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Jar file cannot find SWT library, but Eclipse can

I have an Ant build (see build.xml below) that compiles and runs as I expect within Eclipse.
When I run the build via the command-line (java -jar swtgui.jar), however, I receive the following error:
Error: A JNI error has occurred, please check your installation and try again
Exception in thread "main" java.lang.NoClassDefFoundError: org/eclipse/swt/widgets/Layout
at java.lang.Class.getDeclaredMethods0(Native Method)
...
etc
build.xml
<?xml version="1.0" encoding="UTF-8"?>
<project default="run" name="My Project ">
<target name="run" depends="createjar">
<java classname="com.company.program.project.MyMainClass">
<classpath path="staging">
<fileset dir="C:\COMPANY\Eclipse\3.6-64\plugins">
<include name="org.eclipse.swt.*.jar" />
</fileset>
</classpath>
</java>
</target>
<target name="createjar" depends="compile">
<jar destfile="./builds/jars/swtgui.jar" basedir="staging" filesetmanifest="mergewithoutmain">
<manifest>
<attribute name="Main-Class" value="com.company.program.project.MyMainClass" />
</manifest>
<fileset dir="C:\COMPANY\Eclipse\3.6-64\plugins\" includes="org.eclipse.swt.win32.win32.x86_64_3.6.0.v3650b.jar" />
</jar>
</target>
<target name="compile">
<javac includeantruntime="false" srcdir="./src" destdir="staging">
<classpath>
<fileset dir="C:\COMPANY\Eclipse\3.6-64\plugins">
<include name="org.eclipse.swt.*.jar" />
</fileset>
</classpath>
</javac>
</target>
<record name="./MyMainClass.log" loglevel="verbose" action="start"/>
The error doesn't make sense to me since I specify the same SWT library path for the compile target as I do for the createjar target.
If the SWT library is found for the compile target, why is it not found for the createjar target?

How can I tell my netbeans build.xml where to find my servlets-api.jar?

I am trying to resurrect on old project and get it compiling in netbeans again. Previously - as in 7 years ago - it worked fine but now on a new rig I have to reconfigure everything. The part of the old project I am trying to recompile is just a small java utilities project - not even a full application by itself. The project needs the servlets-api.jar file to compile. The IDE editor works fine - it seems to find it as I get no red lines under the javax.* import line. Only when I try to compile do I get the errors like so:
error: package javax.servlet does not exist
import javax.servlet.ServletException;
My old build script is :
<?xml version="1.0"?>
<project name="javautils" default="package" basedir=".">
<property file="build.properties" />
<path id="classpath">
<pathelement path="classes"/>
<pathelement location="${jdbc.jar}"/>
<pathelement location="${lib.dir}"/>
<pathelement location="${servletjars.home}"/>
</path>
<presetdef name="javac">
<javac includeantruntime="false" />
</presetdef>
<target name="clean">
<delete dir="classes" />
</target>
<target name="prepare">
<mkdir dir="classes" />
</target>
<target name="compile" depends="prepare" description="compile classes">
<javac srcdir="${source.dir}" destdir="${build.dir}">
<classpath refid="classpath" />
</javac>
</target>
<target name="package" depends="compile" description="Packages the web archive file">
<echo message="Packaging ${app.name}'s web archive file ..."/>
<!--
<delete file="${basedir}/${app.name}.war"/>
<jar jarfile="${basedir}/${app.name}.war">
<fileset dir="${basedir}/war" includes="**"/>
</jar>
-->
<jar jarfile="${basedir}/${app.name}.jar">
<fileset dir="${basedir}/classes" includes="**"/>
</jar>
<copy todir="${specialjars.home}">
<fileset dir="${basedir}">
<include name="**/*.jar"/>
</fileset>
</copy>
<copy todir="${standardjars.home}">
<fileset dir="${basedir}">
<include name="**/*.jar"/>
</fileset>
</copy>
</target>
</project>
and my build.properties file is like so:
source.dir=src
build.dir=classes
app.name=JavaUtils
standardjars.home=f:/glassfishv3/glassfish/lib
servletjars.home=f:/glassfishv3/glassfish/modules/javax.servlet.jar
specialjars.home=f:/javaprojects/lib
I know all the servletjars.home path has to be upgraded to point to the tomcat file at C:\Program Files\Apache Software Foundation\Tomcat 8.5\lib\servlets-api.jar but when I do so the compile fails all the same.
I have read a ton of other posts from other users asking the same thing but so far no answers seem address my situation. It has been so long since I did this kind of java programming I have to relearn how to work with some of this stuff.
I am now using windows 10, netbeans 8.2, java 1.8, ant 1.10.1, tomcat 8.5 and MySQL (previously I was using Oracle XE till it crashes and I couldn't revive the DB files).
Please help!

