org.teiid.language.visitor.DelegatingHierarchyVisitor Maven / Gradle / Ivy
/*
* Copyright Red Hat, Inc. and/or its affiliates
* and other contributors as indicated by the @author tags and
* the COPYRIGHT.txt file distributed with this work.
*
* 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.teiid.language.visitor;
import org.teiid.connector.DataPlugin;
import org.teiid.language.LanguageObject;
/**
* Delegates pre- and post-processing for each node in the hierarchy to
* delegate visitors.
*/
public class DelegatingHierarchyVisitor extends HierarchyVisitor {
private LanguageObjectVisitor postVisitor = null;
private LanguageObjectVisitor preVisitor = null;
public DelegatingHierarchyVisitor(LanguageObjectVisitor preProcessingDelegate,
LanguageObjectVisitor postProcessingDelegate) {
if (preProcessingDelegate == null && postProcessingDelegate == null) {
throw new IllegalArgumentException(DataPlugin.Util.getString("DelegatingHierarchyVisitor.The_pre-_and_post-processing_visitors_cannot_both_be_null._1")); //$NON-NLS-1$
}
this.preVisitor = preProcessingDelegate;
this.postVisitor = postProcessingDelegate;
}
protected LanguageObjectVisitor getPostVisitor() {
return postVisitor;
}
protected LanguageObjectVisitor getPreVisitor() {
return preVisitor;
}
@Override
public void visitNode(LanguageObject obj) {
if (obj == null) {
return;
}
if (preVisitor != null) {
obj.acceptVisitor(preVisitor);
}
super.visitNode(obj);
if (postVisitor != null) {
obj.acceptVisitor(postVisitor);
}
}
/**
* This utility method can be used to execute the behaviorVisitor in a pre-order walk
* of the language objects. "Pre-order" in this case means that the visit method of the
* behaviorVisitor will be called before the visit method of it's children. It is expected
* that the behavior visit does NOT perform iteration, as that function will be performed
* by the HierarchyVisitor.
* @param behaviorVisitor The visitor specifying what behavior is performed at each node type
* @param object The root of the object tree to perform visitation on
*/
public static void preOrderVisit(LanguageObjectVisitor behaviorVisitor, LanguageObject object) {
DelegatingHierarchyVisitor hierarchyVisitor = new DelegatingHierarchyVisitor(behaviorVisitor, null);
object.acceptVisitor(hierarchyVisitor);
}
/**
* This utility method can be used to execute the behaviorVisitor in a post-order walk
* of the language objects. "Post-order" in this case means that the visit method of the
* behaviorVisitor will be called after the visit method of it's children. It is expected
* that the behavior visit does NOT perform iteration, as that function will be performed
* by the HierarchyVisitor.
* @param behaviorVisitor The visitor specifying what behavior is performed at each node type
* @param object The root of the object tree to perform visitation on
*/
public static void postOrderVisit(LanguageObjectVisitor behaviorVisitor, LanguageObject object) {
DelegatingHierarchyVisitor hierarchyVisitor = new DelegatingHierarchyVisitor(null, behaviorVisitor);
object.acceptVisitor(hierarchyVisitor);
}
}