maven-assembly-plugin 的includeBaseDirectory研究

 

需求：

这个问题一度困扰了我好几个小时，我一开始使用maven-assembly-plugin构建tar分发包的时候，发现每次最终打包，都会在最外层有个包装层，比如我要构建的tar分发包的artifactId为abc ,那么最终打包完的tar文件总是内含abc目录，然后才是其他子目录sub1,sub2。而我们所希望的是当untar时候，能够直接出来的是子目录(sub1,sub2)，而不是abc目录+abc目录里的子目录(/abc/sub1,/abc/sub2)的形式。

解决方案：

其实只要在assembly.xml中加上元素，并且让其设为false就可以了，如下：

<assembly>

  <id>tarballid>

  <formats>

    <format>tarformat>

  formats>





  <includeBaseDirectory>falseincludeBaseDirectory>



  <fileSets>

 ...

关于这个参数的含义，可以参见maven-assembly-plugin的官网：

http://maven.apache.org/plugins/maven-assembly-plugin/assembly.html

 

深入分析：

为什么这样可以呢，我们可以对maven-assembly-plugin的源代码进行研究。

首先，当我们在pom.xml中使用maven-assembly-plugin并且在中配置了assembly.xml文件的位置时候：

<build>
                 <plugins>
                          <plugin>
                                   <groupId>org.apache.maven.pluginsgroupId>
                                   <artifactId>maven-assembly-pluginartifactId>
                                   <version>2.2.1version>
                                   <configuration>
                                            <appendAssemblyId>falseappendAssemblyId>
                                            <descriptors>
                                                    <descriptor>src/main/assembly/assembly.xmldescriptor>
                                            descriptors>
                                   configuration>
                                   <executions>
                                            <execution>
                                                    <id>make-assemblyid>
                                                    <phase>packagephase>
                                                    <goals>
                                                             <goal>singlegoal>
                                                    goals>
                                            execution>
                                   executions>
                          plugin>
                         .....
                 plugins>
         build>

 

插件会去调用DefaultAssemblyReader的readAssemblies()方法，然后调用如下代码进行遍历元素：

for ( int i = 0; i < descriptors.length; i++ )
          {
              getLogger().info( "Reading assembly descriptor: " + descriptors[i] );
              addAssemblyFromDescriptor( descriptors[i], locator, configSource, assemblies );
          }
      }

 

我们继续跟进到addAssemblyFromDescriptor方法，可以看出它其实是用来读取一个asssembly descriptor文件（也就是我们例子中的assembly.xml），忽略参数检查，它其实核心代码如下：

private Assembly addAssemblyFromDescriptor( final String spec, final Locator locator,
                                               final AssemblerConfigurationSource configSource,
                                               final List<Assembly> assemblies )
       throws AssemblyReadException, InvalidAssemblerConfigurationException
   {
      ...
       Reader r = null;
       try
       {
           // TODO use ReaderFactory.newXmlReader() when plexus-utils is upgraded to 1.4.5+
           r = new InputStreamReader( location.getInputStream(), "UTF-8" );

           File dir = null;
           if ( location.getFile() != null )
           {
               dir = location.getFile().getParentFile();
           }

           final Assembly assembly = readAssembly( r, spec, dir, configSource );

           assemblies.add( assembly );

           return assembly;
       }
     ...
   }

所以这里可以看出，它最终在11行新建InputStreamReader，并在第19行读取assembly descriptor文件，最终读取的结果存储在Assembly对象模型中，而Assembly这个模型是有includeBaseDirectory这个成员变量的：

/**
    * Set includes a base directory in the final archive. For
    * example,
    *             if you are creating an assembly named
    * "your-app", setting
    *             includeBaseDirectory to true will create an
    * archive that
    *             includes this base directory. If this option is
    * set to false
    *             the archive created will unzip its content to
    * the current
    *             directory. Default value is true.
    *
    * @param includeBaseDirectory
    */
   public void setIncludeBaseDirectory( boolean includeBaseDirectory )
   {
       this.includeBaseDirectory = includeBaseDirectory;
   } //-- void setIncludeBaseDirectory( boolean )

 

