patternvalidator.java

实现了Jms的服务器源码,支持多种适配器,DB,FTP,支持多种数据库

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 */

package org.exolab.jms.selector.parser;

import org.exolab.jms.selector.SelectorException;


/**
 * This class validates the format of patterns and escape characters used
 * in 'like' expressions.
 *
 * @version     $Revision: 1.4 $ $Date: 2003/08/09 15:49:50 $
 * @author      <a href="mailto:[e-mail]">Tim Anderson</a>
 * @see         SelectorAST
 * @see         SelectorParser
 */
final class PatternValidator {

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

    /**
     * Validate a pattern and escape
     *
     * @param patternNode the pattern node
     * @param escapeNode the escape node. May be null.
     * @throws SelectorException if the pattern or escape node are invalid
     */
    public static void validate(final SelectorAST patternNode,
                                final SelectorAST escapeNode)
        throws SelectorException {

        String pattern = patternNode.getText();

        if (escapeNode != null) {
            String escape = escapeNode.getText();
            if (escape.length() != 1) {
                String msg = "escape must be a single character";
                throw new SelectorException(escapeNode.getContext(), msg);
            }

            char esc = escape.charAt(0);
            for (int i = 0; i < pattern.length(); ++i) {
                char ch = pattern.charAt(i);
                if (pattern.charAt(i) == esc) {
                    if (++i >= pattern.length()) {
                        String msg = "invalid pattern: no character "
                            + "following last escape character";
                        throw new SelectorException(patternNode.getContext(),
                                                    msg);
                    }
                }
            }
        }
    }

} //-- PatternValidator