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, Jan 19 '11 at 16:26
you need add Exception stackTrace as well. Which class is not found? — fmucar, Jan 19 '11 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, Jan 19 '11 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, Jan 19 '11 at 16:42
That's for sure, ClassNotFound can be effectively thrown only by doing Class.forName [or ClassLoader.loadClass], so you dont have mysql driver in the classpath, like most of the answers suggest. — bestsss, Jan 19 '11 at 17:00
@Jason Rogers which buildpath ? Are you using Netbeans, Eclipse, something else ? Sounds like a "buildpath" would be only for building, you'd need something similar when you run your app. — nos, Jan 19 '11 at 17:33
Thanks for your help, the problem was that I hadn't placed the jar in the WEB-INF/lib folder. — Jason Rogers, Jan 20 '11 at 01:17

score 3 · Accepted Answer · answered Jan 19 '11 at 16:52

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 '11 at 16:52

Amila Domingo

86
3

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 – Jason Rogers Jan 20 '11 at 01:16
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. – BalusC Jan 20 '11 at 01:20

score 2 · Answer 2 · edited Jun 20 '20 at 09:12

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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problem using JDBC to connect to mysql

3 Answers3

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