Package nz.org.riskscape.engine.plugin

Class PluginClassLoader

java.lang.Object

java.lang.ClassLoader

java.security.SecureClassLoader

java.net.URLClassLoader

nz.org.riskscape.engine.plugin.PluginClassLoader

All Implemented Interfaces:

Closeable, AutoCloseable

public class PluginClassLoader
extends URLClassLoader

Each Plugin has classes loaded from its own DefaultPluginClassLoader. These should inherit from the Engine's class loader, so that the plugins can access the core classes. Plugins can also depend on other plugins, which allows classes for this plugin to be loaded/linked from another plugin's class loader.

TODO add some integration tests for the plugin mechanism?

Constructor Summary

Constructors

Constructor	Description
PluginClassLoader(ClassLoader engineClassLoader, URL jarUrl, URL... dependencies)	Create a new plugin class loader

Method Summary

Modifier and Type	Method	Description
void	addDependency(PluginClassLoader classLoader)	Add a plugin dependency to this plugin.
protected boolean	canEqual(Object other)
boolean	equals(Object o)
void	freeze()	Prevent further plugins from being added to this one, just in case...
List<PluginClassLoader>	getDependencies()
ResourceClassLoader	getI18nResourceLoader()
URL	getJarUrl()
URL	getResource(String name)	Get a resource from local resources, engine resources, then falling back to plugin resources
InputStream	getResourceAsStream(String name)
Enumeration<URL>	getResources(String name)
int	hashCode()
protected Class<?>	loadClass(String name, boolean resolve)
protected Class<?>	loadClassLocally(String name, boolean resolve)	Attempt to load a class directly from this classloader's classpath, without delegating the search anywhere else.
static PluginClassLoader	newDummy()	Returns a plugin class loader to use in test situations.
void	setPluginDescriptor(nz.org.riskscape.engine.plugin.PluginDescriptor toSet)	Assign the PluginDescriptor that uses this class loader - this should be a strictly 1-1 relationship.
String	toString()

Methods inherited from class java.net.URLClassLoader

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

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Details

PluginClassLoader

public PluginClassLoader(ClassLoader engineClassLoader,
 URL jarUrl,
 URL... dependencies)

Create a new plugin class loader

Parameters:

jarUrl - primary library that constitutes this plugin's code

dependencies - Array of urls to subsidiary dependencies with own libraries and all exported libraries of plugins that are required for this plugin.

engineClassLoader - the parent class loader, expected to be the engine's class loader

Method Details

newDummy

public static PluginClassLoader newDummy()

Returns a plugin class loader to use in test situations. Likely to go bang if you try and load classes from it

setPluginDescriptor

public void setPluginDescriptor(nz.org.riskscape.engine.plugin.PluginDescriptor toSet)

Assign the PluginDescriptor that uses this class loader - this should be a strictly 1-1 relationship.

addDependency

public void addDependency(PluginClassLoader classLoader)

Add a plugin dependency to this plugin. The given class loader will be searched for classes once loading fails from this classloader's resources, the engine's classloader, and finally the system class path.

freeze

public void freeze()

Prevent further plugins from being added to this one, just in case... who knows what that will do?

loadClass

protected Class<?> loadClass(String name,
 boolean resolve)
                      throws ClassNotFoundException

Overrides:

loadClass in class ClassLoader

Throws:

ClassNotFoundException

loadClassLocally

protected Class<?> loadClassLocally(String name,
 boolean resolve)
                             throws ClassNotFoundException

Attempt to load a class directly from this classloader's classpath, without delegating the search anywhere else. This is used by other PluginClassLoader's to search for their dependencies, and is never called from this.

NB it does end up searching the engine's classpath as well, which is harmless but wasteful. I'm a little shy of changing this class loader too much, due to general ignorance and inexperience with implementing custom classloaders

Throws:

ClassNotFoundException

getResource

public URL getResource(String name)

Get a resource from local resources, engine resources, then falling back to plugin resources

Overrides:

getResource in class ClassLoader

getResources

public Enumeration<URL> getResources(String name)
                              throws IOException

Overrides:

getResources in class ClassLoader

Throws:

IOException

getResourceAsStream

public InputStream getResourceAsStream(String name)

Overrides:

getResourceAsStream in class URLClassLoader

toString

public String toString()

Overrides:

toString in class Object

getI18nResourceLoader

public ResourceClassLoader getI18nResourceLoader()

Returns:

a lazily-created ResourceClassLoader that is configured to load resources (and not classes) from the i18n directory next to the code plugin code.

equals

public boolean equals(Object o)

Overrides:

equals in class Object

canEqual

protected boolean canEqual(Object other)

hashCode

public int hashCode()

Overrides:

hashCode in class Object

getDependencies

public List<PluginClassLoader> getDependencies()

getJarUrl

public URL getJarUrl()