Is there anything like VirtualEnv for Java?
Question:
Is there anything similar to Python virtualenv for Java or JVM Languages?
Answers:
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.
Java as a language does not need the sandboxing features of virtualenv but a JVM Language like Jython can have VirtualEnv to use different environments without any conflict.
It is outlined in this blog post
Quote:
Get virtualenv installed for Jython. Just type “jeasy_install
virtualenv”. Once that finishes you should have a ‘virtualenv’ tool in
the Jython installation’s bin folder.
So when using Jython different frameworks and packages can be used without any conflict with global packages.
Maven, you can explicitly specify which packages you would use in a java project
Build tools like Ant, Maven, and gradle are the the closest thing to pip or easy_install.
The concept of virtualenv is done by the classpath. So there is no real need of virtualenv for Java
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
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.
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.
Yes(see http://www.jenv.be/), like many other languages (Ruby, Python, Go, R, Php, etc. etc.).
Is there anything similar to Python virtualenv for Java or JVM Languages?
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.
Java as a language does not need the sandboxing features of virtualenv but a JVM Language like Jython can have VirtualEnv to use different environments without any conflict.
It is outlined in this blog post
Quote:
Get virtualenv installed for Jython. Just type “jeasy_install
virtualenv”. Once that finishes you should have a ‘virtualenv’ tool in
the Jython installation’s bin folder.
So when using Jython different frameworks and packages can be used without any conflict with global packages.
Maven, you can explicitly specify which packages you would use in a java project
Build tools like Ant, Maven, and gradle are the the closest thing to pip or easy_install.
The concept of virtualenv is done by the classpath. So there is no real need of virtualenv for Java
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
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.
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.
Yes(see http://www.jenv.be/), like many other languages (Ruby, Python, Go, R, Php, etc. etc.).