[编织消息框架][JAVA核心技术]动态代理应用9-扫描class

Posted 2020-09-10 solq321

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

 1 public class PackageScanner {
 2     private static final Logger LOGGER = LoggerFactory.getLogger(PackageScanner.class);
 3 
 4     /**
 5      * @param packageNames
 6      *            过滤的包名，如果为NULL即扫描所有类
 7      */
 8     public static void scan(Consumer<Class<?>> atcion, final String... packageNames) {
 9         Set<String> classPath = new HashSet<>();
10         Set<String> filterPackage = new HashSet<>();
11         if (packageNames == null || packageNames.length == 0) {
12             String classpathProp = System.getProperty("java.class.path");
13             if (classpathProp != null) {
14             String[] classpathEntries = classpathProp.split(File.pathSeparator);
15             for (String cpe : classpathEntries) {
16                 cpe = trimr(cpe, \'/\');
17                 classPath.add(new File(cpe).getAbsolutePath());
18             }
19             }
20             ClassLoader cl = ClassLoader.getSystemClassLoader();
21             URL[] urls = ((URLClassLoader) cl).getURLs();
22             for (URL url : urls) {
23             String path = trimr(url.getPath(), \'/\');
24             classPath.add(new File(path).getAbsolutePath());
25             }
26         } else {
27             Collections.addAll(classPath, packageNames);
28             Collections.addAll(filterPackage, packageNames);
29         }
30         
31         /***
32          * 扫描有三种策略
33          * 1.jar文件
34          * 2.class文件
35          * 3.classPath目录
36          * */
37         
38         for (String path : classPath) {
39             try {
40                 if (path.endsWith(".jar")) {
41                     parseJar(path, filterPackage, atcion);
42                 }else if (new File(path).isDirectory()) {
43                     parseFile(path, null, filterPackage, atcion);
44                 } else {
45                     final String packageDirectory = path.replace(\'.\', \'/\');
46                     final Enumeration<URL> urls = Thread.currentThread().getContextClassLoader().getResources(packageDirectory);
47                     while (urls.hasMoreElements()) {
48                         final URL url = urls.nextElement();
49                         if ("file".equals(url.getProtocol())) {
50                             parseFile(url.getPath(), url.getPath().replace(packageDirectory, ""), filterPackage,atcion);
51                         } else if ("jar".equals(url.getProtocol())) {
52                             parseJar(url.getPath(),filterPackage, atcion);
53                         }
54                     }
55                 }
56             } catch (Exception exception) {
57                 throw new RuntimeException(exception);
58             }
59         }
60     }
61 }

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：

 1 public class TestScanClass {
 2 
 3     @Test
 4     public void testAll() {
 5         PackageScanner.scan((clz) -> {
 6             // System.out.println(clz);
 7         });
 8     }
 9 
10     @Test
11     public void testFilter1() {
12         PackageScanner.scan((clz) -> {
13             System.out.println(clz);
14         } , "com.eyu.onequeue");
15     }
16 
17     @Test
18     public void testFilter() {
19         Set<Class<?>> values = new HashSet<>();
20         PackageScanner.scan((clz) -> {
21             QModel modelAnno = ReflectUtil.getAnno(clz, QModel.class);
22             if (modelAnno == null) {
23                 return;
24             }
25             values.add(clz);
26         } , "com.eyu.onequeue");
27         for (Class<?> clz : values) {
28             if (clz.isInterface()) {
29                 QRpcFactory.registerSendProxy(clz);
30                 System.out.println("registerSendProxy : " + clz);
31             } else {
32                 try {
33                     QRpcFactory.registerReceiveProxy(clz.newInstance());
34                     System.out.println("registerReceiveProxy : " + clz);
35                 } catch (Exception e) {
36                     e.printStackTrace();
37                 }
38             }
39         }
40     }
41 }