创建一个Uber / Shadow对象意味着Maven或Gradle也可以用来处理所有的库依赖关系。
如果是这样，一个解决方案是从Java运行Maven或Gradle构建命令行arg（使用Runtime.exec()命令）。
以编程方式执行此操作的一个用例是作为Java集成测试的一部分，其中需要Uber Jar（参见Testing custom Kafka Connect SMT using Test Containers的示例）。
以下解决方案同时支持Gradle / Maven。

Maven

确保pom.xml包含Maven Shade Plugin插件，例如：

<?xml version="1.0" encoding="UTF-8"?>
<project>
    <modelVersion>4.0.0</modelVersion>

    <groupId>test</groupId>
    <artifactId>helloworld</artifactId>
    <version>1.0</version>
    <packaging>jar</packaging>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <jdk.version>1.11</jdk.version>
        <maven.compiler.plugin.version>3.8.1</maven.compiler.plugin.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
            <version>3.13.0</version>
        </dependency>
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter-engine</artifactId>
            <version>5.8.0</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter-api</artifactId>
            <version>5.8.0</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.assertj</groupId>
            <artifactId>assertj-core</artifactId>
            <version>3.24.2</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>3.5.1</version>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

</project>

在项目中安装Maven wrapper也很有用（例如，运行mvn wrapper:wrapper）。
要测试，请运行./mvnw package.

$ ./mvnw package

[INFO] Scanning for projects...
...
[INFO] Replacing original artifact with shaded artifact.
[INFO] Replacing /Users/bobmarks/code/test/fatjar/target/helloworld-1.0.jar with /Users/bobmarks/code/test/fatjar/target/helloworld-1.0-shaded.jar
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  1.129 s
[INFO] Finished at: 2023-10-12T12:05:04+01:00
[INFO] ------------------------------------------------------------------------

...并确保文件存在于target文件夹中：

$ ls -al target/*.jar 

-rw-r--r--@ 1 user  group  1336348 Oct 12 12:05 target/helloworld-1.0.jar
-rw-r--r--@ 1 user  group     1675 Oct 12 12:05 target/original-helloworld-1.0.jar

请注意，较大的文件（helloworld-1.0.jar）是Uber Jar。

Gradle

对于Gradle，我们应该确保Gradle Shadow插件存在于build.gradle文件的plugins部分，例如：

plugins {
    id("com.github.johnrengelman.shadow") version "6.0.0"
}

apply plugin: 'java'

java {
    sourceCompatibility = 1.11
    targetCompatibility = 1.11
}

repositories {
    mavenCentral()
}

test {
    useJUnitPlatform()
}

dependencies {
    implementation 'org.apache.commons:commons-lang3:3.13.0'

    testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.8.0'
    testImplementation 'org.junit.jupiter:junit-jupiter-api:5.8.0'
    testImplementation 'org.assertj:assertj-core:3.24.2'
}

还有settings.gradle

rootProject.name = 'helloworld'

另外，Gradle wrapper（例如，运行gradle wrapper）。
要测试，请运行./gradlew shadowJar...

$ ./gradlew shadowJar

BUILD SUCCESSFUL in 554ms
2 actionable tasks: 1 executed, 1 up-to-date

...并确保文件存在于build/libs文件夹中：

$ ls -al build/libs/*.jar 

-rw-r--r--@ 1 user  group  632280 Oct 12 12:39 build/libs/helloworld-all.jar

使用Java创建Jar文件

创建UberJars的代码如下：

import java.io.IOException;
import java.util.Scanner;

public class UberJar {

    public static void createUberJarMaven() {
        createUberJar("mvnw.cmd", "./mvnw", "package -DskipTests", "BUILD SUCCESS");
    }

    public static void createUberJarGradle() {
        createUberJar("gradlew.bat", "./gradlew", "shadowJar", "BUILD SUCCESSFUL");
    }

    private static void createUberJar(String cmdWindows, String cmdLinux, String cmdBuild, String outputSuccess) {
        String cmd = isWindows() ? cmdWindows : cmdLinux;
        String output = execCmd(cmd + " " + cmdBuild);
        if (output == null || !output.contains(outputSuccess)) {
            throw new RuntimeException("Ubar JAR creation unsuccessful\n\n" + output);
        }
    }

    private static String execCmd(String cmd) {
        try {
            Scanner s = new Scanner(Runtime.getRuntime().exec(cmd).getInputStream()).useDelimiter("\\A");
            return s.hasNext() ? s.next() : "";
        } catch (IOException ioEx) {
            throw new RuntimeException("Error executing: " + cmd, ioEx);
        }
    }

    private static boolean isWindows() {
        return System.getProperty("os.name").toLowerCase().startsWith("windows");
    }

}

测试这两种情况的单元测试如下：

import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.Test;
import java.io.File;
import static org.assertj.core.api.Assertions.assertThat;

public class UbarJarTest {

    private static final File MAVEN_UBER_FILE = new File("target/helloworld-1.0.jar");
    private static final File GRADLE_UBER_FILE = new File("build/libs/helloworld-all.jar");

    @BeforeAll
    public static void setup() {
        if (MAVEN_UBER_FILE.exists()) {
            MAVEN_UBER_FILE.delete();
        }
        if (GRADLE_UBER_FILE.exists()) {
            GRADLE_UBER_FILE.delete();
        }
    }

    @Test
    public void should_create_uber_jar_maven() {
        assertThat(MAVEN_UBER_FILE).doesNotExist();

        UberJar.createUberJarMaven();

        assertThat(MAVEN_UBER_FILE).exists();
    }

    @Test
    public void should_create_uber_jar_gradle() {
        assertThat(GRADLE_UBER_FILE).doesNotExist();

        UberJar.createUberJarGradle();

        assertThat(GRADLE_UBER_FILE).exists();
    }

}