org.daisy.dotify.common.java.ManifestRetriever Maven / Gradle / Ivy
package org.daisy.dotify.common.java;
import java.io.IOException;
import java.net.URL;
import java.util.jar.Manifest;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* Retrieves a jar manifest, if available.
*
* @author Joel Håkansson
*/
public class ManifestRetriever {
private static final Logger logger = Logger.getLogger(ManifestRetriever.class.getCanonicalName());
private final Class clazz;
private boolean failed = false;
private Manifest manifest;
/**
* @param clazz a class in the jar to get a manifest for
*/
public ManifestRetriever(Class clazz) {
this.clazz = clazz;
this.manifest = null;
}
/**
* Returns the jar manifest associated with this instance.
*
* @return returns a manifest. If the class is not in a jar, the manifest is empty
*/
public Manifest getManifest() {
if (failed || manifest != null) {
return manifest;
}
String className = clazz.getSimpleName() + ".class";
String classPath = clazz.getResource(className).toString();
if (!classPath.startsWith("jar")) {
// Class not from JAR
failed = true;
manifest = new Manifest();
} else {
String manifestPath = classPath.substring(0, classPath.lastIndexOf("!") + 1) +
"/META-INF/MANIFEST.MF";
try {
manifest = new Manifest(new URL(manifestPath).openStream());
} catch (IOException e) {
failed = true;
logger.log(Level.WARNING, "Failed to read manifest.", e);
}
}
return manifest;
}
/**
* Returns true if getManifest has been called and the manifest could not be read.
*
* @return true if getManifest previously failed, false otherwise
*/
public boolean failed() {
return failed;
}
}