在Eclipse Oxygen 4.7中导入Java-9-Jigsaw-Maven-Project无法正常工作 [英] Import of a Java-9-Jigsaw-Maven-Project in Eclipse Oxygen 4.7 does not work

问题描述

我使用:

• JDK 9 build 9-ea + 172
• Maven 3.5.0
• Eclipse Oxygen 4.7 RC3版本 从2017-05-31开始4.7.0.I20170531-2000
• Eclipse插件:
  • 具有针对氧气开发流1.1.1.v20170526-0728_BETA_JAVA9的Java 9支持(BETA)的Eclipse JDT(Java开发工具)补丁程序
  • m2e-用于Eclipse的Maven集成(包括孵化 组件)，1.8.0.20170516-2043
  • JDK 9 build 9-ea+172
  • Maven 3.5.0
  • Eclipse Oxygen 4.7 RC3 Version 4.7.0.I20170531-2000 from 2017-05-31
  • Eclipse-Plugins:
    • Eclipse JDT (Java Development Tools) Patch with Java 9 support (BETA) for Oxygen development stream, 1.1.1.v20170526-0728_BETA_JAVA9
    • m2e - Maven Integration for Eclipse (includes Incubating components), 1.8.0.20170516-2043

    创建一个新的Jigsaw-Maven-Project:

    mkdir proj1\a\src\main\java\a\a
    cd proj1
    

    在目录proj1中的文件pom.xml:

    In directory proj1 the file 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>test</groupId>
      <artifactId>Proj1</artifactId>
      <version>1.0</version>
      <packaging>pom</packaging>
      <modules>
        <module>a</module>
      </modules>
      <build>
        <plugins>
          <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.6.1</version>
            <configuration>
              <source>9</source>
              <target>9</target>
              <showWarnings>true</showWarnings>
              <showDeprecation>true</showDeprecation>
            </configuration>
          </plugin>
        </plugins>
      </build>
    </project>
    

    在目录proj1\a中的文件pom.xml:

    In directory proj1\a the file 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>
      <parent>
        <groupId>test</groupId>
        <artifactId>Proj1</artifactId>
        <version>1.0</version>
      </parent>
      <artifactId>a</artifactId>
      <packaging>jar</packaging>
      <build>
        <sourceDirectory>src/main/java/a</sourceDirectory>
      </build>
    </project>
    

    在目录proj1\a\src\main\java\a中的文件module-info.java:

    In directory proj1\a\src\main\java\a the file module-info.java:

    module a { }
    

    在目录proj1\a\src\main\java\a\a中的文件App.java:

    In directory proj1\a\src\main\java\a\a the file App.java:

    package a;
    
    public class App {
       public static void main( String[] args ) {
          System.out.println( "CLASSPATH:           " + System.getProperty( "java.class.path" ) );
          System.out.println( "Class / Modul:       " + App.class.getSimpleName() + " from " + App.class.getModule() );
          java.lang.ModuleLayer lr = App.class.getModule().getLayer();
          if( lr != null ) {
             System.out.println( "Layer.Configuration: " + lr.configuration() );
          } else {
             System.out.println( "Error:               ModuleLayer is null" );
          }
       }
    }
    

    在命令行上运行项目:

    cd proj1
    mvn clean package
    java -p a\target\a-1.0.jar -m a/a.App  
    

    ->

    CLASSPATH:
    Class / Modul:       App from module a
    Layer.Configuration: java..., ...  
    

    ->
    完美运行，没有错误(CLASSPATH为空，getModule()中的名称正确，并且ModuleLayer有效).

    -->
    Works perfect without error (CLASSPATH is empty, name from getModule() is correct, and ModuleLayer is valid).

    在IntelliJ IDEA 2017.2 EAP中打开项目
    ->
    完美运行，没有错误(CLASSPATH为空，getModule()中的名称正确，并且ModuleLayer有效).

    Opening the project in IntelliJ IDEA 2017.2 EAP
    -->
    Works perfect without error (CLASSPATH is empty, name from getModule() is correct, and ModuleLayer is valid).

    在Eclipse Oxygen 4.7 RC3中导入项目:
    ->

    CLASSPATH:           ...\proj1\a\target\classes
    Class / Modul:       App from unnamed module @68f7aae2
    Error:               ModuleLayer is null
    

    ->
    这三行都是错误的.

    -->
    All three lines are wrong.

    如何避免出现此错误?

    推荐答案

    这是Eclipse Oxygen 4.7 RC3中的错误，请参见:
    Eclipse错误517777:在Eclipse Oxygen 4.7中运行Java 9应用程序未设置模块路径 ( https://bugs.eclipse.org/bugs/show_bug.cgi?id = 517777 )
    和
    Eclipse错误514760:运行配置应支持模块概念 ( https://bugs.eclipse.org/bugs/show_bug.cgi?id = 514760 )

    This is a bug in Eclipse Oxygen 4.7 RC3, see:
    Eclipse Bug 517777: Running a Java 9 application in Eclipse Oxygen 4.7 does not set the module path (https://bugs.eclipse.org/bugs/show_bug.cgi?id=517777)
    and
    Eclipse Bug 514760: Run configuration should support notion of modules (https://bugs.eclipse.org/bugs/show_bug.cgi?id=514760)

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