What is Shaded jar?

One of the ways to avoid dependency-hell in Java.

Suppose the original code base depends on version X of library A. I want to add a new library B to this codebase. However, library B depends on version Y of library A, Consider the situation where versions X and Y of library A are incompatible.

CodeBase
 |- Library A, Version X
 |- Library B
    |- Library A, Version Y # Conflict!!!

As it is, regardless of whether you select version X or Y of library A, new functions and existing functions You can't move both at the same time.

This is where shaded-jar comes in. The method is to bundle all the Class Y classes of Library A with Library B and create Library B'without dependencies.

CodeBase
 |- Library A, Version X
 |- Library B' (include Library A, Version Y)

relocation However, as it is, the class included in library A and the class of library A included in library B'are placed in the same classpath, so the conflict cannot be resolved.

`libraryA-versionX.jar`


com.foo.libraryA.Bar.class
...

`libraryB'.jar`


com.bar.libraryB.Example.class
...
com.foo.libraryA.Bar.class # Conflict!!
...

This is where relocation comes in. By changing the package name of library A included in library B, class conflicts are resolved.

`libraryB'.jar`


com.bar.libraryB.Example.class
...
shaded.com.foo.libraryA.Bar.class # No Conflict :)
...

In this example, com.foo.libraryA is changed to shaded.com.foo.libraryA. The point is not only to rename it, but also to rewrite all the references to the class of library A included in library B.

How to make shaded-jar

In this article, I will explain how to use maven.

Add the library you want to add as an example com.google.firebase: firebase-admin, Let's say the library you want to avoid conflicts with is com.google.guava: guava.

First, prepare the following pom file.

`pom.xml`


<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<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/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.example</groupId>
    <artifactId>shadeex</artifactId>
    <packaging>jar</packaging>
    <version>1.0.0</version>
    <dependencies>
        <!-- https://mvnrepository.com/artifact/com.google.firebase/firebase-admin -->
        <dependency>
            <groupId>com.google.firebase</groupId>
            <artifactId>firebase-admin</artifactId>
            <version>6.13.0</version>
        </dependency>
    </dependencies>
        
</project>

Let's check the dependency of firebase-admin.

