com.sun.istack.tools.ParallelWorldClassLoader Maven / Gradle / Ivy
package com.sun.istack.tools;
import java.io.InputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.net.URL;
import java.net.MalformedURLException;
import java.util.Enumeration;
/**
* Load classes/resources from a side folder, so that
* classes of the same package can live in a single jar file.
*
*
* For example, with the following jar file:
*
* /
* +- foo
* +- X.class
* +- bar
* +- X.class
*
*
* {@link ParallelWorldClassLoader}("foo/") would load X.class from
* /foo/X.class (note that X is defined in the root package, not
* foo.X.
*
*
* This can be combined with {@link MaskingClassLoader} to mask classes which are loaded by the parent
* class loader so that the child class loader
* classes living in different folders are loaded
* before the parent class loader loads classes living the jar file publicly
* visible
* For example, with the following jar file:
*
* /
* +- foo
* +- X.class
* +- bar
* +-foo
* +- X.class
*
*
* {@link ParallelWorldClassLoader}(MaskingClassLoader.class.getClassLoader()) would load foo.X.class from
* /bar/foo.X.class not the foo.X.class in the publicly visible place in the jar file, thus
* masking the parent classLoader from loading the class from foo.X.class
* (note that X is defined in the package foo, not
* bar.foo.X.
*
* @author Kohsuke Kawaguchi
*/
public class ParallelWorldClassLoader extends ClassLoader {
/**
* Strings like "prefix/", "abc/", or "" to indicate
* classes should be loaded normally.
*/
private final String prefix;
public ParallelWorldClassLoader(ClassLoader parent,String prefix) {
super(parent);
this.prefix = prefix;
}
protected Class findClass(String name) throws ClassNotFoundException {
StringBuffer sb = new StringBuffer(name.length()+prefix.length()+6);
sb.append(prefix).append(name.replace('.','/')).append(".class");
InputStream is = getParent().getResourceAsStream(sb.toString());
if (is==null)
throw new ClassNotFoundException(name);
try {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] buf = new byte[1024];
int len;
while((len=is.read(buf))>=0)
baos.write(buf,0,len);
buf = baos.toByteArray();
int packIndex = name.lastIndexOf('.');
if (packIndex != -1) {
String pkgname = name.substring(0, packIndex);
// Check if package already loaded.
Package pkg = getPackage(pkgname);
if (pkg == null) {
definePackage(pkgname, null, null, null, null, null, null, null);
}
}
return defineClass(name,buf,0,buf.length);
} catch (IOException e) {
throw new ClassNotFoundException(name,e);
}
}
protected URL findResource(String name) {
return getParent().getResource(prefix+name);
}
protected Enumeration findResources(String name) throws IOException {
return getParent().getResources( prefix+name);
}
/**
* Given the URL inside jar, returns the URL to the jar itself.
*/
public static URL toJarUrl(URL res) throws ClassNotFoundException, MalformedURLException {
String url = res.toExternalForm();
if(!url.startsWith("jar:"))
throw new ClassNotFoundException("Loaded outside a jar "+url);
url = url.substring(4); // cut off jar:
url = url.substring(0,url.lastIndexOf('!')); // cut off everything after '!'
return new URL(url);
}
}