/*
* $Id: IterateTag.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 org.apache.struts.util.IteratorAdapter;
import org.apache.struts.util.MessageResources;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.BodyTagSupport;
import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.Map;
/**
* Custom tag that iterates the elements of a collection, which can be either
* an attribute or the property of an attribute. The collection can be any of
* the following: an array of objects, an Enumeration, an Iterator, a
* Collection (which includes Lists, Sets and Vectors), or a Map (which
* includes Hashtables) whose elements will be iterated over.
*
* @version $Rev: 471754 $ $Date: 2004-11-03 14:20:47 -0500 (Wed, 03 Nov 2004)
* $
*/
public class IterateTag extends BodyTagSupport {
/**
* The message resources for this package.
*/
protected static MessageResources messages =
MessageResources.getMessageResources(
"org.apache.struts.taglib.logic.LocalStrings");
// ----------------------------------------------------- Instance Variables
/**
* Iterator of the elements of this collection, while we are actually
* running.
*/
protected Iterator iterator = null;
/**
* The number of elements we have already rendered.
*/
protected int lengthCount = 0;
/**
* The actual length value (calculated in the start tag).
*/
protected int lengthValue = 0;
/**
* The actual offset value (calculated in the start tag).
*/
protected int offsetValue = 0;
/**
* Has this tag instance been started?
*/
protected boolean started = false;
// ------------------------------------------------------------- Properties
/**
* The collection over which we will be iterating.
*/
protected Object collection = null;
/**
* The name of the scripting variable to be exposed.
*/
protected String id = null;
/**
* The name of the scripting variable to be exposed as the current index.
*/
protected String indexId = null;
/**
* The length value or attribute name (<=0 means no limit).
*/
protected String length = null;
/**
* The name of the collection or owning bean.
*/
protected String name = null;
/**
* The starting offset (zero relative).
*/
protected String offset = null;
/**
* The property name containing the collection.
*/
protected String property = null;
/**
* The scope of the bean specified by the name property, if any.
*/
protected String scope = null;
/**
* The Java class of each exposed element of the collection.
*/
protected String type = null;
public Object getCollection() {
return (this.collection);
}
public void setCollection(Object collection) {
this.collection = collection;
}
public String getId() {
return (this.id);
}
public void setId(String id) {
this.id = id;
}
/**
* <p>Return the zero-relative index of the current iteration through the
* loop. If you specify an <code>offset</code>, the first iteration
* through the loop will have that value; otherwise, the first iteration
* will return zero.</p>
*
* <p>This property is read-only, and gives nested custom tags access to
* this information. Therefore, it is <strong>only</strong> valid in
* between calls to <code>doStartTag()</code> and <code>doEndTag()</code>.
* </p>
*/
public int getIndex() {
if (started) {
return ((offsetValue + lengthCount) - 1);
} else {
return (0);
}
}
public String getIndexId() {
return (this.indexId);
}
public void setIndexId(String indexId) {
this.indexId = indexId;
}
public String getLength() {
return (this.length);
}
public void setLength(String length) {
this.length = length;
}
public String getName() {
return (this.name);
}
public void setName(String name) {
this.name = name;
}
public String getOffset() {
return (this.offset);
}
public void setOffset(String offset) {
this.offset = offset;
}
public String getProperty() {
return (this.property);
}
public void setProperty(String property) {
this.property = property;
}
public String getScope() {
return (this.scope);
}
public void setScope(String scope) {
this.scope = scope;
}
public String getType() {
return (this.type);
}
public void setType(String type) {
this.type = type;
}
// --------------------------------------------------------- Public Methods
/**
* Construct an iterator for the specified collection, and begin looping
* through the body once per element.