$ mvn dependency:tree
...
INFO] --- maven-dependency-plugin:2.8:tree (default-cli) @ shadeex ---
[INFO] com.example:shadeex:jar:1.0.0
[INFO] \- com.google.firebase:firebase-admin:jar:6.13.0:compile
[INFO]    +- com.google.api-client:google-api-client:jar:1.30.1:compile
[INFO]    |  +- com.google.oauth-client:google-oauth-client:jar:1.30.1:compile
[INFO]    |  \- com.google.http-client:google-http-client-jackson2:jar:1.30.1:compile
[INFO]    |     \- com.fasterxml.jackson.core:jackson-core:jar:2.9.9:compile
[INFO]    +- com.google.api-client:google-api-client-gson:jar:1.30.1:compile
[INFO]    |  \- com.google.http-client:google-http-client-gson:jar:1.30.1:compile
[INFO]    |     \- com.google.code.gson:gson:jar:2.8.5:compile
[INFO]    +- com.google.http-client:google-http-client:jar:1.30.1:compile
[INFO]    |  +- org.apache.httpcomponents:httpclient:jar:4.5.8:compile
[INFO]    |  |  +- org.apache.httpcomponents:httpcore:jar:4.4.11:compile
[INFO]    |  |  +- commons-logging:commons-logging:jar:1.2:compile
[INFO]    |  |  \- commons-codec:commons-codec:jar:1.11:compile
[INFO]    |  +- com.google.code.findbugs:jsr305:jar:3.0.2:compile
[INFO]    |  +- com.google.j2objc:j2objc-annotations:jar:1.3:compile
[INFO]    |  +- io.opencensus:opencensus-api:jar:0.21.0:compile
[INFO]    |  |  \- io.grpc:grpc-context:jar:1.19.0:compile
[INFO]    |  \- io.opencensus:opencensus-contrib-http-util:jar:0.21.0:compile
[INFO]    +- com.google.api:api-common:jar:1.8.1:compile
[INFO]    |  \- javax.annotation:javax.annotation-api:jar:1.3.2:compile
[INFO]    +- com.google.auth:google-auth-library-oauth2-http:jar:0.17.1:compile
[INFO]    |  +- com.google.auto.value:auto-value-annotations:jar:1.6.6:compile
[INFO]    |  \- com.google.auth:google-auth-library-credentials:jar:0.17.1:compile
[INFO]    +- com.google.cloud:google-cloud-storage:jar:1.91.0:compile
[INFO]    |  +- com.google.cloud:google-cloud-core-http:jar:1.90.0:compile
[INFO]    |  |  +- com.google.cloud:google-cloud-core:jar:1.90.0:compile
[INFO]    |  |  |  +- com.google.protobuf:protobuf-java-util:jar:3.9.1:compile
[INFO]    |  |  |  |  \- com.google.errorprone:error_prone_annotations:jar:2.3.2:compile
[INFO]    |  |  |  \- com.google.api.grpc:proto-google-iam-v1:jar:0.12.0:compile
[INFO]    |  |  +- com.google.http-client:google-http-client-appengine:jar:1.31.0:compile
[INFO]    |  |  \- com.google.api:gax-httpjson:jar:0.65.1:compile
[INFO]    |  |     \- org.threeten:threetenbp:jar:1.3.3:compile
[INFO]    |  \- com.google.apis:google-api-services-storage:jar:v1-rev20190624-1.30.1:compile
[INFO]    +- com.google.cloud:google-cloud-firestore:jar:1.31.0:compile
[INFO]    |  +- com.google.cloud:google-cloud-core-grpc:jar:1.91.3:compile
[INFO]    |  |  +- com.google.api:gax:jar:1.49.1:compile
[INFO]    |  |  \- com.google.api:gax-grpc:jar:1.49.1:compile
[INFO]    |  |     +- io.grpc:grpc-stub:jar:1.23.0:compile
[INFO]    |  |     |  \- io.grpc:grpc-api:jar:1.23.0:compile
[INFO]    |  |     +- io.grpc:grpc-auth:jar:1.23.0:compile
[INFO]    |  |     +- io.grpc:grpc-protobuf:jar:1.23.0:compile
[INFO]    |  |     |  \- io.grpc:grpc-protobuf-lite:jar:1.23.0:compile
[INFO]    |  |     +- io.grpc:grpc-netty-shaded:jar:1.23.0:compile
[INFO]    |  |     |  \- io.grpc:grpc-core:jar:1.23.0:compile (version selected from constraint [1.23.0,1.23.0])
[INFO]    |  |     |     +- com.google.android:annotations:jar:4.1.1.4:compile
[INFO]    |  |     |     +- io.perfmark:perfmark-api:jar:0.17.0:compile
[INFO]    |  |     |     \- io.opencensus:opencensus-contrib-grpc-metrics:jar:0.21.0:compile
[INFO]    |  |     \- io.grpc:grpc-alts:jar:1.23.0:compile
[INFO]    |  |        +- io.grpc:grpc-grpclb:jar:1.23.0:compile
[INFO]    |  |        \- org.apache.commons:commons-lang3:jar:3.5:compile
[INFO]    |  +- com.google.api.grpc:proto-google-cloud-firestore-admin-v1:jar:1.31.0:compile
[INFO]    |  |  +- com.google.protobuf:protobuf-java:jar:3.10.0:compile
[INFO]    |  |  \- com.google.api.grpc:proto-google-common-protos:jar:1.17.0:compile
[INFO]    |  +- com.google.api.grpc:proto-google-cloud-firestore-v1:jar:1.31.0:compile
[INFO]    |  +- com.google.api.grpc:proto-google-cloud-firestore-v1beta1:jar:0.84.0:compile
[INFO]    |  \- io.opencensus:opencensus-contrib-grpc-util:jar:0.24.0:compile
[INFO]    +- com.google.guava:guava:jar:26.0-android:compile
[INFO]    |  +- org.checkerframework:checker-compat-qual:jar:2.5.2:compile
[INFO]    |  \- org.codehaus.mojo:animal-sniffer-annotations:jar:1.14:compile
[INFO]    +- org.slf4j:slf4j-api:jar:1.7.25:compile
[INFO]    +- io.netty:netty-codec-http:jar:4.1.45.Final:compile
[INFO]    |  +- io.netty:netty-common:jar:4.1.45.Final:compile
[INFO]    |  +- io.netty:netty-buffer:jar:4.1.45.Final:compile
[INFO]    |  \- io.netty:netty-codec:jar:4.1.45.Final:compile
[INFO]    +- io.netty:netty-handler:jar:4.1.45.Final:compile
[INFO]    \- io.netty:netty-transport:jar:4.1.45.Final:compile
[INFO]       \- io.netty:netty-resolver:jar:4.1.45.Final:compile
...

