get Manifest Attribute - Java Reflection

Java examples for Reflection:Jar

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Description

get Manifest Attribute

Demo Code


//package com.java2s;
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);
    }/*from  w w  w . j a va 2  s  .c om*/

    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;
        boolean isJar = urlPath.charAt(itemEnd - 1) == '!';
        if (isJar)
            itemEnd--;
        else
            return true;
        int lastDash = urlPath.lastIndexOf('/', itemEnd - 1);
        int itemStart = lastDash >= 0 ? lastDash + 1 : 0;
        String urlItem = urlPath.substring(itemStart, itemEnd);
        return pattern.matcher(urlItem).find();
    }
}

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