Windows Locked files in Jetty Maven Plugin

If you are developing Java webapps using maven on Windows and using jetty:run to deploy, you have surely come across the problem when you cannot save html, js or vm files. JSPs work fine because they are compiled and deployed. Its surely irritating when that happens.

Jetty has documentation to explain the problem. Many web searches will point to this document. The problem is basically with the NIO connector that jetty uses. Others have suggested that using the old BIO connector is easy way to solve this. The problem is that the Jetty documentation solution requires using a hardcoded location for the new webdefaults.xml. We don’t want to make changes to the source of our project, just because we are on Windows.

My suggested solution is to just edit the maven jetty plugin to not use the FileMappedBuffer. Edit the webdefault.xml that is found in the jar file and that’s all. Browse to your maven repo location. e.g. for 6.1.26 of the plugin go here – USERHOME\.m2\repository\org\mortbay\jetty\jetty\6.1.26\jetty-6.1.26.jar . Open the jar file and find the file at org/mortbay/jetty/webapp/webdefault.xml , and edit the file:

<init-param>
  <param-name>useFileMappedBuffer</param-name>
  <param-value>false</param-value> <!—change from true to false -->
</init-param>

Save the file and replace the jar with this file. Now whenever you run jetty:run, it will use this file and you will not find windows locking the files when jetty deploys it

Speeding up Unit Tests by running them in parallel

I just discovered an interesting parameter in the maven-surefire-plugin when using JUnit 4.7+, that tests can be executed in parallel. With multi-threaded CPUs, OS and the like, this helps a lot when you want to decrease the time of your test suites.

So, what are the configurations options that you have:

1. Running test methods in parallel:
   

   <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-surefire-plugin</artifactId>
      <version>2.9</version>
      <configuration>
        <parallel>methods</parallel>
      </configuration>
   </plugin>

   
   
2. Running test classes in parallel:

   <plugin>
     <groupId>org.apache.maven.plugins</groupId>
     <artifactId>maven-surefire-plugin</artifactId>
     <version>2.9</version>
     <configuration>
       <parallel>classes</parallel>
     </configuration>
   </plugin>

There are some things to take care when running unit tests in parallel. Some of them might not be independent, isolated and reproducible. There are times when you have some test methods that might depend on other methods in the test class. That time you should use the parallel test class execution. You may also want to tweak the number of threads and core on which these threads run, using this configuration:

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-surefire-plugin</artifactId>
  <version>2.9</version>
  <configuration>
    <parallel>methods</parallel>
    <threadCount>4</threadCount>
    <perCoreThreadCount>true</perCoreThreadCount>
  </configuration>
</plugin>

Maven dependency for tools.jar in JDK7

Although it has been known for sometime now that JDK7 will bring the change to vendor properties name change from “Sun Microsystems Inc.” to “Oracle Corporation”, I thought it would serve as a good reminder since Java 7 final was just released.

If you have a maven project that uses tools.jar and adds that as a dependency to the project as follows:

...
  <profiles>
    <profile>
      <id>default-tools.jar</id>
      <activation>
        <property>
          <name>java.vendor</name>
          <value>Sun Microsystems Inc.</value>
        </property>
      </activation>
      <dependencies>
        <dependency>
          <groupId>com.sun</groupId>
          <artifactId>tools</artifactId>
          <version>1.4.2</version>
          <scope>system</scope>
          <systemPath>${java.home}/../lib/tools.jar</systemPath>
        </dependency>
      </dependencies>
    </profile>
  </profiles>
  ...

For making this work with JDK 7, you have to change the java.vendor value to Oracle Corporation like this:

...
  <profiles>
    <profile>
      <id>default-tools.jar</id>
      <activation>
        <property>
          <name>java.vendor</name>
          <value>Oracle Corporation</value>
        </property>
      </activation>
      <dependencies>
        <dependency>
          <groupId>com.sun</groupId>
          <artifactId>tools</artifactId>
          <version>1.4.2</version>
          <scope>system</scope>
          <systemPath>${java.home}/../lib/tools.jar</systemPath>
        </dependency>
      </dependencies>
    </profile>
  </profiles>
  ...