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Spring Framework example source code file (JRubyScriptUtils.java)

This example Spring Framework source code file (JRubyScriptUtils.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Spring Framework tags/keywords

class, classnode, classnode, irubyobject, irubyobject, newlinenode, node, node, object, object, reflection, ruby, rubynil, rubyobjectinvocationhandler, string, util

The Spring Framework JRubyScriptUtils.java source code

/*
 * Copyright 2002-2007 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.scripting.jruby;

import java.lang.reflect.Array;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.Collections;
import java.util.List;

import org.jruby.Ruby;
import org.jruby.RubyArray;
import org.jruby.RubyException;
import org.jruby.RubyNil;
import org.jruby.ast.ClassNode;
import org.jruby.ast.Colon2Node;
import org.jruby.ast.NewlineNode;
import org.jruby.ast.Node;
import org.jruby.exceptions.JumpException;
import org.jruby.exceptions.RaiseException;
import org.jruby.javasupport.JavaEmbedUtils;
import org.jruby.runtime.DynamicScope;
import org.jruby.runtime.builtin.IRubyObject;

import org.springframework.aop.support.AopUtils;
import org.springframework.core.NestedRuntimeException;
import org.springframework.util.ClassUtils;
import org.springframework.util.ObjectUtils;
import org.springframework.util.ReflectionUtils;
import org.springframework.util.StringUtils;

/**
 * Utility methods for handling JRuby-scripted objects.
 *
 * <p>Note: As of Spring 2.0.4, this class requires JRuby 0.9.8 or 0.9.9.
 * As of Spring 2.0.6 / 2.1, it supports JRuby 1.0 as well.
 *
 * @author Rob Harrop
 * @author Juergen Hoeller
 * @author Rick Evans
 * @since 2.0
 */
public abstract class JRubyScriptUtils {

	// Determine whether the old JRuby 0.9 parse method is available (incompatible with 1.0)
	private final static Method oldParseMethod = ClassUtils.getMethodIfAvailable(
			Ruby.class, "parse", new Class[] {String.class, String.class, DynamicScope.class});


	/**
	 * Create a new JRuby-scripted object from the given script source,
	 * using the default {@link ClassLoader}.
	 * @param scriptSource the script source text
	 * @param interfaces the interfaces that the scripted Java object is to implement
	 * @return the scripted Java object
	 * @throws JumpException in case of JRuby parsing failure
	 * @see ClassUtils#getDefaultClassLoader()
	 */
	public static Object createJRubyObject(String scriptSource, Class[] interfaces) throws JumpException {
		return createJRubyObject(scriptSource, interfaces, ClassUtils.getDefaultClassLoader());
	}

	/**
	 * Create a new JRuby-scripted object from the given script source.
	 * @param scriptSource the script source text
	 * @param interfaces the interfaces that the scripted Java object is to implement
	 * @param classLoader the {@link ClassLoader} to create the script proxy with
	 * @return the scripted Java object
	 * @throws JumpException in case of JRuby parsing failure
	 */
	public static Object createJRubyObject(String scriptSource, Class[] interfaces, ClassLoader classLoader) {
		Ruby ruby = initializeRuntime();

		Node scriptRootNode = (oldParseMethod != null ?
				(Node) ReflectionUtils.invokeMethod(oldParseMethod, ruby, new Object[] {scriptSource, "", null}) :
				ruby.parse(scriptSource, "", null, 0));
		IRubyObject rubyObject = ruby.eval(scriptRootNode);

		if (rubyObject instanceof RubyNil) {
			String className = findClassName(scriptRootNode);
			rubyObject = ruby.evalScript("\n" + className + ".new");
		}
		// still null?
		if (rubyObject instanceof RubyNil) {
			throw new IllegalStateException("Compilation of JRuby script returned RubyNil: " + rubyObject);
		}

		return Proxy.newProxyInstance(classLoader, interfaces, new RubyObjectInvocationHandler(rubyObject, ruby));
	}

	/**
	 * Initializes an instance of the {@link org.jruby.Ruby} runtime.
	 */
	private static Ruby initializeRuntime() {
		return JavaEmbedUtils.initialize(Collections.EMPTY_LIST);
	}

	/**
	 * Given the root {@link Node} in a JRuby AST will locate the name of the
	 * class defined by that AST.
	 * @throws IllegalArgumentException if no class is defined by the supplied AST
	 */
	private static String findClassName(Node rootNode) {
		ClassNode classNode = findClassNode(rootNode);
		if (classNode == null) {
			throw new IllegalArgumentException("Unable to determine class name for root node '" + rootNode + "'");
		}
		Colon2Node node = (Colon2Node) classNode.getCPath();
		return node.getName();
	}

