org.apache.storm.sql.javac

Class CompilingClassLoader

java.lang.Object

java.lang.ClassLoader

org.apache.storm.sql.javac.CompilingClassLoader

public class CompilingClassLoader
extends ClassLoader

This is a Java ClassLoader that will attempt to load a class from a string of source code.

Example

String className = "com.foo.MyClass";
String classSource =
  "package com.foo;\n" +
  "public class MyClass implements Runnable {\n" +
  "  @Override public void run() {\n" +
  "   log(\"Hello world\");\n" +
  "  }\n" +
  "}";

// Load class from source.
ClassLoader classLoader = new CompilingClassLoader(
    parentClassLoader, className, classSource);
Class myClass = classLoader.loadClass(className);

// Use it.
Runnable instance = (Runnable)myClass.newInstance();
instance.run();

Only one chunk of source can be compiled per instance of CompilingClassLoader. If you need to compile more, create multiple CompilingClassLoader instances.

Uses Java 1.6’s in built compiler API.

If the class cannot be compiled, loadClass() will throw a ClassNotFoundException and log the compile errors to System.err. If you don’t want the messages logged, or want to explicitly handle the messages you can provide your own DiagnosticListener through {#setDiagnosticListener()}.

See Also:

ClassLoader, JavaCompiler

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	CompilingClassLoader.CompilerException Thrown when code cannot be compiled.

Constructor Summary

Constructors

Constructor and Description
CompilingClassLoader(ClassLoader parent, String className, String sourceCode, DiagnosticListener<JavaFileObject> diagnosticListener)

Method Summary

Modifier and Type	Method and Description
Class<?>	findClass(String name) Override ClassLoader’s class resolving method.
Map<String,ByteArrayOutputStream>	getClasses()

Methods inherited from class java.lang.ClassLoader

clearAssertionStatus, defineClass, defineClass, defineClass, defineClass, definePackage, findLibrary, findLoadedClass, findResource, findResources, findSystemClass, getClassLoadingLock, getPackage, getPackages, getParent, getResource, getResourceAsStream, getResources, getSystemClassLoader, getSystemResource, getSystemResourceAsStream, getSystemResources, loadClass, loadClass, registerAsParallelCapable, 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

CompilingClassLoader

public CompilingClassLoader(ClassLoader parent,
                            String className,
                            String sourceCode,
                            DiagnosticListener<JavaFileObject> diagnosticListener)
                     throws CompilingClassLoader.CompilerException

Parameters:

parent - Parent classloader to resolve dependencies from.

className - Name of class to compile. eg. “com.foo.MyClass”.

sourceCode - Java source for class. e.g. “package com.foo; class MyClass { … }”.

diagnosticListener - Notified of compiler errors (may be null).

Throws:

CompilingClassLoader.CompilerException

Method Detail

getClasses

public Map<String,ByteArrayOutputStream> getClasses()

findClass

public Class<?> findClass(String name)
                   throws ClassNotFoundException

Override ClassLoader’s class resolving method. Don’t call this directly, instead use ClassLoader.loadClass(String).

Overrides:

findClass in class ClassLoader

Throws:

ClassNotFoundException