regexpfactory.java

来自「OpenJMS是一个开源的Java Message Service API 1.」· Java 代码 · 共 144 行

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 *    copy of this document.
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 *    please contact [e-mail].
 *
 * 4. Products derived from this Software may not be called "Exolab"
 *    nor may "Exolab" appear in their names without prior written
 *    permission of Exoffice Technologies. Exolab is a registered
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 * 5. Due credit should be given to the Exolab Project
 *    (http://www.exolab.org/).
 *
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 */

package org.exolab.jms.selector;

import org.apache.oro.text.regex.MalformedPatternException;
import org.apache.oro.text.regex.Pattern;
import org.apache.oro.text.regex.Perl5Compiler;


/**
 * Regular expression factory. This creates a regular expression for a given
 * SQL92 pattern and escape character.
 *
 * @version     $Revision: 1.1 $ $Date: 2004/11/26 01:50:44 $
 * @author      <a href="mailto:[e-mail]">Tim Anderson</a>
 */
final class RegexpFactory {

    /**
     * Private constructor
     */
    private RegexpFactory() {
    }

    /**
     * Converts the pattern and escape to an ORO <code>Pattern</code>
     *
     * @param pattern the pattern
     * @param escape the escape character. May be null
     * @return an ORO <code>Pattern</code> corresponding to
     * <code>pattern</code> and <code>escape</code>
     * @throws InvalidRegexpException if <code>pattern</code> or
     * <code>escape</code> are invalid
     */
    public static Pattern create(final String pattern, final Character escape)
        throws InvalidRegexpException {
        StringBuffer buff = new StringBuffer();
        buff.append('^');

        for (int i = 0; i < pattern.length(); ++i) {
            boolean escaped = false;
            char ch = pattern.charAt(i);
            if (escape != null && ch == escape.charValue()) {
                if (++i < pattern.length()) {
                    ch = pattern.charAt(i);
                    escaped = true;
                } else {
                    throw new InvalidRegexpException(pattern);
                }
            }

            switch (ch) {
                case '_':
                    if (escaped) {
                        buff.append(ch);
                    } else {
                        buff.append('.');
                    }
                    break;
                case '%':
                    if (escaped) {
                        buff.append(ch);
                    } else {
                        buff.append(".*");
                    }
                    break;
                case '.':
                case '[':
                case ']':
                case '\\':
                case '+':
                case '?':
                case '{':
                case '}':
                case '$':
                case '^':
                case '|':
                case '(':
                case ')':
                    // the above are all special characters that need to be
                    // escaped.
                    buff.append('\\');
                    buff.append(ch);
                    break;
                default:
                    buff.append(ch);
            }
        }
        buff.append('$');

        Pattern result = null;
        try {
            Perl5Compiler compiler = new Perl5Compiler();
            result = compiler.compile(buff.toString());
        } catch (MalformedPatternException exception) {
            // coding error if this gets thrown here...
            throw new InvalidRegexpException(pattern);
        }
        return result;
    }

} //-- RegexpFactory