/*
* $Id: EmptyTag.java 471754 2006-11-06 14:55:09Z husted $
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.struts.taglib.logic;
import org.apache.struts.taglib.TagUtils;
import javax.servlet.jsp.JspException;
import java.lang.reflect.Array;
import java.util.Collection;
import java.util.Map;
/**
* Evalute the nested body content of this tag if the specified value is empty
* for this request.
*
* @version $Rev: 471754 $ $Date: 2004-10-16 12:38:42 -0400 (Sat, 16 Oct 2004)
* $
* @since Struts 1.1
*/
public class EmptyTag extends ConditionalTagBase {
// ------------------------------------------------------ Protected Methods
/**
* Evaluate the condition that is being tested by this particular tag, and
* return <code>true</code> if the nested body content of this tag should
* be evaluated, or <code>false</code> if it should be skipped. This
* method must be implemented by concrete subclasses.
*
* @throws JspException if a JSP exception occurs
*/
protected boolean condition()
throws JspException {
return (condition(true));
}
/**
* Evaluate the condition that is being tested by this particular tag, and
* return <code>true</code> if the nested body content of this tag should
* be evaluated, or <code>false</code> if it should be skipped. This
* method must be implemented by concrete subclasses.
*
* @param desired Desired outcome for a true result
* @throws JspException if a JSP exception occurs
*/
protected boolean condition(boolean desired)
throws JspException {
if (this.name == null) {
JspException e =
new JspException(messages.getMessage("empty.noNameAttribute"));
TagUtils.getInstance().saveException(pageContext, e);
throw e;
}
Object value = null;
if (this.property == null) {
value = TagUtils.getInstance().lookup(pageContext, name, scope);
} else {
value =
TagUtils.getInstance().lookup(pageContext, name, property, scope);
}
boolean empty = true;
if (value == null) {
empty = true;
} else if (value instanceof String) {
String strValue = (String) value;
empty = (strValue.length() < 1);
} else if (value instanceof Collection) {
Collection collValue = (Collection) value;
empty = collValue.isEmpty();
} else if (value instanceof Map) {
Map mapValue = (Map) value;
empty = mapValue.isEmpty();
} else if (value.getClass().isArray()) {
empty = Array.getLength(value) == 0;
} else {
empty = false;
}
return (empty == desired);
}
}