Alert for wrongly inserting password

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I am very new to java, Here i want to redirect to next page and show login error if i type a wrong password that was not saved in my mysql database?

System.out.println("Select count from users where pword='"+spword+"' and uname='"+suname+"');
rsT = stmt.executeQuery("select count from users where pword='" + spword + "' and uname='"+suname+"'");
if(rsT.next())
{

integer result = rsT.getint(1>);
result= <jsp:forward page="Menu.jsp" />;
}
else
{
integer result = rsT.getint(0);
result ="<center><h2>Invalid password</h2></center>";
errFlag = true;
}
rsT.close();

What I have tried:

I am very new to java, Here i want to know how to show login error if i type a wrong password that was not saved in my mysql database?

Posted 8-Aug-22 2:11am

N Mohamed rafi

Updated 9-Aug-22 19:06pm

v3

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Comments

Richard MacCutchan 10-Aug-22 3:30am

You have updated your question but you are still using string concatenation which is dangerous. Read again the suggestions below by OriginalGriff.

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OriginalGriff · Answer 1 · 2022-08-08T02:17:00

So little code,so many problems ...

1) Never concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Always use Parameterized queries instead.

When you concatenate strings, you cause problems because SQL receives commands like:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'Baker's Wood'

The quote the user added terminates the string as far as SQL is concerned and you get problems. But it could be worse. If I come along and type this instead: "x';DROP TABLE MyTable;--" Then SQL receives a very different command:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'x';DROP TABLE MyTable;--'

Which SQL sees as three separate commands:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'x';

A perfectly valid SELECT

SQL

DROP TABLE MyTable;

A perfectly valid "delete the table" command

SQL

--'

And everything else is a comment.
So it does: selects any matching rows, deletes the table from the DB, and ignores anything else.

So ALWAYS use parameterized queries! Or be prepared to restore your DB from backup frequently. You do take backups regularly, don't you?

2) Never store passwords in clear text - it is a major security risk. There is some information on how to do it here: Password Storage: How to do it.[^]

And remember: if this is web based and you have any European Union users then GDPR applies and that means you need to handle passwords as sensitive data and store them in a safe and secure manner. Text is neither of those and the fines can be .... um ... outstanding. In December 2018 a German company received a relatively low fine of €20,000 for just that.