以上是解析assembly descriptor并且设置了includeBaseDirectory,现在我们来看下如何使用这个属性。很显然，在不看代码之前，我们很容易猜想到，它肯定影响了最终打包的行为，正如我们所期望的一样。

 

所以，我们很轻松就找到了DefaultAssemblyArchiver的createArchive()方法,这个方法做了一系列打包的动作。

public File createArchive( final Assembly assembly, final String fullName, final String format,
                               final AssemblerConfigurationSource configSource )
        throws ArchiveCreationException, AssemblyFormattingException, InvalidAssemblerConfigurationException
    {
        validate( assembly );

        String filename = fullName;
        if ( !configSource.isIgnoreDirFormatExtensions() || !format.startsWith( "dir" ) )
        {
            filename += "." + format;
        }

        AssemblyFileUtils.verifyTempDirectoryAvailability( configSource.getTemporaryRootDirectory(), getLogger() );

        final File outputDirectory = configSource.getOutputDirectory();

        final File destFile = new File( outputDirectory, filename );

        try
        {
            final String finalName = configSource.getFinalName();
            final String specifiedBasedir = assembly.getBaseDirectory();

            String basedir = finalName;

            if ( specifiedBasedir != null )
            {
                basedir =
                    AssemblyFormatUtils.getOutputDirectory( specifiedBasedir, configSource.getProject(), null,
                                                            finalName, configSource );
            }

            final List containerHandlers =
                selectContainerDescriptorHandlers( assembly.getContainerDescriptorHandlers(), configSource );

            final Archiver archiver =
                createArchiver( format, assembly.isIncludeBaseDirectory(), basedir, configSource, containerHandlers );

            archiver.setDestFile( destFile );

            final AssemblyContext context = new DefaultAssemblyContext();

            dependencyResolver.resolve( assembly, configSource, context );

            for ( final Iterator phaseIterator = assemblyPhases.iterator(); phaseIterator.hasNext(); )
            {
                final AssemblyArchiverPhase phase = phaseIterator.next();

                phase.execute( assembly, archiver, configSource, context );
            }

            archiver.createArchive();
        }
   ...

        return destFile;
    }

从第36行可以看出，在最终创建archiver时候（createArchiver方法），它会吧assembly.isIncludeBaseDirectory()作为参数传递进去，我们看下如果这个参数设置为false的行为。

 

protected Archiver createArchiver( final String format, final boolean includeBaseDir, final String finalName,
                                     final AssemblerConfigurationSource configSource,
                                     final List containerHandlers )
      throws ArchiverException, NoSuchArchiverException
  {
      Archiver archiver;
      if ( format.startsWith( "tar" ) )
      {
          archiver = createTarArchiver( format, configSource.getTarLongFileMode() );
      }
      else if ( "war".equals( format ) )
      {
          archiver = createWarArchiver();
      }
      else
      {
          archiver = archiverManager.getArchiver( format );
      }

      final List extraSelectors = new ArrayList();
      final List extraFinalizers = new ArrayList();
      if ( archiver instanceof JarArchiver )
      {
          extraSelectors.add( new JarSecurityFileSelector() );

          extraFinalizers.add( new ManifestCreationFinalizer( configSource.getProject(),
                                                              configSource.getJarArchiveConfiguration() ) );

      }

      if ( configSource.getArchiverConfig() != null )
      {
          configureArchiver( archiver, configSource );
      }

      String prefix = "";
      if ( includeBaseDir )
      {
          prefix = finalName;
      }

      archiver =
          new AssemblyProxyArchiver( prefix, archiver, containerHandlers, extraSelectors, extraFinalizers,
                                     configSource.getWorkingDirectory(), getLogger(), configSource.isDryRun() );

      archiver.setUseJvmChmod( configSource.isUpdateOnly() );
      archiver.setIgnorePermissions( configSource.isIgnorePermissions() );
      archiver.setForced( !configSource.isUpdateOnly() );

      return archiver;
  }

这里，从36到40行可以看出来，当includeBaseDirectory为true时候，prefix为artifact的finalName,如果为false,则设置为"",而这个finalName就是分发包的最外层。所以，当我们吧includeBaseDirectory设置为false,就没有包装层了。这个结果正和官网上对这个参数的说明一致。具体打包过程见AssemblyProxyArchiver,我就不展开了。