Accessing your Maven project’s version from the command line is a crucial skill for any developer working with Maven-based projects. Whether you’re scripting deployments, automating builds, or simply need to quickly check the version of your project, having this information readily available can significantly streamline your workflow. This article delves into various methods to achieve this, offering practical examples and clear explanations to equip you with the knowledge you need. We’ll explore techniques using Maven itself, along with bash scripting approaches to extract this vital piece of information.

Using the mvn Command Directly

The most straightforward approach involves using the mvn command itself. Maven provides a built-in mechanism to display project properties, including the version. This method is efficient and reliable, making it a preferred choice for many developers.

Execute the following command in your project’s root directory:

mvn help:evaluate -Dexpression=project.version -q -DforceStdout

This command leverages the help:evaluate goal to evaluate the expression project.version and print the result to the standard output. The -q flag minimizes the output, while -DforceStdout ensures the version is printed to the console. This is a clean and effective way to retrieve the version information.

Extracting the Version with Bash

For more complex scenarios, integrating this process within a bash script can be beneficial. This allows you to dynamically use the project version within your scripts for various purposes like tagging releases or generating build artifacts.

Here’s an example bash script snippet:

VERSION=$(mvn help:evaluate -Dexpression=project.version -q -DforceStdout) echo "Project Version: $VERSION"

This script captures the output of the mvn command into the VERSION variable. You can then use this variable anywhere within your script. This technique provides flexibility in managing your project versions programmatically.

Parsing the pom.xml File

Another approach involves directly parsing the pom.xml file, the heart of your Maven project. This method is particularly useful if you need to extract other information from the POM file alongside the version.

You can use tools like xmllint or xpath to extract the version from the pom.xml. Here’s an example using xmllint:

VERSION=$(xmllint --xpath '/[local-name()="project"]/[local-name()="version"]/text()' pom.xml) echo "Project Version: $VERSION"

This command uses XPath to navigate the XML structure of the pom.xml and extract the value of the version element.

Alternative Approaches and Considerations

While the methods mentioned above are generally sufficient, alternative approaches exist depending on your specific needs. For instance, some build tools and plugins offer dedicated tasks for retrieving the project version. Understanding these alternatives provides a more comprehensive view of version management in Maven projects.

Consider using the Maven Properties Plugin for more advanced property management within your builds. Explore other plugins that might integrate seamlessly with your build process for specific version-related tasks.

• Use mvn -v to display the Maven version itself, distinct from the project version.
• Ensure your pom.xml is well-formed to avoid parsing issues.

Placeholder for Infographic: Visualizing the different methods of retrieving Maven project version.

Frequently Asked Questions

Q: How do I handle parent POM inheritance and versioning?

A: When using parent POMs, the child project inherits the version from the parent unless explicitly overridden. Use the techniques described above within the child project context to access its specific version.

1. Navigate to the project’s root directory.
2. Execute the chosen command.
3. Utilize the version information in your script or workflow.

Successfully retrieving your Maven project’s version from the command line empowers you to automate tasks, streamline builds, and manage your project more effectively. Whether you choose the direct mvn command, bash scripting, or XML parsing, each method offers distinct advantages for different scenarios. By understanding these techniques and their nuances, you’ll be well-equipped to integrate version management seamlessly into your development workflow. Consider exploring related topics like Maven profiles and property management to further enhance your build process and leverage the full power of Maven. Check out more resources on Maven on Apache Maven, Spring Boot Maven Plugin and this informative guide.

• Explore Maven profiles to manage different build configurations and versions effectively.
• Delve into Maven property management to handle complex versioning schemes.

Question & Answer :
Previous I issued a question on how to change Maven project vesion from command line which lead me to a new issue.

Previously I was able to get the version number since the version was stored as a property that was easy to grep and parse from the command line (bash). Now that the pom.xml <version> element is used for this, it no longer is unique since all the dependencies and maybe some others too use this. I think there is no way to get the current version number with a bash script without external tools for parsing XML or some very context-aware sed command.

The most clean solution in my opinion would be for Maven to hand out this version information. I was thinking of writing a custom maven plugin for retrieving different properties but I thought I’d ask here first.

So, is there any easy way to get the value of ${project.version} to the command line?

Solution

I had to cd to the directory manually but that can be done easily. In my bash script I have:

version=`cd $project_loc && mvn org.apache.maven.plugins:maven-help-plugin:2.1.1:evaluate -Dexpression=project.version | sed -n -e '/^\[.*\]/ !{ /^[0-9]/ { p; q } }'` 

Which gives me the current version that I can then advance. Grepping might be simpler but I thought I’d like as robust as possible, so I’m satisfied with the first line that starts with a number and try to handle this as a version number.

# Advances the last number of the given version string by one. function advance_version () { local v=$1 # Get the last number. First remove any suffixes (such as '-SNAPSHOT'). local cleaned=`echo $v | sed -e 's/[^0-9][^0-9]*$//'` local last_num=`echo $cleaned | sed -e 's/[0-9]*\.//g'` local next_num=$(($last_num+1)) # Finally replace the last number in version string with the new one. echo $v | sed -e "s/[0-9][0-9]*\([^0-9]*\)$/$next_num/" } 

And I use this by simply calling:

new_version=$(advance_version $version) 

The Maven Help Plugin is somehow already proposing something for this:

• help:evaluate evaluates Maven expressions given by the user in an interactive mode.

Here is how you would invoke it on the command line to get the ${project.version}:

mvn org.apache.maven.plugins:maven-help-plugin:2.1.1:evaluate \ -Dexpression=project.version 

As noted in the comments by Seb T, to only print the version without the maven INFO logs, additionally use -q -DforceStdout:

mvn help:evaluate -Dexpression=project.version -q -DforceStdout