Develop Reference

Glassfish 4.1.1 and offline JSP compiler (JSP and OSGI)

As everyone knows jsp can't work with classes outside current osgi web archive bundle. This is a bug in GF. The developers of glassfish for workaround of this bug https://java.net/jira/browse/GLASSFISH-11208 offer to use offline jsp compiler (by other words to compile jsp files not during deployment time but during archive building time). Ok, and I used jspc-maven-plugin to compile my jsp during wab building.
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>jspc-maven-plugin</artifactId>
<version>1.4.6</version>
<executions>
<execution>
<goals>
<goal>compile</goal>
</goals>
<id>compile</id>
</execution>
</executions>
<configuration>
</configuration>
</plugin>
The jsp are compiled and I see their .classes in built web archive.
Now the problem - how can I make glassfish use my compiled jsp but not to compile it itself? Because I see that GF ignores compiled .classes and generate .javas and compile them itself.
EDIT 1 What I make up to now:
1) I added to glassfish-web.xml
<jsp-config>
<property name="usePrecompiled" value="true"/>
<!-- to see it doesn't generate .javas -->
<property name="keepgenerated" value="true" />
</jsp-config>
2)And when I build my wab archive I have jsp classes in WEB-INF/classes/jsp/... However, I get exception that jsp file not found. When I manually move jsp classes to WEB-INF/classes/org/apache/jsp... I see that container now sees these classes but I get
StandardWrapperValve[default]: Servlet.service() for servlet default threw exception
java.lang.NoClassDefFoundError: org/apache/jsp/... (wrong name: jsp/...)
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:760)
at org.apache.felix.framework.BundleWiringImpl$BundleClassLoader.defineClass(BundleWiringImpl.java:2370)
at org.apache.felix.framework.BundleWiringImpl$BundleClassLoader.findClass(BundleWiringImpl.java:2154)
at org.apache.felix.framework.BundleWiringImpl.findClassOrResourceByDelegation(BundleWiringImpl.java:1542)
at org.apache.felix.framework.BundleWiringImpl.access$400(BundleWiringImpl.java:79)
at org.apache.felix.framework.BundleWiringImpl$BundleClassLoader.loadClass(BundleWiringImpl.java:2018)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at org.apache.felix.framework.Felix.loadBundleClass(Felix.java:1925)
at org.apache.felix.framework.BundleImpl.loadClass(BundleImpl.java:978)
at org.glassfish.osgijavaeebase.BundleClassLoader.loadClass(BundleClassLoader.java:79)
at org.glassfish.osgiweb.OSGiWebDeploymentContext$WABClassLoader.loadClass(OSGiWebDeploymentContext.java:169)
at org.glassfish.osgiweb.OSGiWebDeploymentContext$WABClassLoader.loadClass(OSGiWebDeploymentContext.java:154)
at org.apache.jasper.JspCompilationContext.load(JspCompilationContext.java:654)
at org.apache.jasper.servlet.JspServletWrapper.getServlet(JspServletWrapper.java:202)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:388)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:473)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:377)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
at org.apache.catalina.core.ApplicationDispatcher.doInvoke(ApplicationDispatcher.java:875)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:739)
at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:695)
at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:626)
So know this is the right path - org/apache/jsp. The question is how to make maven plugin to output to this direction?
EDIT 2
So I found the settings of this maven plugin -
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>jspc-maven-plugin</artifactId>
<version>1.4.6</version>
<executions>
<execution>
<goals>
<goal>compile</goal>
</goals>
<id>compile</id>
<configuration>
<packageName>org.apache.jsp</packageName>
</configuration>
</execution>
</executions>
<configuration>
</configuration>
</plugin>
However, this is the final point but not result. As I get no exception, bute the returned http request is empty (blank page in browser). Seems I should use another maven plugin but which one?

