同时具有java和scala的maven项目答案

【问题标题】：maven project which has both java and scala同时具有java和scala的maven项目
【发布时间】：2018-01-18 18:25:01
【问题描述】：

我想构建一个同时具有 java 和 scala 源代码的 maven 项目。我已经在 eclipse 中安装了 scala IDE 插件，并在 pom.xml 中添加了 "scala-maven-plugin" 但是在 scala 文件中导入 java 类会产生编译错误。构建此类混合项目的最佳 IDE 是哪个？

项目结构是

pom.xml

<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.apache.spark</groupId>
  <artifactId>spark-examples_2.11</artifactId>
  <version>0.0.1-SNAPSHOT</version>


<dependencies>
    <dependency>
        <groupId>org.scala-lang</groupId>
        <artifactId>scala-library</artifactId>
        <version>2.11.7</version>
    </dependency>
</dependencies>
<build>
<pluginManagement>
    <plugins>
<!-- This plugin compiles Scala files -->
        <plugin>
            <groupId>net.alchim31.maven</groupId>
            <artifactId>scala-maven-plugin</artifactId>
            <executions>
                <execution>
                    <id>scala-compile-first</id>
                    <phase>process-resources</phase>
                    <goals>
                        <goal>add-source</goal>
                        <goal>compile</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
<!-- This plugin compiles Java files -->
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <configuration>
                <source>1.8</source>
                <target>1.8</target>
            </configuration>
            <executions>
                <execution>
                    <phase>compile</phase>
                    <goals>
                        <goal>compile</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
<!-- This plugin adds all dependencies to JAR file during 'package' command.
Pay EXTRA attention to the 'mainClass' tag. 
You have to set name of class with entry point to program ('main' method) -->
        <plugin>
            <artifactId>maven-assembly-plugin</artifactId>
            <version>2.5.3</version>
            <configuration>
                <descriptorRefs>
                    <descriptorRef>jar-with-dependencies</descriptorRef>
                </descriptorRefs>
                <archive>
                    <manifest>
                        <mainClass>ScalaRunner</mainClass>
                    </manifest>
                </archive>
            </configuration>
            <executions>
                <execution>
                    <phase>package</phase>
                    <goals>
                        <goal>single</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
  </pluginManagement>  
</build>
</project>

【问题讨论】：

首先你应该把你的 Scala 移到一个不同于default的包中...

标签： java eclipse scala maven

【解决方案1】：

从您的代码结构看来，您的 Scala 类依赖于 Java，而不是相反。然而，在您的 Maven 配置中，Scala 会首先被编译。改成Java类后编译。

以下插件序列适用于我的项目：

<build>
    <plugins>
        <plugin>
            <artifactId>maven-compiler-plugin</artifactId>
            <configuration>
                <source>1.8</source>
                <target>1.8</target>
            </configuration>
        </plugin>
        <plugin>
            <groupId>net.alchim31.maven</groupId>
            <artifactId>scala-maven-plugin</artifactId>
            <executions>
                <execution>
                    <goals>
                        <goal>compile</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
        <plugin>
            <artifactId>maven-assembly-plugin</artifactId>
            <executions>
                <execution>
                    <phase>package</phase>
                    <goals>
                        <goal>single</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

【讨论】：