获取清单属性

/** 
来 自 
N o w J a v a . c o m - 时  代  Java
**/

//package com.nowjava;

import java.io.*;

import java.net.*;

import java.util.*;

import java.util.jar.*;

import java.util.regex.*;


public class Main {

    private static final String MANIFEST_PATH = "META-INF/MANIFEST.MF";


    public static String getManifestAttribute(String classpathItem,

            String attrName) throws IOException {

        return getManifestAttribute(null, classpathItem, null, attrName);

    }
// 来 自 时代Java - N o w  J a v a . c o m

    public static String getManifestAttribute(String classpathItem,

            String implementationTitle, String attrName) throws IOException {

        return getManifestAttribute(null, classpathItem,

                implementationTitle, attrName);

    }


    public static String getManifestAttribute(ClassLoader classLoader,

            String classpathItem, String implementationTitle,

            String attrName) throws IOException {

        Pattern classpathPattern = classpathItem != null ? Pattern

                .compile(classpathItem) : null;

        for (Enumeration<URL> urls = classLoader != null ? classLoader

                .getResources(MANIFEST_PATH) : ClassLoader

                .getSystemResources(MANIFEST_PATH); urls.hasMoreElements();) {

            URL url = urls.nextElement();

            if (classpathPattern == null

                    || matchesClasspath(classpathPattern, url)) {

                try (InputStream in = new BufferedInputStream(

                        url.openStream())) {

                    Attributes attributes = new Manifest(in)

                            .getMainAttributes();

                    if (implementationTitle == null

                            || implementationTitle

                                    .equals(attributes

                                            .getValue(Attributes.Name.IMPLEMENTATION_TITLE)))

                        return attributes.getValue(attrName);

                }

            }

        }

        return "Unknown";

    }


    private static boolean matchesClasspath(Pattern pattern, URL url) {

        String urlPath = url.toString();

        int itemEnd = urlPath.length() - MANIFEST_PATH.length() - 1;