So, to all steps which I did and explained in my edit it is necessary to modify web.xml file because plugin will add there mapping for servlets generated from jsp pages. So, the final settings are :
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>jspc-maven-plugin</artifactId>
<version>1.4.6</version>
<executions>
<execution>
<goals>
<goal>compile</goal>
</goals>
<id>compile</id>
<configuration>
<!-- package where the compiled jsp classes will be put -->
<packageName>org.apache.jsp</packageName>
<!-- the plugin adds servlets to this web.xml file -->
<outputWebXml>${project.build.directory}/web.xml</outputWebXml>
<verbose>true</verbose>
<target>8</target>
<source>8</source>
</configuration>
</execution>
</executions>
<configuration>
</configuration>
</plugin>
EDIT
Finally I found out that the version of jasper in GlassFish 4.1 is not known or even can be modified -> I got exceptions that such method not found etc. So I ended with the following - I donwloaded the sources of this plugin and made it use the version of the jasper in glassfish. I did not do any modifications in source code of the plugin, only in pom.xml. So the final pom became:
<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">
<!--<parent>
<artifactId>mojo</artifactId>
<groupId>org.codehaus.mojo</groupId>
<version>11</version>
</parent>-->
<modelVersion>4.0.0</modelVersion>
<groupId>org.codehaus.mojo</groupId>
<artifactId>jspc-maven-plugin</artifactId>
<version>1.4.6</version>
<packaging>maven-plugin</packaging>
<name>Maven Jspc plugin</name>
<developers>
<developer>
<name>Jeff Genender</name>
<email>jgenender#apache.org</email>
<organization>Savoir Technologies</organization>
<organizationUrl>http://www.savoirtech.com</organizationUrl>
<timezone>-7</timezone>
</developer>
</developers>
<contributors>
<contributor>
<name>Grzegorz Slowikowski</name>
<email>gs#tiger.com.pl</email>
<organization>Scott Tiger S.A.</organization>
<organizationUrl>http://www.tiger.com.pl</organizationUrl>
<timezone>+1</timezone>
</contributor>
<contributor>
<name>Pawel Pastula</name>
<email>pablo#tiger.com.pl</email>
<organization>Scott Tiger S.A.</organization>
<organizationUrl>http://www.tiger.com.pl</organizationUrl>
<timezone>+1</timezone>
</contributor>
</contributors>
<dependencies>
<!-- from glassfish 4.1.1 modules folder we need:
javax.servlet.jsp.jar
javax.servlet-api.jar
javax.servlet.jsp-api.jar
javax.el.jar
javax.servlet.jsp.jstl-api.jar
javax.servlet.jsp.jstl.jar
what versions of this jar you can find out in parent pom of glassfish
http://repo.maven.apache.org/maven2/org/glassfish/main/glassfish-parent/4.1.1/glassfish-parent-4.1.1.pom
and in manifest file
-->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.1.0</version>
</dependency>
<dependency>
<groupId>javax.servlet.jsp</groupId>
<artifactId>javax.servlet.jsp-api</artifactId>
<version>2.3.2-b01</version>
</dependency>
<dependency>
<groupId>org.glassfish.web</groupId>
<artifactId>javax.servlet.jsp</artifactId>
<version>2.3.3-b02</version>
</dependency>
<dependency>
<groupId>org.glassfish</groupId>
<artifactId>javax.el</artifactId>
<version>3.0.0</version>
</dependency>
<dependency>
<groupId>javax.servlet.jsp.jstl</groupId>
<artifactId>javax.servlet.jsp.jstl-api</artifactId>
<version>1.2.1</version>
</dependency>
<dependency>
<groupId>org.glassfish.web</groupId>
<artifactId>javax.servlet.jsp.jstl</artifactId>
<version>1.2.4</version>
</dependency>
<!-- we need this dependency as it contais tld files for core tag library -->
<dependency>
<groupId>org.eclipse.jetty.orbit</groupId>
<artifactId>org.apache.jasper.glassfish</artifactId>
<version>2.2.2.v201112011158</version>
</dependency>
<dependency>
<groupId>ant</groupId>
<artifactId>ant</artifactId>
<version>1.6.5</version>
</dependency>
<dependency>
<groupId>org.apache.maven</groupId>
<artifactId>maven-plugin-api</artifactId>
<version>2.0</version>
</dependency>
<dependency>
<groupId>org.apache.maven</groupId>
<artifactId>maven-project</artifactId>
<version>2.0</version>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.13</version>
<scope>runtime</scope>
</dependency>
</dependencies>
</project>
When you will compile you bundle you will have to add the following dependencies:
<dependency>
<groupId>org.glassfish.web</groupId>
<artifactId>javax.servlet.jsp</artifactId>
<version>2.3.3-b02</version>
</dependency>
<dependency>
<groupId>org.glassfish.web</groupId>
<artifactId>javax.servlet.jsp.jstl</artifactId>
<version>1.2.4</version>
</dependency>
Besides you will need to import some packages from glassfish to make it work. So in result you can use precompiled jps files with glassfish, but you need to make some things before it. And as you see you link your code to GF.
The most important thing - you can work with classes from other osgi bundles in jsp! For those who work with osgi in java-ee this can be very important. After doing all these steps I must conclude that GF IS NOT SUPPORTED TO BE USED WITH PRECOMPILED JPS FILES in spite of suggestions from the developers.
I hope at least one will appreciate all the solution, because it seems to me this is the first description in internet how to use precompiled jps pages with GF. By the way if you use osgi and it complains it can't find classes import the necessary packages.

