Load jar into classpath and access resources in it at runtime

[mike]

Hi,

I have created a jar file, test-example.jar, and added under src/test/resources
and now I want to make sure that when I run the testcase
this jar file is loaded so I can access files in it. I am using java 11.

Q1: How to load jar, in testcase, at runtime?
Q2: How to access resource in jar. Resource resides in jar with the following path suites/tools/device/nc/testng2.xml

br,

//mike

[Arne Vajhøj]

On 6/21/2022 11:38 AM, mike wrote:
> I have created a jar file, test-example.jar, and added under src/test/resources
> and now I want to make sure that when I run the testcase
> this jar file is loaded so I can access files in it. I am using java 11.
>
> Q1: How to load jar, in testcase, at runtime?

Standard technique is to instantiate a URLClassLoader for the
jar file and use that to load files from the jar file.

> Q2: How to access resource in jar. Resource resides in jar with the following path suites/tools/device/nc/testng2.xml

Maybe:

theclassloader.getResourceAsStream("suites/tools/device/nc/testng2.xml"));

Arne

[Daniele Futtorovic]

Normally, what you put under /src is what you want packaged (in a JAR,
WAR, etc.).
If you put a JAR there, and your sources are packaged as a JAR, you'll
end up with JAR inside your JAR. Which I would say is definitely
technically workable. I'm not sure whether it's a recommended practice
or not.

To load such a JAR file, you'd have to load it as a resource

Thread.getThread().getContextClassLoader().getResource(NAME_OF_THE_JAR_FILE)

, then create a new ClassLoader for that resource -- which will be
binary, so not a URLCLassLoader... Then load the resource/class you need
from that classloader.

Perhaps instead of the above, one could simply create a URLClassLoader
with a "classpath:/NAME_OF_THE_JAR_FILE" URL. I mention it in case, but
IIRC the "classpath:/" resource prefix is something that Spring code
brings, it's not out of the box. Not sure.

Alternatives to all of the above include:
- at or before build time, extracting the files you need from the JAR
and putting them in your /src tree flat;
- putting the JAR file alongside your source tree (in a lib directory)
and making sure it's added to the classpath when the runtime is
launched, in which case you could access classes and resources from it
as though they were in your /src tree.

--
DF.

[e.d.pro...@gmail.com]

On Thursday, June 23, 2022 at 6:32:11 AM UTC-4, Daniele Futtorovic wrote:
> On 21/06/2022 17:38, mike wrote:
> > Hi,
> >
> > I have created a jar file, test-example.jar, and added under src/test/resources
> > and now I want to make sure that when I run the testcase
> > this jar file is loaded so I can access files in it. I am using java 11.
> >
> > Q1: How to load jar, in testcase, at runtime?
> > Q2: How to access resource in jar. Resource resides in jar with the following path suites/tools/device/nc/testng2.xml
> >
> > br,
> >
> > //mike
> Normally, what you put under /src is what you want packaged (in a JAR,
> WAR, etc.).
> If you put a JAR there, and your sources are packaged as a JAR, you'll
> end up with JAR inside your JAR. Which I would say is definitely
> technically workable. I'm not sure whether it's a recommended practice
> or not.
>
> To load such a JAR file, you'd have to load it as a resource
>
> Thread.getThread().getContextClassLoader().getResource(NAME_OF_THE_JAR_FILE)
>

op didn't say if they're trying to package a jar inside another jar or just build a war.
That Thread command is definitely the way to read a resource, at least in a maven war project from the src/main/resources folder.
If you're building a war, dependent jars should end up in WEB-INF/lib.
If the jar is provided on the classpath, the context class loader should work. Normally files loaded as resources are not packaged inside a file (jar) wrapped in another file (jar/war).

[Daniele Futtorovic]

On 23/06/2022 14:20, e.d.pro...@gmail.com wrote:

> op didn't say if they're trying to package a jar inside another jar or just build a war.

On 21/06/2022 17:38, mike wrote:
> Hi,
>
> I have created a jar file, test-example.jar, and added under
src/test/resources

--
DF.

[e.d.pro...@gmail.com]

On Thursday, June 23, 2022 at 9:33:17 AM UTC-4, Daniele Futtorovic wrote:
> > op didn't say if they're trying to package a jar inside another jar or just build a war.
> On 21/06/2022 17:38, mike wrote:
> > Hi,
> >
> > I have created a jar file, test-example.jar, and added under
> src/test/resources
> --
> DF.

sounds like test-example.jar is a jar file in the src/test/resources path, not what they're trying to build