problem using JDBC to connect to mysql

Question

I'm trying to set up a connection between my applet and my mysql server using jdbc

I added the jar mysql-connector-java-5.1.14-bin.jar to the project

then I used this code

public void databaseTesting(){
        Connection con;
        try {
            Class.forName("com.mysql.jdbc.Driver").newInstance();

            con = DriverManager.getConnection( "jdbc:mysql://localhost:3306/test", "root","");
            System.err.println("connected !");

            Statement stmt = con.createStatement();
            ResultSet rs = stmt.executeQuery("SELECT * FROM `test`.`test`;");
            while (rs.next()) {
                int A = rs.getInt("columnA");
                int B = rs.getInt("columnB");
                System.err.println("A "+A+" B "+B);
            }
        } catch (SQLException e) {
            System.err.println("failed to connect");
        } catch (InstantiationException e) {
            System.err.println("InstantiationException");
        } catch (IllegalAccessException e) {
            System.err.println("IllegalAccessException");
        } catch (ClassNotFoundException e) {
            System.err.println("ClassNotFoundException");
        }
    }

and for some reason I keep getting ClassNotFoundException.

edit

the jar is added to the build path and appears in the Referenced Libraries.

the exception is thrown by

Class.forName("com.mysql.jdbc.Driver").newInstance();

Anybody got an idea why ?

Thanks in advance jason

What do you mean by "added the jar mysql-connector-java-5.1.14-bin.jar to the project"? Did you add the JAR to the classpath or did you just drop it in the project? — Thomas Owens
– Thomas Owens, Commented Jan 19, 2011 at 16:26
you need add Exception stackTrace as well. Which class is not found? — fmucar
– fmucar, Commented Jan 19, 2011 at 16:28
@faith: given the code in the try block, that can be only one possible missing class. Others (i.e. the ones present during compiletime) would rather have produced a NoClassDefFoundError during runtime if it were really missing. — BalusC
– BalusC, Commented Jan 19, 2011 at 16:30
added the jar to the buildpath already. and the exception is thrown by Class.forName("com.mysql.jdbc.Driver").newInstance(); — Jason Rogers
– Jason Rogers, Commented Jan 19, 2011 at 16:42
Thanks for your help, the problem was that I hadn't placed the jar in the WEB-INF/lib folder. — Jason Rogers
– Jason Rogers, Commented Jan 20, 2011 at 1:17

Amila Domingo · Accepted Answer · 2011-01-19 16:52:24Z

3

Do you run this application through eclipse? Is it a Dynamic web project, if so then try adding the jar file to the WEB-INF\lib folder

answered Jan 19, 2011 at 16:52

Amila Domingo

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2 Comments

Jason Rogers Over a year ago

I give you the green mark because it was effectively to problem I had, I didn't find any mention of WEB-INF/lib in the tutorials I read about the

BalusC Over a year ago

You also didn't mention that you was running this piece of code in a servletcontainer as runtime environment. For future questions, it's pretty important to mention the actual runtime environment used. The /WEB-INF/lib as container for 3rd party JAR's which are to be part of the runtime environment is however enough mentioned in the average JSP/Servlet tutorials.

Community · Accepted Answer · 2020-06-20 09:12:55Z

Then the JAR is not in the runtime classpath.

Since you explicitly mentioned "project", I'll assume that you're using an IDE. You have to add the JAR file to the so-called Build Path (which represents both the compiletime and runtime classpath). In Eclipse for example, rightclick the JAR file you dropped in the project folder, choose Build Path > Add to Build Path and that should be it.

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