It seems to depend on com.google.guava: guava: jar: 26.0-android: compile. It's unpleasant to depend on the version for ʻandroid, so rewrite it to the version for jdk` Let's add it to the dependency.

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<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/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.example</groupId>
    <artifactId>shadeex</artifactId>
    <packaging>jar</packaging>
    <version>1.0.0</version>
    <dependencies>
        <!-- https://mvnrepository.com/artifact/com.google.firebase/firebase-admin -->
        <dependency>
            <groupId>com.google.firebase</groupId>
            <artifactId>firebase-admin</artifactId>
            <version>6.13.0</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/com.google.guava/guava -->
        <dependency>
            <groupId>com.google.guava</groupId>
            <artifactId>guava</artifactId>
            <version>26.0-jre</version>
        </dependency>
    </dependencies>
        
</project>

If you check the dependency again, it will be as follows.

$ mvn dependency:tree
...
[INFO] --- maven-dependency-plugin:2.8:tree (default-cli) @ shadeex ---
[INFO] com.example:shadeex:jar:1.0.0
[INFO] +- com.google.firebase:firebase-admin:jar:6.13.0:compile
[INFO] |  +- com.google.api-client:google-api-client:jar:1.30.1:compile
[INFO] |  |  +- com.google.oauth-client:google-oauth-client:jar:1.30.1:compile
[INFO] |  |  \- com.google.http-client:google-http-client-jackson2:jar:1.30.1:compile
[INFO] |  |     \- com.fasterxml.jackson.core:jackson-core:jar:2.9.9:compile
[INFO] |  +- com.google.api-client:google-api-client-gson:jar:1.30.1:compile
[INFO] |  |  \- com.google.http-client:google-http-client-gson:jar:1.30.1:compile
[INFO] |  |     \- com.google.code.gson:gson:jar:2.8.5:compile
[INFO] |  +- com.google.http-client:google-http-client:jar:1.30.1:compile
[INFO] |  |  +- org.apache.httpcomponents:httpclient:jar:4.5.8:compile
[INFO] |  |  |  +- org.apache.httpcomponents:httpcore:jar:4.4.11:compile
[INFO] |  |  |  +- commons-logging:commons-logging:jar:1.2:compile
[INFO] |  |  |  \- commons-codec:commons-codec:jar:1.11:compile
[INFO] |  |  +- io.opencensus:opencensus-api:jar:0.21.0:compile
[INFO] |  |  |  \- io.grpc:grpc-context:jar:1.19.0:compile
[INFO] |  |  \- io.opencensus:opencensus-contrib-http-util:jar:0.21.0:compile
[INFO] |  +- com.google.api:api-common:jar:1.8.1:compile
[INFO] |  |  \- javax.annotation:javax.annotation-api:jar:1.3.2:compile
[INFO] |  +- com.google.auth:google-auth-library-oauth2-http:jar:0.17.1:compile
[INFO] |  |  +- com.google.auto.value:auto-value-annotations:jar:1.6.6:compile
[INFO] |  |  \- com.google.auth:google-auth-library-credentials:jar:0.17.1:compile
[INFO] |  +- com.google.cloud:google-cloud-storage:jar:1.91.0:compile
[INFO] |  |  +- com.google.cloud:google-cloud-core-http:jar:1.90.0:compile
[INFO] |  |  |  +- com.google.cloud:google-cloud-core:jar:1.90.0:compile
[INFO] |  |  |  |  +- com.google.protobuf:protobuf-java-util:jar:3.9.1:compile
