利用spring，实现package下的类扫描

项目中需要用到包扫描的情况是很多的，一般是在项目初始化的时候，根据一些条件来对某个package下的类进行特殊处理。现在想实现的功能是，在一个filter或interceptor初始化的时候，扫描指定的一些package路径，遍历下面的每个class，找出method上使用了一个特殊注解的所有方法，然后缓存起来，当方法拦截器工作的时候，就不用再挨个判断方法是否需要拦截了

网上有很多自己编码实现scan package功能的例子，但是如果有工具已经帮你实现了，并且经受了普遍的验证，那么，自己造轮子的必要性就不大了
   spring框架中有扫描包的类ClassPathBeanDefinitionScanner 里面的findCandidateComponents方法是我们进行改造的依据

/**
 * Scan the class path for candidate components.
 * @param basePackage the package to check for annotated classes
 * @return a corresponding Set of autodetected bean definitions
 */
public Set<BeanDefinition> findCandidateComponents(String basePackage) {
   Set<BeanDefinition> candidates = new LinkedHashSet<BeanDefinition>();
   try {
      String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX +
            resolveBasePackage(basePackage) + "/" + this.resourcePattern;
      Resource[] resources = this.resourcePatternResolver.getResources(packageSearchPath);
      boolean traceEnabled = logger.isTraceEnabled();
      boolean debugEnabled = logger.isDebugEnabled();
      for (Resource resource : resources) {
         if (traceEnabled) {
            logger.trace("Scanning " + resource);
         }
         if (resource.isReadable()) {
            try {
               MetadataReader metadataReader = this.metadataReaderFactory.getMetadataReader(resource);
               if (isCandidateComponent(metadataReader)) {
                  ScannedGenericBeanDefinition sbd = new ScannedGenericBeanDefinition(metadataReader);
                  sbd.setResource(resource);
                  sbd.setSource(resource);
                  if (isCandidateComponent(sbd)) {
                     if (debugEnabled) {
                        logger.debug("Identified candidate component class: " + resource);
                     }
                     candidates.add(sbd);
                  }
                  else {
                     if (debugEnabled) {
                        logger.debug("Ignored because not a concrete top-level class: " + resource);
                     }
                  }
               }
               else {
                  if (traceEnabled) {
                     logger.trace("Ignored because not matching any filter: " + resource);
                  }
               }
            }
            catch (Throwable ex) {
               throw new BeanDefinitionStoreException(
                     "Failed to read candidate component class: " + resource, ex);
            }
         }
         else {
            if (traceEnabled) {
               logger.trace("Ignored because not readable: " + resource);
            }
         }
      }
   }
   catch (IOException ex) {
      throw new BeanDefinitionStoreException("I/O failure during classpath scanning", ex);
   }
   return candidates;
}

改造如下：

方法loadCheckClassMethods的入参是逗号分隔的包路径，如com.xx

利用Spring的

ResourcePatternResolver来寻找包下面的资源Resource，因为我们的扫描pattern是.class文件，所以这里的Resource就是class文件

protected static final String DEFAULT_RESOURCE_PATTERN = "**/*.class";

　　

/**
 * 根据扫描包的配置
 * 加载需要检查的方法
 */
private void loadCheckClassMethods(String scanPackages) {
    String[] scanPackageArr = scanPackages.split(",");
    ResourcePatternResolver resourcePatternResolver = new PathMatchingResourcePatternResolver();
    MetadataReaderFactory metadataReaderFactory = new CachingMetadataReaderFactory(resourcePatternResolver);
    for (String basePackage : scanPackageArr) {
        if (StringUtils.isBlank(basePackage)) {
            continue;
        }
        String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX +
                ClassUtils.convertClassNameToResourcePath(SystemPropertyUtils.resolvePlaceholders(basePackage)) + "/" + DEFAULT_RESOURCE_PATTERN;
        try {
            Resource[] resources = resourcePatternResolver.getResources(packageSearchPath);
            for (Resource resource : resources) {
                //检查resource，这里的resource都是class
                loadClassMethod(metadataReaderFactory, resource);
            }
        } catch (Exception e) {
            log.error("初始化SensitiveWordInterceptor失败", e);
        }

