jetty-env.xml with DataSource leads to failing WebAppContext on mvn jetty:run

Question

I have a really simple webapp project with maven and jetty that has been working very well until now. But now I need to setup MySQL connection pooling with JNDI as the database connections always time out.

First of all here is the relevant content of my pom.xml:

<modelVersion>4.0.0</modelVersion>
...
<packaging>war</packaging>
...
<properties> 
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <jetty-version>8.1.0.v20120127</jetty-version>
</properties> 
<dependencies>
    ...
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.20</version>
    </dependency>
    <dependency>
        <groupId>org.mortbay.jetty</groupId>
        <artifactId>jetty-maven-plugin</artifactId>
        <version>${jetty-version}</version>
        <type>maven-plugin</type>
    </dependency>
</dependencies>
...
<build>
    <plugins>
    <plugin>
        <groupId>org.mortbay.jetty</groupId>
        <artifactId>jetty-maven-plugin</artifactId>
        <version>${jetty-version}</version>
        <configuration>
                <scanIntervalSeconds>10</scanIntervalSeconds>
            </configuration>
        </plugin>
    </plugins>
    ...
</build>

Now I created a jetty-env.xml in the folder /src/main/webapp/WEB-INF with the following content:

<Configure class="org.eclipse.jetty.webapp.WebAppContext">  
    <New id="project-db" class="org.eclipse.jetty.plus.jndi.Resource">
        <Arg>jdbc/db</Arg>
        <Arg>
            <New class="com.mysql.jdbc.jdbc2.optional.MysqlConnectionPoolDataSource">
                <Set name="url">jdbc:mysql://www.example.com:3306/mydb</Set>
                <Set name="username">dbuser</Set>
                <Set name="password">dbpass</Set>
            </New>
        </Arg>
    </New>
</Configure>

But the problem is that I can't even test if this connection works as the jetty-maven-plugin fails to start on the goal

mvn jetty:run

with the following error:

WARN:oejw.WebAppContext:Failed startup of context o.m.j.p.JettyWebAppContext
{/,file:/D:/documents/programmierung/workspace/battleships-trunk/src/main/webapp/}
,file:/D:/documents/programmierung/workspace/battleships-trunk/src/main/webapp/

java.lang.IllegalArgumentException: Object of class 
'org.mortbay.jetty.plugin.JettyWebAppContext' is not of type 
'org.eclipse.jetty.webapp.WebAppContext'. 
Object Class and type Class are from different loaders.

So how can I get this to work? I'm forced to use Jetty version 8.x as I need WebSocket support and as the remote productive server will be running Jetty 8.

EDIT Before Pavel Veller's answer I tried the following: Deployed the assembled war to the remote jetty8 server and got the same error only that the previous error now reads as follows:

java.lang.IllegalArgumentException: Object of class 
'org.eclipse.jetty.webapp.WebAppContext' is not of type 
'org.eclipse.jetty.webapp.WebAppContext'. 
Object Class and type Class are from different loaders.

So it seems as if there are multiple class loaders conflicting.

EDIT2 As requested by Pavel I recreated the error with a simplified webapp which you can find here on Dropbox. It is a zipped eclipse maven project.

Answer 1

Try removing the dependency on jetty-maven-plugin- this dependency adds the plugin to the WAR, which you don't want.

If you need to use any classes from Jetty itself, add a dependency for the specific version of Jetty (rather than the plugin) with a scope of provided.