Maven:以编程方式获取所有依赖项

Question

如何以编程方式获取Maven模块在Maven执行环境之外的所有依赖项？

到目前为止,我有:

通过maven-core:

Path pomPath = ...;
MavenXpp3Reader reader = new MavenXpp3Reader();
try (InputStream is = Files.newInputStream(pomPath)) {
    Model model = reader.read(is);
    this.mavenProject = new MavenProject(model);
}

并通过jcabi-aether:

File localRepo = Paths.get(System.getProperty("user.home"), ".m2").toFile();
new Classpath(mavenProject, localRepo, "runtime")

到目前为止这一般是正确的吗？

现在的问题是我得到一个NullPointerException:

Caused by: java.lang.NullPointerException
    at com.jcabi.aether.Aether.mrepos(Aether.java:197)
    at com.jcabi.aether.Aether.<init>(Aether.java:140)
    at com.jcabi.aether.Classpath.<init>(Classpath.java:125)

因为mavenProject.getRemoteProjectRepositories()返回null.

如何初始化MavenProject以包含已配置的远程repos,同时考虑settings.xml文件(镜像,代理,存储库等)？

Answer 1

在Maven插件之外,对工件进行操作的方式是通过Aether.该团队有一个示例项目,用于获取所调用的给定工件的传递依赖性ResolveTransitiveDependencies.一旦你设置了Aether依赖项(如此处所示),你可以简单地:

public static void main(final String[] args) throws Exception {
    DefaultServiceLocator locator = MavenRepositorySystemUtils.newServiceLocator();
    RepositorySystem system = newRepositorySystem(locator);
    RepositorySystemSession session = newSession(system);

    RemoteRepository central = new RemoteRepository.Builder("central", "default", "http://repo1.maven.org/maven2/").build();

    Artifact artifact = new DefaultArtifact("group.id:artifact.id:version");

    CollectRequest collectRequest = new CollectRequest(new Dependency(artifact, JavaScopes.COMPILE), Arrays.asList(central));
    DependencyFilter filter = DependencyFilterUtils.classpathFilter(JavaScopes.COMPILE);
    DependencyRequest request = new DependencyRequest(collectRequest, filter);
    DependencyResult result = system.resolveDependencies(session, request);

    for (ArtifactResult artifactResult : result.getArtifactResults()) {
        System.out.println(artifactResult.getArtifact().getFile());
    }
}

private static RepositorySystem newRepositorySystem(DefaultServiceLocator locator) {
    locator.addService(RepositoryConnectorFactory.class, BasicRepositoryConnectorFactory.class);
    locator.addService(TransporterFactory.class, FileTransporterFactory.class);
    locator.addService(TransporterFactory.class, HttpTransporterFactory.class);
    return locator.getService(RepositorySystem.class);
}

private static RepositorySystemSession newSession(RepositorySystem system) {
    DefaultRepositorySystemSession session = MavenRepositorySystemUtils.newSession();
    LocalRepository localRepo = new LocalRepository("target/local-repo");
    session.setLocalRepositoryManager(system.newLocalRepositoryManager(session, localRepo));
    return session;
}

它将下载工件并将其放入"target/local-repo".

请注意,您可以使用DefaultProxySelector和DefaultMirrorSelector在系统会话上配置代理和镜像.有可能读取Maven设置文件并用它来填充会话,但事情变得非常难看......

如果你想要与Maven本身紧密耦合,因为你有权访问要处理的POM并想要考虑设置,那么以编程方式直接调用Maven要简单得多.在这种情况下,您对给定POM文件的每个依赖项的路径感兴趣,包括传递依赖项.对于该dependency:list目标,加上设置outputAbsoluteArtifactFilename到true,会给(几乎)正是这样.

要以编程方式调用Maven,可以使用Invoker API.将依赖项添加到项目中:

<dependency>
  <groupId>org.apache.maven.shared</groupId>
  <artifactId>maven-invoker</artifactId>
  <version>2.2</version>
</dependency>

你可以有:

InvocationRequest request = new DefaultInvocationRequest();
request.setPomFile(new File(pomPath));
request.setGoals(Arrays.asList("dependency:list"));
Properties properties = new Properties();
properties.setProperty("outputFile", "dependencies.txt"); // redirect output to a file
properties.setProperty("outputAbsoluteArtifactFilename", "true"); // with paths
properties.setProperty("includeScope", "runtime"); // only runtime (scope compile + runtime)
// if only interested in scope runtime, you may replace with excludeScope = compile
request.setProperties(properties);

Invoker invoker = new DefaultInvoker();
// the Maven home can be omitted if the "maven.home" system property is set
invoker.setMavenHome(new File("/path/to/maven/home"));
invoker.setOutputHandler(null); // not interested in Maven output itself
InvocationResult result = invoker.execute(request);
if (result.getExitCode() != 0) {
    throw new IllegalStateException("Build failed.");
}

Pattern pattern = Pattern.compile("(?:compile|runtime):(.*)");
try (BufferedReader reader = Files.newBufferedReader(Paths.get("dependencies.txt"))) {
    while (!"The following files have been resolved:".equals(reader.readLine()));
    String line;
    while ((line = reader.readLine()) != null && !line.isEmpty()) {
        Matcher matcher = pattern.matcher(line);
        if (matcher.find()) {
            // group 1 contains the path to the file
            System.out.println(matcher.group(1));
        }
    }
}

这将创建一个调用请求,其中包含:要调用的目标和系统属性,就像mvn dependency:list -Dprop=value在命令行上启动一样.将设置要使用的路径将默认的标准位置"${user.home}/settings.xml",但它也将是可以指定与设置的路径request.setUserSettingsFile(...)和request.setGlobalSettingsFile(...).调用者需要设置Maven home(即安装目录),但仅限于"maven.home"未设置系统属性.

调用的结果dependency:list被重定向到一个文件,稍后进行后处理.该目标的输出包括格式中的依赖项列表(如果没有,则分类器可能不存在):

group.id:artifact.id:type[:classifier]:version:scope:pathname

没有办法只输出已解析工件文件的路径,并且分类器可能不存在这一事实使解析变得复杂(我们无法分割:限制,因为路径可能包含:.. ).首先,已解析的工件"The following files have been resolved:"位于输出文件中的行下方,然后,由于所需的范围仅为compile或者runtime,我们可以使用简单的正则表达式获取工件文件的路径,该表达式采用在compile:或之后的所有内容runtime:.那条路径可以直接用作a new File.

如果后期处理过程中的箍看起来太脆弱,我猜你可以创建自己的插件,只输出已解析的工件文件名.