2

我在这里学习教程： 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

但是 mvn compile 失败并出现错误：找不到符号
显然在抱怨引用唯一 scala 类的地方。

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

在运行（失败的）mvn compile 之后再次出现在这里：（我可以看到 Hello.class 在 target/classes 下）

.
├── 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

主.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();
  } 
}

你好.scala：

class Hello {
  def hello() { println("Hello (class)") }
}

object Hello {
  def hello() { println("Hello (object)") }
}

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

我可以找到关于类似问题的其他问题，但尽我最大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
4

1 回答 1

2

解决了，

按照http://scala-ide.org/docs/current-user-doc/gettingstarted/index.html上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 中缺少包声明并在 Main.java 和 Foo.java 中导入，文件现在看起来像这样：

你好.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();
  }
}

主.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。

于 2016-04-28T13:32:04.197 回答