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Groovy example source code file (BuilderSupport.java)

This example Groovy source code file (BuilderSupport.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

buildersupport, buildersupport, closure, closure, groovyobjectsupport, list, map, map, object, object, util

The Groovy BuilderSupport.java source code

/*
 * Copyright 2003-2008 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,
 * 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 groovy.util;

import groovy.lang.Closure;
import groovy.lang.GroovyObjectSupport;
import groovy.lang.MissingMethodException;
import org.codehaus.groovy.runtime.InvokerHelper;

import java.util.List;
import java.util.Map;

/**
 * An abstract base class for creating arbitrary nested trees of objects
 * or events
 *
 * @author <a href="mailto:james@coredevelopers.net">James Strachan
 * @version $Revision: 14613 $
 */
public abstract class BuilderSupport extends GroovyObjectSupport {

    private Object current;
    private Closure nameMappingClosure;
    private final BuilderSupport proxyBuilder;

    public BuilderSupport() {
        this.proxyBuilder = this;
    }

    public BuilderSupport(BuilderSupport proxyBuilder) {
        this(null, proxyBuilder);
    }

    public BuilderSupport(Closure nameMappingClosure, BuilderSupport proxyBuilder) {
        this.nameMappingClosure = nameMappingClosure;
        this.proxyBuilder = proxyBuilder;
    }

    /**
     * Convenience method when no arguments are required
     *
     * @param methodName the name of the method to invoke
     * @return the result of the call
     */
    public Object invokeMethod(String methodName) {
        return invokeMethod(methodName, null);
    }

    public Object invokeMethod(String methodName, Object args) {
        Object name = getName(methodName);
        return doInvokeMethod(methodName, name, args);
    }

    protected Object doInvokeMethod(String methodName, Object name, Object args) {
        Object node = null;
        Closure closure = null;
        List list = InvokerHelper.asList(args);

        //System.out.println("Called invokeMethod with name: " + name + " arguments: " + list);

        switch (list.size()) {
            case 0:
                node = proxyBuilder.createNode(name);
                break;
            case 1: {
                Object object = list.get(0);
                if (object instanceof Map) {
                    node = proxyBuilder.createNode(name, (Map) object);
                } else if (object instanceof Closure) {
                    closure = (Closure) object;
                    node = proxyBuilder.createNode(name);
                } else {
                    node = proxyBuilder.createNode(name, object);
                }
            }
            break;
            case 2: {
                Object object1 = list.get(0);
                Object object2 = list.get(1);
                if (object1 instanceof Map) {
                    if (object2 instanceof Closure) {
                        closure = (Closure) object2;
                        node = proxyBuilder.createNode(name, (Map) object1);
                    } else {
                        node = proxyBuilder.createNode(name, (Map) object1, object2);
                    }
                } else {
                    if (object2 instanceof Closure) {
                        closure = (Closure) object2;
                        node = proxyBuilder.createNode(name, object1);
                    } else if (object2 instanceof Map) {
                        node = proxyBuilder.createNode(name, (Map) object2, object1);
                    } else {
                        throw new MissingMethodException(name.toString(), getClass(), list.toArray(), false);
                    }
                }
            }
            break;
            case 3: {
                Object arg0 = list.get(0);
                Object arg1 = list.get(1);
                Object arg2 = list.get(2);
                if (arg0 instanceof Map && arg2 instanceof Closure) {
                    closure = (Closure) arg2;
                    node = proxyBuilder.createNode(name, (Map) arg0, arg1);
                } else if (arg1 instanceof Map && arg2 instanceof Closure) {
                    closure = (Closure) arg2;
                    node = proxyBuilder.createNode(name, (Map) arg1, arg0);
                } else {
                    throw new MissingMethodException(name.toString(), getClass(), list.toArray(), false);
                }
            }
            break;
            default: {
                throw new MissingMethodException(name.toString(), getClass(), list.toArray(), false);
            }

        }

        if (current != null) {
            proxyBuilder.setParent(current, node);
        }

        if (closure != null) {
            // push new node on stack
            Object oldCurrent = getCurrent();
            setCurrent(node);
            // let's register the builder as the delegate
            setClosureDelegate(closure, node);
            closure.call();
            setCurrent(oldCurrent);
        }

        proxyBuilder.nodeCompleted(current, node);
        return proxyBuilder.postNodeCompletion(current, node);
    }

    /**
     * A strategy method to allow derived builders to use
     * builder-trees and switch in different kinds of builders.
     * This method should call the setDelegate() method on the closure
     * which by default passes in this but if node is-a builder
     * we could pass that in instead (or do something wacky too)
     *
     * @param closure the closure on which to call setDelegate()
     * @param node    the node value that we've just created, which could be
     *                a builder
     */
    protected void setClosureDelegate(Closure closure, Object node) {
        closure.setDelegate(this);
    }

    protected abstract void setParent(Object parent, Object child);

    protected abstract Object createNode(Object name);

    protected abstract Object createNode(Object name, Object value);

    protected abstract Object createNode(Object name, Map attributes);

    protected abstract Object createNode(Object name, Map attributes, Object value);

    /**
     * A hook to allow names to be converted into some other object
     * such as a QName in XML or ObjectName in JMX.
     *
     * @param methodName the name of the desired method
     * @return the object representing the name
     */
    protected Object getName(String methodName) {
        if (nameMappingClosure != null) {
            return nameMappingClosure.call(methodName);
        }
        return methodName;
    }


    /**
     * A hook to allow nodes to be processed once they have had all of their
     * children applied.
     *
     * @param node   the current node being processed
     * @param parent the parent of the node being processed
     */
    protected void nodeCompleted(Object parent, Object node) {
    }

    /**
     * A hook to allow nodes to be processed once they have had all of their
     * children applied and allows the actual node object that represents
     * the Markup element to be changed
     *
     * @param node   the current node being processed
     * @param parent the parent of the node being processed
     * @return the node, possibly new, that represents the markup element
     */
    protected Object postNodeCompletion(Object parent, Object node) {
        return node;
    }

    protected Object getCurrent() {
        return current;
    }

    protected void setCurrent(Object current) {
        this.current = current;
    }
}

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