*
* @throws JspException if a JSP exception has occurred
*/
public int doStartTag() throws JspException {
// Acquire the collection we are going to iterate over
Object collection = this.collection;
if (collection == null) {
collection =
TagUtils.getInstance().lookup(pageContext, name, property,
scope);
}
if (collection == null) {
JspException e =
new JspException(messages.getMessage("iterate.collection"));
TagUtils.getInstance().saveException(pageContext, e);
throw e;
}
// Construct an iterator for this collection
if (collection.getClass().isArray()) {
try {
// If we're lucky, it is an array of objects
// that we can iterate over with no copying
iterator = Arrays.asList((Object[]) collection).iterator();
} catch (ClassCastException e) {
// Rats -- it is an array of primitives
int length = Array.getLength(collection);
ArrayList c = new ArrayList(length);
for (int i = 0; i < length; i++) {
c.add(Array.get(collection, i));
}
iterator = c.iterator();
}
} else if (collection instanceof Collection) {
iterator = ((Collection) collection).iterator();
} else if (collection instanceof Iterator) {
iterator = (Iterator) collection;
} else if (collection instanceof Map) {
iterator = ((Map) collection).entrySet().iterator();
} else if (collection instanceof Enumeration) {
iterator = new IteratorAdapter((Enumeration) collection);
} else {
JspException e =
new JspException(messages.getMessage("iterate.iterator"));
TagUtils.getInstance().saveException(pageContext, e);
throw e;
}
// Calculate the starting offset
if (offset == null) {
offsetValue = 0;
} else {
try {
offsetValue = Integer.parseInt(offset);
} catch (NumberFormatException e) {
Integer offsetObject =
(Integer) TagUtils.getInstance().lookup(pageContext,
offset, null);
if (offsetObject == null) {
offsetValue = 0;
} else {
offsetValue = offsetObject.intValue();
}
}
}
if (offsetValue < 0) {
offsetValue = 0;
}
// Calculate the rendering length
if (length == null) {
lengthValue = 0;
} else {
try {
lengthValue = Integer.parseInt(length);
} catch (NumberFormatException e) {
Integer lengthObject =
(Integer) TagUtils.getInstance().lookup(pageContext,
length, null);
if (lengthObject == null) {
lengthValue = 0;
} else {
lengthValue = lengthObject.intValue();
}
}
}
if (lengthValue < 0) {
lengthValue = 0;
}
lengthCount = 0;
// Skip the leading elements up to the starting offset
for (int i = 0; i < offsetValue; i++) {
if (iterator.hasNext()) {
iterator.next();
}
}
// Store the first value and evaluate, or skip the body if none
if (iterator.hasNext()) {
Object element = iterator.next();
if (element == null) {
pageContext.removeAttribute(id);
} else {
pageContext.setAttribute(id, element);
}
lengthCount++;
started = true;
if (indexId != null) {
pageContext.setAttribute(indexId, new Integer(getIndex()));
}
return (EVAL_BODY_TAG);
} else {
return (SKIP_BODY);
}
}
/**
* Make the next collection element available and loop, or finish the
* iterations if there are no more elements.
*
* @throws JspException if a JSP exception has occurred
*/
public int doAfterBody() throws JspException {
// Render the output from this iteration to the output stream
if (bodyContent != null) {
TagUtils.getInstance().writePrevious(pageContext,
bodyContent.getString());
bodyContent.clearBody();
}
// Decide whether to iterate or quit
if ((lengthValue > 0) && (lengthCount >= lengthValue)) {
return (SKIP_BODY);
}
if (iterator.hasNext()) {
Object element = iterator.next();
if (element == null) {
pageContext.removeAttribute(id);
} else {
pageContext.setAttribute(id, element);
}
lengthCount++;
if (indexId != null) {
pageContext.setAttribute(indexId, new Integer(getIndex()));
}
return (EVAL_BODY_TAG);
} else {
return (SKIP_BODY);
}
}
/**
* Clean up after processing this enumeration.
*
* @throws JspException if a JSP exception has occurred
*/
public int doEndTag() throws JspException {
// Clean up our started state
started = false;
iterator = null;
// Continue processing this page
return (EVAL_PAGE);
}
/**
* Release all allocated resources.
*/
public void release() {
super.release();
iterator = null;
lengthCount = 0;
lengthValue = 0;
offsetValue = 0;
id = null;
collection = null;
length = null;
name = null;
offset = null;
property = null;
scope = null;
started = false;
}
}