Need to make a ant build file for eclipse project

I have a simple game implemented in eclipse. It consists of about 8 classes.
It is for my school assignment.
In the turn in specification, there is written:
"Send me all source codes, documentation and ant build file, which allows the project to be compiled and generate javadoc documentation".
I really do not understand how ant works. I googled some tutorials, but I cannot understand them either. I tried to generate build.xml file in eclipse, but the teacher said that this doesnt work either.
Could someone give me some simple steps or give me link to some really basic tutorial? Thanks for help.
This is the eclipse generated ant (export project as antbuildfile):
And it is kind of weird, because the class BasicPaint I deleted a long time ago.
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!-- WARNING: Eclipse auto-generated file.
Any modifications will be overwritten.
To include a user specific buildfile here, simply create one in the same
directory with the processing instruction <?eclipse.ant.import?>
as the first entry and export the buildfile again. --><project basedir="." default="build" name="Snakes_and_Adders">
<property environment="env"/>
<property name="debuglevel" value="source,lines,vars"/>
<property name="target" value="1.8"/>
<property name="source" value="1.8"/>
<path id="Snakes_and_Adders.classpath">
<pathelement location="bin"/>
</path>
<target name="init">
<mkdir dir="bin"/>
<copy includeemptydirs="false" todir="bin">
<fileset dir="src">
<exclude name="**/*.java"/>
</fileset>
</copy>
</target>
<target name="clean">
<delete dir="bin"/>
</target>
<target depends="clean" name="cleanall"/>
<target depends="build-subprojects,build-project" name="build"/>
<target name="build-subprojects"/>
<target depends="init" name="build-project">
<echo message="${ant.project.name}: ${ant.file}"/>
<javac debug="true" debuglevel="${debuglevel}" destdir="bin" includeantruntime="false" source="${source}" target="${target}">
<src path="src"/>
<classpath refid="Snakes_and_Adders.classpath"/>
</javac>
</target>
<target description="Build all projects which reference this project. Useful to propagate changes." name="build-refprojects"/>
<target name="BasicPaint">
<java classname="snakes_and_adders.BasicPaint" failonerror="true" fork="yes">
<classpath refid="Snakes_and_Adders.classpath"/>
</java>
</target>
<target name="Game">
<java classname="snakes_and_adders.Game" failonerror="true" fork="yes">
<classpath refid="Snakes_and_Adders.classpath"/>
</java>
</target>
<target name="NewGame">
<java classname="snakes_and_adders.NewGame" failonerror="true" fork="yes">
<classpath refid="Snakes_and_Adders.classpath"/>
</java>
</target>
<target name="PaintingExample">
<java classname="snakes_and_adders.PaintingExample" failonerror="true" fork="yes">
<classpath refid="Snakes_and_Adders.classpath"/>
</java>
</target>

Ant is used to perform tasks that are useful to build applications. You have tasks like <javac> <jar> etc.. To compile your classes and put them in a jar file.
I don't see why the build.xml generated file wouldn't work.. But you can take it as an example to understand how ant works. You can also adapt that build.xml file to make it work anywhere.
This tutorial looks well explained at first sight: http://www.javaworld.com/article/2076208/java-app-dev/automate-your-build-process-using-java-and-ant.html
I find that ant can be pretty complex easily, it'll take you time to understand it well but it's really doable.

Ant include external .jar

I want to include external jar to my java project. I'm using ant. External .jar is in folder lib. My build.xml looks something like that:
<?xml version="1.0" encoding="UTF-8"?>
<project>
<path id="classpath">
<fileset dir="lib" includes="**/*.jar"/>
</path>
<target name="clean">
<delete dir="build"/>
</target>
<target name="compile">
<mkdir dir="build"/>
<javac srcdir="src" destdir="build" classpathref="classpath" />
</target>
<target name="jar">
<mkdir dir="trash"/>
<jar destfile="trash/test.jar" basedir="build">
<zipgroupfileset dir="lib" includes="**/*.jar"/>
<manifest>
<attribute name="Main-Class" value="com.Test"/>
</manifest>
</jar>
</target>
<target name="run">
<java jar="trash/test.jar" fork="true"/>
</target>
</project>
But it doesn't work. When I want to import something from the external .jar, there is an error after command ant compile: package com.something does not exist.. What should I edit to get it working?
Exact error:
Compiling 23 source files to xy/build
xy/src/com/Test.java:5: package com.thoughtworks.xstream does not exist
import com.thoughtworks.xstream.*;
^
1 error

