edu.emory.mathcs.util.classloader.ResourceHandle Maven / Gradle / Ivy
/*
* Written by Dawid Kurzyniec and released to the public domain, as explained
* at http://creativecommons.org/licenses/publicdomain
*/
package edu.emory.mathcs.util.classloader;
import java.io.*;
import java.net.*;
import java.security.cert.*;
import java.util.jar.*;
/**
* This class represents a handle (a connection) to some resource, which may
* be a class, native library, text file, image, etc. Handles are returned
* by {@link ResourceLoader}'s get methods.
* Having the resource handle, in addition to accessing the resource data
* (using methods {@link #getInputStream} or {@link #getBytes}) as well as
* access resource metadata, such as attributes, certificates, etc.
*
* As soon as the handle is no longer in use, it should be explicitly
* {@link #close}d, similarly to I/O streams.
*
* @author Dawid Kurzyniec
* @version 1.0
*/
public abstract class ResourceHandle {
/**
* Return the name of the resource. The name is a "/"-separated path
* name that identifies the resource.
*/
public abstract String getName();
/**
* Returns the URL of the resource.
*/
public abstract URL getURL();
/**
* Returns the CodeSource URL for the class or resource.
*/
public abstract URL getCodeSourceURL();
/**
* Returns and InputStream for reading this resource data.
*/
public abstract InputStream getInputStream() throws IOException;
/**
* Returns the length of this resource data, or -1 if unknown.
*/
public abstract int getContentLength();
/**
* Returns this resource data as an array of bytes.
*/
public byte[] getBytes() throws IOException {
byte[] buf;
InputStream in = getInputStream();
int len = getContentLength();
try {
if (len != -1) {
// read exactly len bytes
buf = new byte[len];
while (len > 0) {
int read = in.read(buf, buf.length - len, len);
if (read < 0) {
throw new IOException("unexpected EOF");
}
len -= read;
}
} else {
// read until end of stream is reached
buf = new byte[2048];
int total = 0;
while ((len = in.read(buf, total, buf.length - total)) >= 0) {
total += len;
if (total >= buf.length) {
byte[] aux = new byte[total * 2];
System.arraycopy(buf, 0, aux, 0, total);
buf = aux;
}
}
// trim if necessary
if (total != buf.length) {
byte[] aux = new byte[total];
System.arraycopy(buf, 0, aux, 0, total);
buf = aux;
}
}
} finally {
in.close();
}
return buf;
}
/**
* Returns the Manifest of the JAR file from which this resource
* was loaded, or null if none.
*/
public Manifest getManifest() throws IOException {
return null;
}
/**
* Return the Certificates of the resource, or null if none.
*/
public Certificate[] getCertificates() {
return null;
}
/**
* Return the Attributes of the resource, or null if none.
*/
public Attributes getAttributes() throws IOException {
Manifest m = getManifest();
if (m == null) return null;
String entry = getURL().getFile();
return m.getAttributes(entry);
}
/**
* Closes a connection to the resource indentified by this handle. Releases
* any I/O objects associated with the handle.
*/
public void close() {
}
//
// /**
// * Ensures that {@link #release()} method is eventually called when this
// * object is finalized.
// */
// protected void finalize() throws Throwable {
// super.finalize();
// release();
// }
public String toString() {
return "[" + getName() + ": " + getURL() + "; code source: " + getCodeSourceURL() + "]";
}
}