Conflict between httpclient version and Apache Spark

I'm developing a Java application using Apache Spark. I use this version:
<dependency>
<groupId>org.apache.spark</groupId>
<artifactId>spark-core_2.10</artifactId>
<version>1.2.2</version>
</dependency>
In my code, there is a transitional dependency:
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>4.5.2</version>
</dependency>
I package my application into a single JAR file. When deploying it on EC2 instance using spark-submit, I get this error.
Caused by: java.lang.NoSuchFieldError: INSTANCE
at org.apache.http.conn.ssl.SSLConnectionSocketFactory.<clinit>(SSLConnectionSocketFactory.java:144)
at com.amazonaws.http.apache.client.impl.ApacheConnectionManagerFactory.getPreferredSocketFactory(ApacheConnectionManagerFactory.java:87)
at com.amazonaws.http.apache.client.impl.ApacheConnectionManagerFactory.create(ApacheConnectionManagerFactory.java:65)
at com.amazonaws.http.apache.client.impl.ApacheConnectionManagerFactory.create(ApacheConnectionManagerFactory.java:58)
at com.amazonaws.http.apache.client.impl.ApacheHttpClientFactory.create(ApacheHttpClientFactory.java:50)
at com.amazonaws.http.apache.client.impl.ApacheHttpClientFactory.create(ApacheHttpClientFactory.java:38)
This error shows clearly that SparkSubmit has loaded an older version of the same Apache httpclient library and this conflict happens for this reason.
What is a good way to solve this issue?
For some reason, I cannot upgrade Spark on my Java code. However, I could do that with the EC2 cluster easily. Is it possible to deploy my java code on a cluster with a higher version say 1.6.1 version?