	/**
	 * Find the first {@link ClassNode} under the supplied {@link Node}.
	 * @return the found <code>ClassNode, or null
	 * if no {@link ClassNode} is found
	 */
	private static ClassNode findClassNode(Node node) {
		if (node instanceof ClassNode) {
			return (ClassNode) node;
		}
		List children = node.childNodes();
		for (int i = 0; i < children.size(); i++) {
			Node child = (Node) children.get(i);
			if (child instanceof ClassNode) {
				return (ClassNode) child;
			} else if (child instanceof NewlineNode) {
				NewlineNode nn = (NewlineNode) child;
				Node found = findClassNode(nn.getNextNode());
				if (found instanceof ClassNode) {
					return (ClassNode) found;
				}
			}
		}
		for (int i = 0; i < children.size(); i++) {
			Node child = (Node) children.get(i);
			Node found = findClassNode(child);
			if (found instanceof ClassNode) {
				return (ClassNode) found;
			}
		}
		return null;
	}


	/**
	 * InvocationHandler that invokes a JRuby script method.
	 */
	private static class RubyObjectInvocationHandler implements InvocationHandler {

		private final IRubyObject rubyObject;

		private final Ruby ruby;

		public RubyObjectInvocationHandler(IRubyObject rubyObject, Ruby ruby) {
			this.rubyObject = rubyObject;
			this.ruby = ruby;
		}

		public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
			if (AopUtils.isEqualsMethod(method)) {
				return (isProxyForSameRubyObject(args[0]) ? Boolean.TRUE : Boolean.FALSE);
			}
			if (AopUtils.isHashCodeMethod(method)) {
				return new Integer(this.rubyObject.hashCode());
			}
			if (AopUtils.isToStringMethod(method)) {
				String toStringResult = this.rubyObject.toString();
				if (!StringUtils.hasText(toStringResult)) {
					toStringResult = ObjectUtils.identityToString(this.rubyObject);
				}
				return "JRuby object [" + toStringResult + "]";
			}
			try {
				IRubyObject[] rubyArgs = convertToRuby(args);
				IRubyObject rubyResult =
						this.rubyObject.callMethod(this.ruby.getCurrentContext(), method.getName(), rubyArgs);
				return convertFromRuby(rubyResult, method.getReturnType());
			}
			catch (RaiseException ex) {
				throw new JRubyExecutionException(ex);
			}
		}

		private boolean isProxyForSameRubyObject(Object other) {
			if (!Proxy.isProxyClass(other.getClass())) {
				return false;
			}
			InvocationHandler ih = Proxy.getInvocationHandler(other);
			return (ih instanceof RubyObjectInvocationHandler &&
					this.rubyObject.equals(((RubyObjectInvocationHandler) ih).rubyObject));
		}

		private IRubyObject[] convertToRuby(Object[] javaArgs) {
			if (javaArgs == null || javaArgs.length == 0) {
				return new IRubyObject[0];
			}
			IRubyObject[] rubyArgs = new IRubyObject[javaArgs.length];
			for (int i = 0; i < javaArgs.length; ++i) {
				rubyArgs[i] = JavaEmbedUtils.javaToRuby(this.ruby, javaArgs[i]);
			}
			return rubyArgs;
		}

		private Object convertFromRuby(IRubyObject rubyResult, Class returnType) {
			Object result = JavaEmbedUtils.rubyToJava(this.ruby, rubyResult, returnType);
			if (result instanceof RubyArray && returnType.isArray()) {
				result = convertFromRubyArray(((RubyArray) result).toJavaArray(), returnType);
			}
			return result;
		}

		private Object convertFromRubyArray(IRubyObject[] rubyArray, Class returnType) {
			Class targetType = returnType.getComponentType();
			Object javaArray = Array.newInstance(targetType, rubyArray.length);
			for (int i = 0; i < rubyArray.length; i++) {
				IRubyObject rubyObject = rubyArray[i];
				Array.set(javaArray, i, convertFromRuby(rubyObject, targetType));
			}
			return javaArray;
		}
	}


	/**
	 * Exception thrown in response to a JRuby {@link RaiseException}
	 * being thrown from a JRuby method invocation.
	 * <p>Introduced because the RaiseException class does not
	 * have useful {@link Object#toString()}, {@link Throwable#getMessage()},
	 * and {@link Throwable#printStackTrace} implementations.
	 */
	public static class JRubyExecutionException extends NestedRuntimeException {

		/**
		 * Create a new <code>JRubyException,
		 * wrapping the given JRuby <code>RaiseException.
		 * @param ex the cause (must not be <code>null)
		 */
		public JRubyExecutionException(RaiseException ex) {
			super(buildMessage(ex), ex);
		}

		private static String buildMessage(RaiseException ex) {
			RubyException rubyEx = ex.getException();
			return (rubyEx != null && rubyEx.message != null) ? rubyEx.message.toString() : "Unexpected JRuby error";
		}
	}

}

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