You should try without the includes attribute:
<fileset dir="lib" />
And in the jar part you include the classes like this:
<zipgroupfileset includes="*.jar" dir="lib"/>

You can't put external libraries into a jar and expect the classloader to use those jars. Unfortunately this is not supported.
There are ant tasks like one jar that help you, to create a jar file, that contains everything you need.
This bit is from the background information of one jar:
Unfortunately this is does not work. The Java Launcher$AppClassLoader
does not know how to load classes from a Jar inside a Jar with this
kind of Class-Path. Trying to use
jar:file:jarname.jar!/commons-logging.jar also leads down a dead-end.
This approach will only work if you install (i.e. scatter) the
supporting Jar files into the directory where the jarname.jar file is
installed.
Another approach is to unpack all dependent Jar files and repack them
inside the jarname.jar file. This approach tends to be fragile and
slow, and can suffer from duplicate resource issues.
Other Alternative:
jarjar: Jar Jar Links is a utility that makes it easy to repackage Java libraries and embed them into your own distribution

I also use ant to include a number of dependency JARs in my JAR. My compile task looks like this. Perhaps something similar will work for you.
<target name="compile" depends="init">
<javac srcdir="${src}" destdir="${build}" includeantruntime="false">
<classpath>
<pathelement path="${classpath}" />
<fileset dir="${deps}">
<include name="**/*.jar"/>
</fileset>
</classpath>
</javac>
<copy todir="${build}">
<fileset dir="${src}" excludes="**/*.java"/>
</copy>
</target>

sometimes u can use jar contents directly, just unzip
<unzip src="/Developer-Java/mysql-connector-java/mysql-connector-java-5.1.22-bin.jar" dest="${build_dir}" />

Ant built does not generate class files

I'm using build.xml to build my src. However it failed to generate class files without any error message. The full script is
<?xml version="1.0"?>
<project name="auxiliary" basedir="." default="dist">
<property name="src.dir" value="../auxiliary-src/com/nextbio/drugbank"/>
<property name="dist.dir" value="dist"/>
<property name="lib.dir" value="../jboss_config/common_app_jars"/>
<property name="temp.dir" value="temp"/>
<property name="foo_dist.dir" value="../foo/dist"/>
<path id="libs-classpath">
<fileset dir="${foo_dist.dir}">
<include name="foo.jar"/>
</fileset>
</path>
<target name="dist" depends="auxiliary-dist" />
<target name="auxiliary-cleanup">
<delete dir="${temp.dir}"/>
<delete dir="${dist.dir}"/>
<echo message="cleaned up. ${temp.dir}, and ${dist.dir} have been deleted."/>
</target>
<target name ="auxiliary-dist">
<delete dir="${temp.dir}"/>
<echo message="delete ${temp.dir}" />
<mkdir dir="${temp.dir}"/>
<javac destdir="${temp.dir}" source="1.6" target="1.6" debug="on" fork="true" memorymaximumsize="1024m">
<src path="${src.dir}"/>
<classpath>
<path refid="libs-classpath"/>
</classpath>
<include name="com/car/**"/> <!-- troubled line -->
</javac>
<!--<copy overwrite="true" todir="${temp.dir}">
<fileset dir="${src.dir}">
<exclude name="**/*.java"/>
<exclude name="**/*.sql"/>
<exclude name="**/*.txt"/>
</fileset>
</copy>
<delete dir="${dist.dir}"/>
<mkdir dir="${dist.dir}"/>
<jar destfile="${dist.dir}/auxiliary.jar" basedir="${temp.dir}"/> -->
</target>
There is no class file in ${temp.dir} after this step, and no error message. I double checked it, and found it is because of the "troubled line". I tried to add some files to the classpath. I don't know why it is wrong.

The source path should point to the root of the package tree. You make it point to a specific package inside the sources : ../auxiliary-src/com/nextbio/drugbank.
And in the javac task, you ask it to compile all the files matching the pattern com/car/**. That means that it will compile the Java source files in ../auxiliary-src/com/nextbio/drugbank/com/car or in a subdirectory. If that's the case, you have very unconventional package names.

I had the same problem.
My project complilated well but the classes there weren't in nowhere and It didn't have any error message.
My problem was the classpath. The eclipse wizard added EclipseLink 2.5.1 jars.
I removed it and the problem is gone.
I suggest make a simple HelloWord and remove all jars
reference from the classpath and try again.

I encountered this "ant, javac, compile" problem related with the classpath to.
No debug or verbose message shown.
This behavior appear because in classpath exists not compatible (superior) version jar packages and that cause no output classes.