解析xml工具类

XmlUtils.java
 
/*
 
 * Copyright 2007 The JA-SIG Collaborative. All rights reserved. See license
 
 * distributed with this file and available online at
 
 * http://www.ja-sig.org/products/cas/overview/license/index.html
 
 */
 
package org.jasig.cas.client.util;
 

import org.apache.commons.logging.Log;
 
import org.apache.commons.logging.LogFactory;
 
import org.xml.sax.Attributes;
 
import org.xml.sax.InputSource;
 
import org.xml.sax.SAXException;
 
import org.xml.sax.XMLReader;
 
import org.xml.sax.helpers.DefaultHandler;
 
import org.xml.sax.helpers.XMLReaderFactory;
 

import java.io.StringReader;
 
import java.util.ArrayList;
 
import java.util.List;
 

/**
 
 * Common utilities for easily parsing XML without duplicating logic.
 
 *
 
 * @author Scott Battaglia
 
 * @version $Revision: 11729 $ $Date: 2007-09-26 14:22:30 -0400 (Tue, 26 Sep 2007) $
 
 * @since 3.0
 
 */
 
public final class XmlUtils {
 

    /**
 
     * Static instance of Commons Logging.
 
     */
 
    private final static Log LOG = LogFactory.getLog(XmlUtils.class);
 

    /**
 
     * Get an instance of an XML reader from the XMLReaderFactory.
 
     *
 
     * @return the XMLReader.
 
     */
 
    public static XMLReader getXmlReader() {
 
        try {
 
            return XMLReaderFactory.createXMLReader();
 
        } catch (final SAXException e) {
 
            throw new RuntimeException("Unable to create XMLReader", e);
 
        }
 
    }
 

    /**
 
     * Retrieve the text for a group of elements. Each text element is an entry
 
     * in a list.
 
     * <p>This method is currently optimized for the use case of two elements in a list.
 
     *
 
     * @param xmlAsString the xml response
 
     * @param element     the element to look for
 
     * @return the list of text from the elements.
 
     */
 
    public static List getTextForElements(final String xmlAsString,
 
                                          final String element) {
 
        final List elements = new ArrayList(2);
 
        final XMLReader reader = getXmlReader();
 

        final DefaultHandler handler = new DefaultHandler() {
 

            private boolean foundElement = false;
 

            private StringBuffer buffer = new StringBuffer();
 

            public void startElement(final String uri, final String localName,
 
                                     final String qName, final Attributes attributes)
 
                    throws SAXException {
 
                if (localName.equals(element)) {
 
                    this.foundElement = true;
 
                }
 
            }
 

            public void endElement(final String uri, final String localName,
 
                                   final String qName) throws SAXException {
 
                if (localName.equals(element)) {
 
                    this.foundElement = false;
 
                    elements.add(this.buffer.toString());
 
                    this.buffer = new StringBuffer();
 
                }
 
            }
 

            public void characters(char[] ch, int start, int length)
 
                    throws SAXException {
 
                if (this.foundElement) {
 
                    this.buffer.append(ch, start, length);
 
                }
 
            }
 
        };
 

        reader.setContentHandler(handler);
 
        reader.setErrorHandler(handler);
 

        try {
 
            reader.parse(new InputSource(new StringReader(xmlAsString)));
 
        } catch (final Exception e) {
 
            LOG.error(e, e);
 
            return null;
 
        }
 

        return elements;
 
    }
 

    /**
 
     * Retrieve the text for a specific element (when we know there is only
 
     * one).
 
     *
 
     * @param xmlAsString the xml response
 
     * @param element     the element to look for
 
     * @return the text value of the element.
 
     */
 
    public static String getTextForElement(final String xmlAsString,
 
                                           final String element) {
 
        final XMLReader reader = getXmlReader();
 
        final StringBuffer buffer = new StringBuffer();
 

        final DefaultHandler handler = new DefaultHandler() {
 

            private boolean foundElement = false;
 

            public void startElement(final String uri, final String localName,
 
                                     final String qName, final Attributes attributes)
 
                    throws SAXException {
 
                if (localName.equals(element)) {
 
                    this.foundElement = true;
 
                }
 
            }
 

            public void endElement(final String uri, final String localName,
 
                                   final String qName) throws SAXException {
 
                if (localName.equals(element)) {
 
                    this.foundElement = false;
 
                }
 
            }
 

            public void characters(char[] ch, int start, int length)
 
                    throws SAXException {
 
                if (this.foundElement) {
 
                    buffer.append(ch, start, length);
 
                }
 
            }
 
        };
 

        reader.setContentHandler(handler);
 
        reader.setErrorHandler(handler);
 

        try {
 
            reader.parse(new InputSource(new StringReader(xmlAsString)));
 
        } catch (final Exception e) {
 
            LOG.error(e, e);
 
            return null;
 
        }
 

        return buffer.toString();
 
    }
 
}