How to configure a manifest file of a jar file by using the maven assembly plugin?

Question

how can I configure the content of a manifest file, which is include in a Jar file? Now I am using the maven assembly plugin to configure my jar file. I have defined some XML Tags, which includes pom.xml´s different values.

<plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-assembly-plugin</artifactId>
            <configuration>
                <descriptorRefs>
                    <descriptorRef>
                        jar-with-dependencies
                    </descriptorRef>
                </descriptorRefs>
                <archive>
                    <addMavenDescriptor>false</addMavenDescriptor>
                    <manifestEntries>                                   
                        <Source-JDK>${source.jdk}</Source-JDK>
                        <Target-JDK>${target.jdk}</Target-JDK>
                        <GroupId.ArtifactId>${project.groupId}.${project.artifactId}</GroupId.ArtifactId>
                        <Project.Version>${project.version}</Project.Version>                           
                        <Project.Build.SourceEncoding>UTF-8</Project.Build.SourceEncoding>  
                        <Maven.Build.Timestamp>${maven.build.timestamp}</Maven.Build.Timestamp>
                    </manifestEntries>
                    <manifest>                      
                        <addDefaultImplementationEntries>true</addDefaultImplementationEntries>
                        <addDefaultSpecificationEntries>true</addDefaultSpecificationEntries>
                        <addClasspath>true</addClasspath>
                        <classpathPrefix>lib/</classpathPrefix>
                        <mainClass>${project.groupId}.myMainClass</mainClass>
                    </manifest>
                </archive>
                <appendAssemblyId>false</appendAssemblyId>
            </configuration>
            <executions>
                <execution>
                    <id>assembly-jar-Id</id>
                    <phase>package</phase>
                    <goals>
                        <goal>single</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>

In this solution, the manifest file of my jar file includes all tags, which are important for me. But if I use one of these specific tags, I get an error message likte this during executing my jar file:

 Error: An unexpected error occurred while trying to open file ./myJarFile.jar

I can solve this problem, if I delete all specific tags in the xml tag "manifestEntries".

Answer 1

This could be related to the use of invalid characters in the manifest attribute names. Valid characters are [0-9a-zA-Z_-] . This is discussed in the JavaDocs for the Attributes class:

http://docs.oracle.com/javase/7/docs/api/java/util/jar/Attributes.html

Also see the jar file specification, particularly the grammar specification for headerchar :

http://docs.oracle.com/javase/7/docs/technotes/guides/jar/jar.html#Name-Value_pairs_and_Sections

Some of your attribute names don't match the specified pattern, such as GroupId.ArtifactId . I recommend testing removal of each attribute one by one (or changing names to fit the spec) to confirm if particular attribute names are causing the problem.