/*
* Copyright 2002-2014 the original author or authors.
*
* Licensed 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.springframework.web.servlet.tags.form;
import java.util.Collection;
import java.util.Map;
import javax.servlet.jsp.JspException;
import org.springframework.util.ObjectUtils;
import org.springframework.web.bind.WebDataBinder;
import org.springframework.web.servlet.support.BindStatus;
/**
* Databinding-aware JSP tag that renders an HTML '{@code select}'
* element.
*
* <p>Inner '{@code option}' tags can be rendered using one of the
* approaches supported by the OptionWriter class.
*
* <p>Also supports the use of nested {@link OptionTag OptionTags} or
* (typically one) nested {@link OptionsTag}.
*
* @author Rob Harrop
* @author Juergen Hoeller
* @since 2.0
* @see OptionTag
*/
@SuppressWarnings("serial")
public class SelectTag extends AbstractHtmlInputElementTag {
/**
* The {@link javax.servlet.jsp.PageContext} attribute under
* which the bound value is exposed to inner {@link OptionTag OptionTags}.
*/
public static final String LIST_VALUE_PAGE_ATTRIBUTE =
"org.springframework.web.servlet.tags.form.SelectTag.listValue";
/**
* Marker object for items that have been specified but resolve to null.
* Allows to differentiate between 'set but null' and 'not set at all'.
*/
private static final Object EMPTY = new Object();
/**
* The {@link Collection}, {@link Map} or array of objects used to generate the inner
* '{@code option}' tags.
*/
private Object items;
/**
* The name of the property mapped to the '{@code value}' attribute
* of the '{@code option}' tag.
*/
private String itemValue;
/**
* The name of the property mapped to the inner text of the
* '{@code option}' tag.
*/
private String itemLabel;
/**
* The value of the HTML '{@code size}' attribute rendered
* on the final '{@code select}' element.
*/
private String size;
/**
* Indicates whether or not the '{@code select}' tag allows
* multiple-selections.
*/
private Object multiple;
/**
* The {@link TagWriter} instance that the output is being written.
* <p>Only used in conjunction with nested {@link OptionTag OptionTags}.
*/
private TagWriter tagWriter;
/**
* Set the {@link Collection}, {@link Map} or array of objects used to
* generate the inner '{@code option}' tags.
* <p>Required when wishing to render '{@code option}' tags from
* an array, {@link Collection} or {@link Map}.
* <p>Typically a runtime expression.
* @param items the items that comprise the options of this selection
*/
public void setItems(Object items) {
this.items = (items != null ? items : EMPTY);
}
/**
* Get the value of the '{@code items}' attribute.
* <p>May be a runtime expression.
*/
protected Object getItems() {
return this.items;
}
/**
* Set the name of the property mapped to the '{@code value}'
* attribute of the '{@code option}' tag.
* <p>Required when wishing to render '{@code option}' tags from
* an array or {@link Collection}.
* <p>May be a runtime expression.
*/
public void setItemValue(String itemValue) {
this.itemValue = itemValue;
}
/**
* Get the value of the '{@code itemValue}' attribute.
* <p>May be a runtime expression.
*/
protected String getItemValue() {
return this.itemValue;
}
/**
* Set the name of the property mapped to the label (inner text) of the
* '{@code option}' tag.
* <p>May be a runtime expression.
*/
public void setItemLabel(String itemLabel) {
this.itemLabel = itemLabel;
}
/**
* Get the value of the '{@code itemLabel}' attribute.
* <p>May be a runtime expression.
*/
protected String getItemLabel() {
return this.itemLabel;
}
/**
* Set the value of the HTML '{@code size}' attribute rendered
* on the final '{@code select}' element.
*/
public void setSize(String size) {
this.size = size;
}
/**
* Get the value of the '{@code size}' attribute.
*/
protected String getSize() {
return this.size;
}
/**
* Set the value of the HTML '{@code multiple}' attribute rendered
* on the final '{@code select}' element.
*/
public void setMultiple(Object multiple) {
this.multiple = multiple;
}
/**
* Get the value of the HTML '{@code multiple}' attribute rendered
* on the final '{@code select}' element.
*/
protected Object getMultiple() {
return this.multiple;
}
/**
* Renders the HTML '{@code select}' tag to the supplied
* {@link TagWriter}.
