java.lang.ClassNotFoundException in spite of using CLASSPATH environment variable

Question

I am trying to connect to mysql database using java on windows7. In spite of adding the complete url of jdbcdriver jar file in CLASSPATH, java.lang.ClassNotFoundException: com.mysql.jdbc.Driver is thrown. Could anyone tell me what i am missing here? It works if I add the jar file in project library but I want to do it by CLASSPATH itself. My classpath looks like this- C:\jython2.5.1\javalib\mysql-connector-java-5.1.12-bin.jar

I want to make it clear that this is not the actual project i am working on. I am actually using Django with Jython, which requires the JDBC driver to access the database. That is the reason why I have to do it using CLASSPATH only.

Ginglymus

with what are you building your project? – Borlow

...and if you're doing this from a command prompt, can you also show the exact command-line you're using? – Laureate

i am using netbeans ide. Actually i was getting this error while using django with jython, so i thought i should try connecting to mysql database from plain java. – Ginglymus

Answer 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 IDEs like Eclipse, Netbeans and IDEA.

That environment variable is in real world also considered a poor practice since it breaks portability. I.e. program X will run successfully while program Y won't run without altering the CLASSPATH. It's only "useful" for Sun Oracle to prevent that starters get tired of typing the same classpath again and again in the -cp or -classpath arguments when following Java tutorials. In real world, batch/shell files are preferred where just the entire command with -cp/-classpath argument is specified.

In your case you're using an IDE. The classpath is there called the "Build Path". In plain Java projects, it represents both the 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 about using the CLASSPATH environment variable. It was a mistake by Sun Oracle. They thought to convince starters, but it ended up to be only more confusing to starters as they incorrectly interpret that environment variable as the classpath.

See also:

• How to add JAR libraries to WAR project without facing java.lang.ClassNotFoundException? Classpath vs Build Path vs /WEB-INF/lib

Conscience

Thanx for you reply, Actually my project is on django and jython. jython runs on jvm and it needs jdbc drivers to access db. I dnt know of any other way to include a jar file. – Ginglymus

The detailed answer depends on the runtime environment. At least, you can use sys.path environment variable (which is by the way similar to CLASSPATH and thus also unportable), or the command argument -Dpython.path. – Conscience

Answer 2

What finally helped me out was to copy the mysql-connector-java-5.1.15-bin.jar to \jre\lib and to \jre\lib\ext both(!) even though I did all the classpathing circus Java offers :) Environment was pure notepad/commandline though.

Bolinger

Here is a link as of today, you can download the platform independent one from here: dev.mysql.com/downloads/connector/j/#downloads – Idelson

Complete path is yout actual java platform. For example in Linux amd64 can be /usr/lib/jvm/java-7-openjdk-amd64/jre/lib/ – Susceptible

Answer 3

What worked with me using Netbeans was: Run > Set Project Configuration > Customize. Under Libraries > Add Library. Added MySQL JDBC Driver (I assume it appeared in list because I copied the jar file to the jre\lib\ext folder. And it worked seamlessly.

I tried setting classpath but that did not work. I am using Netbeans 7.0

Patinated

Thank god for this answer. I've been fighting with this problem for the last 2 1/2 hours, and you fixed it for me. – Sibeal

OMG you're the best! Setting classpath didn't work for me either! I'm using eclipse but it's similar. So for those of you that are using eclipse: right click on the project -> Run Configuration -> Classpath -> add it there. – Delhi

Thanks @DaoLam that worked for me. Up Vote for you! and you too, nandan – Rameau

Answer 4

simply do a right click on your project in "Netbeans" select properties then click on "libraries " then click on "add library..." button then select "MySQL JDBC Driver" and click on "add library" button then on "OK" button

Piacular

Answer 5

I also had this problem before, but after I put/added mysql-connector-java-5.1.34-bin.jar (Download it from here) into the apache-tomcat-8.0.15\lib folder, and then ran my project, it really did work.

Note : Even after adding the jar file the error persists, then restart the Tomcat server and rerun you project again.

Acrobat

Worked for me. Java newbie. added this .jar to eclipse buildpath. Thanks! – Propitiatory

Answer 6

1. Open Netbeans IDE
2. Right-click your Project.
3. Select Properties.
4. On the left-hand side click Libraries.
5. Under "Compile" tab - click Add Jar/Folder button.
6. Select Downloaded "mysql-connector-java-5.1.25-bin.jar" file (Download Connector/J from dev.mysql.com)
7. Click OK
8. Run Again... Its work.

Educable

Answer 7

If you are using maven, add the dependency to pom.xml should solve the problem.

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.36</version>
</dependency>

Sadden

Solved it! If you are using maven then just use this! – Humoresque

Answer 8

In Netbeans IDE just Check the properties of Project on which you working on,in properties window go to 'library' tag, in diolog box just add your mysql-connector-java-**.jar file.

Glottochronology

Answer 9

I had this same problem in Netbeans. Because I was using a tomcat connection pool as defined in context.xml I needed to add the jdbc jar to both the project (Properties->Libraries) and to the lib/ folder within my Tomcat server so it could be seen on startup.

Hildie