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问读取Maven项目中的Java构建路径条目
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Stack Overflow用户

提问于 2016-12-13 16:23:38

回答 3查看 2.2K关注 0票数 12

我有一个项目，它的类路径(Java buildpath)中有依赖项。现在，我已经将其转换为maven项目，并使用我定制的Maven插件对其进行编译。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>

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，覆盖编译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，我需要类路径中存在的JAR文件的列表。我怎么才能得到它呢？我已经尝试过了--但大多数都返回了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

java

maven

maven-plugin

回答 3

Stack Overflow用户

发布于 2016-12-15 21:58:17

您缺少的关键成分是requiresDependencyResolution，它表示插件将可用的一组依赖项。来自the Mojo API reference

将此Mojo标记为需要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，那么mojo就不能对与Maven项目相关联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依赖项

其中，还有访问运行时范围依赖项的COMPILE_PLUS_RUNTIME，或者添加测试范围依赖项的TEST。当该参数不存在于Maven插件时，Maven项目的类路径元素将不可用，这就是您遇到的行为。

因此，如果您希望Maven插件获得作为当前Maven项目的依赖项的compile- files文件的列表，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);
        }
    }

}

getCompileClasspathElements()方法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源文件。上面的代码可以简单地打印出这个列表。类似地，您可以结合使用getTestClasspathElements()和ResolutionScope.TEST来获得测试范围的依赖项列表，以及编译时依赖项的列表。

如果您只需要依赖项的JAR文件的路径，而不需要项目本身的类，则可以改用getArtifacts()方法：

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)已经运行。这些列表是懒惰地填充的。如果插件声明了TEST的requiresDependencyResolution，那么运行mvn clean test将确保插件能够访问测试范围依赖项。类似地，如果插件声明了requiresDependencyResolution of COMPILE，那么运行mvn clean compile (同时将阶段更改为<phase>compile</phase>)将确保插件能够访问编译范围的依赖项。

几个附注：

文件lifecycle.xml必须位于src/main/resources/META-INF/maven内部。注意，这个文件实际上在您的设置中完全没有使用，因为您没有在components.xml中使用新的customLifeCycle，而是覆盖了ear；
文件components.xml必须位于src/main/resources/META-INF/plexus中。注意，<compile>com.test:my-maven-plugin:mycompile</compile>必须与插件的组id和工件id相匹配；
测试项目需要像这样使用插件：

ear org.apache.maven maven-core 3.0 com.test my-maven-plugin 0.0.1-SNAPSHOT true

然后，您可以运行mvn clean package，插件将正确打印maven-core (例如)及其dependencies.的JAR文件的路径

票数 4

Stack Overflow用户

发布于 2016-12-13 17:19:39

这对我很有效。

我在这里找到的https://www.mkyong.com/java/how-to-print-out-the-current-project-classpath/

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());
        }
    }
}

票数 0

Stack Overflow用户

发布于 2016-12-18 22:57:25

作为上一个答案的补充，您可以像这样读取所有Class-Path：

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;
}

如果您需要更深入地了解依赖关系：

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)
                        for (String lib : classpath.split(" ")) {
                            try {
                                list.addAll(getClassPathsFromJar(lib));
                            } catch (IOException ioe)
                            {
                                list.add(lib);
                            }
                        }
                }
            }
            catch (Exception e) {
                // Silently ignore wrong manifests or stop the compilation
            }
        }
    } catch (IOException e1) {
    // Silently ignore wrong manifests or stop the compilation
    }
    return list;
}

public static List<String> getClassPathsFromJar(String lib) throws IOException {
    List<String> entries = new ArrayList<String>();
    JarFile jar = new JarFile(lib);
    Manifest manifest = jar.getManifest();
    if (manifest == null) {
        entries.add(lib);
        return entries;
    }
    Attributes mainAttribs = manifest.getMainAttributes();
    String classpath = mainAttribs.getValue("Class-Path");
    if (classpath == null) {
        entries.add(lib);
        return entries;
    }
    for (String l : classpath.split(" ")) {
        entries.addAll(getClassPathsFromJar(l));
    }
    return entries;
}

票数 0

页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持

原文链接：

https://stackoverflow.com/questions/41116511

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