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Groovy example source code file (ClosureTriggerBinding.java)

This example Groovy source code file (ClosureTriggerBinding.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 - Groovy tags/keywords

bindpath, bindpathsnooper, bindpathsnooper, closure, closure, closuretriggerbinding, deadendexception, deadendexception, deadendobject, exception, object, object, reflection, runtimeexception, security, triggerbinding, util

The Groovy ClosureTriggerBinding.java source code

 * Copyright 2008 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,
 * See the License for the specific language governing permissions and
 * limitations under the License.
package org.codehaus.groovy.binding;

import groovy.lang.Closure;
import groovy.lang.GroovyObjectSupport;
import groovy.lang.Reference;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.security.PrivilegedAction;
import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

public class ClosureTriggerBinding implements TriggerBinding, SourceBinding {

    Map<String, TriggerBinding> syntheticBindings;
    Closure closure;

    public ClosureTriggerBinding(Map<String, TriggerBinding> syntheticBindings) {
        this.syntheticBindings = syntheticBindings;

    public Closure getClosure() {
        return closure;

    public void setClosure(Closure closure) {
        this.closure = closure;

    private BindPath createBindPath(String propertyName, BindPathSnooper snooper) {
        BindPath bp = new BindPath();
        bp.propertyName = propertyName;
        List<BindPath> childPaths = new ArrayList();
        for (Map.Entry<String, BindPathSnooper> entry : snooper.fields.entrySet()) {
            childPaths.add(createBindPath(entry.getKey(), entry.getValue()));
        bp.children = childPaths.toArray(new BindPath[childPaths.size()]);
        return bp;

    public FullBinding createBinding(SourceBinding source, TargetBinding target) {
        if (source != this) {
            throw new RuntimeException("Source binding must the Trigger Binding as well");
        final BindPathSnooper delegate = new BindPathSnooper();
        try {
            // create our own local copy of the closure
            final Class closureClass = closure.getClass();

            // do in privileged block since we may be looking at private stuff
            Closure closureLocalCopy = java.security.AccessController.doPrivileged(new PrivilegedAction<Closure>() {
                public Closure run() {
                    // assume closures have only 1 constructor, of the form (Object, Reference*)
                    Constructor constructor = closureClass.getConstructors()[0];
                    int paramCount = constructor.getParameterTypes().length;
                    Object[] args = new Object[paramCount];
                    args[0] = delegate;
                    for (int i = 1; i < paramCount; i++) {
                        args[i] = new Reference(new BindPathSnooper());
                    try {
                        boolean acc = constructor.isAccessible();
                        Closure localCopy = (Closure) constructor.newInstance(args);
                        if (!acc) { constructor.setAccessible(false); }
                        for (Field f:closureClass.getDeclaredFields()) {
                            acc = f.isAccessible();
                            if (f.getType() == Reference.class) {
                                        (BindPathSnooper) ((Reference) f.get(localCopy)).get());
                            if (!acc) { f.setAccessible(false); }
                        return localCopy;
                    } catch (Exception e) {
                        throw new RuntimeException("Error snooping closure", e);
            try {
            } catch (DeadEndException e) {
                // we want this exception exposed.
                throw e;
            } catch (Exception e) {
                // ignore it, likely failing because we are faking out properties
                // such as a call to Math.min(int, BindPathSnooper)
        } catch (Exception e) {
            throw new RuntimeException("A closure expression binding could not be created because of " + e.getClass().getName() + ":\n\t" + e.getMessage());
        List<BindPath> rootPaths = new ArrayList();
        for (Map.Entry<String, BindPathSnooper> entry : delegate.fields.entrySet()) {
            BindPath bp =createBindPath(entry.getKey(), entry.getValue());
            bp.currentObject = closure;
        PropertyPathFullBinding fb = new PropertyPathFullBinding();
        fb.setSourceBinding(new ClosureSourceBinding(closure));
        fb.bindPaths = rootPaths.toArray(new BindPath[rootPaths.size()]);
        return fb;

    public Object getSourceValue() {
        return closure.call();

class DeadEndException extends RuntimeException {
    DeadEndException(String message) { super(message); }

class DeadEndObject {
    public Object getProperty(String property) {
        throw new DeadEndException("Cannot bind to a property on the return value of a method call");
    public Object invokeMethod(String name, Object args) {
        return this;

class BindPathSnooper extends GroovyObjectSupport {
    static final DeadEndObject DEAD_END = new DeadEndObject();

    Map<String, BindPathSnooper> fields = new LinkedHashMap();

    public Object getProperty(String property) {
        if (fields.containsKey(property)) {
            return fields.get(property);
        } else {
            BindPathSnooper snooper = new BindPathSnooper();
            fields.put(property, snooper);
            return snooper;

    public Object invokeMethod(String name, Object args) {
        return DEAD_END;

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