如何在我的jar中包含外部类

Question

I have a problem with a service I am trying to write. I am trying to create a service that runs in the background on a windows system but uses java. I have seen several ways of doing this, but decided on one method that seemed to meet my requirements. The service will check a database for items it needs to work on. When it finds an item in the DB that it needs to do it will run some system commands to take care of them.

I found a way to use the tomcat7.exe file to run a jar as a service and that worked pretty well for basic stuff. Anything I write and compile into my jar file "myService.jar" we'll can call it goes well enough. The problem is that we already have several classes written for accessing the DB and running commands that are precompiled in a library of classes called BGLib-1.0.jar.

I have used this library in writing several jenkins plugins and had no problems calling functions from it. They all work fine when I create an hpi file and deploy it in Jenkins. There the compiler (Eclipse using Maven) packages the BGLib jar in with the plugin jar and Jenkins figures out how to get them to see one another.

When I build my service jar, however, it doesn't work when I deploy it.

I run a command like this to install the Tomcat exe renames to myservice.exe:

d:\myService\bin>myService.exe //IS//myService --Install=D:\myService\bin\myService.exe --Description="run some commands
Java Service" --Jvm=auto --Classpath=D:\myService\jar\myService.jar;D:\myService\jar\BGLib-1.0.jar --StartMode=jvm --
StartClass=com.myCompany.myService.myService --StartMethod=windowsService --StartParams=start --StopMode=jvm --StopClass
=com.myCompany.myService.myService --StopMethod=windowsService --StopParams=stop --LogPath=D:\myService\logs --StdOutpu
t=auto --StdError=auto

When I deploy this with code solely within the myService.jar the service behaves as expected, but when I try to call functions within the BGLib-1.0.jar I get nothing. The jvm appears to crash or become unresponsive. Debugging is a little tricky but it looks like I am getting class not found errors.

I tried adding the entry below in the POM file to see if changing the classpath entry in the manifest would help, but it didn't change the manifest. I am still kind of clueless ass to how the manifest file works. Any documentation on that would be cool. I have been to Maven's site and it doesn't seem to have comprehensive documentation on the tags available. Is there something I need to change in the manifest to get my jar to see external classes? Or is there something I can add that will get Maven to compile the classes from that jar in with my jar?

thanks in advance.

<configuration>
          <archive>
            <manifest>
              <addClasspath>true</addClasspath>
              <mainClass>com.myCompany.myService.myService</mainClass>
              <customClasspathLayout>BGLib-1.0.jar</customClasspathLayout>
            </manifest>
          </archive>
        </configuration>

Answer 1

To answer mainly the question of the title, you can the shade plugin to include dependencies into your final jar. You can even even relocate the class files (eg change package name) within the final jar so that the included classes don't conflict with different versions of the shaded dependency on the classpath. Not sure if this is the best solution for your particular problem though.

Answer 2

You can use the maven-dependency-plugin unpack-dependencies goal to include the contents of a dependency in the resulting artifact.

An example of how to do this would be:

        <plugin>
            <artifactId>maven-dependency-plugin</artifactId>
            <executions>
                <execution>
                    <id>${project.artifactId}-fetch-deps</id>
                    <phase>generate-sources</phase>
                    <goals>
                        <goal>unpack-dependencies</goal>
                    </goals>
                    <configuration>
                        <outputDirectory>${project.build.outputDirectory}</outputDirectory>
                        <stripVersion>true</stripVersion>
                        <excludeTransitive>true</excludeTransitive>
                        <includeArtifactIds>protobuf-java</includeArtifactIds>
                    </configuration>
                </execution>
            </executions>
        </plugin>

This will expand the protobuf-java dependency (flatten it) and include the contents in the resulting artifact generated by your build.

Answer 3

在我看来，您实际上想使用appassembler-maven-plugin ，否则我会去买maven-shade-plugin。