我在这里关注教程： http://scala-tools.org/mvnsites/maven-scala-plugin/example_java.html在同一个项目中使用带有scala文件的java
然而mvn编译失败并出现错误：找不到符号
显然抱怨唯一的scala类被引用的地方。
这是我的项目结构：
.
├── pom.xml
├── src
│ ├── main
│ │ ├── java
│ │ │ └── com
│ │ │ └── dummy
│ │ │ └── foo
│ │ │ ├── Foo.java
│ │ │ └── Main.java
│ │ ├── resources
│ │ └── scala
│ │ └── com
│ │ └── dummy
│ │ └── hello
│ │ └── Hello.scala
│ └── test
│ ├── java
│ ├── resources
│ └── scala
├── tree-pre-compile
在这里再次运行（失败的）mvn编译后:(我可以看到Hello.class在目标/类下面）
.
├── pom.xml
├── src
│ ├── main
│ │ ├── java
│ │ │ └── com
│ │ │ └── dummy
│ │ │ └── foo
│ │ │ ├── Foo.java
│ │ │ └── Main.java
│ │ ├── resources
│ │ └── scala
│ │ └── com
│ │ └── dummy
│ │ └── hello
│ │ └── Hello.scala
│ └── test
│ ├── java
│ ├── resources
│ └── scala
├── target
│ ├── classes
│ │ ├── Hello.class
│ │ └── META-INF
│ │ ├── MANIFEST.MF
│ │ └── maven
│ │ └── com.dummy.java-scala-poc
│ │ └── mixed-java-scala-poc
│ │ ├── pom.properties
│ │ └── pom.xml
│ ├── classes.timestamp
│ └── test-classes
└── tree-text
Main.java：
package com.dummy.foo;
public class Main {
public static void main(String[] args) {
System.out.print("mixing java and scala");
Foo foo = new Foo();
foo.foo();
new Hello().hello();
}
}
Foo.java：
package com.dummy.foo;
public class Foo {
public void foo() {
System.out.print("mixing java and scala");
new Hello().hello();
}
}
Hello.scala：
class Hello {
def hello() { println("Hello (class)") }
}
object Hello {
def hello() { println("Hello (object)") }
}
的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>com.dummy.java-scala-poc</groupId>
<artifactId>mixed-java-scala-poc</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>mixed-java-scala-poc</name>
<packaging>jar</packaging>
<dependencies>
<dependency>
<groupId>org.scala-lang</groupId>
<artifactId>scala-library</artifactId>
<version>2.11.8</version>
</dependency>
</dependencies>
<repositories>
<repository>
<id>scala-tools.org</id>
<name>Scala-tools Maven2 Repository</name>
<url>http://scala-tools.org/repo-releases</url>
</repository>
</repositories>
<pluginRepositories>
<pluginRepository>
<id>scala-tools.org</id>
<name>Scala-tools Maven2 Repository</name>
<url>http://scala-tools.org/repo-releases</url>
</pluginRepository>
</pluginRepositories>
<build>
<pluginManagement>
<plugins>
<plugin>
<groupId>org.scala-tools</groupId>
<artifactId>maven-scala-plugin</artifactId>
<version>2.9.1</version>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.0.2</version>
</plugin>
</plugins>
</pluginManagement>
<plugins>
<plugin>
<groupId>org.scala-tools</groupId>
<artifactId>maven-scala-plugin</artifactId>
<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>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<executions>
<execution>
<phase>compile</phase>
<goals>
<goal>compile</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
使用的IDE是JBoss Developer Studio版本：8.1.0.GA
我可以在类似的问题上找到关于SO的其他问题，但是我的努力似乎没有任何效果。
这是mvn编译输出：
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building mixed-java-scala-poc 0.0.1-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-resources-plugin:2.3:resources (default-resources) @ mixed-java-scala-poc ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] Copying 0 resource
[INFO]
[INFO] --- maven-scala-plugin:2.9.1:add-source (scala-compile-first) @ mixed-java-scala-poc ---
[INFO] Add Source directory: /home/hatieh/git/intelligence-ws/mixed-java-scala-poc/src/main/scala
[INFO] Add Test Source directory: /home/hatieh/git/intelligence-ws/mixed-java-scala-poc/src/test/scala
[INFO]
[INFO] --- maven-scala-plugin:2.9.1:compile (scala-compile-first) @ mixed-java-scala-poc ---
[ERROR] /home/hatieh/git/intelligence-ws/mixed-java-scala-poc/src/main/java
[ERROR] /home/hatieh/git/intelligence-ws/mixed-java-scala-poc/src/main/scala
[ERROR] /home/hatieh/git/intelligence-ws/mixed-java-scala-poc/src/test/scala
[INFO] Compiling 3 source files to /home/hatieh/git/intelligence-ws/mixed-java-scala-poc/target/classes
[INFO]
[INFO] --- maven-compiler-plugin:2.0.2:compile (default-compile) @ mixed-java-scala-poc ---
[INFO] Compiling 2 source files to /home/hatieh/git/intelligence-ws/mixed-java-scala-poc/target/classes
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 2.301s
[INFO] Finished at: Thu Apr 28 15:25:55 EEST 2016
[INFO] Final Memory: 12M/145M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:2.0.2:compile (default-compile) on project mixed-java-scala-poc: Compilation failure: Compilation failure:
[ERROR] /home/hatieh/git/intelligence-ws/mixed-java-scala-poc/src/main/java/com/dummy/foo/Foo.java:[6,8] error: cannot find symbol
[ERROR]
[ERROR] could not parse error message: symbol: class Hello
[ERROR] location: class Foo
[ERROR] /home/hatieh/git/intelligence-ws/mixed-java-scala-poc/src/main/java/com/dummy/foo/Main.java:9: error: cannot find symbol
[ERROR] new Hello().hello();
[ERROR] ^
[ERROR] -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException
答案 0 :(得分：2)
解决了它，
按照http://scala-ide.org/docs/current-user-doc/gettingstarted/index.html下面的指南下载并安装了eclipse的Scala IDE插件，该指南反过来（插件）指出了问题......
愚蠢的我，我在Hello.scala中缺少包声明，在Main.java和Foo.java中导入，文件现在看起来像这样：
Hello.scala：
package com.dummy.hello;
class Hello {
def hello() { println("Hello (class)") }
}
object Hello {
def hello() { println("Hello (object)") }
}
Foo.java：
package com.dummy.foo;
import com.dummy.hello.Hello;
public class Foo {
public void foo() {
System.out.print("mixing java and scala");
new Hello().hello();
}
}
Main.java：
package com.dummy.foo;
import com.dummy.hello.Hello;
public class Main {
public static void main(String[] args) {
System.out.print("mixing java and scala");
Foo foo = new Foo();
foo.foo();
new Hello().hello();
}
}
我希望有人觉得这很有帮助。