Class MemoryClassLoader

java.lang.Object

java.lang.ClassLoader

java.security.SecureClassLoader

java.net.URLClassLoader

org.dellroad.stuff.java.MemoryClassLoader

All Implemented Interfaces:

Closeable, AutoCloseable

public class MemoryClassLoader
extends URLClassLoader

An URLClassLoader that maintains an updatable cache of class files (as byte[] arrays) in memory from which classes may be loaded.

The internal cache of classes is initially empty. Binary class files may be added (or removed) via putClass(), and retrieved via getClass(). The byte[] arrays passed to and from these methods are copied to ensure immutability.

Classes defined by this loader are assigned URLs that look like memory:/com.example.MyClass.

This class is thread safe and parallel capable.

Field Summary

Fields

Modifier and Type	Field	Description
static final String	MEMORY_URL_SCHEME

Constructor Summary

Constructors

Constructor	Description
MemoryClassLoader()	Default constructor.
MemoryClassLoader(ClassLoader parent)	Constructor.

Method Summary

Modifier and Type	Method	Description
void	addURL(URL url)
protected Class<?>	findClass(String className)
URL	findResource(String resourceName)
Enumeration<URL>	findResources(String resourceName)
byte[]	getClass(String className)	Get the class from this loader that was previously added via putClass(), if any.
void	linkClass(Class<?> c)	Links the specified class.
void	putClass(String className, byte[] classbytes)	Add a class to this loader, making it available for class resolution.

Methods inherited from class URLClassLoader

close, definePackage, getPermissions, getResourceAsStream, getURLs, newInstance, newInstance

Methods inherited from class SecureClassLoader

defineClass, defineClass

Methods inherited from class ClassLoader

clearAssertionStatus, defineClass, defineClass, defineClass, defineClass, definePackage, findClass, findLibrary, findLoadedClass, findResource, findSystemClass, getClassLoadingLock, getDefinedPackage, getDefinedPackages, getName, getPackage, getPackages, getParent, getPlatformClassLoader, getResource, getResources, getSystemClassLoader, getSystemResource, getSystemResourceAsStream, getSystemResources, getUnnamedModule, isRegisteredAsParallelCapable, loadClass, loadClass, registerAsParallelCapable, resolveClass, resources, setClassAssertionStatus, setDefaultAssertionStatus, setPackageAssertionStatus, setSigners

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

MEMORY_URL_SCHEME

public static final String MEMORY_URL_SCHEME

See Also:

• Constant Field Values

Constructor Details

MemoryClassLoader

public MemoryClassLoader()

Default constructor.

Uses the current thread's context loader as the parent loader.

MemoryClassLoader

public MemoryClassLoader(ClassLoader parent)

Constructor.

Parameters:

parent - parent class loader, possibly null

Method Details

putClass

public void putClass(String className,
 byte[] classbytes)

Add a class to this loader, making it available for class resolution.

If an existing class already exists under className, it will be replaced. The classbytes array is copied to ensure immutability.

If classbytes is null, any existing class will be removed.

Parameters:

className - Java class name

classbytes - Java class file data

Throws:

IllegalArgumentException - if either parameter is null

getClass

public byte[] getClass(String className)

Get the class from this loader that was previously added via putClass(), if any.

The returned array is a copy to ensure immutability.

Parameters:

className - Java class name

Returns:

class file previously added under the name className, or null if none exists

linkClass

public void linkClass(Class<?> c)

Links the specified class.

This method just invokes this.resolveClass(c).

Parameters:

c - the class to link

See Also:

• ClassLoader.resolveClass(Class)

addURL

public void addURL(URL url)

Overrides:

addURL in class URLClassLoader

findClass

protected Class<?> findClass(String className)
                      throws ClassNotFoundException

Overrides:

findClass in class URLClassLoader

Throws:

ClassNotFoundException

findResource

public URL findResource(String resourceName)

Overrides:

findResource in class URLClassLoader

findResources

public Enumeration<URL> findResources(String resourceName)
                               throws IOException

Overrides:

findResources in class URLClassLoader

Throws:

IOException