Question

我有一个在其类路径（Java buildpath）中具有依赖项的项目。现在我已将其转换为maven项目并使用我自定义的Maven插件进行编译。以下是我的POM文件 -

<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.test</groupId>
  <artifactId>test</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>ear</packaging>


  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <build>
      <plugins>
         <plugin>
            <groupId>com.my.maven.plugin</groupId>
            <artifactId>my-maven-plugin</artifactId>
            <version>0.0.1</version>
            <extensions>true</extensions>
         </plugin>
      </plugins>
  </build>
</project>

在my-maven-plugin中，我已经覆盖了编译阶段 -

maven-plugin pom-

    <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.test</groupId>
  <artifactId>my-maven-plugin</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>maven-plugin</packaging>

  <name>my-maven-plugin</name>
  <url>http://maven.apache.org</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <dependencies>
    <dependency>
        <groupId>org.apache.maven</groupId>
        <artifactId>maven-core</artifactId>
        <version>3.3.9</version>
    </dependency>
    <dependency>
      <groupId>org.apache.maven</groupId>
      <artifactId>maven-plugin-api</artifactId>
      <version>3.3.9</version>
    </dependency>
    <dependency>
      <groupId>org.apache.maven</groupId>
      <artifactId>maven-compat</artifactId>
      <version>3.3.9</version>
    </dependency>   
    <dependency>
      <groupId>org.apache.maven</groupId>
      <artifactId>maven-embedder</artifactId>
      <version>3.3.9</version>
    </dependency>
    <dependency>
      <groupId>org.apache.maven</groupId>
      <artifactId>maven-archiver</artifactId>
      <version>2.5</version>
    </dependency>
    <dependency>
      <groupId>commons-io</groupId>
      <artifactId>commons-io</artifactId>
      <version>2.2</version>
    </dependency>
    <dependency>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-compiler-plugin</artifactId>
      <version>3.5</version>
    </dependency>
    <dependency>
      <groupId>org.apache.maven.plugin-tools</groupId>
      <artifactId>maven-plugin-annotations</artifactId>
      <version>3.4</version>
      <scope>provided</scope>
    </dependency>

    <dependency>
      <groupId>org.apache.maven.surefire</groupId>
      <artifactId>maven-surefire-common</artifactId>
      <version>2.19.1</version>
    </dependency>
    <dependency>
      <groupId>org.apache.maven.surefire</groupId>
      <artifactId>surefire-api</artifactId>
      <version>2.19.1</version>
    </dependency>
    <dependency>
        <groupId>org.codehaus.plexus</groupId>
        <artifactId>plexus-component-annotations</artifactId>
        <version>1.6</version>
        <exclusions>
            <exclusion>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
    <dependency>
       <groupId>org.apache.maven.surefire</groupId>
       <artifactId>surefire-junit47</artifactId>
       <version>2.19.1</version>
    </dependency>
  </dependencies>
</project>

lifecycle.xml -

<?xml version="1.0" encoding="UTF-8"?>
<lifecycles>  
  <lifecycle>  
    <id>customLifeCycle</id>  
    <phases>  
      <phase>  
        <id>compile</id>  
        <executions>  
          <execution>  
            <goals>  
              <goal>mycompile</goal>  
            </goals>  
          </execution>  
        </executions>  
      </phase> 
    </phases>  
  </lifecycle>  
</lifecycles>

的components.xml

 <?xml version="1.0" encoding="UTF-8"?>
<component-set>
  <components>
    <component>
      <role>org.apache.maven.artifact.handler.ArtifactHandler</role>
      <role-hint>ear</role-hint>
      <implementation>org.apache.maven.artifact.handler.DefaultArtifactHandler</implementation>
      <configuration>
        <type>ear</type>
        <extension>ear</extension>
        <language>java</language>
        <packaging>ear</packaging>        
      </configuration>
    </component>

   <component>
      <role>org.apache.maven.lifecycle.mapping.LifecycleMapping</role>
      <role-hint>ear</role-hint>
      <implementation>org.apache.maven.lifecycle.mapping.DefaultLifecycleMapping</implementation>
      <configuration>
        <phases>
          <process-resources>org.apache.maven.plugins:maven-resources-plugin:resources</process-resources>
          <compile>com.test:my-maven-plugin:mycompile</compile>
          <process-test-resources>org.apache.maven.plugins:maven-resources-plugin:testResources</process-test-resources>
          <test-compile>org.apache.maven.plugins:maven-compiler-plugin:testCompile</test-compile>
          <test>org.apache.maven.plugins:maven-surefire-plugin:test</test>
          <install>org.apache.maven.plugins:maven-install-plugin:install</install>
          <deploy>org.apache.maven.plugins:maven-deploy-plugin:deploy</deploy>
        </phases>
      </configuration>
    </component>
  </components>
</component-set>

并且，重写编译mojo -

 @Mojo( name = "mycompile", defaultPhase = LifecyclePhase.COMPILE )
 public class MyCompileMojo extends AbstractMojo{

   @Parameter( defaultValue = "${project}", readonly = true, required = true )
    private MavenProject project;
    public void execute() throws MojoExecutionException, MojoFailureException {
    }
}

现在，在编译阶段，我想要一个存在于classpath中的JAR文件列表。我怎么才能得到它？我试过跟随 - 但大多数都返回目标文件夹路径和类文件夹路径

List<String> list1 = project.getCompileClasspathElements();
List<String> list2 = project.getRuntimeClasspathElements();
List<String> list3 = project.getSystemClasspathElements();
List<String> list4 = project.getTestClasspathElements();
List<Dependency> list5 = project.getCompileDependencies();
Properties list6 = project.getProperties();
List<Dependency> list7 = project.getSystemDependencies();
List<Dependency> list8 = project.getRuntimeDependencies();

