Is there anything like VirtualEnv for Java?

Question

Is there anything similar to Python virtualenv for Java or JVM Languages?

Solution 1

From what I understand, virtualenv enables you to have separate library installation paths, effectively separate "virtual" Python installations.

Java doesn't have the concept of a "system-wide installed" library^(*): It always searches the classpath for the libraries to be loaded. Since the classpath can be (and needs to be!) defined for each application, each application can pick-and-choose which libraries and which versions it wants to load.

If you go down one level deeper and have a single application that somehow needs two different versions of the same library at the same time, then you can do even that with some classpath trickery. It can get complicated, but it's definitely possible (OSGi is one example where this is supported, even Tomcat with two separate webapplications does this).

I've seens some references to security in the virtualenv description: Java has a pretty thorough security system built in. In server applications it's often turned off because it's just easier to configure this way, but you can easily configure what exactly a Java application is allowed to do.

^{(*) Almost, there are extensions or extension libraries, but they aren't used a lot and even those can easily be loaded from arbitrary directories.}

Solution 2

Yes(see http://www.jenv.be/), like many other languages (Ruby, Python, Go, R, Php, etc. etc.).

Solution 3

I know this may be a little late , but Groovy/Java has gvm http://gvmtool.net/ which is the Groovy version of Ruby's renv.

I would respectfully agree with Gautam K, luthur. Dependency and package version management for projects is not the same as an isolated self-contained virtual environment to maintain different project.

My 2 cents -W

Solution 4

I'm confused by the assertion that "Java doesn't have the concept of a 'system-wide installed' library". What would you call the jar files in $JAVA_HOME/jre/lib and $JAVA_HOME/jre/lib/ext?

Regardless of whether or not Java "needs" a tool like virtualenv, it seems that something that allowed you to quickly switch between different Java environments (e.g. Java 6 with such-and-such security extensions, Java 7, etc.) would be handy - even if all it was actually doing under the covers was manipulating the PATH, JAVA_HOME, and CLASSPATH env variables.

Solution 5

I have also been looking for a similar solution to simplify switching context between projects that use different Maven versions/settings and/or Java SDKs without having to modify M2_HOME and JAVA_HOME settings every time.

To this end, I developed a solution that helps execute mvn commands with the appropriate configuration based on per-project settings (stored in a .mvn folder).

See: https://github.com/AlejandroRivera/maven-env

Be aware that this only helps if you're using Maven to build and/or run your project.

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Comments

[Gautam]

Maven is a build tool and has nothing in common with virtualenv ! Which is a totally different concept .

[luthur]

!!!!!!!!maven config file can specify which version and packages you would use in a specific java project, isn't it!!!!!!!!!!!!!!!!

[jiggy]

OP's question is a classic XY problem. He is asking how to map a Python solution to Java instead of asking how to solve a problem. The question should be "How do I manage dependencies in Java?" and the correct answer is to use Maven or one of it's competitors.

[Joachim Sauer]

I think this should have been a comment on my answer. I didn't see it before, so sorry for my late response: The jre/lib/ext holds extension libraries, which I've mentioned briefly in the footnote and they are indeed not used a lot. Yes, I agree there is some utility in quickly switching between JREs/JDKs and some such tools exist (for example Debian/Ubuntu has the alternatives system which allows you to switch the JDK used for the different java commands (among many other things)).

[mblakesley]

This may be true for packages, but another thing python virtual environments help manage is versions of python itself. How do Java devs handle working on projects that use different versions of Java?

[Vüsal]

Why not to use Maven profiles ?

[greenmarker]

Script starting Java application that needs a specific installation of Java virtual machine, usually sets path to it in the JAVA_HOME variable.

[Rob Audenaerde]

The Java install also depends on some system libraries.

[Rob Audenaerde]

@jiggy you can't know what problem he is trying to solve (as he does not ask this). He could be 'just curious' as well