JavaMail error with "java -jar" on 1.6

Question

The following code sends an email. The following ant build script compiles the code, creates a jar, runs the program using "java Test", and runs the program using "java -jar test.jar". Both runs work with Sun's 1.5 JRE. With Sun's 1.6 JRE, it does not work when using "java -jar" (my output is following the code). I am not sure why. I thought it might be conflicting versions of JavaMail and the JAF in Java6, but I have the latest JavaMail. I guess it is an issue with how libraries are loaded when using "java -jar", but I am not sure how to resolve this.
If you want to run this, simply drop mail-1.4.1.jar and activation-1.1.1.jar into the same directory as these two files, set your.mail.server.here and [email protected], and run ant.
Test.java
import java.util.Properties;
import javax.mail.*;
import javax.mail.internet.*;
public class Test {
    public static void main( String[] args )
        throws Exception {
        String host = "your.mail.server.here";
        String from = "[email protected]";
        String to = from;
        String subject = "Test JavaMail";
        Address[] toRecipients = new Address[1];
        toRecipients[0] = new InternetAddress( to );
        Properties properties = System.getProperties();
        properties.put( "mail.smtp.host" , host );
        Session session = Session.getDefaultInstance( properties, null );
        MimeMessage message = new MimeMessage( session );
        Address fromAddress = new InternetAddress( from );
        message.setFrom( fromAddress );
        message.setRecipients( Message.RecipientType.TO, toRecipients );
        message.setSubject( subject );
        message.setText( "this is the body" );
        Transport.send( message );
build.xml
<project name="test" basedir="." default="all">
    <property name="jar.path" value="test.jar" />
    <path id="classpath">
        <pathelement location="mail-1.4.1.jar" />
        <pathelement location="activation-1.1.1.jar" />
    </path>
    <target name="clean">
        <delete>
            <fileset dir=".">
                <include name="${jar.path}" />
                <include name="Test.class" />
            </fileset>
        </delete>
    </target>
    <target name="build">
        <javac destdir="." srcdir=".">
            <classpath refid="classpath" />
            <include name="Test.java" />
        </javac>
    </target>
    <target name="jar">
        <manifestclasspath property="mf.classpath" jarfile="${jar.path}">
            <classpath refid="classpath" />
        </manifestclasspath>
        <jar destfile="${jar.path}" basedir="." update="no" index="true">
            <include name="Test.class" />
            <manifest>
                <attribute name="Manifest-Version" value="1" />
                <attribute name="Class-Path" value="${mf.classpath}" />
                <attribute name="Main-Class" value="Test" />
            </manifest>
            <indexjars>
                <path refid="classpath" />
            </indexjars>
        </jar>
    </target>
    <target name="run">
        <echo message="This will work in 1.5 and 1.6" />
        <java classname="Test">
            <classpath refid="classpath" />
            <classpath location="${jar.path}" />
        </java>
    </target>
    <target name="runjar">
        <echo message="This will not work in 1.6" />
        <java jar="${jar.path}" fork="true" />
    </target>
    <target name="all" depends="clean,build,jar,run,runjar" />
</project>
output (with 1.6)
     [java] Exception in thread "main" javax.mail.MessagingException: IOException while sending message;
     [java]   nested exception is:
     [java]     javax.activation.UnsupportedDataTypeException: no object DCH for MIME type text/plain; charset=us-ascii
     [java]     at com.sun.mail.smtp.SMTPTransport.sendMessage(SMTPTransport.java:676)
     [java]     at javax.mail.Transport.send0(Transport.java:189)
     [java]     at javax.mail.Transport.send(Transport.java:118)
     [java]     at Test.main(Unknown Source)
     [java] Caused by: javax.activation.UnsupportedDataTypeException: no object DCH for MIME type text/plain; charset=us-ascii
     [java]     at javax.activation.ObjectDataContentHandler.writeTo(DataHandler.java:870)
     [java]     at javax.activation.DataHandler.writeTo(DataHandler.java:301)
     [java]     at javax.mail.internet.MimeBodyPart.writeTo(MimeBodyPart.java:1403)
     [java]     at javax.mail.internet.MimeMessage.writeTo(MimeMessage.java:1745)
     [java]     at com.sun.mail.smtp.SMTPTransport.sendMessage(SMTPTransport.java:636)
     [java]     ... 3 more

Answer 1

I spent quite a bit of time looking into this. Thanks for the reproducible test
case, it was essential to figuring out the problem!
The problem appears to be a bug in the jar file index. The jar file index doesn't
include the META-INF directory, which means JavaMail can't find the config
files it's looking for in mail.jar. If you change the ant build file to set index="false",
it will work as expected. If you really need the index, you can fix it by using
the jar command explicitly - "jar i test.jar".
It looks like this is a bug in ant.