Java:未捕获故意的 BadPaddingException

Question

我的应用程序提示用户输入用于加密控制文件的密码。如果输入了错误的密码，应用程序将通过创建新的控制文件进行响应。因此，我需要捕获 BadPaddingException，以便我可以触发适当的响应。

这是应该生成异常的代码片段

private void existingHashFile(String file) {
        psUI = new passwordUI(new javax.swing.JFrame(), true, "existing");
        psUI.setVisible(true);
        this.key = passwordUI.key;
        try {
            hash.decryptHashFile(file, this.key); //this is line 240
        } catch (BadPaddingException ex) {
            Logger.getLogger(homePage.class.getName()).log(Level.SEVERE, null, ex);
            //then the file was not decrypted
            System.out.println("BPE 2!");
        } catch (Exception ex) {
            Logger.getLogger(homePage.class.getName()).log(Level.SEVERE, null, ex);
            System.out.println("BPE 3!");
        }

为了完整起见，这里是上面调用的decryptHashFile方法

public void decryptHashFile(String filename, String key) throws BadPaddingException, UnsupportedEncodingException, Exception {
        FileInputStream fis = null;
        FileOutputStream fos = null;
        CipherInputStream cis = null;   
        String outFile = filename.replace(".enc", "");
        byte[] byteKey = key.getBytes("UTF-8");

        Cipher cipher = getCipher(byteKey, "decrypt");

        try {
            fis = new FileInputStream(filename);
            fos = new FileOutputStream(outFile);
            cis = new CipherInputStream(fis, cipher);
            byte[] buffer = new byte[1024];
            int read = cis.read(buffer);
            while (read != -1) {
                fos.write(buffer, 0, read);
                read = cis.read(buffer); //this is line 197
            }
        } catch (IOException  ex) {
            Logger.getLogger(hashListClass.class.getName()).log(Level.SEVERE, null, ex);
        } finally {
            if (fos != null) {
                fos.close();
            }
            if (cis != null) {
               cis.close(); 
            }
            if (fis != null) {
               fis.close(); 
            }
        }
    }

当我故意输入错误的密码时，我会看到此堆栈跟踪，但我的代码(我在示例中使用了 println)未执行:

Dec 02, 2017 2:31:34 PM appwatch.hashListClass decryptHashFile
SEVERE: null
java.io.IOException: javax.crypto.BadPaddingException: Given final block not properly padded
    at javax.crypto.CipherInputStream.getMoreData(CipherInputStream.java:121)
    at javax.crypto.CipherInputStream.read(CipherInputStream.java:239)
    at javax.crypto.CipherInputStream.read(CipherInputStream.java:215)
    at appwatch.hashListClass.decryptHashFile(hashListClass.java:197)
    at appwatch.homePage.existingHashFile(homePage.java:240)

Answer 1

CipherInputStream.read (第 197 行)抛出 IOException，而不是 BadPaddingException，因此该异常被后续的 catch (IOException ex) 捕获。

此后，您不会显式抛出其他异常，因此在 decryptHashFile 之后没有其他内容可捕获。