Class CachingJavaSourceClassLoader

java.lang.Object

java.lang.ClassLoader

org.codehaus.commons.compiler.AbstractJavaSourceClassLoader

org.codehaus.janino.JavaSourceClassLoader

org.codehaus.janino.CachingJavaSourceClassLoader

public class CachingJavaSourceClassLoader
extends JavaSourceClassLoader

A JavaSourceClassLoader that uses a resource storage provided by the application to cache compiled classes and thus saving unnecessary recompilations.

The application provides access to the resource storage through a pair of a ResourceFinder and a ResourceCreator (see CachingJavaSourceClassLoader(ClassLoader, ResourceFinder, String, ResourceFinder, ResourceCreator).

See AbstractJavaSourceClassLoader.main(String[]) for an example how to use this class.

Notice: You must NOT rely on that this class stores some particular data in some particular resources through the given classFileCacheResourceFinder/Creator! These serve only as a means for the CachingJavaSourceClassLoader to persistently cache some data between invocations. In other words: If you want to compile .java files into .class files, then don't use this class but Compiler instead!

Nested Class Summary

Nested classes/interfaces inherited from class AbstractJavaSourceClassLoader

AbstractJavaSourceClassLoader.ProtectionDomainFactory

Field Summary

Fields

Modifier and Type	Field	Description
private final ResourceCreator	classFileCacheResourceCreator
private final ResourceFinder	classFileCacheResourceFinder
private final ResourceFinder	sourceFinder

Fields inherited from class AbstractJavaSourceClassLoader

protectionDomainFactory

Constructor Summary

Constructors

Constructor	Description
CachingJavaSourceClassLoader(ClassLoader parentClassLoader, File[] sourcePath, String characterEncoding, File cacheDirectory)	See CachingJavaSourceClassLoader(ClassLoader, ResourceFinder, String, ResourceFinder, ResourceCreator).
CachingJavaSourceClassLoader(ClassLoader parentClassLoader, ResourceFinder sourceFinder, String characterEncoding, ResourceFinder classFileCacheResourceFinder, ResourceCreator classFileCacheResourceCreator)	Notice that this class is thread-safe if and only if the classFileCacheResourceCreator stores its data atomically, i.e.

Method Summary

Modifier and Type	Method	Description
protected Map<String,byte[]>	generateBytecodes(String className)	Overrides JavaSourceClassLoader.generateBytecodes(String) to implement class file caching.
private static byte[]	readResource(Resource r)	Reads all bytes from the given resource.
private static void	writeResource(ResourceCreator resourceCreator, String resourceName, byte[] data)	Creates a resource with the given name and store the data in it.

Methods inherited from class JavaSourceClassLoader

findClass, setCompileErrorHandler, setDebuggingInfo, setSourceCharset, setSourceFinder, setSourcePath, setTargetVersion, setWarningHandler

Methods inherited from class AbstractJavaSourceClassLoader

getResourceAsStream, main, setProtectionDomainFactory, setSourceFileCharacterEncoding

Methods inherited from class ClassLoader

clearAssertionStatus, defineClass, defineClass, defineClass, defineClass, definePackage, findClass, findLibrary, findLoadedClass, findResource, findResource, findResources, 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

classFileCacheResourceFinder

private final ResourceFinder classFileCacheResourceFinder

classFileCacheResourceCreator

private final ResourceCreator classFileCacheResourceCreator

sourceFinder

private final ResourceFinder sourceFinder

Constructor Details

CachingJavaSourceClassLoader

public CachingJavaSourceClassLoader(ClassLoader parentClassLoader,
 @Nullable
 File[] sourcePath,
 @Nullable
 String characterEncoding,
 File cacheDirectory)

See CachingJavaSourceClassLoader(ClassLoader, ResourceFinder, String, ResourceFinder, ResourceCreator).

Parameters:

sourcePath - Directories to scan for source files

cacheDirectory - Directory to use for caching generated class files (see class description)

CachingJavaSourceClassLoader

public CachingJavaSourceClassLoader(ClassLoader parentClassLoader,
 ResourceFinder sourceFinder,
 @Nullable
 String characterEncoding,
 ResourceFinder classFileCacheResourceFinder,
 ResourceCreator classFileCacheResourceCreator)

Notice that this class is thread-safe if and only if the classFileCacheResourceCreator stores its data atomically, i.e. the classFileCacheResourceFinder sees the resource written by the classFileCacheResourceCreator only after the OutputStream is closed.

In order to make the caching scheme work, both the classFileCacheResourceFinder and the sourceFinder must support the Resource.lastModified() method, so that the modification time of the source and the class files can be compared.

Parameters:

parentClassLoader - Attempt to load classes through this one before looking for source files

sourceFinder - Finds Java source for class pkg.Cls in resource pkg/Cls.java

characterEncoding - Encoding of Java source or null for platform default encoding

classFileCacheResourceFinder - Finds precompiled class pkg.Cls in resource pkg/Cls.class (see class description)

classFileCacheResourceCreator - Stores compiled class pkg.Cls in resource pkg/Cls.class (see class description)

Method Details

generateBytecodes

@Nullable
protected Map<String,byte[]> generateBytecodes(String className)
                                        throws ClassNotFoundException

Overrides JavaSourceClassLoader.generateBytecodes(String) to implement class file caching.

Overrides:

generateBytecodes in class JavaSourceClassLoader

Returns:

String name => byte[] bytecode, or null if no source code could be found

Throws:

ClassNotFoundException - Compilation problems or class file cache I/O problems

readResource

private static byte[] readResource(Resource r)
                            throws IOException

Reads all bytes from the given resource.

Throws:

IOException

writeResource

private static void writeResource(ResourceCreator resourceCreator,
 String resourceName,
 byte[] data)
                           throws IOException

Creates a resource with the given name and store the data in it.

Throws:

IOException