[INFO] |  |  |  |  |  \- com.google.errorprone:error_prone_annotations:jar:2.3.2:compile
[INFO] |  |  |  |  \- com.google.api.grpc:proto-google-iam-v1:jar:0.12.0:compile
[INFO] |  |  |  +- com.google.http-client:google-http-client-appengine:jar:1.31.0:compile
[INFO] |  |  |  \- com.google.api:gax-httpjson:jar:0.65.1:compile
[INFO] |  |  |     \- org.threeten:threetenbp:jar:1.3.3:compile
[INFO] |  |  \- com.google.apis:google-api-services-storage:jar:v1-rev20190624-1.30.1:compile
[INFO] |  +- com.google.cloud:google-cloud-firestore:jar:1.31.0:compile
[INFO] |  |  +- com.google.cloud:google-cloud-core-grpc:jar:1.91.3:compile
[INFO] |  |  |  +- com.google.api:gax:jar:1.49.1:compile
[INFO] |  |  |  \- com.google.api:gax-grpc:jar:1.49.1:compile
[INFO] |  |  |     +- io.grpc:grpc-stub:jar:1.23.0:compile
[INFO] |  |  |     |  \- io.grpc:grpc-api:jar:1.23.0:compile
[INFO] |  |  |     +- io.grpc:grpc-auth:jar:1.23.0:compile
[INFO] |  |  |     +- io.grpc:grpc-protobuf:jar:1.23.0:compile
[INFO] |  |  |     |  \- io.grpc:grpc-protobuf-lite:jar:1.23.0:compile
[INFO] |  |  |     +- io.grpc:grpc-netty-shaded:jar:1.23.0:compile
[INFO] |  |  |     |  \- io.grpc:grpc-core:jar:1.23.0:compile (version selected from constraint [1.23.0,1.23.0])
[INFO] |  |  |     |     +- com.google.android:annotations:jar:4.1.1.4:compile
[INFO] |  |  |     |     +- io.perfmark:perfmark-api:jar:0.17.0:compile
[INFO] |  |  |     |     \- io.opencensus:opencensus-contrib-grpc-metrics:jar:0.21.0:compile
[INFO] |  |  |     \- io.grpc:grpc-alts:jar:1.23.0:compile
[INFO] |  |  |        +- io.grpc:grpc-grpclb:jar:1.23.0:compile
[INFO] |  |  |        \- org.apache.commons:commons-lang3:jar:3.5:compile
[INFO] |  |  +- com.google.api.grpc:proto-google-cloud-firestore-admin-v1:jar:1.31.0:compile
[INFO] |  |  |  +- com.google.protobuf:protobuf-java:jar:3.10.0:compile
[INFO] |  |  |  \- com.google.api.grpc:proto-google-common-protos:jar:1.17.0:compile
[INFO] |  |  +- com.google.api.grpc:proto-google-cloud-firestore-v1:jar:1.31.0:compile
[INFO] |  |  +- com.google.api.grpc:proto-google-cloud-firestore-v1beta1:jar:0.84.0:compile
[INFO] |  |  \- io.opencensus:opencensus-contrib-grpc-util:jar:0.24.0:compile
[INFO] |  +- org.slf4j:slf4j-api:jar:1.7.25:compile
[INFO] |  +- io.netty:netty-codec-http:jar:4.1.45.Final:compile
[INFO] |  |  +- io.netty:netty-common:jar:4.1.45.Final:compile
[INFO] |  |  +- io.netty:netty-buffer:jar:4.1.45.Final:compile
[INFO] |  |  \- io.netty:netty-codec:jar:4.1.45.Final:compile
[INFO] |  +- io.netty:netty-handler:jar:4.1.45.Final:compile
[INFO] |  \- io.netty:netty-transport:jar:4.1.45.Final:compile
[INFO] |     \- io.netty:netty-resolver:jar:4.1.45.Final:compile
[INFO] \- com.google.guava:guava:jar:26.0-jre:compile
[INFO]    +- com.google.code.findbugs:jsr305:jar:3.0.2:compile
[INFO]    +- org.checkerframework:checker-qual:jar:2.5.2:compile
[INFO]    +- com.google.j2objc:j2objc-annotations:jar:1.1:compile
[INFO]    \- org.codehaus.mojo:animal-sniffer-annotations:jar:1.14:compile
...

