org.springframework.web.servlet.tags.form.LabelTag Maven / Gradle / Ivy
/*
* Copyright 2002-2007 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 javax.servlet.jsp.JspException;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;
/**
* Databinding-aware JSP tag for rendering an HTML 'label' element
* that defines text that is associated with a single form element.
*
* The {@link #setFor(String) 'for'} attribute is required.
*
*
See the "formTags" showcase application that ships with the
* full Spring distribution for an example of this class in action.
*
* @author Rob Harrop
* @author Juergen Hoeller
* @since 2.0
*/
public class LabelTag extends AbstractHtmlElementTag {
/**
* The HTML 'label' tag.
*/
private static final String LABEL_TAG = "label";
/**
* The name of the 'for' attribute.
*/
private static final String FOR_ATTRIBUTE = "for";
/**
* The {@link TagWriter} instance being used.
*
Stored so we can close the tag on {@link #doEndTag()}.
*/
private TagWriter tagWriter;
/**
* The value of the 'for' attribute.
*/
private String forId;
/**
* Set the value of the 'for' attribute.
*
Defaults to the value of {@link #getPath}; may be a runtime expression.
* @throws IllegalArgumentException if the supplied value is null
*/
public void setFor(String forId) {
Assert.notNull(forId, "'forId' must not be null");
this.forId = forId;
}
/**
* Get the value of the 'id' attribute.
*
May be a runtime expression.
*/
public String getFor() {
return this.forId;
}
/**
* Writes the opening 'label' tag and forces a block tag so
* that body content is written correctly.
* @return {@link javax.servlet.jsp.tagext.Tag#EVAL_BODY_INCLUDE}
*/
protected int writeTagContent(TagWriter tagWriter) throws JspException {
tagWriter.startTag(LABEL_TAG);
tagWriter.writeAttribute(FOR_ATTRIBUTE, resolveFor());
writeDefaultAttributes(tagWriter);
tagWriter.forceBlock();
this.tagWriter = tagWriter;
return EVAL_BODY_INCLUDE;
}
/**
* Overrides {@link #getName()} to always return the empty string "",
* because the 'name' attribute is not supported by the
* 'label' tag.
* @return the value for the HTML 'name' attribute
*/
protected String getName() throws JspException {
// This also suppresses the 'id' attribute (which is okay for a )
return "";
}
/**
* Returns the value that must be used for the 'for' attribute.
*/
protected final String resolveFor() throws JspException {
if (StringUtils.hasText(this.forId)) {
return getDisplayString(evaluate(FOR_ATTRIBUTE, this.forId));
}
else {
return getCompletePath();
}
}
/**
* Close the 'label' tag.
* @return {@link javax.servlet.jsp.tagext.Tag#EVAL_PAGE}
*/
public int doEndTag() throws JspException {
this.tagWriter.endTag();
return EVAL_PAGE;
}
/**
* Disposes of the {@link TagWriter} instance.
*/
public void doFinally() {
super.doFinally();
this.tagWriter = null;
}
}