org.apache.hadoop.hbase.coprocessor
Class CoprocessorClassLoader

java.lang.Object
  extended by java.lang.ClassLoader
      extended by java.security.SecureClassLoader
          extended by java.net.URLClassLoader
              extended by org.apache.hadoop.hbase.coprocessor.CoprocessorClassLoader

public class CoprocessorClassLoader
extends URLClassLoader

ClassLoader used to load Coprocessor instances. This ClassLoader always tries to load classes from the Coprocessor jar first before delegating to the parent ClassLoader, thus avoiding dependency conflicts between HBase's classpath and classes in the coprocessor's jar. Certain classes are exempt from being loaded by this ClassLoader because it would prevent them from being cast to the equivalent classes in the region server. For example, the Coprocessor interface needs to be loaded by the region server's ClassLoader to prevent a ClassCastException when casting the coprocessor implementation. This ClassLoader also handles resource loading. In most cases this ClassLoader will attempt to load resources from the coprocessor jar first before delegating to the parent. However, like in class loading, some resources need to be handled differently. For all of the Hadoop default configurations (e.g. hbase-default.xml) we will check the parent ClassLoader first to prevent issues such as failing the HBase default configuration version check.


Constructor Summary
CoprocessorClassLoader(List<URL> paths, ClassLoader parent)
          Creates a CoprocessorClassLoader that loads classes from the given paths.
 
Method Summary
 URL getResource(String name)
           
protected  boolean isClassExempt(String name)
          Determines whether the given class should be exempt from being loaded by this ClassLoader.
 Class<?> loadClass(String name)
           
protected  boolean loadResourceUsingParentFirst(String name)
          Determines whether we should attempt to load the given resource using the parent first before attempting to load the resource using this ClassLoader.
 
Methods inherited from class java.net.URLClassLoader
addURL, definePackage, findClass, findResource, findResources, getPermissions, getURLs, newInstance, newInstance
 
Methods inherited from class java.security.SecureClassLoader
defineClass, defineClass
 
Methods inherited from class java.lang.ClassLoader
clearAssertionStatus, defineClass, defineClass, defineClass, defineClass, definePackage, findLibrary, findLoadedClass, findSystemClass, getPackage, getPackages, getParent, getResourceAsStream, getResources, getSystemClassLoader, getSystemResource, getSystemResourceAsStream, getSystemResources, loadClass, resolveClass, setClassAssertionStatus, setDefaultAssertionStatus, setPackageAssertionStatus, setSigners
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

CoprocessorClassLoader

public CoprocessorClassLoader(List<URL> paths,
                              ClassLoader parent)
Creates a CoprocessorClassLoader that loads classes from the given paths.

Parameters:
paths - paths from which to load classes.
parent - the parent ClassLoader to set.
Method Detail

loadClass

public Class<?> loadClass(String name)
                   throws ClassNotFoundException
Overrides:
loadClass in class ClassLoader
Throws:
ClassNotFoundException

getResource

public URL getResource(String name)
Overrides:
getResource in class ClassLoader

isClassExempt

protected boolean isClassExempt(String name)
Determines whether the given class should be exempt from being loaded by this ClassLoader.

Parameters:
name - the name of the class to test.
Returns:
true if the class should *not* be loaded by this ClassLoader; false otherwise.

loadResourceUsingParentFirst

protected boolean loadResourceUsingParentFirst(String name)
Determines whether we should attempt to load the given resource using the parent first before attempting to load the resource using this ClassLoader.

Parameters:
name - the name of the resource to test.
Returns:
true if we should attempt to load the resource using the parent first; false if we should attempt to load the resource using this ClassLoader first.


Copyright © 2013 The Apache Software Foundation. All Rights Reserved.