* <p>Renders nested '{@code option}' tags if the
* {@link #setItems items} property is set, otherwise exposes the
* bound value for the nested {@link OptionTag OptionTags}.
*/
@Override
protected int writeTagContent(TagWriter tagWriter) throws JspException {
tagWriter.startTag("select");
writeDefaultAttributes(tagWriter);
if (isMultiple()) {
tagWriter.writeAttribute("multiple", "multiple");
}
tagWriter.writeOptionalAttributeValue("size", getDisplayString(evaluate("size", getSize())));
Object items = getItems();
if (items != null) {
// Items specified, but might still be empty...
if (items != EMPTY) {
Object itemsObject = evaluate("items", items);
if (itemsObject != null) {
final String selectName = getName();
String valueProperty = (getItemValue() != null ?
ObjectUtils.getDisplayString(evaluate("itemValue", getItemValue())) : null);
String labelProperty = (getItemLabel() != null ?
ObjectUtils.getDisplayString(evaluate("itemLabel", getItemLabel())) : null);
OptionWriter optionWriter =
new OptionWriter(itemsObject, getBindStatus(), valueProperty, labelProperty, isHtmlEscape()) {
@Override
protected String processOptionValue(String resolvedValue) {
return processFieldValue(selectName, resolvedValue, "option");
}
};
optionWriter.writeOptions(tagWriter);
}
}
tagWriter.endTag(true);
writeHiddenTagIfNecessary(tagWriter);
return SKIP_BODY;
}
else {
// Using nested <form:option/> tags, so just expose the value in the PageContext...
tagWriter.forceBlock();
this.tagWriter = tagWriter;
this.pageContext.setAttribute(LIST_VALUE_PAGE_ATTRIBUTE, getBindStatus());
return EVAL_BODY_INCLUDE;
}
}
/**
* If using a multi-select, a hidden element is needed to make sure all
* items are correctly unselected on the server-side in response to a
* {@code null} post.
*/
private void writeHiddenTagIfNecessary(TagWriter tagWriter) throws JspException {
if (isMultiple()) {
tagWriter.startTag("input");
tagWriter.writeAttribute("type", "hidden");
String name = WebDataBinder.DEFAULT_FIELD_MARKER_PREFIX + getName();
tagWriter.writeAttribute("name", name);
tagWriter.writeAttribute("value", processFieldValue(name, "1", "hidden"));
tagWriter.endTag();
}
}
private boolean isMultiple() throws JspException {
Object multiple = getMultiple();
if (multiple != null) {
String stringValue = multiple.toString();
return ("multiple".equalsIgnoreCase(stringValue) || Boolean.parseBoolean(stringValue));
}
return forceMultiple();
}
/**
* Returns '{@code true}' if the bound value requires the
* resultant '{@code select}' tag to be multi-select.
*/
private boolean forceMultiple() throws JspException {
BindStatus bindStatus = getBindStatus();
Class<?> valueType = bindStatus.getValueType();
if (valueType != null && typeRequiresMultiple(valueType)) {
return true;
}
else if (bindStatus.getEditor() != null) {
Object editorValue = bindStatus.getEditor().getValue();
if (editorValue != null && typeRequiresMultiple(editorValue.getClass())) {
return true;
}
}
return false;
}
/**
* Returns '{@code true}' for arrays, {@link Collection Collections}
* and {@link Map Maps}.
*/
private static boolean typeRequiresMultiple(Class<?> type) {
return (type.isArray() || Collection.class.isAssignableFrom(type) || Map.class.isAssignableFrom(type));
}
/**
* Closes any block tag that might have been opened when using
* nested {@link OptionTag options}.
*/
@Override
public int doEndTag() throws JspException {
if (this.tagWriter != null) {
this.tagWriter.endTag();
writeHiddenTagIfNecessary(tagWriter);
}
return EVAL_PAGE;
}
/**
* Clears the {@link TagWriter} that might have been left over when using
* nested {@link OptionTag options}.
*/
@Override
public void doFinally() {
super.doFinally();
this.tagWriter = null;
this.pageContext.removeAttribute(LIST_VALUE_PAGE_ATTRIBUTE);
}
}