在ClassLoader中加载Spring Boot类-Java 学习之路

我需要读一个Spring Boot jar并加载ClassLoader上的所有clases .

我的问题，在spring引导类中位于“/ BOOT-INF / classes”目录而不是根目录 .

有谁知道如何在我的ClassLoader中加载这些类？

我试着这样做：

private URLClassLoader getURLClassLoaderFromJar(Path jarPath) throws MalformedURLException {
        return URLClassLoader
                .newInstance(new URL[] { new URL("jar:file:" + jarPath.toAbsolutePath().toString() + "!/") });
}

这加载jar，但没有类/ BOOT-INF / classes中的类

2 回答

我最后在一个临时目录中选择了解压缩de jar并使用以下条目创建一个URLClassloader：一个到根目录 . 一个到BOOT-INF / classes，一个用于BOOT-INT / lib中的每个jar

Path warDirectory = decompressWar(absolutePathFile);

File rootDir = new File(warDirectory.toAbsolutePath().toString());
File springBootDir = new File(warDirectory.toAbsolutePath().toString() + "/BOOT-INF/classes/");

List<URL> listaURL = new ArrayList<URL>();
listaURL.add(rootDir.toURI().toURL());
listaURL.add(springBootDir.toURI().toURL());

//This scan the BOOT-INF/lib folder and return a List<URL> with all the libraries.
listaURL.addAll(getURLfromSpringBootJar(warDirectory));


URL[] urls = new URL[listaURL.size()];
urls = listaURL.toArray(urls);
cl = new URLClassLoader(urls);

//This explore the JAR and load all the .class fulies to get the className.
resultClassesBean = loadJars(Collections.singletonList(pathJarFile), cl);

if(resultClassesBean != null && resultClassesBean.getListResultClasses() != null && !resultClassesBean.getListResultClasses().isEmpty()) {
    for(String clazz : resultClassesBean.getListResultClasses()) {
        cl.loadClass(clazz);
    }
}

回复于 2024-04-26T18:29:07+08:00

调查一下spring boot如何加载第三方（Liquibase）类，我会这样：

鉴于您知道要加载的包名称

Resource[] scan(ClassLoader loader, String packageName) throws IOException {
        ResourcePatternResolver resolver = new PathMatchingResourcePatternResolver(
                loader);
        String pattern = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX
                + ClassUtils.convertClassNameToResourcePath(packageName) + "/**/*.class";
        Resource[] resources = resolver.getResources(pattern);
        return resources;
    }


void findAllClasses(String packageName, ClassLoader loader) throws ClassNotFoundException {
        MetadataReaderFactory metadataReaderFactory = new CachingMetadataReaderFactory(
                loader);
        try {
            Resource[] resources = scan(loader, packageName);
            for (Resource resource : resources) {
                MetadataReader reader = metadataReaderFactory.getMetadataReader(resource);
                ClassUtils.forName(reader.getClassMetadata().getClassName(), loader)
            }
        } catch (IOException ex) {
            throw new IllegalStateException(ex);
        }
    }

也可以使用带有加载jar的类加载器：

findAllClasses("com.package", getURLClassLoaderFromJar(pathToJar));

此变体可以安全地与Spring Boot打包的可执行JAR一起使用

回复于 2024-04-26T18:29:07+08:00

在ClassLoader中加载Spring Boot类

2 回答

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