As said in your post, Spark is loading an older version of the httpclient. The solution is to use the Maven's relocation facility to produce a neat conflict-free project.
Here's an example of how to use it in your pom.xml file :
<project>
<!-- Your project definition here, with the groupId, artifactId, and it's dependencies -->
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-shade-plugin</artifactId>
<version>2.4.3</version>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>shade</goal>
</goals>
<configuration>
<relocations>
<relocation>
<pattern>org.apache.http.client</pattern>
<shadedPattern>shaded.org.apache.http.client</shadedPattern>
</relocation>
</relocations>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
This will move all files from org.apache.http.client to shaded.org.apache.http.client, resolving the conflict.
Original post :
If this is simply a matter of transitive dependencies, you could just add this to your spark-core dependency to exclude the HttpClient used by Spark :
<dependency>
<groupId>org.apache.spark</groupId>
<artifactId>spark-core_2.10</artifactId>
<version>1.2.2</version>
<scope>provided</scope>
<exclusions>
<exclusion>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
</exclusion>
</exclusions>
</dependency>
I also added the scope as provided in your dependency as it will be provided by your cluster.
However, that might muck around with Spark's internal behaviour. If you still get an error after doing this, you could try using Maven's relocation facility that should produce a neat conflict-free project.
Regarding the fact you can't upgrade Spark's version, did you use exactly this dependency declaration from mvnrepository ?
Spark being backwards compatible, there shouldn't be any problem deploying your job on a cluster with a higher version.

NoSuchMethodError: com.google.common.util.concurrent.MoreExecutors.directExecutor conflits on Elastic Search jar

While creating Elasticsearch Client, I'm getting the exception java.lang.NoSuchMethodError: com.google.common.util.concurrent.MoreExecutors.directExecutor()Ljava/util/concurrent/Executor;
After some lookup, seams like the Guava-18 is being overwrite by an older version at runtime, and Guava-18 only works during compile task.
My Maven configuration is the follow:
<build>
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.0</version>
<configuration>
<source>1.7</source>
<target>1.7</target>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-shade-plugin</artifactId>
<version>2.4.1</version>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>shade</goal>
</goals>
<configuration>
<transformers>
<transformer implementation="org.apache.maven.plugins.shade.resource.ServicesResourceTransformer"/>
</transformers>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
How can i force the Guava-18 version at execution time?

You should try to find where the "old" version of guava is taken from and to exclude it once for all.
Find the dependency :
mvn dependency:tree | grep guava
Exclude it :
<dependency>
<groupId>org.whatever</groupId>
<artifactId>the_lib_that_includes_guava</artifactId>
<version>0.97</version>
<exclusions>
<exclusion>
<artifactId>com.google</artifactId>
<groupId>guava</groupId>
</exclusion>
</exclusions>
</dependency>
See https://maven.apache.org/guides/introduction/introduction-to-optional-and-excludes-dependencies.html for more info on the dependency exclusion.

I add the correct dependency of elasticsearch resolve the problem
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>18.0</version>
</dependency>

Add a dependencyManagement block solves this problem:
<dependencyManagement>
<!-- enforce dependency guava version 20.0 -->
<dependencies>
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>20.0</version>
</dependency>
</dependencies>
</dependencyManagement>
Reference:
http://techidiocy.com/maven-dependency-version-conflict-problem-and-resolution/

I was also seeing the error message mentioned by the OP when creating an Elasticsearch Client instance. In my case it was occurring in a Spring Boot app at application startup. Spring Boot was attempting to auto-configure the Elasticsearch Client via dependencies brought in by spring-boot-starter-data-elasticsearch. The underlying guava version being brought in was:
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>18.0</version>
</dependency>
This was all working fine until I introduced the following google-api-client dependency...
<dependency>
<groupId>com.google.api-client</groupId>
<artifactId>google-api-client</artifactId>
<version>1.23.0</version>
</dependency>
...which depends on following guava dependency:
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava-jdk5</artifactId>
<version>17.0</version>
</dependency>
This caused a class path collision and the fix was to exclude the older guava version from the google-api-client like so:
<dependency>
<groupId>com.google.api-client</groupId>
<artifactId>google-api-client</artifactId>
<version>1.23.0</version>
<exclusions>
<exclusion>
<groupId>com.google.guava</groupId>
<artifactId>guava-jdk5</artifactId>
</exclusion>
</exclusions>
</dependency>

The best soltion is to use the shade plugin for maven. Adding this to your pom.xml should fix it:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-shade-plugin</artifactId>
<version>3.2.1</version>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>shade</goal>
</goals>
<configuration>
<relocations>
<relocation>
<pattern>com.google.common</pattern>
<shadedPattern>shaded.com.google.common</shadedPattern>
</relocation>
</relocations>
<artifactSet>
<includes>
<include>com.google.guava:guava</include>
</includes>
</artifactSet>
</configuration>
</execution>
</executions>
</plugin>
This will create an upper jar with the same name including only a shaded guava inside.

