[编织消息框架][JAVA核心技术]动态代理应用9-扫描class

之前介绍的annotationProcessor能在编译时生成自定义class,但有个缺点，只能每次添加/删除java文件才会执行，那天换了个人不清楚就坑大了

还记得之前介绍的编译时处理，懒处理，还有个预处理没介绍对吧

预处理：应用程序启动前做的处理，如setup

扫描class处理

1.从ClassLoader 和 System.getProperty("java.class.path") 读取所有classPath

2.解释每个classPath ，用正则匹配jar/class 文件

3.正则提取class文件类名，转换成class给上层处理

 public class PackageScanner {
     private static final Logger LOGGER = LoggerFactory.getLogger(PackageScanner.class);

     /**
      * @param packageNames
      *            过滤的包名，如果为NULL即扫描所有类
      */
     public static void scan(Consumer<Class<?>> atcion, final String... packageNames) {
         Set<String> classPath = new HashSet<>();
         Set<String> filterPackage = new HashSet<>();
         if (packageNames == null || packageNames.length == 0) {
             String classpathProp = System.getProperty("java.class.path");
             if (classpathProp != null) {
             String[] classpathEntries = classpathProp.split(File.pathSeparator);
             for (String cpe : classpathEntries) {
                 cpe = trimr(cpe, '/');
                 classPath.add(new File(cpe).getAbsolutePath());
             }
             }
             ClassLoader cl = ClassLoader.getSystemClassLoader();
             URL[] urls = ((URLClassLoader) cl).getURLs();
             for (URL url : urls) {
             String path = trimr(url.getPath(), '/');
             classPath.add(new File(path).getAbsolutePath());
             }
         } else {
             Collections.addAll(classPath, packageNames);
             Collections.addAll(filterPackage, packageNames);
         }

         /***
          * 扫描有三种策略
          * 1.jar文件
          * 2.class文件
          * 3.classPath目录
          * */

         for (String path : classPath) {
             try {
                 if (path.endsWith(".jar")) {
                     parseJar(path, filterPackage, atcion);
                 }else if (new File(path).isDirectory()) {
                     parseFile(path, null, filterPackage, atcion);
                 } else {
                     final String packageDirectory = path.replace('.', '/');
                     final Enumeration<URL> urls = Thread.currentThread().getContextClassLoader().getResources(packageDirectory);
                     while (urls.hasMoreElements()) {
                         final URL url = urls.nextElement();
                         if ("file".equals(url.getProtocol())) {
                             parseFile(url.getPath(), url.getPath().replace(packageDirectory, ""), filterPackage,atcion);
                         } else if ("jar".equals(url.getProtocol())) {
                             parseJar(url.getPath(),filterPackage, atcion);
                         }
                     }
                 }
             } catch (Exception exception) {
                 throw new RuntimeException(exception);
             }
         }
     }
 }

parseJar，parseFile 比较长，感兴趣读者可查源码分析

有的JAR里的类读会出错,原因是没有依赖完整的包

测试：

 public class TestScanClass {

     @Test
     public void testAll() {
         PackageScanner.scan((clz) -> {
             // System.out.println(clz);
         });
     }

     @Test
     public void testFilter1() {
         PackageScanner.scan((clz) -> {
             System.out.println(clz);
         } , "com.eyu.onequeue");
     }

     @Test
     public void testFilter() {
         Set<Class<?>> values = new HashSet<>();
         PackageScanner.scan((clz) -> {
             QModel modelAnno = ReflectUtil.getAnno(clz, QModel.class);
             if (modelAnno == null) {
                 return;
             }
             values.add(clz);
         } , "com.eyu.onequeue");
         for (Class<?> clz : values) {
             if (clz.isInterface()) {
                 QRpcFactory.registerSendProxy(clz);
                 System.out.println("registerSendProxy : " + clz);
             } else {
                 try {
                     QRpcFactory.registerReceiveProxy(clz.newInstance());
                     System.out.println("registerReceiveProxy : " + clz);
                 } catch (Exception e) {
                     e.printStackTrace();
                 }
             }
         }
     }
 }