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'databene commons' is an open source Java library by Volker Bergmann. It provides extensions to the Java core library by utility classes, abstract concepts and concrete implementations.

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/*
 * Copyright (C) 2004-2015 Volker Bergmann ([email protected]).
 * All rights reserved.
 *
 * 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.databene.commons.ui.swing;

import java.awt.Color;

import javax.swing.JTextField;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
import javax.swing.text.BadLocationException;

import org.databene.commons.xml.XPathUtil;

/**
 * Allows the user to enter an XPath definition, rendering illegal expressions in red.
 * Created: 25.05.2016 16:46:53
 * @since 1.0.11
 * @author Volker Bergmann
 */

public class XPathField extends JTextField {
	
	private static final long serialVersionUID = 1L;

	public XPathField(int columns) {
		this("", columns);
	}
	
	public XPathField(String text, int columns) {
		super(text, columns);
		getDocument().addDocumentListener(new XPathDocumentListener());
	}
	
	public boolean isXPathValid() {
		try {
			String text = getDocument().getText(0, getDocument().getLength());
			return XPathUtil.isValidXPath(text);
		} catch (BadLocationException e) {
			throw new RuntimeException("Internal error", e);
		}
	}
	
	protected class XPathDocumentListener implements DocumentListener {
		
		@Override
		public void changedUpdate(DocumentEvent evt) {
			checkValidity();
		}

		@Override
		public void insertUpdate(DocumentEvent evt) {
			checkValidity();
		}

		@Override
		public void removeUpdate(DocumentEvent evt) {
			checkValidity();
		}

		private void checkValidity() {
			setForeground(isXPathValid() ? Color.BLACK : Color.RED);
		}
	}
	
}