Maven：将Scala代码和Java代码一起构建到胖JAR

Question

我有一个Scala项目，我将其构建到Fat JAR中。今天，我需要向项目中添加一些Java类，但是现在我的Maven构建失败了。

我的项目结构看起来（大致）如下：

.
├── src
│   └── main
│       ├── resources
│       │   └── Log4j.properties
|       ├── java
│       │   └── com
│       │       └── myorg
│       │           └── myproject
│       │               └── MyPublicJavaClass.java
│       └── scala
│           └── com
│               └── myorg
│                   └── myproject
│                       └── spark
│                           └── Main.scala
└── pom.xml

这是我的POM文件的样子：

<?xml version="1.0"?>
<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>
  <name>myproject</name>
  <url>http://maven.apache.org</url>

  <groupId>com.myorg</groupId>
  <artifactId>myproject</artifactId>
  <packaging>jar</packaging>
  <version>0.1.0-RELEASE</version>

  <properties>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
    <encoding>UTF-8</encoding>
    <scala.tools.version>2.11</scala.tools.version>
    <scala.version>2.11.8</scala.version>
    <spark.version>2.4.0</spark.version>
    <aws.sdk.version>1.11.553</aws.sdk.version>
  </properties>

  <build>
    <sourceDirectory>src/main/scala</sourceDirectory>
    <testSourceDirectory>src/test/scala</testSourceDirectory>
    <resources>
      <resource>
        <directory>src/main/resources</directory>
      </resource>
    </resources>
    <testResources>
      <testResource>
        <directory>src/test/resources</directory>
      </testResource>
    </testResources>

    <plugins>
      <!-- I added this plugin today to try and make it compile the Java code -->
      <plugin>
        <groupId>org.codehaus.mojo</groupId>
        <artifactId>build-helper-maven-plugin</artifactId>
        <version>3.0.0</version>
        <executions>
          <execution>
            <phase>generate-sources</phase>
            <configuration>
              <sources>
                <source>src/main/java</source>
              </sources>
            </configuration>
          </execution>
        </executions>
      </plugin>

      <!-- This compiles the Scala code -->
      <plugin>
        <groupId>org.scala-tools</groupId>
        <artifactId>maven-scala-plugin</artifactId>
        <version>2.15.2</version>
        <executions>
          <execution>
            <goals>
              <goal>compile</goal>
              <goal>testCompile</goal>
            </goals>
          </execution>
        </executions>
      </plugin>

      <!-- This builds the fat JAR -->
      <plugin>
        <artifactId>maven-assembly-plugin</artifactId>
        <configuration>
          <archive>
            <manifest>
              <mainClass>com.myorg.myproject.spark.Main</mainClass>
            </manifest>
          </archive>
          <descriptorRefs>
            <descriptorRef>jar-with-dependencies</descriptorRef>
          </descriptorRefs>
        </configuration>
        <executions>
          <execution>
            <id>make-assembly</id>
            <phase>package</phase>
            <goals>
              <goal>single</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>

  <dependencies>
    <dependency>
      <groupId>org.scala-lang</groupId>
      <artifactId>scala-library</artifactId>
      <version>${scala.version}</version>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupId>org.apache.spark</groupId>
      <artifactId>spark-core_${scala.tools.version}</artifactId>
      <version>${spark.version}</version>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupId>org.apache.spark</groupId>
      <artifactId>spark-sql_${scala.tools.version}</artifactId>
      <version>${spark.version}</version>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupId>com.amazonaws</groupId>
      <artifactId>aws-java-sdk-core</artifactId>
      <version>${aws.sdk.version}</version>
    </dependency>
    <dependency>
      <groupId>com.amazonaws</groupId>
      <artifactId>aws-java-sdk-dynamodb</artifactId>
      <version>${aws.sdk.version}</version>
    </dependency>
    <dependency>
      <groupId>com.amazon.emr</groupId>
      <artifactId>emr-dynamodb-hadoop</artifactId>
      <version>4.8.0</version>
    </dependency>
    <dependency>
      <groupId>com.github.scopt</groupId>
      <artifactId>scopt_${scala.tools.version}</artifactId>
      <version>3.7.1</version>
    </dependency>
    <dependency>
      <groupId>org.apache.logging.log4j</groupId>
      <artifactId>log4j-scala</artifactId>
      <version>11.0</version>
      <type>pom</type>
    </dependency>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.8.2</version>
      <scope>test</scope>
    </dependency>
  </dependencies>
</project>

