### Question:
PlainPermissionLoader { private void watch() { try { String watchFilePath = fileHome + fileName; FileWatchService fileWatchService = new FileWatchService(new String[] {watchFilePath}, new FileWatchService.Listener() { @Override public void onChanged(String path) { log.info("The plain acl yml changed, reload the context"); load(); } }); fileWatchService.start(); log.info("Succeed to start AclWatcherService"); this.isWatchStart = true; } catch (Exception e) { log.error("Failed to start AclWatcherService", e); } } PlainPermissionLoader(); void load(); PlainAccessResource buildPlainAccessResource(PlainAccessConfig plainAccessConfig); void validate(PlainAccessResource plainAccessResource); boolean isWatchStart();  }### Answer:
@Test public void testWatch() throws IOException, IllegalAccessException ,InterruptedException{ System.setProperty("rocketmq.home.dir", "src/test/resources"); System.setProperty("rocketmq.acl.plain.file", "/conf/plain_acl-test.yml"); String fileName =System.getProperty("rocketmq.home.dir", "src/test/resources")+System.getProperty("rocketmq.acl.plain.file", "/conf/plain_acl.yml"); File transport = new File(fileName); transport.delete(); transport.createNewFile(); FileWriter writer = new FileWriter(transport); writer.write("accounts:\r\n"); writer.write("- accessKey: watchrocketmq\r\n"); writer.write(" secretKey: 12345678\r\n"); writer.write(" whiteRemoteAddress: 127.0.0.1\r\n"); writer.write(" admin: true\r\n"); writer.flush(); writer.close(); PlainPermissionLoader plainPermissionLoader = new PlainPermissionLoader(); Assert.assertTrue(plainPermissionLoader.isWatchStart()); { Map<String, PlainAccessResource> plainAccessResourceMap = (Map<String, PlainAccessResource>) FieldUtils.readDeclaredField(plainPermissionLoader, "plainAccessResourceMap", true); PlainAccessResource accessResource = plainAccessResourceMap.get("watchrocketmq"); Assert.assertNotNull(accessResource); Assert.assertEquals(accessResource.getSecretKey(), "12345678"); Assert.assertTrue(accessResource.isAdmin()); } writer = new FileWriter(new File(fileName), true); writer.write("- accessKey: watchrocketmq1\r\n"); writer.write(" secretKey: 88888888\r\n"); writer.write(" whiteRemoteAddress: 127.0.0.1\r\n"); writer.write(" admin: false\r\n"); writer.flush(); writer.close(); Thread.sleep(1000); { Map<String, PlainAccessResource> plainAccessResourceMap = (Map<String, PlainAccessResource>) FieldUtils.readDeclaredField(plainPermissionLoader, "plainAccessResourceMap", true); PlainAccessResource accessResource = plainAccessResourceMap.get("watchrocketmq1"); Assert.assertNotNull(accessResource); Assert.assertEquals(accessResource.getSecretKey(), "88888888"); Assert.assertFalse(accessResource.isAdmin()); } transport.delete(); System.setProperty("rocketmq.home.dir", "src/test/resources"); System.setProperty("rocketmq.acl.plain.file", "/conf/plain_acl.yml"); }