    }
}
/**
 * 加载资源，判断里面的方法
 *
 * @param metadataReaderFactory spring中用来读取resource为class的工具
 * @param resource              这里的资源就是一个Class
 * @throws IOException
 */
private void loadClassMethod(MetadataReaderFactory metadataReaderFactory, Resource resource) throws IOException {
    try {
        if (resource.isReadable()) {
            MetadataReader metadataReader = metadataReaderFactory.getMetadataReader(resource);
            if (metadataReader != null) {
                String className = metadataReader.getClassMetadata().getClassName();
                try {
                    tryCacheMethod(className);
                } catch (ClassNotFoundException e) {
                    log.error("检查" + className + "是否含有需要信息失败", e);
                }
            }
        }
    } catch (Exception e) {
        log.error("判断类中的方法实现需要检测xxx失败", e);
    }
}
/**
 * 把action下面的所有method遍历一次，标记他们是否需要进行xxx验证
 * 如果需要，放入cache中
 *
 * @param fullClassName
 */
private void tryCacheMethod(String fullClassName) throws ClassNotFoundException {
    Class<?> clz = Class.forName(fullClassName);
    Method[] methods = clz.getDeclaredMethods();
    for (Method method : methods) {
        if (method.getModifiers() != Modifier.PUBLIC) {
            continue;
        }
        if (CheckXXX.class.isAssignableFrom(CHECK_ANNOTATION)) {
            CheckXXX checkXXX = (CheckXXX) method.getAnnotation(CHECK_ANNOTATION);
            if (checkXXX != null && checkXXX.check()) {
                cache.put(fullClassName + "." + method.getName(), checkXXX);
                log.info("检测到需要检查xxx的方法:" + fullClassName + "." + method.getName());
            }
        }
    }
}

tryCacheMethod做的事就是缓存需要处理的public方法

经测试，这种方式可以取到web的class文件和jar包中的class文件

加强版，package父子集合判断

package utils;
import org.apache.commons.lang3.StringUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.core.io.Resource;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.core.io.support.ResourcePatternResolver;
import org.springframework.core.type.classreading.CachingMetadataReaderFactory;
import org.springframework.core.type.classreading.MetadataReader;
import org.springframework.core.type.classreading.MetadataReaderFactory;
import org.springframework.util.SystemPropertyUtils;

import java.io.IOException;
import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

/**
 * Created by cdliujian1 on 2016/1/13.
 * 包工具，根据package路径，加载class
 */
public class PackageUtil {

    private final static Log log = LogFactory.getLog(PackageUtil.class);
    //扫描  scanPackages 下的文件的匹配符
    protected static final String DEFAULT_RESOURCE_PATTERN = "**/*.class";

    /**
     * 结合spring的类扫描方式
     * 根据需要扫描的包路径及相应的注解，获取最终测method集合
     * 仅返回public方法，如果方法是非public类型的，不会被返回
     * 可以扫描工程下的class文件及jar中的class文件
     *
     * @param scanPackages
     * @param annotation
     * @return
     */
    public static Set<Method> findClassAnnotationMethods(String scanPackages, Class<? extends Annotation> annotation) {
        //获取所有的类
        Set<String> clazzSet = findPackageClass(scanPackages);
        Set<Method> methods = new HashSet<Method>();
        //遍历类，查询相应的annotation方法
        for (String clazz : clazzSet) {
            try {
                Set<Method> ms = findAnnotationMethods(clazz, annotation);
                if (ms != null) {
                    methods.addAll(ms);
                }
            } catch (ClassNotFoundException ignore) {
            }
        }
        return methods;
    }

