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I encountered this confusing issue when working on a larger project, so I’ve created a simple reproduction project to better reproduce and explain my issue. I’m not sure if it is possible for me to upload a zip with the whole structure, but it is only 5 files: https://paste.gg/p/anonymous/f502a8e613a64aeeae671b4c41587c43.

EDIT: The 5 files in my reproduction are also included at the bottom of this question — not just on an external site — as requested. I initially figured it would unnecessarily clutter this page due to the general verbosity of Maven.

I have a parent module MavenTest with 3 submodules: A, B, and C.

A only contains the class org.example.maventest.A.

B shades A like so:

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-shade-plugin</artifactId>
            <version>3.6.0</version>
            <executions>
                <execution>
                    <phase>package</phase>
                    <goals>
                        <goal>shade</goal>
                    </goals>
                    <configuration>
                        <relocations>
                            <relocation>
                                <pattern>org.example.maventest</pattern>
                                <shadedPattern>org.example.maventest.a</shadedPattern>
                            </relocation>
                        </relocations>
                    </configuration>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

This relocates the org.example.maventest.A class to org.example.maventest.a.A.

C shades B like so:

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-shade-plugin</artifactId>
            <version>3.6.0</version>
            <executions>
                <execution>
                    <phase>package</phase>
                    <goals>
                        <goal>shade</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

This should simply shade in the relocated org.example.maventest.a.A class from module B into C’s jar.

Expected behavior: running mvn clean install to build all the modules should create a jar C that only includes the relocated org.example.maventest.a.A file.

Actual behavior: When the shade plugin runs for module C, it reports this:

[INFO] --- shade:3.6.0:shade (default) @ C ---
[INFO] Including org.example:B:jar:1.0-SNAPSHOT in the shaded jar.
[INFO] Including org.example:A:jar:1.0-SNAPSHOT in the shaded jar.
[INFO] Dependency-reduced POM written at: /MavenTest/C/dependency-reduced-pom.xml

It seems that module C is inheriting the module A dependency from module B, which causes the original A class to be shaded in as well (using IntelliJ to look inside the jar):

The strange part, is that if I only build module C using mvn clean install -pl :C, maven correctly only includes the relocated class A:

[INFO] --- shade:3.6.0:shade (default) @ C ---
[INFO] Including org.example:B:jar:1.0-SNAPSHOT in the shaded jar.
[INFO] Dependency-reduced POM written at: /MavenTest/C/dependency-reduced-pom.xml

It seems that in this case, module C is looking at the dependency reduced pom of B produced by the shade plugin where the compile dependency on module A is removed. So, during the full build, I want to reproduce this behavior of C looking at B’s dependency reduced pom.

This also seems to affect compilation. For example, if I add this class to module C:

public class C {
    org.example.maventest.A first = null;
    org.example.maventest.a.A second = null;
}

When I run the full build (or look at it statically with IntelliJ), this code compiles.

However, when I build module C independently, this code fails because the org.example.maventest.A class cannot be found. I want the behavior of the independent build, where module A is seemingly excluded from the compile classpath.

Reproduction files

Directory structure:

MavenTest/A/src/main/java/org/example/maventest/A.java

    
package org.example.maventest;
 
public class A {
}

MavenTest/A/pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <artifactId>MavenTest</artifactId>
        <groupId>org.example</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
 
    <artifactId>A</artifactId>
</project>

MavenTest/B/pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <artifactId>MavenTest</artifactId>
        <groupId>org.example</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
 
    <artifactId>B</artifactId>
 
    <dependencies>
        <dependency>
            <groupId>org.example</groupId>
            <artifactId>A</artifactId>
            <version>${project.version}</version>
            <scope>compile</scope>
        </dependency>
    </dependencies>
 
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>3.6.0</version>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                        <configuration>
                            <relocations>
                                <relocation>
                                    <pattern>org.example.maventest</pattern>
                                    <shadedPattern>org.example.maventest.a</shadedPattern>
                                </relocation>
                            </relocations>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

MavenTest/C/pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <artifactId>MavenTest</artifactId>
        <groupId>org.example</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
 
    <artifactId>C</artifactId>
 
    <dependencies>
        <dependency>
            <groupId>org.example</groupId>
            <artifactId>B</artifactId>
            <version>${project.version}</version>
            <scope>compile</scope>
        </dependency>
    </dependencies>
 
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>3.6.0</version>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

MavenTest/pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
 
    <groupId>org.example</groupId>
    <artifactId>MavenTest</artifactId>
    <version>1.0-SNAPSHOT</version>
 
    <packaging>pom</packaging>
    <modules>
        <module>A</module>
        <module>B</module>
        <module>C</module>
    </modules>
</project>

Output of running Maven

(I tried to include these directly in the question, but StackOverflow complained I exceeded the maximum amount of characters).

mvn clean install (Full build, incorrect final C jar): https://paste.gg/p/anonymous/ce82a48c1db14a7f9c7c86020b4b79d6

mvn clean install -pl :C -X (Just module C, correct final jar): https://paste.gg/p/anonymous/dc7c21fcbb6442619a8159d0a0315e0c

Thiết kế website giá rẻ

Danh mục

How to get Maven to use dependency reduced pom when building a multi-module project?

Reproduction files

Output of running Maven