Now, let's set shaded-jar from here.

`pom.xml`


<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<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/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.example</groupId>
    <artifactId>shadeex</artifactId>
    <packaging>jar</packaging>
    <version>1.0.0</version>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>3.2.4</version>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                        <configuration>
                          ...
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
    ... 
</project>

Use maven-shade-plugin to create shade-jar.

The following are important, so let's explain in detail.

<configuration>
    <artifactSet>
        <includes>
            <include>com.google.guava:guava</include>
            <include>com.google.firebase:firebase-admin</include>
        </includes>
    </artifactSet>
    <relocations>
        <relocation>
            <pattern>com.google</pattern>
            <shadedPattern>com.example.shaded.com.google</shadedPattern>
            <excludes>
                <exclude>com.google.firebase.**</exclude>
            </excludes>
        </relocation>
    </relocations>
</configuration>

Use <artifactSet> to set the list of artifacts included in shaded-jar. This time, the main firebase-admin and the dependent library guava that you want to bundle are specified.

Set relocation with <relocations>. Add the prefix of the java package you want to relocate to <pattern>. guava.jar containscom.google.common. **andcom.google.thirdparty. ** So I specified com.google. On the other hand, firebase-admin containscom.google.firebase. **, Since it is not necessary to relocate firebase-admin itself, it is excluded by<excludes>.

This completes the settings. Let's run it and see what kind of jar is created.

$ mvn package

shaded-jar is output to target / shadeex-1.0.0.jar. If you check the contents, you can see that the class included in guava.jar is certainly relocated.

$ unzip -l target/shadeex-1.0.0.jar  | grep 'com/example/shaded' | head
        0  04-13-2020 17:23   com/example/shaded/
        0  04-13-2020 17:23   com/example/shaded/com/
        0  04-13-2020 17:23   com/example/shaded/com/google/
        0  04-13-2020 17:23   com/example/shaded/com/google/common/
        0  04-13-2020 17:23   com/example/shaded/com/google/common/annotations/
      624  04-13-2020 17:23   com/example/shaded/com/google/common/annotations/Beta.class
      678  04-13-2020 17:23   com/example/shaded/com/google/common/annotations/GwtCompatible.class
      686  04-13-2020 17:23   com/example/shaded/com/google/common/annotations/GwtIncompatible.class
      312  04-13-2020 17:23   com/example/shaded/com/google/common/annotations/VisibleForTesting.class
        0  04-13-2020 17:23   com/example/shaded/com/google/common/base/

On the other hand, the firebase-admin.jar class has not been relocated.

$ unzip -l target/shadeex-1.0.0.jar  | grep -v 'shaded' | grep 'com/google' | head
        0  05-14-2020 19:36   com/google/
        0  05-14-2020 19:36   com/google/firebase/
        0  05-14-2020 19:36   com/google/firebase/messaging/
     1647  05-14-2020 19:36   com/google/firebase/messaging/Notification$Builder.class
     4528  05-14-2020 19:36   com/google/firebase/messaging/AndroidConfig$Builder.class
     1340  05-14-2020 19:36   com/google/firebase/messaging/AndroidFcmOptions$Builder.class
      277  05-14-2020 19:36   com/google/firebase/messaging/TopicManagementResponse$1.class
     1492  05-14-2020 19:36   com/google/firebase/messaging/TopicManagementResponse$Error.class
      409  05-14-2020 19:36   com/google/firebase/messaging/BatchResponse.class
     2910  05-14-2020 19:36   com/google/firebase/messaging/CriticalSound.class

Also, the classes of other dependent libraries are not included.

