Unable to load com.mysql.jdbc.Driver

问题:

when I run ant for a Testng application, I am unable to load com.mysql.jdbc.Driver.

Below is the exception thrown.

[testng] java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
[testng] at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
[testng] at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
[testng] at java.security.AccessController.doPrivileged(Native Method)

Thanks and regards, Sreekanth

回答1:

The CLASSPATH environment variable is only used by the java.exe command and even then only when used without any of the -cp, -classpath, -jar arguments. It is ignored by IDE's.

That environment variable is in real world also considered a poor practice since it breaks portability. It's only "useful" for Sun to prevent that starters get tired of typing the same classpath again and again in the -cp or -classpath arguments. In real world, batch/shell files are preferred.

If you're using an IDE, The classpath is called the "build path" (it represents both compiletime and runtime classpath). You can configure it in the project's properties. You can add a complete folder, you can add individual/external JAR files, you can link projects, etcetera. Make use of it. Forget the whole CLASSPATH environment variable.

For command prompt,

You have to put the full path to the jarfile in the classpath (including the filename):

.;C:\j2sdk1.4.2_16\jre\lib;
C:\Program Files\mysql-connector-java-3.1.144\mysql-connector-java-3.1.14-bin.jar

As Hippo said, you have to restart cmd after changing that. If it doesn't work, launch your program like this:

java -cp ".;C:\j2sdk1.4.2_16\jre\lib;
C:\Program Files\mysql-connector-java-3.1.144\mysql-connector-java-3.1.14-bin.jar"
my.class.Name