我要编译的项目结构

Answer 1

您缺少的关键因素是requiresDependencyResolution，它代表了插件可用的一组依赖项。来自the Mojo API reference：

将此Mojo标记为要求在执行之前解析指定类路径中的依赖项。 [...]如果注释根本不存在，则mojo不得对与Maven项目相关的工件做出任何假设。

要访问项目的编译时依赖项，可以使用ResolutionScope.COMPILE：

compile解析范围= compile + system + provided个依赖关系

除此之外，还有COMPILE_PLUS_RUNTIME也可以访问运行时范围的依赖项，或者TEST来添加测试范围的依赖项。当Maven插件不存在此参数时，Maven项目的类路径元素将不可用，这是您遇到的行为。

因此，如果您希望Maven插件获取当前Maven项目的依赖项的编译块JAR文件列表，您可以：

@Mojo(name = "mycompile", defaultPhase = LifecyclePhase.COMPILE, requiresDependencyResolution = ResolutionScope.COMPILE)
public class MyCompileMojo extends AbstractMojo {

    @Parameter(defaultValue = "${project}", readonly = true, required = true)
    private MavenProject project;

    public void execute() throws MojoExecutionException, MojoFailureException {
        try {
            List<String> list = project.getCompileClasspathElements();
            getLog().info(list.toString());
        } catch (DependencyResolutionRequiredException e) {
            throw new MojoFailureException("Couldn't resolve compile dependencies", e);
        }
    }

}

方法getCompileClasspathElements()返回每个编译时依赖项的JAR文件的路径列表。它还将包含当前Maven项目的target/classes文件夹的路径，因为它包含项目的已编译主Java源代码。上面的代码只会打印此列表。类似地，您可以将getTestClasspathElements()与ResolutionScope.TEST一起使用，以获得测试范围依赖项列表以及编译时依赖项。

如果您只想要依赖项的JAR文件的路径，而没有项目本身的类，则可以使用方法getArtifacts()代替：

public void execute() throws MojoExecutionException, MojoFailureException {
    Set<Artifact> artifacts = project.getArtifacts();
    for (Artifact artifact : artifacts) {
        System.out.println(artifact.getFile());
    }
}

请注意，要使其正常工作，您需要确保compile阶段（或test-compile）已运行。这些名单是人口稠密的。运行mvn clean test将确保插件可以访问测试范围依赖项，如果它声明requiresDependencyResolution TEST。同样，运行mvn clean compile（以及将阶段更改为<phase>compile</phase>）将确保插件可以访问编译范围依赖项，如果它声明requiresDependencyResolution COMPILE。< / p>

一些旁注：

文件lifecycle.xml必须位于src/main/resources/META-INF/maven内。请注意，此文件在您的设置中实际上完全未使用，因为您未在customLifeCycle内使用新components.xml，而是覆盖ear;
文件components.xml必须位于src/main/resources/META-INF/plexus内。请注意，<compile>com.test:my-maven-plugin:mycompile</compile>必须与插件的组ID和工件ID匹配;

测试项目需要像这样使用插件：

<packaging>ear</packaging> <!-- because your lifecycle mapping override ear -->
<dependencies>
  <!-- some dependencies like maven-core -->
  <dependency>
    <groupId>org.apache.maven</groupId>
    <artifactId>maven-core</artifactId>
    <version>3.0</version>
  </dependency>
</dependencies>
<build>
  <plugins>
    <plugin>
      <groupId>com.test</groupId>
      <artifactId>my-maven-plugin</artifactId>
      <version>0.0.1-SNAPSHOT</version>
      <extensions>true</extensions>
    </plugin>
  </plugins>
</build>

然后您可以运行mvn clean package，插件将正确打印maven-core（例如）及其依赖项的JAR文件的路径。

Answer 2

这对我有用。

我在a recent bug

找到了它

package com.mkyong.io;

import java.net.URL;
import java.net.URLClassLoader;

public class App{

    public static void main (String args[]) {

        ClassLoader cl = ClassLoader.getSystemClassLoader();
        URL[] urls = ((URLClassLoader)cl).getURLs();

        for(URL url: urls){
            System.out.println(url.getFile());
        }
    }
}

Answer 3

完成上一个答案后，您可以阅读所有类路径：

console.log

如果您需要深入了解依赖项：

public static List<String> getClassPaths() {
    List<String> list = new ArrayList<String>();
    Enumeration res;
    try {
        res = Thread.currentThread().getContextClassLoader().getResources(JarFile.MANIFEST_NAME);
        while (res.hasMoreElements()) {
            try {
                URL url = (URL)res.nextElement();
                InputStream is = url.openStream();
                if (is != null) {
                    Manifest manifest = new Manifest(is);
                    Attributes mainAttribs = manifest.getMainAttributes();
                    String classpath = mainAttribs.getValue("Class-Path");
                    if (classpath != null)
                        list.add(classpath);
                }
            }
            catch (Exception e) {
                // Silently ignore wrong manifests or stop the compilation
            }
        }
    } catch (IOException e1) {
    // Silently ignore wrong manifests or stop the compilation
    }
    return list;
}

阅读Maven项目中的Java构建路径条目

3 个答案: