java.lang.NoClassDefFoundError: javax/mail/Authenticator, whats wrong?

Question

Send to Email.java

package helper;

//Mail.java - smtp sending starttls (ssl) authentication enabled
//1.Open a new Java class in netbeans (         


        

Answer 1

You need to add two jars into the WEB-INF/lib directory or your webapp (or lib directory of the server):

• mail.jar - contains the actual smtp implmentation
• activation.jar - needed by mail.jar

Answer 2

When I had this problem, I had included the mail-api.jar in my maven pom file. That's the API specification only. The fix is to replace this:

<!-- DO NOT USE - it's just the API, not an implementation -->
<groupId>javax.mail</groupId>
<artifactId>javax.mail-api</artifactId>

with the reference implementation of that api:

<groupId>com.sun.mail</groupId>
<artifactId>javax.mail</artifactId>

I know it has sun in the package name, but that's the latest version. I learned this from https://stackoverflow.com/a/28935760/1128668

Answer 3

Even I was facing a similar error. Try below 2 steps (the first of which has been recommended here already) - 1. Add the dependencies to your pom.xml

         <dependency>
            <groupId>javax.mail</groupId>
            <artifactId>mail</artifactId>
            <version>1.4.5</version>
        </dependency>

        <dependency>
            <groupId>javax.activation</groupId>
            <artifactId>activation</artifactId>
            <version>1.1.1</version>
        </dependency>

2. If that doesn't work, manually place the jar files in your .m2\repository\javax\<folder>\<version>\ directory.

Answer 4

Add following to your maven dependency

    <dependency>
        <groupId>javax.mail</groupId>
        <artifactId>mail</artifactId>
        <version>1.4.5</version>
    </dependency>

    <dependency>
        <groupId>javax.activation</groupId>
        <artifactId>activation</artifactId>
        <version>1.1.1</version>
    </dependency>

Answer 5

While it's possible that this is due to a jar file missing from your classpath, it may not be.

It is important to keep two or three different exceptions strait in our head in this case:

1. java.lang.ClassNotFoundException This exception indicates that the class was not found on the classpath. This indicates that we were trying to load the class definition, and the class did not exist on the classpath.

2. java.lang.NoClassDefFoundError This exception indicates that the JVM looked in its internal class definition data structure for the definition of a class and did not find it. This is different than saying that it could not be loaded from the classpath. Usually this indicates that we previously attempted to load a class from the classpath, but it failed for some reason - now we're trying again, but we're not even going to try to load it, because we failed loading it earlier. The earlier failure could be a ClassNotFoundException or an ExceptionInInitializerError (indicating a failure in the static initialization block) or any number of other problems. The point is, a NoClassDefFoundError is not necessarily a classpath problem.

I would look at the source for javax.mail.Authenticator, and see what it is doing in it's static initializer. (Look at static variable initialization and the static block, if there is one.) If you aren't getting a ClassNotFoundException prior to the NoClassDefFoundError, you're almost guaranteed that it's a static initialization problem.

I have seen similar errors quite frequently when the hosts file incorrectly defines the localhost address, and the static initialization block relies on InetAddress.getLocalHost(). 127.0.0.1 should point to 'localhost' (and probably also localhost.localdomain). It should NOT point to the actual host name of the machine (although for some reason, many older RedHat Linux installers liked to set it incorrectly).

Answer 6

I once ran into this situation and I had the dependencies in classpath. The solution was to include javax.mail and javax.activation libraries in the container's (eg. tomcat) lib folder. Using maven -set them to provided scope and it should work. You will have shared email libs in classpath for all projects.

Useful source: http://haveacafe.wordpress.com/2008/09/26/113/