if (rs.next()) { System.out.println(rs.getString(1)); } } catch (SQLException ex) { Logger lgr = Logger.getLogger(Version.class.getName()); if (con != null) { con.close(); } } catch (SQLException ex) { Logger lgr = Logger.getLogger(Version.class.getName()); The getString() method retrieves the value of a specified column. The first column has index 1. } catch (SQLException ex) { Logger lgr = Logger.getLogger(Version.class.getName()); lgr.log(Level

get("data/subdir"); try { Path newDir = Files.createDirectory(path); } catch(FileAlreadyExistsException e){ // the directory already exists. } catch (IOException e) { //something else went wrong e.printStackTrace(); properties"); try { Files.copy(sourcePath, destinationPath); } catch(FileAlreadyExistsException e) { //destination file already exists } catch (IOException e) { //something else went wrong e.printStackTrace(); destinationPath, StandardCopyOption.REPLACE_EXISTING); } catch(FileAlreadyExistsException e) { //destination file already exists } catch (IOException e) { //something else went wrong e.printStackTrace();

//无异常，说明就是我们想要的! } catch ( UnknownAccountException uae ) { //username 不存在，给个错误提示? } catch ( IncorrectCredentialsException ice ) { //password 不匹配，再输入? } catch ( LockedAccountException lae ) { //账号锁住了，不能登入。给个提示? } ... 更多类型异常 ... } catch ( AuthenticationException ae ) { //未考虑到的问题 - 错误? } 这里有许多不同类别的异常你可以检测到，也可以抛出你自己异常。详见 AuthenticationException JavaDoc 小贴士： 最好的 login(token); } catch (UnknownAccountException uae) { log.info("There is no user with username of " + token.getPrincipal()); } catch (IncorrectCredentialsException

异常处理机制 异常处理结构 O 异常处理结构 1 try { 2 ... //可能产生异常的代码，试图捕获异常 4 } catch (ExceptionName1 e) { 5 ... //当产生 ExceptionName1 型异常时的处��� 7 } catch (ExceptionName2 e) { 8 ... //当产生 ExceptionName2 型异常时的处��� 10 不论 try 代码块中是否发生了异常事件，finally 块中的语句 都会被执行。当 catch 语句块中出现 return 语句时，finally 语句块同样会执行。 大纲 异常的概念及分类 Java 异常处理机制 操作异常对象 发生异常时，系统将自动创建异常类对象，并将作为实参传递给 匹配的 catch 语句块的形参，这样就可以在语句块中操纵该异常 对象。 O 异常类的父类 Throwable 常用，在没有找到适合的异常处理代码时，系统也 会自动调用该方法输出错误信息。 大纲 异常的概念及分类 Java 异常处理机制 操作异常对象 发生异常时，系统将自动创建异常类对象，并将作为实参传递给 匹配的 catch 语句块的形参，这样就可以在语句块中操纵该异常 对象。 O 异常类的父类 Throwable 中定义的方法 getMessage() 返回描述当前异常的详细消息字符串。 printStackTrace()

/ 共 306 页 2.1. JAVA 语言基础 � 2 � 表 2.3 Java 语言的关键字（保留字） abstract assert boolean break byte case catch char class continue default do double else enum extends false final finally float for if implements equals(””)) { 13 System.out.println(”Read: ” + s); 14 s = br.readLine(); 15 } 16 br. close (); 17 } catch (IOException e) { 18 e.printStackTrace(); 19 } 20 } 21 } 对上述程序的几点解释： • System.in 为 InputStream s); 14 s = br.readLine(); } 15 br. close (); 16 } catch (FileNotFoundException e1) { 17 System.err.println(”File not found: ” + fname); 18 } catch (IOException e2) { 19 e2.printStackTrace(); 20 }

UsernamePasswordToken("zhang", "123"); try { //4、登录，即身份验证 subject.login(token); } catch (AuthenticationException e) { //5、身份验证失败 } Assert.assertEquals(true, subject login(token); } catch (UnknownAccountException e) { error = "用户名/密码错误"; } catch (IncorrectCredentialsException e) { error = "用户名/密码错误"; } catch (AuthenticationException (AuthenticationException e) { //其他错误，比如锁定，如果想单独处理请单独 catch 处理 error = "其他错误：" + e.getMessage(); } if(error != null) {//出错了，返回登录页面 req.setAttribute("error"

try { currentUser.login(token); } catch (UnknownAccountException uae) { log.info("There is no user with username of " + token.getPrincipal()); } catch(IncorrectCredentialsException ice) { log "); } catch(LockedAccountException lae) { log.info("The account for username " + token.getPrincipal() + " is locked. " + "Please contact your administrator to unlock it."); } // … catch more exceptions exceptions here (maybe custom ones specific to your application? catch (AuthenticationException ae) { //unexpected condition? error? } } //say who they are: //print their identifying principal

getServletContext() .getRealPath("/image"), fileName); try { multipartFile.transferTo(imageFile); } catch (IOException e) { e.printStackTrace(); } } } model.addAttribute("product", product); return "ProductDetails"; i); i = bis.read(buffer); } catch (IOException e) { // do something, probably forward to an Error page. } finally { if (bis != null) { try { bis.close(); } catch (IOException e) { if (fis != null) null) { try { fis.close(); } catch (IOException e) { return null; } } } } } } 大纲 Spring 文件上传 Spring 文件下载 Spring 用户登录 监听器 示例：隐藏资源 LoginForm.jsp

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equals("")) { 13 System.out.println("Read:␣" + s); 14 s = br.readLine(); 15 } 16 br.close(); 17 } catch (IOException e) { 18 e.printStackTrace(); 19 } 20 } 21 } 15 41 ���程序����� System.in 为 InputStream s); 14 s = br.readLine(); } 15 br.close(); 16 } catch (FileNotFoundException e1) { 17 System.err.println("File␣not␣found:␣" + fname); 18 } catch (IOException e2) { 19 e2.printStackTrace(); 20 } 15 } 16 in.close(); // 关闭 BufferedReader 输入流 17 out.close(); // 关闭连接文件的 PrintWriter 输出流 18 } catch (IOException e) { 19 e.printStackTrace(); 20 } 21 } 22 } 24 41 ���������� 1. 写文件�����文件�������行��出������

code can actually recover from a transaction failure, the application developer can still choose to catch and handle TransactionException. The salient point is that developers are not forced to do so. The rollback: Java public void resolvePosition() { try { // some business logic... } catch (NoProductInStockException ex) { // trigger rollback programmatically TransactionAspectSupport setRollbackOnly(); } } 24 Kotlin fun resolvePosition() { try { // some business logic... } catch (ex: NoProductInStockException) { // trigger rollback programmatically TransactionAspectSupport