tabletagextrainfo.java

一个比较不错的java分页标签,有源代码,开发者 可以学习学习

/**
 * Licensed under the Artistic License; you may not use this file
 * except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://displaytag.sourceforge.net/license.html
 *
 * THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */
package org.displaytag.tags;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import javax.servlet.jsp.tagext.TagAttributeInfo;
import javax.servlet.jsp.tagext.TagData;
import javax.servlet.jsp.tagext.TagExtraInfo;
import javax.servlet.jsp.tagext.VariableInfo;


/**
 * TEI for TableTag, defines 3 variables.
 * <ul>
 * <li>table uid = object contained in row</li>
 * <li>table uid + ROWNUM_SUFFIX = row number</li>
 * </ul>
 * @author Fabrizio Giustina
 * @version $Revision: 763 $ ($Author: fgiust $)
 */
public class TableTagExtraInfo extends TagExtraInfo
{

    /**
     * Suffix added to id for saving row number in pagecontext.
     */
    public static final String ROWNUM_SUFFIX = "_rowNum"; //$NON-NLS-1$

    /**
     * Java keywords.
     */
    private static final String[] KEYWORDS = {"abstract", //$NON-NLS-1$
        "assert", //$NON-NLS-1$
        "boolean", //$NON-NLS-1$
        "break", //$NON-NLS-1$
        "byte", //$NON-NLS-1$
        "case", //$NON-NLS-1$
        "catch", //$NON-NLS-1$
        "char", //$NON-NLS-1$
        "class", //$NON-NLS-1$
        "const", //$NON-NLS-1$
        "continue", //$NON-NLS-1$
        "default", //$NON-NLS-1$
        "do", //$NON-NLS-1$
        "double", //$NON-NLS-1$
        "else", //$NON-NLS-1$
        "enum", //$NON-NLS-1$
        "extends", //$NON-NLS-1$
        "false", //$NON-NLS-1$
        "final", //$NON-NLS-1$
        "finally", //$NON-NLS-1$
        "float", //$NON-NLS-1$
        "for", //$NON-NLS-1$
        "goto", //$NON-NLS-1$
        "if", //$NON-NLS-1$
        "implements", //$NON-NLS-1$
        "import", //$NON-NLS-1$
        "instanceof", //$NON-NLS-1$
        "int", //$NON-NLS-1$
        "interface", //$NON-NLS-1$
        "long", //$NON-NLS-1$
        "native", //$NON-NLS-1$
        "new", //$NON-NLS-1$
        "null", //$NON-NLS-1$
        "package", //$NON-NLS-1$
        "private", //$NON-NLS-1$
        "protected", //$NON-NLS-1$
        "public", //$NON-NLS-1$
        "return", //$NON-NLS-1$
        "short", //$NON-NLS-1$
        "static", //$NON-NLS-1$
        "strictfp", //$NON-NLS-1$
        "super", //$NON-NLS-1$
        "switch", //$NON-NLS-1$
        "synchronized", //$NON-NLS-1$
        "this", //$NON-NLS-1$
        "throw", //$NON-NLS-1$
        "throws", //$NON-NLS-1$
        "transient", //$NON-NLS-1$
        "true", //$NON-NLS-1$
        "try", //$NON-NLS-1$
        "void", //$NON-NLS-1$
        "volatile", //$NON-NLS-1$
        "while"}; //$NON-NLS-1$

    /**
     * Variables TableTag makes available in the pageContext.
     * @param data TagData
     * @return VariableInfo[]
     * @see javax.servlet.jsp.tagext.TagData
     * @see javax.servlet.jsp.tagext.VariableInfo
     */
    public VariableInfo[] getVariableInfo(TagData data)
    {
        List variables = new ArrayList(2);

        Object idObj = data.getAttribute(TagAttributeInfo.ID);

        // handle both the id and uid attributes
        if (idObj == null)
        {
            idObj = data.getAttribute("uid"); //$NON-NLS-1$
        }

        // avoid errors, but "id" and "id_rownum" will not be defined
        if (idObj != TagData.REQUEST_TIME_VALUE && idObj != null)
        {
            String tagId = idObj.toString();

            // don't try to add variables if id is not a valid java identifier.
            if (isJavaId(tagId))
            {
                // current row
                variables.add(new VariableInfo(tagId, Object.class.getName(), true, VariableInfo.NESTED));
                // current row number
                variables.add(new VariableInfo(
                    tagId + ROWNUM_SUFFIX,
                    Integer.class.getName(),
                    true,
                    VariableInfo.NESTED));
            }
        }

        return (VariableInfo[]) variables.toArray(new VariableInfo[]{});
    }

    /**
     * isJavaId Returns true if the name is a valid java identifier.
     * @param id to check
     * @return boolean true/false
     */
    public static boolean isJavaId(String id)
    {
        if (id == null
            || id.length() == 0
            || Arrays.binarySearch(KEYWORDS, id) >= 0
            || !Character.isJavaIdentifierStart(id.charAt(0)))
        {
            return false;
        }

        for (int j = 1; j < id.length(); j++)
        {
            if (!Character.isJavaIdentifierPart(id.charAt(j)))
            {
                return false;
            }
        }
        return true;
    }

}