Performing uniform Maven project preconditions in teams

Posted on
Using Maven Enforce Plugin to add constraints and control Maven projects configs

Guys,

In this post, I will share a bit about amazing things we can do using Maven.
There are good plugins in Maven that we rarely hear about it. Sad.
Maven Enforcer Plugin is one of them.

Well,
Working with Maven we deal with many configs, plugins, dependencies, and your versions.
Doing the management of it, sometimes, can make your head hurt.

We can work alone, or, we can work in a team.
And people are incredibly stunning, each one with your own style.
When I say style, it’s in a full context(IDE, numbers of space in tabs(2 of 4?, =D), versions of software, and so on).

Let’s begin with the more simple one.

Everybody knows that Java is free, open-source, etc.
We can download it, create a program, make it works, lunch that in Production…. huh… Nah!
But, maybe, you could forget that Oracle JDK it’s not allowed to be put in Production without a license - yeah.
Now, imagine, a member of your team, using that one to compile, create an artifact, and push it to Nexus, running pipeline and Voilà it’s there on Production, and we have a huge problem now.

Note: I know there’s OpenJDK version, but, that’s not the point, OK?
Thanks for understanding, kisses/hugs, and going on. (=

Let’s imagine we are working on a team using only AWS stack.
At that moment, after talking with a team, we’ve decided to use only Amazon Vendor JDK Corretto.
Only just for better compatibility and, you know, it has improvements performing to the cloud.

How can we ensure those two points:

  1. Do not put Oracle JDK binaries without license in Production
  2. Only use the vendor-specific to our architecture

Using Maven Enforcer Plugin!

Step one is declare the plugin and setup the version:

1
2
3
4
5
6
7
8
9
10
11
<build>
  <pluginManagement>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-enforcer-plugin</artifactId>
        <version>3.0.0</version>
      </plugin>
    </plugins>
  </pluginManagement>
</build>

Step two is setup the plugin:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
<plugins>
  <plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-enforcer-plugin</artifactId>
    <execution>
      <id>enforce-vendor</id>
      <goals>
        <goal>enforce</goal>
      </goals>
      <configuration>
        <rules>
          <requireJavaVendor>
            <includes>
              <include>Amazon.com Inc.</include>
            </includes>
          </requireJavaVendor>
        </rules>
      </configuration>
    </execution>
  </plugin>
</plugins>

In this example I’m using the wrong Oracle’s JDK:

1
2
3
4
❯ java -version                                            
java version "17.0.2" 2022-01-18 LTS
Java(TM) SE Runtime Environment (build 17.0.2+8-LTS-86)
Java HotSpot(TM) 64-Bit Server VM (build 17.0.2+8-LTS-86, mixed mode, sharing)

But, OK, we can confirm that JVM is from Oracle Corporation that easy way:

1
2
3
4
5
6
7
8
9
❯ jshell
|  Welcome to JShell -- Version 17.0.2
|  For an introduction type: /help intro

jshell> System.out.println(System.getProperty("java.vendor"));
Oracle Corporation

jshell> /exit
|  Goodbye

Oh, you notice? JShell said bye to me. Oh, my lovely Java. So polite. <3

When I try to compile, or, use any other Maven phase, it will fail like that:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
❯ mvn compile             
[INFO] Scanning for projects...
[INFO] 
[INFO] -----------------< dev.artsman:maven-enforcer-plugin >------------------
[INFO] Building maven-enforcer-plugin 1.0-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO] 
[INFO] --- maven-enforcer-plugin:3.0.0:enforce (enforce-maven) @ maven-enforcer-plugin ---
[INFO] 
[INFO] --- maven-enforcer-plugin:3.0.0:enforce (enforce-vendor) @ maven-enforcer-plugin ---
[WARNING] Rule 0: org.apache.maven.plugins.enforcer.RequireJavaVendor failed with message:
Oracle Corporation is not an included Required Java Vendor
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  0.523 s
[INFO] Finished at: 2022-03-06T18:48:18-03:00
[INFO] ------------------------------------------------------------------------

The interesting in here is, that constraint verification runs at the first goal in Maven Lifecycle: validation.
That’s super cool, isn’t it?

Bonus… we can do more!

Imagine there’s already a Maven version 3.9 and you want force that specific one.
Mine’s completely wrong at this momento, right?

1
2
❯ mvn --version
Apache Maven 3.8.4 (9b656c72d54e5bacbed989b64718c159fe39b537)

Running Maven:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
❯ mvn compile  
[INFO] Scanning for projects...
[INFO] 
[INFO] -----------------< dev.artsman:maven-enforcer-plugin >------------------
[INFO] Building maven-enforcer-plugin 1.0-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO] 
[INFO] --- maven-enforcer-plugin:3.0.0:enforce (enforce-maven) @ maven-enforcer-plugin ---
[WARNING] Rule 0: org.apache.maven.plugins.enforcer.RequireMavenVersion failed with message:
Detected Maven Version: 3.8.4 is not in the allowed range 3.9.
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  0.962 s
[INFO] Finished at: 2022-03-06T15:45:20-03:00
[INFO] ------------------------------------------------------------------------

Also you can specify the Java Version ignoring the vendor at this moment!

1
2
❯ java --version
openjdk 17.0.2 2022-01-18

But, for now, i want only be able to use Java 11.
Running Maven:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
❯ mvn compile                            
[INFO] Scanning for projects...
[INFO] 
[INFO] -----------------< dev.artsman:maven-enforcer-plugin >------------------
[INFO] Building maven-enforcer-plugin 1.0-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO] 
[INFO] --- maven-enforcer-plugin:3.0.0:enforce (enforce-maven) @ maven-enforcer-plugin ---
[INFO] 
[INFO] --- maven-enforcer-plugin:3.0.0:enforce (enforce-vendor) @ maven-enforcer-plugin ---
[INFO] 
[INFO] --- maven-enforcer-plugin:3.0.0:enforce (enforce-jdk) @ maven-enforcer-plugin ---
[WARNING] Rule 0: org.apache.maven.plugins.enforcer.RequireJavaVersion failed with message:
Detected JDK Version: 17.0.2 is not in the allowed range [11,11].
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  0.906 s
[INFO] Finished at: 2022-03-06T18:54:20-03:00
[INFO] ------------------------------------------------------------------------

There are more cooll stuffs.

But, in my opinion, that three constraints are the essentials:

  1. Maven version
  2. JDK vendor
  3. JDK version

That’s all for today.

The codebase is on my GitHub.

xoff.