/*
* $Id$
*
* 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.struts2.components;
import java.io.Writer;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import org.apache.struts2.components.Param.UnnamedParametric;
import org.apache.struts2.util.MakeIterator;
import org.apache.struts2.util.MergeIteratorFilter;
import org.apache.struts2.views.annotations.StrutsTag;
import org.apache.struts2.views.annotations.StrutsTagAttribute;
import com.opensymphony.xwork2.util.ValueStack;
import com.opensymphony.xwork2.util.logging.Logger;
import com.opensymphony.xwork2.util.logging.LoggerFactory;
/**
* <!-- START SNIPPET: javadoc -->
* <p>Component for MergeIteratorTag, which job is to merge iterators and successive
* call to the merged iterator will cause each merge iterator to have a chance to
* expose its element, subsequently next call will allow the next iterator to expose
* its element. Once the last iterator is done exposing its element, the first iterator
* is allowed to do so again (unless it is exhausted of entries).</P>
*
* <p>Internally the task are delegated to MergeIteratorFilter</p>
*
* <p>Example if there are 3 lists being merged, each list have 3 entries, the following will
* be the logic.</P>
* <ol>
* <li>Display first element of the first list</li>
* <li>Display first element of the second list</li>
* <li>Display first element of the third list</li>
* <li>Display second element of the first list</li>
* <li>Display second element of the second list</li>
* <li>Display second element of the third list</li>
* <li>Display third element of the first list</li>
* <li>Display thrid element of the second list</li>
* <li>Display third element of the thrid list</li>
* </ol>
* <!-- END SNIPPET: javadoc -->
*
* <!-- START SNIPPET: params -->
* <ul>
* <li>id (String) - the id where the resultant merged iterator will be stored in the stack's context</li>
* </ul>
* <!-- END SNIPPET: params -->
*
*
* <!-- START SNIPPET: javacode -->
* public class MergeIteratorTagAction extends ActionSupport {
*
* private List myList1;
* private List myList2;
* private List myList3;
*
* public List getMyList1() {
* return myList1;
* }
*
* public List getMyList2() {
* return myList2;
* }
*
* public List getMyList3() {
* return myList3;
* }
*
*
* public String execute() throws Exception {
*
* myList1 = new ArrayList();
* myList1.add("1");
* myList1.add("2");
* myList1.add("3");
*
* myList2 = new ArrayList();
* myList2.add("a");
* myList2.add("b");
* myList2.add("c");
*
* myList3 = new ArrayList();
* myList3.add("A");
* myList3.add("B");
* myList3.add("C");
*
* return "done";
* }
* }
* <!-- END SNIPPET: javacode -->
*
* <!-- START SNIPPET: example -->
* <s:merge var="myMergedIterator1">
* <s:param value="%{myList1}" />
* <s:param value="%{myList2}" />
* <s:param value="%{myList3}" />
* </s:merge>
* <s:iterator value="%{#myMergedIterator1}">
* <s:property />
* </s:iterator>
* <!-- END SNIPPET: example -->
*
* <!-- START SNIPPET: description -->
* This wil generate "1aA2bB3cC".
* <!-- START SNIPPET: description -->
*
* @see org.apache.struts2.util.MergeIteratorFilter
* @see org.apache.struts2.views.jsp.iterator.MergeIteratorTag
*
*/
@StrutsTag(name="merge", tldTagClass="org.apache.struts2.views.jsp.iterator.MergeIteratorTag", description="Merge the values " +
"of a list of iterators into one iterator")
public class MergeIterator extends ContextBean implements UnnamedParametric {
private static final Logger LOG = LoggerFactory.getLogger(MergeIterator.class);
private MergeIteratorFilter mergeIteratorFilter = null;
private List _parameters;
public MergeIterator(ValueStack stack) {
super(stack);
}
public boolean start(Writer writer) {
mergeIteratorFilter = new MergeIteratorFilter();
_parameters = new ArrayList();
return super.start(writer);
}
public boolean end(Writer writer, String body) {
for (Iterator parametersIterator = _parameters.iterator(); parametersIterator.hasNext(); ) {
Object iteratorEntryObj = parametersIterator.next();
if (! MakeIterator.isIterable(iteratorEntryObj)) {
if (LOG.isWarnEnabled()) {
LOG.warn("param with value resolved as "+iteratorEntryObj+" cannot be make as iterator, it will be ignored and hence will not appear in the merged iterator");
}
continue;
}
mergeIteratorFilter.setSource(MakeIterator.convert(iteratorEntryObj));
}
mergeIteratorFilter.execute();
// if id exists, we put it in the stack's context
putInContext(mergeIteratorFilter);
mergeIteratorFilter = null;
return super.end(writer, body);
}
@StrutsTagAttribute(description="The name where the resultant merged iterator will be stored in the stack's context")
public void setVar(String var) {
super.setVar(var);
}
// == UnnamedParametric interface implementation ---------------------
public void addParameter(Object value) {
_parameters.add(value);
}
}