在我添加Java类以及今天的build-helper-maven-plugin之前，Maven能够毫无问题地构建此项目。但是现在，看来我没有正确配置该插件，或者也许我没有使用正确的插件？

我的Scala代码正在尝试使用MyPublicJavaClass类型的对象，因此现在我在Maven中看到的构建错误看起来像这样：

  

[错误]〜/ src / main / scala / com / myorg / myproject / spark / Main.scala：227：错误：找不到：输入MyPublicJavaClass

     

...

     

[错误]无法在项目myproject上执行目标org.scala-tools：maven-scala-plugin：2.15.2：compile（默认）：包装：org.apache.commons.exec.ExecuteException：流程退出错误：1（退出值：1）-> [帮助1]

我认为build-helper-maven-plugin会告诉它将Java代码的源目录添加到要在编译之前生成的源列表中，但是显然没有。我该如何解决？

Answer 1

您正在使用非常老的插件进行Scala编译（最新版本2.15.2已发布Feb 6 2011）。

我建议您首先升级到更新的插件，例如scala-maven-plugin（最新发布的4.0.2于2019年5月11日）。

然后您可以找到一个包含Scala / Java混合源in the docs的示例。在这种情况下，无需使用build-helper-maven-plugin，也无需配置sourceDirectory和testSourceDirectory。使用此插件检查这个简单的pom.xml（我刚刚从本地重现问题时提供的示例中删除了未使用的依赖项）：

<?xml version="1.0"?>
<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>
  <name>myproject</name>
  <url>http://maven.apache.org</url>

  <groupId>com.myorg</groupId>
  <artifactId>myproject</artifactId>
  <packaging>jar</packaging>
  <version>0.1.0-RELEASE</version>

  <properties>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
    <encoding>UTF-8</encoding>
    <scala.tools.version>2.11</scala.tools.version>
    <scala.version>2.11.8</scala.version>
  </properties>

  <build>
    <plugins>
      <plugin>
        <groupId>net.alchim31.maven</groupId>
        <artifactId>scala-maven-plugin</artifactId>
        <version>4.0.2</version>
          <executions>
            <execution>
              <id>scala-compile-first</id>
              <phase>process-resources</phase>
              <goals>
                <goal>add-source</goal>
                <goal>compile</goal>
              </goals>
            </execution>
            <execution>
              <id>scala-test-compile</id>
              <phase>process-test-resources</phase>
              <goals>
                <goal>testCompile</goal>
              </goals>
          </execution>
        </executions>
      </plugin>

      <!-- This builds the fat JAR -->
      <plugin>
        <artifactId>maven-assembly-plugin</artifactId>
        <configuration>
          <archive>
            <manifest>
              <mainClass>com.myorg.myproject.spark.Main</mainClass>
            </manifest>
          </archive>
          <descriptorRefs>
            <descriptorRef>jar-with-dependencies</descriptorRef>
          </descriptorRefs>
        </configuration>
        <executions>
          <execution>
            <id>make-assembly</id>
            <phase>package</phase>
            <goals>
              <goal>single</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>

  <dependencies>
    <dependency>
      <groupId>org.scala-lang</groupId>
      <artifactId>scala-library</artifactId>
      <version>${scala.version}</version>
      <scope>provided</scope>
    </dependency>
  </dependencies>
</project>