如何从类路径中的 Java 包中读取所有类? [英] How do I read all classes from a Java package in the classpath?

问题描述

我需要读取 Java 包中包含的类.这些类在类路径中.我需要直接从 Java 程序执行此任务.你知道一个简单的方法吗?

I need to read classes contained in a Java package. Those classes are in classpath. I need to do this task from a Java program directly. Do you know a simple way to do?

List<Class> classes = readClassesFrom("my.package")

推荐答案

如果你有 Spring在你的类路径中，下面会做.

If you have Spring in you classpath then the following will do it.

查找包中所有用 XmlRootElement 注释的类:

Find all classes in a package that are annotated with XmlRootElement:

private List<Class> findMyTypes(String basePackage) throws IOException, ClassNotFoundException
{
    ResourcePatternResolver resourcePatternResolver = new PathMatchingResourcePatternResolver();
    MetadataReaderFactory metadataReaderFactory = new CachingMetadataReaderFactory(resourcePatternResolver);

    List<Class> candidates = new ArrayList<Class>();
    String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX +
                               resolveBasePackage(basePackage) + "/" + "**/*.class";
    Resource[] resources = resourcePatternResolver.getResources(packageSearchPath);
    for (Resource resource : resources) {
        if (resource.isReadable()) {
            MetadataReader metadataReader = metadataReaderFactory.getMetadataReader(resource);
            if (isCandidate(metadataReader)) {
                candidates.add(Class.forName(metadataReader.getClassMetadata().getClassName()));
            }
        }
    }
    return candidates;
}

private String resolveBasePackage(String basePackage) {
    return ClassUtils.convertClassNameToResourcePath(SystemPropertyUtils.resolvePlaceholders(basePackage));
}

private boolean isCandidate(MetadataReader metadataReader) throws ClassNotFoundException
{
    try {
        Class c = Class.forName(metadataReader.getClassMetadata().getClassName());
        if (c.getAnnotation(XmlRootElement.class) != null) {
            return true;
        }
    }
    catch(Throwable e){
    }
    return false;
}

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