No output

[arushi tomar]

Hi, I am developing a web application using hibernate and AWS SDK (though I haven't been working on java for long). I have the following servlet and JSP code:

JSP

<sql:setDataSource
		var="myDS"
		driver="com.mysql.jdbc.Driver"
		url="jdbc:mysql://url:3306/development"
		user="arushi" password="arushi123"
	/>
	
	<sql:query var="listCustomers"	dataSource="${myDS}">
		SELECT * FROM CUSTOMER;
	</sql:query>
	
	<div align="center">
		<table border="1" cellpadding="5">
			<h2><caption>List of customers</h2></caption>
			<tr>
				<th>ID</th>
				<th>Name</th>

			</tr>
			<c:forEach var="customer" items="${listCustomers.rows}">
				<tr>
					<td><c:out value="${customer.id}" /></td>

<td><a href="ServiceApp?accountID=${customer.accountID}"><c:out value="${customer.companyName}" /></a></td>

SERVLET

	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		Customer cust = new Customer();
		try {
			Class.forName("com.mysql.jdbc.Driver");

			java.sql.Connection con = DriverManager.getConnection("jdbc:mysql://url:3306/development", "arushi","arushi123");


			String var1 = request.getParameter("secretKey");
			String var2 = request.getParameter("accessKey");
			String sql = "select secretKey, accessKey from CUSTOMER where accountID = ?";
			PreparedStatement stmt = con.prepareStatement(sql);
			stmt.setString(1, var1);
			stmt.setString(2, var2);

			var1 = cust.getAccessKey();
			var2 = cust.getSecretKey();
			try {
				var1 = JavaMD5Hash.decrypt(var1);
				var2 = JavaMD5Hash.decrypt(var2);
			
			} catch (InvalidKeyException e1) {

				e1.printStackTrace();
			} catch (NoSuchAlgorithmException e1) {

				e1.printStackTrace();
			} catch (NoSuchPaddingException e1) {

				e1.printStackTrace();
			}
			 try {
			 DisplayInstance.authentication(var1, var2);
			 DisplayInstance.describeInstances();
				
			 } catch (Exception e) {
			
			 e.printStackTrace();
			 }
			
			 PrintWriter out = response.getWriter();
			 out.println("<h3>Instance started</h3>");
			
			
			con.close();

		} catch (Exception e) {
		}
	}

}

and my authentication method is:

  public static boolean authentication(String var1, String var2)
	{
		try {
			credentials = new BasicAWSCredentials("var1", "var2");
			ec2 = new AmazonEC2Client(credentials);
			Region region=Region.getRegion(Regions.EU_WEST_1);
		  	   ec2.setRegion(region);
			
		} catch (AmazonServiceException ase) {
			System.out.println("Caught Exception: " + ase.getMessage());
			System.out.println("Reponse Status Code: " + ase.getStatusCode());
			System.out.println("Error Code: " + ase.getErrorCode());
			System.out.println("Request ID: " + ase.getRequestId());
			return true;
		}
		return false;
	}

When I run the project, The customer name is displayed, i click the link and next webpage with the url : http://localhost:8080/CustomerRecords/ServiceApp?accountID=12345678 is opened but i do not see anything in either the console or the webpage. I have a table in my database that has columns accesskey, secretkey, accountID, companyName etc. I want to authenticate the user using the secret and access keys from the database of the particular customer I click on my webpage. What am i possibly doing wrong?

NOTE: When I had given the parameters in the authentication method as hard-coded values, and was simply calling my other methods from GET method, I was getting the outputs.

Plus, is there any way that I can use the POST method instead of GET.

Please let me know if I should add more code in my question but I guess that would be enough.
Any help would be much appreciated. Thanks

[Dave Tolls]

        } catch (Exception e) {
        }

You have an empty catch block in your doGet.
You could well be getting an exception and not know anything about it.

[arushi tomar]

There was an empty catch clause so i was unable to see the exceptions, problem is with MD5 decoding. I removed the catch clause and commented the lines from my decode method:

// String decrypted = decrypt(encrypt(str));
// System.out.println("Decrypted: " + decrypted);
although the encoder method works fine.

package com.md5.example;

import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;


import javax.crypto.Cipher;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;

import com.sun.xml.internal.messaging.saaj.packaging.mime.util.BASE64DecoderStream;
import com.sun.xml.internal.messaging.saaj.packaging.mime.util.BASE64EncoderStream;

import javax.crypto.KeyGenerator;

public class JavaMD5Hash {

	private static Cipher ecipher;

	private static Cipher dcipher;

	@SuppressWarnings("restriction")
	public static String encrypt(String str)
			throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException {
		SecretKey key;
		key = KeyGenerator.getInstance("DES").generateKey();
		ecipher = Cipher.getInstance("DES");
		ecipher.init(Cipher.ENCRYPT_MODE, key);

		try {

			byte[] utf8 = str.getBytes("UTF8");

			byte[] enc = ecipher.doFinal(utf8);

			enc = BASE64EncoderStream.encode(enc);

			return new String(enc);
		} catch (Exception e) {

			e.printStackTrace();
		}
		return str;

	}

	public static String decrypt(String str)
			throws InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException {
		SecretKey key;
		key = KeyGenerator.getInstance("DES").generateKey();
		dcipher = Cipher.getInstance("DES");
		dcipher.init(Cipher.DECRYPT_MODE, key);
	//	String decrypted = decrypt(encrypt(str));
	//	System.out.println("Decrypted: " + decrypted);

		try {

			byte[] dec = BASE64DecoderStream.decode(str.getBytes());

			byte[] utf8 = dcipher.doFinal(dec);

			return new String(utf8, "UTF8");
		} catch (Exception e) {

			e.printStackTrace();
		}
		return null;
	}
}

Now i see the following exception :
java.lang.NullPointerException
at com.md5.example.JavaMD5Hash.decrypt(JavaMD5Hash.java:57)
at com.aws.customers.ServiceApp.doGet(ServiceApp.java:18)
java.lang.NullPointerException
at com.md5.example.JavaMD5Hash.decrypt(JavaMD5Hash.java:57)
at com.aws.customers.ServiceApp.doGet(ServiceApp.java:19)

[Roel De Nijs]

You'll get a NullPointerException, so that should be fairly easy to debug.

I would guess str is null for some reason...

And another remark about your code: is there any reason why your static (class) members are not initialized in a static initializer block, but are each time assigned in the encrypt/decrypt methods? If you need another instance with each invocation of the encrypt/decrypt methods, it should not be static (class) members, but local variables! Otherwise you should initialize them in a static initializer block (and marked as final).