$ unzip -l target/shadeex-1.0.0.jar  | grep -v 'shaded' | grep -v 'com/google' 
Archive:  target/shadeex-1.0.0.jar
  Length      Date    Time    Name
---------  ---------- -----   ----
        0  06-11-2020 00:24   META-INF/
      135  06-11-2020 00:24   META-INF/MANIFEST.MF
        0  06-11-2020 00:24   META-INF/maven/
        0  06-11-2020 00:24   META-INF/maven/com.example/
        0  06-11-2020 00:24   META-INF/maven/com.example/shadeex/
     2603  06-11-2020 00:24   META-INF/maven/com.example/shadeex/pom.xml
      103  06-10-2020 23:05   META-INF/maven/com.example/shadeex/pom.properties
      599  05-14-2020 19:36   admin_sdk.properties
        0  05-14-2020 19:36   com/
        0  05-14-2020 19:35   META-INF/maven/com.google.firebase/
        0  05-14-2020 19:35   META-INF/maven/com.google.firebase/firebase-admin/
    19833  05-14-2020 19:35   META-INF/maven/com.google.firebase/firebase-admin/pom.xml
      119  05-14-2020 19:36   META-INF/maven/com.google.firebase/firebase-admin/pom.properties
        0  04-13-2020 17:23   META-INF/maven/com.google.guava/
        0  04-13-2020 17:23   META-INF/maven/com.google.guava/guava/
      133  04-13-2020 17:23   META-INF/maven/com.google.guava/guava/pom.properties
    10920  04-13-2020 17:12   META-INF/maven/com.google.guava/guava/pom.xml
        0  04-13-2020 17:23   com/example/
---------                     -------
  8638864                     2699 files

maven-shade-plugin outputs pom.xml for shaded-jar to dependency-reduced-pom.xml.

`dependency-reduced-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/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.example</groupId>
  <artifactId>shadeex</artifactId>
  <version>1.0.0</version>
  <build>
    <plugins>
      <plugin>
        <artifactId>maven-shade-plugin</artifactId>
        <version>3.2.4</version>
        <executions>
          <execution>
            <phase>package</phase>
            <goals>
              <goal>shade</goal>
            </goals>
            <configuration>
              <artifactSet>
                <includes>
                  <include>com.google.guava:guava</include>
                  <include>com.google.firebase:firebase-admin</include>
                </includes>
              </artifactSet>
              <relocations>
                <relocation>
                  <pattern>com.google</pattern>
                  <shadedPattern>com.example.shaded.com.google</shadedPattern>
                  <excludes>
                    <exclude>com.google.firebase.**</exclude>
                  </excludes>
                </relocation>
              </relocations>
            </configuration>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>
</project>

You can see that the included guava and firebase-admin dependencies have disappeared.

However, there is a problem with this pom. That is, there were other dependent libraries for firebase-admin besides guava.

