How to load cross-module resources/properties in Maven tests? - unit-testing

Question

I have a Maven maintained project with some modules. One module contains one XML file and one parsing class.
Second module depends on the first module. There is a class that calls the parsing class in the first module, but Maven cannot test the class in the second module. The test reports:
java.lang.NullPointerException
at java.util.Properties.loadFromXML(Properties.java:851)
at foo.firstModule.Parser.<init>(Parser.java:92)
at foo.secondModule.Program.<init>(Program.java:84)
In Parser.java (the first module), which uses Properties and InputStream to read/parse an XML file:
InputStream xmlStream = getClass().getResourceAsStream("Data.xml");
Properties properties = new Properties();
properties.loadFromXML(xmlStream);
The Data.xml is located in the first module's resources/foo/firstModule directory and tests OK in the first module.
It seems when testing the second module, Maven cannot correctly load the Data.xml from the first module .
I thought I can solve the problem by using maven-dependency-plugin:unpack. So I added these snippets to the second module's POM file:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<version>2.1</version>
<executions>
<execution>
<id>data-copying</id>
<phase>test-compile</phase>
<goals>
<goal>unpack</goal>
</goals>
<configuration>
<artifactItems>
<artifactItem>
<groupId>foo</groupId>
<artifactId>firstModule</artifactId>
<type>jar</type>
<includes>foo/firstModule/Data.xml</includes>
<outputDirectory>${project.build.directory}/classes</outputDirectory>
</artifactItem>
</artifactItems>
</configuration>
</execution>
</executions>
</plugin>
In this POM file I unpack the first module and copy the Data.xml into classes/foo/firstModule/ directory and then run tests.
I can see that it is indeed copied into the right directory, but Maven test still cannot read it (Properties.loadFromXML() throws NPE).
I also tried a different output directory, such as ${project.build.directory}/resources and ${project.build.directory}/test-classes, but all in vain.
Environments: Maven 2.2.1, eclipse, m2eclipse
---- updated ----
I forget to mention, that the Program in the 2nd module, extends the Parser in the 1st module and in the Parser's constructor properties are loaded and parsed. In fact, Program is another Parser with further capabilities.
I think Program extends Parser may be causing the problem (i.e. ClassLoader issues).
If I disconnect the "inheritance" and initialize a new Parser inside the Program it works OK and the test passes!
I cannot, however, change the inheritance because of the way it's designed.
---- update with full code ----
This is the Parser in the first module :
package foo.firstModule;
import java.io.IOException;
import java.io.InputStream;
import java.util.InvalidPropertiesFormatException;
import java.util.Properties;
public class Parser
{
private Properties properties;
public Parser()
{
InputStream xmlStream = getClass().getResourceAsStream("Data.xml");
properties = new Properties();
try
{
properties.loadFromXML(xmlStream);
}
catch (InvalidPropertiesFormatException e)
{
e.printStackTrace();
}
catch (IOException e)
{
e.printStackTrace();
}
}
public Properties getProperties()
{
return properties;
}
}
This is Parser's test case, which passes.
package foo.firstModule;
import junit.framework.TestCase;
public class ParserTest extends TestCase
{
public void testParser()
{
Parser p = new Parser();
assertEquals(64 , p.getProperties().size());
}
}
This is ParserExtend in the secondModule, which extends Parser in the firstModule:
package foo.secondModule;
import java.util.Properties;
import foo.firstModule.Parser;
public class ParserExtend extends Parser
{
private Properties properties;
public ParserExtend()
{
this.properties = getProperties();
}
public int getSize()
{
return properties.size();
}
}
This is ParserExtend's test case:
package foo.secondModule;
import junit.framework.TestCase;
public class ParserExtendTest extends TestCase
{
public void testParserExtend()
{
ParserExtend pe = new ParserExtend();
assertEquals(64 , pe.getSize());
}
}
The above test case failed because Properties.loadFromXML(Properties.java:851) throws NPE.
However, if I don't extend Parser and just initialize a new Parser:
package foo.secondModule;
import java.util.Properties;
import foo.firstModule.Parser;
public class ParserInit
{
private Properties properties;
public ParserInit()
{
Parser p = new Parser();
this.properties = p.getProperties();
}
public int getSize()
{
return properties.size();
}
}
and test it using:
package foo.secondModule;
import junit.framework.TestCase;
public class ParserInitTest extends TestCase
{
public void testParserInit()
{
ParserInit pi = new ParserInit();
assertEquals(64 , pi.getSize());
}
}
The test case passes!
This is my whole test scenario.
How can I pass the ParserExtend's test case?

Answer 1

It seems when testing the second module , maven cannot correctly load the Data.xml in the first module.
I created the exact same structure and I can't reproduce your problem. My Program class in the second module uses the Parser class from the first module which load properties from an XML file without any problem. Tested under Eclipse and on the command line.
I thought I can solve the problem by using maven-dependency-plugin:unpack to solve it.
Using dependency:unpack is definitely not a solution and if the first JAR contains foo/firstModule/Data.xml, using the Parser class from another module should just work. There must be something wrong somewhere else. If you can upload a representative test project, then please do so and I'll look at ti. Without a project allowing to reproduce, I'm afraid the best answer you'll get is "debug your code" :)

Answer 2

I agree, it sounds like classloader issues.
If you always intend on having Data.xml in /foo/firstModule/Data.xml location, give this a try in foo.firstModule.Parser:
InputStream xmlStream = getClass().getResourceAsStream("/foo/firstModule/Data.xml");
Or, if you're explicitly wanting the behavior of finding a "local" Data.xml should firstModule be reused elsewhere (e.g. secondModule or thirdModule has its own Data.xml), try this:
InputStream xmlStream = Thread.currentThread().getContextClassLoader().getResourceAsStream("Data.xml");