Preventing SQL injection attacks in Java programs

Question

I have to add a statement to my java program to update the database table:

String insert =
    "INSERT INTO customer(name,address,email) VALUES('" + name + "','" + addre + "','" + email + "');";

I've heard this can be exploited via SQL injection, for example:

DROP TABLE customer;

My program has a Java GUI and all name, address and email values ​​are retrieved from Jtextfields. I would like to know how to add the following code (DROP TABLE customer;) to my insert statement and how to prevent this.

Answer 1

For example:

name = "'); DROP TABLE customer; --"

will insert this value into insert:

INSERT INTO customer(name,address,email)     VALUES(''); DROP TABLE customer; --"','"+addre+"','"+email+"');

Using prepared statements and SQL parameters ("steal" example from Matt Fellows):

String insert = "INSERT INTO customer(name,address,email) VALUES(?, ?, ?);";
PreparedStament ps = connection.prepareStatment(insert);

Also parse the values ​​of such variables and ensure that they do not contain any disallowed characters (such as ";" in the name).

Answer 2

You need to use PreparedStatement. For example

String insert = "INSERT INTO customer(name,address,email) VALUES(?, ?, ?);";
PreparedStatement ps = connection.prepareStatement(insert);
ps.setString(1, name);
ps.setString(2, addre);
ps.setString(3, email);

ResultSet rs = ps.executeQuery();

This will prevent injection attacks.

The way a hacker puts this in is if the string you insert comes from an input somewhere - like an input field on a web page, or an input field on a form in an app or similar.