$ mvn dependency:tree
...
INFO] --- maven-dependency-plugin:2.8:tree (default-cli) @ shadeex ---
[INFO] com.example:shadeex:jar:1.0.0
[INFO] \- com.google.firebase:firebase-admin:jar:6.13.0:compile
[INFO]    +- com.google.api-client:google-api-client:jar:1.30.1:compile
[INFO]    |  +- com.google.oauth-client:google-oauth-client:jar:1.30.1:compile
[INFO]    |  \- com.google.http-client:google-http-client-jackson2:jar:1.30.1:compile
[INFO]    |     \- com.fasterxml.jackson.core:jackson-core:jar:2.9.9:compile
[INFO]    +- com.google.api-client:google-api-client-gson:jar:1.30.1:compile
[INFO]    |  \- com.google.http-client:google-http-client-gson:jar:1.30.1:compile
[INFO]    |     \- com.google.code.gson:gson:jar:2.8.5:compile
[INFO]    +- com.google.http-client:google-http-client:jar:1.30.1:compile
[INFO]    |  +- org.apache.httpcomponents:httpclient:jar:4.5.8:compile
[INFO]    |  |  +- org.apache.httpcomponents:httpcore:jar:4.4.11:compile
[INFO]    |  |  +- commons-logging:commons-logging:jar:1.2:compile
[INFO]    |  |  \- commons-codec:commons-codec:jar:1.11:compile
[INFO]    |  +- com.google.code.findbugs:jsr305:jar:3.0.2:compile
[INFO]    |  +- com.google.j2objc:j2objc-annotations:jar:1.3:compile
[INFO]    |  +- io.opencensus:opencensus-api:jar:0.21.0:compile
[INFO]    |  |  \- io.grpc:grpc-context:jar:1.19.0:compile
[INFO]    |  \- io.opencensus:opencensus-contrib-http-util:jar:0.21.0:compile
[INFO]    +- com.google.api:api-common:jar:1.8.1:compile
[INFO]    |  \- javax.annotation:javax.annotation-api:jar:1.3.2:compile
[INFO]    +- com.google.auth:google-auth-library-oauth2-http:jar:0.17.1:compile
[INFO]    |  +- com.google.auto.value:auto-value-annotations:jar:1.6.6:compile
[INFO]    |  \- com.google.auth:google-auth-library-credentials:jar:0.17.1:compile
[INFO]    +- com.google.cloud:google-cloud-storage:jar:1.91.0:compile
[INFO]    |  +- com.google.cloud:google-cloud-core-http:jar:1.90.0:compile
[INFO]    |  |  +- com.google.cloud:google-cloud-core:jar:1.90.0:compile
[INFO]    |  |  |  +- com.google.protobuf:protobuf-java-util:jar:3.9.1:compile
[INFO]    |  |  |  |  \- com.google.errorprone:error_prone_annotations:jar:2.3.2:compile
[INFO]    |  |  |  \- com.google.api.grpc:proto-google-iam-v1:jar:0.12.0:compile
[INFO]    |  |  +- com.google.http-client:google-http-client-appengine:jar:1.31.0:compile
[INFO]    |  |  \- com.google.api:gax-httpjson:jar:0.65.1:compile
[INFO]    |  |     \- org.threeten:threetenbp:jar:1.3.3:compile
[INFO]    |  \- com.google.apis:google-api-services-storage:jar:v1-rev20190624-1.30.1:compile
[INFO]    +- com.google.cloud:google-cloud-firestore:jar:1.31.0:compile
[INFO]    |  +- com.google.cloud:google-cloud-core-grpc:jar:1.91.3:compile
[INFO]    |  |  +- com.google.api:gax:jar:1.49.1:compile
[INFO]    |  |  \- com.google.api:gax-grpc:jar:1.49.1:compile
[INFO]    |  |     +- io.grpc:grpc-stub:jar:1.23.0:compile
[INFO]    |  |     |  \- io.grpc:grpc-api:jar:1.23.0:compile
[INFO]    |  |     +- io.grpc:grpc-auth:jar:1.23.0:compile
[INFO]    |  |     +- io.grpc:grpc-protobuf:jar:1.23.0:compile
[INFO]    |  |     |  \- io.grpc:grpc-protobuf-lite:jar:1.23.0:compile
[INFO]    |  |     +- io.grpc:grpc-netty-shaded:jar:1.23.0:compile
[INFO]    |  |     |  \- io.grpc:grpc-core:jar:1.23.0:compile (version selected from constraint [1.23.0,1.23.0])
[INFO]    |  |     |     +- com.google.android:annotations:jar:4.1.1.4:compile
[INFO]    |  |     |     +- io.perfmark:perfmark-api:jar:0.17.0:compile
[INFO]    |  |     |     \- io.opencensus:opencensus-contrib-grpc-metrics:jar:0.21.0:compile
[INFO]    |  |     \- io.grpc:grpc-alts:jar:1.23.0:compile
[INFO]    |  |        +- io.grpc:grpc-grpclb:jar:1.23.0:compile
[INFO]    |  |        \- org.apache.commons:commons-lang3:jar:3.5:compile
[INFO]    |  +- com.google.api.grpc:proto-google-cloud-firestore-admin-v1:jar:1.31.0:compile
[INFO]    |  |  +- com.google.protobuf:protobuf-java:jar:3.10.0:compile
[INFO]    |  |  \- com.google.api.grpc:proto-google-common-protos:jar:1.17.0:compile
[INFO]    |  +- com.google.api.grpc:proto-google-cloud-firestore-v1:jar:1.31.0:compile
[INFO]    |  +- com.google.api.grpc:proto-google-cloud-firestore-v1beta1:jar:0.84.0:compile
[INFO]    |  \- io.opencensus:opencensus-contrib-grpc-util:jar:0.24.0:compile
[INFO]    +- com.google.guava:guava:jar:26.0-android:compile
[INFO]    |  +- org.checkerframework:checker-compat-qual:jar:2.5.2:compile
[INFO]    |  \- org.codehaus.mojo:animal-sniffer-annotations:jar:1.14:compile
[INFO]    +- org.slf4j:slf4j-api:jar:1.7.25:compile
[INFO]    +- io.netty:netty-codec-http:jar:4.1.45.Final:compile
[INFO]    |  +- io.netty:netty-common:jar:4.1.45.Final:compile
[INFO]    |  +- io.netty:netty-buffer:jar:4.1.45.Final:compile
[INFO]    |  \- io.netty:netty-codec:jar:4.1.45.Final:compile
[INFO]    +- io.netty:netty-handler:jar:4.1.45.Final:compile
[INFO]    \- io.netty:netty-transport:jar:4.1.45.Final:compile
[INFO]       \- io.netty:netty-resolver:jar:4.1.45.Final:compile

