为什么我得到“异常;必须被抓住或宣布被抛出“当我尝试编译我的Java代码？
问题描述：
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import javax.crypto.*;
import javax.crypto.spec.*;
import java.security.*;
import java.io.*;
public class EncryptURL extends JApplet implements ActionListener {
Container content;
JTextField userName = new JTextField();
JTextField firstName = new JTextField();
JTextField lastName = new JTextField();
JTextField email = new JTextField();
JTextField phone = new JTextField();
JTextField heartbeatID = new JTextField();
JTextField regionCode = new JTextField();
JTextField retRegionCode = new JTextField();
JTextField encryptedTextField = new JTextField();
JPanel finishPanel = new JPanel();
public void init() {
//setTitle("Book - E Project");
setSize(800,600);
content = getContentPane();
content.setBackground(Color.yellow);
content.setLayout(new BoxLayout(content, BoxLayout.Y_AXIS));
JButton submit = new JButton("Submit");
content.add(new JLabel("User Name"));
content.add(userName);
content.add(new JLabel("First Name"));
content.add(firstName);
content.add(new JLabel("Last Name"));
content.add(lastName);
content.add(new JLabel("Email"));
content.add(email);
content.add(new JLabel("Phone"));
content.add(phone);
content.add(new JLabel("HeartBeatID"));
content.add(heartbeatID);
content.add(new JLabel("Region Code"));
content.add(regionCode);
content.add(new JLabel("RetRegionCode"));
content.add(retRegionCode);
content.add(submit);
submit.addActionListener(this);
}
public void actionPerformed(ActionEvent e) {
if(e.getActionCommand() == "Submit"){
String subUserName = userName.getText();
String subFName = firstName.getText();
String subLName = lastName.getText();
String subEmail = email.getText();
String subPhone = phone.getText();
String subHeartbeatID = heartbeatID.getText();
String subRegionCode = regionCode.getText();
String subRetRegionCode = retRegionCode.getText();
String concatURL = "user="+ subUserName + "&f="+ subFName + "&l=" +subLName+ "&em=" + subEmail + "&p="+subPhone+"&h="+subHeartbeatID+"&re="+subRegionCode+ "&ret=" + subRetRegionCode;
concatURL = padString(concatURL, ' ', 16);
byte[] encrypted = encrypt(concatURL);
String encryptedString = bytesToHex(encrypted);
content.removeAll();
content.add(new JLabel("Concatenated User Input -->" + concatURL));
content.add(encryptedTextField);
setContentPane(content);
}
}
public static byte[] encrypt(String toEncrypt) throws Exception{
try{
String plaintext = toEncrypt;
String key = "01234567890abcde";
String iv = "fedcba9876543210";
SecretKeySpec keyspec = new SecretKeySpec(key.getBytes(), "AES");
IvParameterSpec ivspec = new IvParameterSpec(iv.getBytes());
Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
cipher.init(Cipher.ENCRYPT_MODE,keyspec,ivspec);
byte[] encrypted = cipher.doFinal(toEncrypt.getBytes());
return encrypted;
}
catch(Exception e){
}
}
public static byte[] decrypt(byte[] toDecrypt) throws Exception{
String key = "01234567890abcde";
String iv = "fedcba9876543210";
SecretKeySpec keyspec = new SecretKeySpec(key.getBytes(), "AES");
IvParameterSpec ivspec = new IvParameterSpec(iv.getBytes());
Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
cipher.init(Cipher.DECRYPT_MODE,keyspec,ivspec);
byte[] decrypted = cipher.doFinal(toDecrypt);
return decrypted;
}
public static String bytesToHex(byte[] data) {
if (data==null)
{
return null;
}
else
{
int len = data.length;
String str = "";
for (int i=0; i<len; i++)
{
if ((data[i]&0xFF)<16)
str = str + "0" + java.lang.Integer.toHexString(data[i]&0xFF);
else
str = str + java.lang.Integer.toHexString(data[i]&0xFF);
}
return str;
}
}
public static String padString(String source, char paddingChar, int size)
{
int padLength = size-source.length()%size;
for (int i = 0; i < padLength; i++) {
source += paddingChar;
}
return source;
}
}
我收到了未报告的异常
java.lang.Exception; must be caught or declared to be thrown
byte[] encrypted = encrypt(concatURL);
以及
.java:109: missing return statement
任何人都可以帮助我解决这些问题问题？
Can anyone help me with solving these problems?
答
所有的问题源于这个
byte[] encrypted = cipher.doFinal(toEncrypt.getBytes());
return encrypted;
其中包含在try，catch块中，问题是如果程序发现异常你没有返回任何东西。把它像这样（修改它作为你的程序逻辑立场）：
Which are enclosed in a try, catch block, the problem is that in case the program found an exception you are not returning anything. Put it like this (modify it as your program logic stands):
public static byte[] encrypt(String toEncrypt) throws Exception{
try{
String plaintext = toEncrypt;
String key = "01234567890abcde";
String iv = "fedcba9876543210";
SecretKeySpec keyspec = new SecretKeySpec(key.getBytes(), "AES");
IvParameterSpec ivspec = new IvParameterSpec(iv.getBytes());
Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
cipher.init(Cipher.ENCRYPT_MODE,keyspec,ivspec);
byte[] encrypted = cipher.doFinal(toEncrypt.getBytes());
return encrypted;
} catch(Exception e){
return null; // Always must return something
}
}
对于第二个必须从加密方法调用中捕获异常，像这样（也可以将其修改为程序逻辑）：
For the second one you must catch the Exception from the encrypt method call, like this (also modify it as your program logic stands):
public void actionPerformed(ActionEvent e)
.
.
.
try {
byte[] encrypted = encrypt(concatURL);
String encryptedString = bytesToHex(encrypted);
content.removeAll();
content.add(new JLabel("Concatenated User Input -->" + concatURL));
content.add(encryptedTextField);
setContentPane(content);
} catch (Exception exc) {
// TODO: handle exception
}
}
您必须从中学习的课程：
The lessons you must learn from this:
- 返回类型的方法必须总是返回该类型的对象，我的意思是在所有可能的情况下
- 所有检查的异常必须始终被处理
- A method with a return-type must always return an object of that type, I mean in all possible scenarios
- All checked exceptions must always be handled