Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
741 views
in Technique[技术] by (71.8m points)

jakarta ee - How to install JDBC driver in Eclipse web project without facing java.lang.ClassNotFoundexception

There is a VERY similar question to mine but in my case I don't have any duplicate jars in my build path, so the solution does not work for me. I've searched google for a couple of hours now, but none of the solutions I've found there actually resolve my issue. I'm creating a web site with some database connectivity for a homework. I'm using a MySQL database, developing in Eclipse and running on Windows.

I keep getting java.lang.ClassNotFoundException: com.mysql.jdbc.Driver with the following code:

import java.sql.*;
//...
public void someMethodInMyServlet(PrintWriter out)
{
    Connection connection = null;
    PreparedStatement query = null;
    try {

        out.println("Create the driver instance.<br>");
        Class.forName("com.mysql.jdbc.Driver").newInstance();

        out.println("Get the connection.<br>");
        connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/test", "root", "secret");
        query = connection.prepareStatement( "SELECT * FROM customers");

        //...
    } catch (Exception e)
    {
        out.println(e.toString()+"<br>");
    }
}
//...

When I run the above code I get the following output:

Create the driver instance.
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver

It doesn't get past the Class.forName... line and I can't figure out why! Here is what I did:

  1. Download mysql-connector.
  2. Put it in my MySQL folder C:Program FilesMySQLmysql-connector-java-5.1.12mysql-connector-java-5.1.12-bin.jar.
  3. Opened the project properties in Eclipse.
  4. Add External Jar to my Build Path and I selected mysql-connector-java-5.1.12-bin.jar.

Every time I attempt to use the servlet I get the same error regardless if I have the jar in there or if I don't. Could you help me figure this out?

Question&Answers:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

As for every "3rd-party" library in flavor of a JAR file which is to be used by the webapp, just copy/drop the physical JAR file in webapp's /WEB-INF/lib. It will then be available in webapp's default classpath. Also, Eclipse is smart enough to notice that. No need to hassle with buildpath. However, make sure to remove all unnecessary references you added before, else it might collide.

An alternative is to install it in the server itself by dropping the physical JAR file in server's own /lib folder. This is required when you're using server-provided JDBC connection pool data source which in turn needs the MySQL JDBC driver.

See also:


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...