import java.util.*;

public class checkVersion {
        JarFile jarFile;
        Manifest manifest;
        Attributes attributes;
        String jarFileName;
        String version;

        public checkVersion(String filename) {
                jarFileName = filename;
        }

        public void printVersion() {
                try {
                        // jar 파일을 읽습니다.
                        jarFile = new JarFile(new File(jarFileName));
                        // jar 파일에서 manifest 정보를 가져옵니다.
                        manifest = jarFile.getManifest();
                        // manifest에서 main 정보를 가져옵니다.
                        attributes = (Attributes)manifest.getMainAttributes();

                        // attribute 중에서 Implementation-Version 정보를 추출한다.
                        version = attributes.getValue("Implementation-Version");
                        System.out.println("@@ " + version);

                        /* 아래처럼 하면 manifest의 main 정보 전체를 확인할 수 있다.
                        for (Iterator it=attributes.keySet().iterator(); it.hasNext(); ) {
                                Attributes.Name attrName = (Attributes.Name)it.next();
                                String attrValue = attributes.getValue(attrName);

                                System.out.println("## " + attrName + " : " + attrValue);
                        }
                        */
                } catch(Exception e) {
                        e.printStackTrace();
                }
        }

        public static void main(String[] args) {
                if( args.length != 1 ) {
                        System.out.println("Usage : ");
                        System.out.println("    java printVersion [jar_file_name]");
                        return;
                }

                /*
                if( !(new File(args[0])).exists() ) {
                        System.out.println("Error : ");
                        System.out.println("[" + args[0] + "] file does not exist.");
                        return;
                }
                */

                checkVersion cv = new checkVersion(args[0]);
                cv.printVersion();
        }
}

Manifest-Version: 1.0
Archiver-Version: Plexus Archiver
Created-By: Apache Maven
Built-By: Niall Pemberton
Build-Jdk: 1.5.0_07
Bundle-License: http://www.apache.org/licenses/LICENSE-2.0.txt
Bundle-ManifestVersion: 2
Bundle-Name: Apache Commons IO Bundle
Bundle-SymbolicName: org.apache.commons.io
Bundle-Vendor: The Apache Software Foundation
Bundle-Version: 1.4
Export-Package: org.apache.commons.io;version=1.4,
 org.apache.commons.io.comparator;version=1.4,
 org.apache.commons.io.filefilter;version=1.4,
 org.apache.commons.io.input;version=1.4,
 org.apache.commons.io.output;version=1.4
Implementation-Title: Commons IO
Implementation-Vendor: The Apache Software Foundation
Implementation-Vendor-Id: org.apache
Implementation-Version: 1.4
Import-Package: org.apache.commons.io;version=1.4,
 org.apache.commons.io.comparator;version=1.4,
 org.apache.commons.io.filefilter;version=1.4,
 org.apache.commons.io.input;version=1.4,
 org.apache.commons.io.output;version=1.4
Specification-Title: Commons IO
Specification-Vendor: The Apache Software Foundation
Specification-Version: 1.4
X-Compile-Source-JDK: 1.3
X-Compile-Target-JDK: 1.3 

weblogic@WAS01[/export/home/weblogic]# java checkVersion commons-net-1.4.1.jar
@@ 1.4.1