I had a similar problem. I created a .jar file (Java source), then I wanted to load that file into the Spark Shell. It turns out that Spark Shell loads jars from something similar to this
spark-[version]-bin-hadoop[version]/jars/".
That directory had an older version of the guava which causes the error. I had the correct version in my pom.xml. I even added exclusions and all suggested responses. In conclusion, it is indeed a wrong version of guava. I copied the version that matches my pom.xml file. Hope this helps. Regards.

SOLVED: I updated the Guava dependency to latest version and it solved the
<!-- https://mvnrepository.com/artifact/com.google.guava/guava -->
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>latest</version>
</dependency>

I was struggling with this issue from past 2 months and finally found the solution.
I added too many external jars in my Project Structure which actually created some jars in Library Root resulting in conflicts whenever something is added in pom.xml.
So what needs to be done is delete all external jar files from your project and keep only the ones which are from maven like Maven:org...
My project structure:

For SBT solution:
Use shading the library in build.sbt
// Shading com.google.**
// We need com.google.guava above 18 version but spark uses version 14 and in that we don't have directExecutor() method
// as spark give preference to spark used libraries, our code was failing
assemblyShadeRules in assembly := Seq(
ShadeRule.rename("com.google.**" -> "shadeio.#1").inAll
)

Exporting dependency dll to resulting war

I have a Java web project using jMUPdf library as an external dependency. As I was not able to find jMUPdf in any public maven repository, I tried to install it to my local m2 repository using install-file
jMUPdf uses jmupdf.jar and a dependent jmupdf64.dll, so I did this:
mvn install:install-file -Dfile=jmupdf.jar -DgroupId=jmupdf -DartifactId=jmupdf -Dversion=0.4.1 -Dpackaging=jar
mvn install:install-file -Dfile=jmupdf64.dll -DgroupId=jmupdf -DartifactId=jmupdfdll64 -Dversion=0.4.1 -Dpackaging=dll
I can see both libraries in my local m2 repository.
This is an excerpt from my pom.xml
<dependency>
<groupId>jmupdf</groupId>
<artifactId>jmupdfdll64</artifactId>
<version>0.4.1</version>
<scope>runtime</scope>
<type>dll</type>
</dependency>
<dependency>
<groupId>jmupdf</groupId>
<artifactId>jmupdf</artifactId>
<version>0.4.1</version>
</dependency>
BUT: After compiling my project (which generates a war file) I only see the jmupdf.jar in \WEB-INF\lib and the DLL is missing. That's of course the reason for a runtime exception regarding the missing jmupdf64.dll
How can I make sure that the dll is part of the resulting war file?
EDIT: ... and that it will also be deployed correctly (e.g. into webapps/MYAPP/WEB-INF/lib on my Tomcat)?

This is my simple solution for my need of integrated security using ms-jdbc...
<dependencies>
<dependency>
<groupId>com.microsoft.sqlserver</groupId>
<artifactId>mssql-jdbc_auth</artifactId>
<version>8.4.1.x64</version>
<type>dll</type>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>com.microsoft.sqlserver</groupId>
<artifactId>mssql-jdbc</artifactId>
<version>8.4.1.jre14</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<version>3.1.1</version>
<executions>
<execution>
<id>copy-dependencies</id>
<phase>prepare-package</phase>
<goals>
<goal>copy-dependencies</goal>
</goals>
<configuration>
<excludeScope>provided</excludeScope>
<includeTypes>dll</includeTypes>
<overWriteIfNewer>true</overWriteIfNewer>
<outputDirectory>${project.build.directory}/${project.build.finalName}/WEB-INF/lib</outputDirectory>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>