    /**
     * 根据扫描包的,查询下面的所有类
     *
     * @param scanPackages 扫描的package路径
     * @return
     */
    public static Set<String> findPackageClass(String scanPackages) {
        if (StringUtils.isBlank(scanPackages)) {
            return Collections.EMPTY_SET;
        }
        //验证及排重包路径,避免父子路径多次扫描
        Set<String> packages = checkPackage(scanPackages);
        ResourcePatternResolver resourcePatternResolver = new PathMatchingResourcePatternResolver();
        MetadataReaderFactory metadataReaderFactory = new CachingMetadataReaderFactory(resourcePatternResolver);
        Set<String> clazzSet = new HashSet<String>();
        for (String basePackage : packages) {
            if (StringUtils.isBlank(basePackage)) {
                continue;
            }
            String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX +
                    org.springframework.util.ClassUtils.convertClassNameToResourcePath(SystemPropertyUtils.resolvePlaceholders(basePackage)) + "/" + DEFAULT_RESOURCE_PATTERN;
            try {
                Resource[] resources = resourcePatternResolver.getResources(packageSearchPath);
                for (Resource resource : resources) {
                    //检查resource，这里的resource都是class
                    String clazz = loadClassName(metadataReaderFactory, resource);
                    clazzSet.add(clazz);
                }
            } catch (Exception e) {
                log.error("获取包下面的类信息失败,package:" + basePackage, e);
            }

        }
        return clazzSet;
    }

    /**
     * 排重、检测package父子关系，避免多次扫描
     *
     * @param scanPackages
     * @return 返回检查后有效的路径集合
     */
    private static Set<String> checkPackage(String scanPackages) {
        if (StringUtils.isBlank(scanPackages)) {
            return Collections.EMPTY_SET;
        }
        Set<String> packages = new HashSet<String>();
        //排重路径
        Collections.addAll(packages, scanPackages.split(","));
        for (String pInArr : packages.toArray(new String[packages.size()])) {
            if (StringUtils.isBlank(pInArr) || pInArr.equals(".") || pInArr.startsWith(".")) {
                continue;
            }
            if (pInArr.endsWith(".")) {
                pInArr = pInArr.substring(0, pInArr.length() - 1);
            }
            Iterator<String> packageIte = packages.iterator();
            boolean needAdd = true;
            while (packageIte.hasNext()) {
                String pack = packageIte.next();
                if (pInArr.startsWith(pack + ".")) {
                    //如果待加入的路径是已经加入的pack的子集，不加入
                    needAdd = false;
                } else if (pack.startsWith(pInArr + ".")) {
                    //如果待加入的路径是已经加入的pack的父集，删除已加入的pack
                    packageIte.remove();
                }
            }
            if (needAdd) {
                packages.add(pInArr);
            }
        }
        return packages;
    }

    /**
     * 加载资源，根据resource获取className
     *
     * @param metadataReaderFactory spring中用来读取resource为class的工具
     * @param resource              这里的资源就是一个Class
     * @throws IOException
     */
    private static String loadClassName(MetadataReaderFactory metadataReaderFactory, Resource resource) throws IOException {
        try {
            if (resource.isReadable()) {
                MetadataReader metadataReader = metadataReaderFactory.getMetadataReader(resource);
                if (metadataReader != null) {
                    return metadataReader.getClassMetadata().getClassName();
                }
            }
        } catch (Exception e) {
            log.error("根据resource获取类名称失败", e);
        }
        return null;
    }

    /**
     * 把action下面的所有method遍历一次，标记他们是否需要进行敏感词验证
     * 如果需要，放入cache中
     *
     * @param fullClassName
     */
    public static Set<Method> findAnnotationMethods(String fullClassName, Class<? extends Annotation> anno) throws ClassNotFoundException {
        Set<Method> methodSet = new HashSet<Method>();
        Class<?> clz = Class.forName(fullClassName);
        Method[] methods = clz.getDeclaredMethods();
        for (Method method : methods) {
            if (method.getModifiers() != Modifier.PUBLIC) {
                continue;
            }
            Annotation annotation = method.getAnnotation(anno);
            if (annotation != null) {
                methodSet.add(method);
            }
        }
        return methodSet;
    }

    public static void main(String[] args) {
        String packages = "com.a,com.ab,com.c,com.as.t,com.as,com.as.ta,com.at.ja,com.at.jc,com.at.";
        System.out.println("检测前的package: " + packages);
        System.out.println("检测后的package: " + StringUtils.join(checkPackage(packages), ","));
    }

}