listisemptytag.java

OA典型例子

/*
 * $Id: ListIsEmptyTag.java,v 1.1 2001/10/18 00:46:05 ro89390 Exp $
 * Copyright 2001 Sun Microsystems, Inc. All rights reserved.
 */

package com.sure.taglibs.list;

import com.sure.taglibs.smart.*;

import javax.servlet.jsp.JspTagException;
import javax.servlet.jsp.tagext.BodyTagSupport;

import java.util.Collection;

/**
 * A conditional tag returning whether a list is empty.
 */
public class ListIsEmptyTag extends ConditionalTag {

    protected boolean doTest(Object o) throws JspTagException {
        if (o == null) {
            return true;
        }
        else if (o instanceof Collection) {
            return ((Collection) o).isEmpty();
        }
        else {
            throw new JspTagException("ListIsEmptyTag: Not a Collection.");
        }
    }
}