Spring 源码中一些小工具

1.  包扫描方法，扫描指定包路径下的类  

 org.springframework.context.annotation.ClassPathBeanDefinitionScanner#doScan

 在指定的基本包内执行扫描，返回注册的bean定义。

 核心扫描逻辑代码 

 org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider#scanCandidateComponents

 可以把这部分源码进行魔改 ，改写成一个工具类 扫描指定路径下的类，参考 componentScan注解的配置方法。

 样例代码：

public class ClassScaner implements ResourceLoaderAware {

    //保存过滤规则要排除的注解
    private final List<TypeFilter> includeFilters = new LinkedList<TypeFilter>();
    private final List<TypeFilter> excludeFilters = new LinkedList<TypeFilter>();

    private ResourcePatternResolver resourcePatternResolver = new PathMatchingResourcePatternResolver();
    private MetadataReaderFactory metadataReaderFactory = new CachingMetadataReaderFactory(this.resourcePatternResolver);

    public static Set<Class> scan(String[] basePackages,
                                  Class<? extends Annotation>... annotations) {
        ClassScaner cs = new ClassScaner();

        if (ArrayUtils.isNotEmpty(annotations)) {
            for (Class anno : annotations) {
                cs.addIncludeFilter(new AnnotationTypeFilter(anno));
            }
        }

        Set<Class> classes = new HashSet<Class>();
        for (String s : basePackages)
            classes.addAll(cs.doScan(s));
        return classes;
    }

    public static Set<Class> scan(String basePackages, Class<? extends Annotation>... annotations) {
        return ClassScaner.scan(StringUtils.tokenizeToStringArray(basePackages, ",; \t\n"), annotations);
    }

    public final ResourceLoader getResourceLoader() {
        return this.resourcePatternResolver;
    }

    public void setResourceLoader(ResourceLoader resourceLoader) {
        this.resourcePatternResolver = ResourcePatternUtils
                .getResourcePatternResolver(resourceLoader);
        this.metadataReaderFactory = new CachingMetadataReaderFactory(
                resourceLoader);
    }

    public void addIncludeFilter(TypeFilter includeFilter) {
        this.includeFilters.add(includeFilter);
    }

    public void addExcludeFilter(TypeFilter excludeFilter) {
        this.excludeFilters.add(0, excludeFilter);
    }

    public void resetFilters(boolean useDefaultFilters) {
        this.includeFilters.clear();
        this.excludeFilters.clear();
    }

    public Set<Class> doScan(String basePackage) {
        Set<Class> classes = new HashSet<Class>();
        try {
            String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX
                    + org.springframework.util.ClassUtils
                    .convertClassNameToResourcePath(SystemPropertyUtils
                            .resolvePlaceholders(basePackage))
                    + "/**/*.class";
            Resource[] resources = this.resourcePatternResolver
                    .getResources(packageSearchPath);

            for (int i = 0; i < resources.length; i++) {
                Resource resource = resources[i];
                if (resource.isReadable()) {
                    MetadataReader metadataReader = this.metadataReaderFactory.getMetadataReader(resource);
                    if ((includeFilters.size() == 0 && excludeFilters.size() == 0)
                            || matches(metadataReader)) {
                        try {
                            classes.add(Class.forName(metadataReader
                                    .getClassMetadata().getClassName()));
                        } catch (ClassNotFoundException e) {
                            e.printStackTrace();
                        }
                    }
                }
            }
        } catch (IOException ex) {
            throw new BeanDefinitionStoreException(
                    "I/O failure during classpath scanning", ex);
        }
        return classes;
    }

    protected boolean matches(MetadataReader metadataReader) throws IOException {
        for (TypeFilter tf : this.excludeFilters) {
            if (tf.match(metadataReader, this.metadataReaderFactory)) {
                return false;
            }
        }
        for (TypeFilter tf : this.includeFilters) {
            if (tf.match(metadataReader, this.metadataReaderFactory)) {
                return true;
            } else {
                return false;
            }
        }
        return true;
    }

    public static void main(String[] args) {
        ClassScaner.scan("com.onion.service", Service.class)
                .forEach(clazz -> System.out.println(clazz));
    }
}

2.获取当前默认的类加载器

  使用 ClassUtils.getDefaultClassLoader()

本文地址：https://blog.csdn.net/oschina_40730821/article/details/107356688