However, dependency-reduced-pom.xml removes the dependencies of these libraries.

The option to solve this problem is <promoteTransitiveDependencies>. By specifying this option, all dependent libraries of firebase-admin will be listed as direct dependencies of dependency-reduced-pom.xml, after which firebase-admin and guava will be removed. ..

Therefore, the dependencies of libraries that are not included can be left correctly.

The final pom.xml looks like this:

`pom.xml`


<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<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/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.example</groupId>
    <artifactId>shadeex</artifactId>
    <packaging>jar</packaging>
    <version>1.0.0</version>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>3.2.4</version>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                        <configuration>
                            <promoteTransitiveDependencies>true</promoteTransitiveDependencies>
                            <artifactSet>
                                <includes>
                                    <include>com.google.guava:guava</include>
                                    <include>com.google.firebase:firebase-admin</include>
                                </includes>
                            </artifactSet>
                            <relocations>
                                <relocation>
                                    <pattern>com.google</pattern>
                                    <shadedPattern>com.example.shaded.com.google</shadedPattern>
                                    <excludes>
                                        <exclude>com.google.firebase.**</exclude>
                                    </excludes>
                                </relocation>
                            </relocations>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

    <dependencies>
        <!-- https://mvnrepository.com/artifact/com.google.firebase/firebase-admin -->
        <dependency>
            <groupId>com.google.firebase</groupId>
            <artifactId>firebase-admin</artifactId>
            <version>6.13.0</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/com.google.guava/guava -->
        <dependency>
            <groupId>com.google.guava</groupId>
            <artifactId>guava</artifactId>
            <version>29.0-jre</version>
        </dependency>
    </dependencies>
        
</project>

On the other hand, the dependency-reduced-pom.xml output by executing the mvn package is as follows.

`dependency-reduced-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/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.example</groupId>
  <artifactId>shadeex</artifactId>
  <version>1.0.0</version>
  <build>
    ...
  </build>
  <dependencies>
    <dependency>
      <groupId>com.google.api-client</groupId>
      <artifactId>google-api-client</artifactId>
      <version>1.30.1</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>com.google.oauth-client</groupId>
      <artifactId>google-oauth-client</artifactId>
      <version>1.30.1</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>com.google.http-client</groupId>
      <artifactId>google-http-client-jackson2</artifactId>
      <version>1.30.1</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-core</artifactId>
      <version>2.9.9</version>
      <scope>compile</scope>
    </dependency>
    ...
  </dependencies>
</project>

The dependent libraries for firebase-admin remain correct.

All you have to do now is upload this jar and dependency-reduced-pom.xml to your internal maven repository.

References

Apache Maven Shade Plugin

[JAVA] How to make shaded-jar

What is Shaded jar?

libraryA-versionX.jar

libraryB'.jar

libraryB'.jar

How to make shaded-jar

pom.xml

pom.xml

dependency-reduced-pom.xml

pom.xml

dependency-reduced-pom.xml

References

`libraryA-versionX.jar`

`libraryB'.jar`

`libraryB'.jar`

`pom.xml`

`pom.xml`

`dependency-reduced-pom.xml`

`pom.xml`

`dependency-reduced-pom.xml`