docs for more details.)
The problem with Glassfish is:
  • You need to take care of its class loader hierarchy and make sure that the logging jars get picked up early enough.
  • Glassfish does some all-too-clever logger manipulation in its LogManagerService which will get in your way if you don't like the Glassfish defaults: It redirects all System.out messages to a logger.
I did not manage to fully supersede Glassfish logging by slf4j and logback, but at least I can copy all Glassfish log events to my logback application log like this:
  • Put the logging libs in [install-root]/lib/endorsed.
  • Build a JAR containing your logback.xml configuration and put it in the same place.
  • Edit an entry in [instance-root]/config/logging.properties, setting
    handlers = org.slf4j.bridge.SLF4JBridgeHandler
Now if you omit a ConsoleAppender from your logging configuration, the Glassfish server.log will no longer contain any log output from your application. It will still contain the log messages from Glassfish itself, but they will also be included in your own logback logfile.

09 May 2010

jeeunit: In-Container Integration Testing for Java EE 6

Recently, I've started working with Java EE 6 in general and Glassfish v3 in particular. Some software engineering best practices do not really depend on the framework or even the language you work with, so I was looking for a convenient way of doing automatic integration tests.

I've been in the habit of using JUnit not just for unit tests, but also for integration or system tests, so this was a natural starting point.

Traditionally, Java EE containers were heavy-weight machinery so that people preferred writing their tests to run out-of-container, paying the price of emulating or mocking some of the container functionality.

Maybe I've been looking in the wrong places, but most of the out-of-container testing approaches like ejb3unit seem to carry more baggage than the container itself, at least when it comes to working with Glassfish v3.

Anyway, as I could not find a ready-to-go solution, I wrote a little JUnit extension called jeeunit together with an example project showing how to set things up with Glassfish v3 and Maven.

The jeeunit project is available from Google Code under an Apache License.