Java Tutorial/XML/Entities

Escapes all necessary characters in the String so that it can be used in an XML doc

/**
 * $Revision: 10205 $
 * $Date: 2008-04-11 15:48:27 -0700 (Fri, 11 Apr 2008) $
 *
 * Copyright (C) 2004-2008 Jive Software. All rights reserved.
 *
 * This software is published under the terms of the GNU Public License (GPL),
 * a copy of which is included in this distribution, or a commercial license
 * agreement with Jive.
 */
import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.text.BreakIterator;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
/**
 * Utility class to peform common String manipulation algorithms.
 */
public class StringUtils {
    // Constants used by escapeHTMLTags
    private static final char[] QUOTE_ENCODE = """.toCharArray();
    private static final char[] AMP_ENCODE = "&".toCharArray();
    private static final char[] LT_ENCODE = "<".toCharArray();
    private static final char[] GT_ENCODE = ">".toCharArray();
    private StringUtils() {
        // Not instantiable.
    }
    /**
     * Escapes all necessary characters in the String so that it can be used
     * in an XML doc.
     *
     * @param string the string to escape.
     * @return the string with appropriate characters escaped.
     */
    public static String escapeForXML(String string) {
        if (string == null) {
            return null;
        }
        char ch;
        int i = 0;
        int last = 0;
        char[] input = string.toCharArray();
        int len = input.length;
        StringBuilder out = new StringBuilder((int)(len * 1.3));
        for (; i < len; i++) {
            ch = input[i];
            if (ch > ">") {
            }
            else if (ch == "<") {
                if (i > last) {
                    out.append(input, last, i - last);
                }
                last = i + 1;
                out.append(LT_ENCODE);
            }
            else if (ch == "&") {
                if (i > last) {
                    out.append(input, last, i - last);
                }
                last = i + 1;
                out.append(AMP_ENCODE);
            }
            else if (ch == """) {
                if (i > last) {
                    out.append(input, last, i - last);
                }
                last = i + 1;
                out.append(QUOTE_ENCODE);
            }
        }
        if (last == 0) {
            return string;
        }
        if (i > last) {
            out.append(input, last, i - last);
        }
        return out.toString();
    }
}

Preventing Expansion of Entity References While Parsing an XML File

import java.io.File;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
public class Main {
  public static void main(String[] argv) throws Exception{
    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    factory.setValidating(true);
    // Prevent expansion of entity references
    factory.setExpandEntityReferences(false);
    // Create the builder and parse the file
    Document doc = factory.newDocumentBuilder().parse(new File("filename"));
  }
}

Resolving entities found in source XML during parsing

import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.Attributes;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.xml.sax.helpers.DefaultHandler;
public class Main {
  public static void main(String[] argv) throws Exception {
    SAXParserFactory factory = SAXParserFactory.newInstance();
    factory.setValidating(true);
    SAXParser parser = factory.newSAXParser();
    SaxHandler handler = new SaxHandler();
    parser.parse("sample.xml", handler);
  }
}
class SaxHandler extends DefaultHandler {
  public InputSource resolveEntity(String publicId, String systemId) {
    if (systemId.equals("http://www.my-company.ru/order-1.0.dtd")) {
      return new InputSource(getClass().getResourceAsStream("order.dtd"));
    } else {
      return null;
    }
  }
  public void startElement(String uri, String localName, String qName, Attributes attrs)
      throws SAXException {
    if (qName.equals("order")) {
    }
  }
  public void error(SAXParseException ex) throws SAXException {
    System.out.println("ERROR: [at " + ex.getLineNumber() + "] " + ex);
  }
  public void fatalError(SAXParseException ex) throws SAXException {
    System.out.println("FATAL_ERROR: [at " + ex.getLineNumber() + "] " + ex);
  }
  public void warning(SAXParseException ex) throws SAXException {
    System.out.println("WARNING: [at " + ex.getLineNumber() + "] " + ex);
  }
}