You have two projects that require different versions of the same package dependency

When you have two projects that require different versions of the same package dependency, you can manage this situation effectively using one of the following strategies:

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1. Use Dependency Management in Parent POM (Maven Multi-Module Project)

If both projects are part of a Maven multi-module project, you can use a parent POM with a <dependencyManagement> section to specify which versions are used in each module.

Parent POM Example:

<dependencyManagement> <dependencies> <dependency> <groupId>com.example</groupId> <artifactId>example-library</artifactId> <version>1.0.0</version> </dependency> </dependencies> </dependencyManagement>

Module-Specific Version Override: In each child module, explicitly include the required version if it differs from the parent.

<!-- Project A uses version 1.0.0 --> <dependency> <groupId>com.example</groupId> <artifactId>example-library</artifactId> <version>1.0.0</version> </dependency> <!-- Project B uses version 2.0.0 --> <dependency> <groupId>com.example</groupId> <artifactId>example-library</artifactId> <version>2.0.0</version> </dependency>

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2. Isolate Dependencies with Maven Profiles

You can use Maven profiles to specify different dependency versions for different builds.

Profile Example:

<profiles> <profile> <id>projectA</id> <dependencies> <dependency> <groupId>com.example</groupId> <artifactId>example-library</artifactId> <version>1.0.0</version> </dependency> </dependencies> </profile> <profile> <id>projectB</id> <dependencies> <dependency> <groupId>com.example</groupId> <artifactId>example-library</artifactId> <version>2.0.0</version> </dependency> </dependencies> </profile> </profiles>

Activate a profile during the build

mvn clean install -PprojectA mvn clean install -PprojectB

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3. Use a Classloader Isolation Approach

If both dependencies need to be used in the same runtime (e.g., in a server or shared environment), you can use classloader isolation to avoid conflicts. This is typically done by:

• Packaging dependencies into different classloader contexts.
• Using tools like OSGi or shading.

Example Using Maven Shade Plugin:

The Maven Shade Plugin can repackage dependencies under different namespaces to avoid conflicts.

Example:

<build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-shade-plugin</artifactId> <executions> <execution> <phase>package</phase> <goals> <goal>shade</goal> </goals> <configuration> <relocations> <relocation> <pattern>com.example.library</pattern> <shadedPattern>com.example.library.v1</shadedPattern> </relocation> </relocations> </configuration> </execution> </executions> </plugin> </plugins> </build>

This renames the package of the dependency (e.g., com.example.library → com.example.library.v1), avoiding runtime conflicts.

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4. Use Separate Maven Repositories

If the projects are unrelated, you can use different local repositories for each project. This avoids conflicts at the repository level.

Command-Line Option:

mvn -Dmaven.repo.local=/path/to/repoA clean install mvn -Dmaven.repo.local=/path/to/repoB clean install

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5. Consider Dockerization or Separate Deployment Environments

If the projects run in isolated environments (e.g., different servers or containers), you can ensure that each project uses its required version without interference.

• Project A: Includes dependency version 1.0.0.
• Project B: Includes dependency version 2.0.0.

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Recommendations:

• If the projects are tightly coupled, use dependency management with profiles or parent POMs.
• If the projects run together in the same runtime, use Maven Shade Plugin or classloader isolation.
• For unrelated or separate environments, use different local repositories or containerized deployments.