GWT using ActiveMQ through Spring problems

Question

I have a standalone Spring command and control application that broadcasts system status using ActiveMQ through the Spring JMS API. This works fine, I have tested it and have a test client program that can register to listen to the topic.

I also have a Spring based GWT application and I am trying to have it register to one of the ActiveMQ topics so it can receive status messages from the C&C application. In the GWT project, I have an applicationContext.xml under WEB-INF:

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

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:amq="http://activemq.apache.org/schema/core"
    xsi:schemaLocation="http://www.springframework.org/schema/beans 
    http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
    http://activemq.apache.org/schema/core
    http://activemq.apache.org/schema/core/activemq-core-5.2.0.xsd">

    <amq:topic id="embedded.sysModel" physicalName="org.apache.activemq.spring.embedded.sysmodel" />
</beans>

When I run the GWT application from Eclipse I get the following error(s).

15:16:20,067 ERROR [org.springframework.web.context.ContextLoader] - Context initialization failed org.springframework.beans.factory.parsing.BeanDefinitionParsingException: Configuration problem: Unable to locate Spring NamespaceHandler for XML schema namespace [http://activemq.apache.org/schema/core] Offending resource: ServletContext resource [/WEB-INF/applicationContext.xml]

Now at this point I do not even have any code in the GWT app that is referencing ActiveMQ or the Spring JMS Template. I did at first, but I backed everything out to find the first point of failure. And it appears to be the amq:topic line. If I comment that line out of the applicationContext.xml file, my GWT app initializes and runs just fine.

Here is my pom.xml for GWT

<?xml version="1.0" encoding="UTF-8"?>
<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">
<!-- POM generated by gwt-maven-plugin archetype -->
<modelVersion>4.0.0</modelVersion>
<groupId>gui-spring-gwt</groupId>
<artifactId>ourappgui</artifactId>
<packaging>war</packaging>
<version>2.0</version>

<properties>

    <!-- convenience to define GWT version in one place -->
    <gwt.version>2.4.0</gwt.version>
    <spring.version>3.0.6.RELEASE</spring.version>

    <!-- tell the compiler we can use 1.5 -->
    <maven.compiler.source>1.6</maven.compiler.source>
    <maven.compiler.target>1.6</maven.compiler.target>

</properties>

<dependencies>

    <!-- GWT dependencies (from central repo) -->
    <dependency>
        <groupId>com.google.gwt</groupId>
        <artifactId>gwt-servlet</artifactId>
        <version>${gwt.version}</version>
        <scope>runtime</scope>
    </dependency>
    <dependency>
        <groupId>com.google.gwt</groupId>
        <artifactId>gwt-user</artifactId>
        <version>${gwt.version}</version>
        <scope>provided</scope>
    </dependency>

    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>servlet-api</artifactId>
        <version>2.5</version>
    </dependency>

    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>${spring.version}</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-web</artifactId>
        <version>${spring.version}</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context-support</artifactId>
        <version>${spring.version}</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-aop</artifactId>
        <version>${spring.version}</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-beans</artifactId>
        <version>${spring.version}</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-test</artifactId>
        <version>${spring.version}</version>
    </dependency>
    <dependency>
        <groupId>log4j</groupId>
        <artifactId>log4j</artifactId>
        <version>1.2.14</version>
    </dependency>
    <!-- test -->
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.7</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.apache.derby</groupId>
        <artifactId>derby</artifactId>
        <version>10.5.3.0_1</version>
    </dependency>
    <dependency>
        <groupId>org.apache.derby</groupId>
        <artifactId>derbyclient</artifactId>
        <version>10.5.3.0_1</version>
    </dependency>
</dependencies>

<build>
    <outputDirectory>war/WEB-INF/classes</outputDirectory>
    <plugins>
        <plugin>
            <groupId>org.codehaus.mojo</groupId>
            <artifactId>gwt-maven-plugin</artifactId>
            <version>2.3.0-1</version>
            <dependencies>
                <dependency>
                    <groupId>com.google.gwt</groupId>
                    <artifactId>gwt-user</artifactId>
                    <version>${gwt.version}</version>
                </dependency>
                <dependency>
                    <groupId>com.google.gwt</groupId>
                    <artifactId>gwt-dev</artifactId>
                    <version>${gwt.version}</version>
                </dependency>
            </dependencies>
            <executions>
                <execution>
                    <goals>
                        <goal>compile</goal>
                        <goal>generateAsync</goal>
                        <goal>test</goal>
                    </goals>
                </execution>
            </executions>
            <configuration>
                <runTarget>pevcogui.html</runTarget>
            </configuration>
        </plugin>
        <!-- If you want to use the target/web.xml file mergewebxml produces, 
            tell the war plugin to use it. Also, exclude what you want from the final 
            artifact here. <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-war-plugin</artifactId> 
            <configuration> <webXml>target/web.xml</webXml> <warSourceExcludes>.gwt-tmp/**</warSourceExcludes> 
            </configuration> </plugin> -->

        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>2.0.2</version>
            <configuration>
                <source>${maven.compiler.source}</source>
                <target>${maven.compiler.target}</target>
            </configuration>
        </plugin>
        <plugin>
            <artifactId>maven-war-plugin</artifactId>
            <version>2.1-beta-1</version>
            <configuration>
                <warSourceDirectory>war</warSourceDirectory>
            </configuration>
        </plugin>

    </plugins>
</build>
</project>

Answer 1

It seems that this problem is rooted in the Eclipse GWT plugin. I found this post : Spring NamespaceHandler issue when launching Maven-based GWT App from Eclipse IDE after migration to Spring 3 which discussed a similar problem. This post on the Spring forum is talks about a similar problem with spring-security.

My workaround is to run the GWT app from the command line using "mvn gwt:run". Launching this way keeps the classpath intact. I get a successful build using maven at the cmd line and I can deploy to Glassfish. Its only when launching from within Eclipse that I get the error.

Answer 2

The problem is that the xsd for http://activemq.apache.org/schema/core can't be found. activemq.xsd is part of the activemq-core-xxx.jar, and will be found when this jar is in your classpath. But you don't have a dependency on that.

So add the dependency to activemq-core if you use xmlns:amq:

<dependency>
    <groupId>org.apache.activemq</groupId>
    <artifactId>activemq-core</artifactId>
    <version>5.5.0</version><!-- or whatever version you use -->
</dependency>