Maven: Missing dependency when using test-jar at runtime

My Maven project foo.web has its source files in src/main and the test sources in src/test. Of course, the test classes make use of the "main" classes. Now I want to use the test classes in another project during runtime, so I followed these instructions on how to create a test-jar.
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>2.4</version>
<executions>
<execution>
<goals>
<goal>test-jar</goal>
</goals>
</execution>
</executions>
</plugin>
This works perfectly well, a jar like web-SNAPSHOT-tests.jar is created and I can include it in my other project.
<dependency>
<groupId>foo</groupId>
<artifactId>web</artifactId>
<version>SNAPSHOT</version>
<type>test-jar</type>
</dependency>
But it seems like the dependency to web-SNAPSHOT is not correctly set, because at runtime I receive NoClassDefFoundErrors of classes which are available in foo.web. So I added another dependency:
<dependency>
<groupId>foo</groupId>
<artifactId>web</artifactId>
<version>SNAPSHOT</version>
<type>war</type>
<scope>runtime</scope>
</dependency>
Unfortunately, this changes nothing. Does anyone know what is wrong here?

WAR archives are structured differently from JARs. When running in an application server such as Tomcat or JBoss, the server will handle the WAR correctly. Since you are running outside of a server, the artifact will be used like to a normal JAR archive. Because WARs use different locations for the .class files, the NoClassDefFoundError is thrown at run time.
In a JAR, the class com.example.Foo will be stored at /com/example/Foo.class. Since WARs are designed to contain libraries, resources etc. the classes should not be stored relative to the root of the archive. Instead, they are contained in the folder /WEB-INF/classes, Foo would be stored as /WEB-INF/classes/com/example/Foo.class.
Fortunately, the Maven developers thought of this issue and added the attachClasses option to the WAR plugin. This option creates an additional JAR with the classes classifier that contains only the Java classes in JAR format (relative the the archive root).
To enable the building of this JAR, you can use this snippet in your WAR project's build section (in addition to the configuration for the maven-jar-plugin to build the test JAR):
<pluginManagement>
<plugins>
<!-- … -->
<plugin>
<!-- build the classes JAR (non-test classes) -->
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<version>2.4</version>
<configuration>
<attachClasses>true</attachClasses>
</configuration>
</plugin>
</plugins>
</pluginManagement>
<plugins>
<!-- … -->
<plugin>
<!-- build the test JAR (test classes) -->
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>2.4</version>
<executions>
<execution>
<goals>
<goal>test-jar</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
Since the classes are attached, they will be installed and deployed by Maven together with the WAR artifact. Note that this only provides you with the contents of the regular WAR archive, to use the test classes, you need to depend on both the classes artifact and the test jar. To do this, you can use:
<dependencies>
<!-- … -->
<dependency>
<!-- test classes only -->
<groupId>foo</groupId>
<artifactId>web</artifactId>
<version>SNAPSHOT</version>
<type>test-jar</type>
</dependency>
<dependency>
<!-- non-test classes only -->
<groupId>foo</groupId>
<artifactId>web</artifactId>
<version>SNAPSHOT</version>
<type>jar</type>
<classifier>classes</classifier>
<scope>runtime</scope>
</dependency>
</dependencies>

Try:
<dependency>
<groupId>foo</groupId>
<artifactId>web</artifactId>
<version>SNAPSHOT</version>
<type>war</type>
<classifier>tests</classifier>
<scope>test</scope>
</dependency>

Maven allows you some configuration regarding snapshots dependancy
<repository>
<id>foo-repository</id>
<url>...</url>
<snapshots>
<enabled>true</enabled>
<updatePolicy>XXX</updatePolicy>
</snapshots>
Check the above config. If its false in pom.xml maven will not update snapshots. Also you will find the following thread useful for your query What exactly is a Maven Snapshot and why do we need it?