org.springframework.web.servlet.tags.form.AbstractHtmlElementBodyTag Maven / Gradle / Ivy
/*
* Copyright 2002-2006 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 org.springframework.util.StringUtils;
import java.io.IOException;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.BodyContent;
import javax.servlet.jsp.tagext.BodyTag;
/**
* Convenient super class for many html tags that render content using the databinding
* features of the {@link AbstractHtmlElementTag AbstractHtmlElementTag}. The only thing sub tags
* need to do is override {@link #renderDefaultContent(TagWriter)}.
*
* @author Rob Harrop
* @since 2.0
*/
public abstract class AbstractHtmlElementBodyTag extends AbstractHtmlElementTag implements BodyTag {
private BodyContent bodyContent;
private TagWriter tagWriter;
protected int writeTagContent(TagWriter tagWriter) throws JspException {
onWriteTagContent();
this.tagWriter = tagWriter;
if (shouldRender()) {
exposeAttributes();
return EVAL_BODY_BUFFERED;
}
else {
return EVAL_PAGE;
}
}
/**
* If {@link #shouldRender rendering}, flush any buffered
* {@link BodyContent} or, if no {@link BodyContent} is supplied,
* {@link #renderDefaultContent render the default content}.
* @return Tag#EVAL_PAGE
*/
public int doEndTag() throws JspException {
if (shouldRender()) {
if (this.bodyContent != null
&& StringUtils.hasText(this.bodyContent.getString())) {
renderFromBodyContent(this.bodyContent, this.tagWriter);
}
else {
renderDefaultContent(this.tagWriter);
}
}
return EVAL_PAGE;
}
/**
* Render the tag contents based on the supplied {@link BodyContent}. The default
* implementation simply {@link #flushBufferedBodyContent flushes} the {@link BodyContent}
* directly to the output. Subclasses may choose to override this to add additional content
* to the output.
*/
protected void renderFromBodyContent(BodyContent bodyContent, TagWriter tagWriter) throws JspException {
flushBufferedBodyContent(this.bodyContent);
}
/**
* Clean up any attributes and stored resources.
*/
public void doFinally() {
super.doFinally();
removeAttributes();
this.tagWriter = null;
this.bodyContent = null;
}
//---------------------------------------------------------------------
// Strategy methods
//---------------------------------------------------------------------
/**
* Called at the start of {@link #writeTagContent} allowing subclasses to perform
* any precondition checks or setup tasks that might be necessary.
*/
protected void onWriteTagContent() {
}
/**
* Should rendering of this tag proceed at all. Returns 'true' by default
* causing rendering to occur always, Subclasses can override this if they
* provide conditional rendering.
*/
protected boolean shouldRender() throws JspException {
return true;
}
/**
* Called during {@link #writeTagContent} allowing subclasses to add any attributes to the
* {@link javax.servlet.jsp.PageContext} as needed.
*/
protected void exposeAttributes() throws JspException {
}
/**
* Called by {@link #doFinally} allowing subclasses to remove any attributes from the
* {@link javax.servlet.jsp.PageContext} as needed.
*/
protected void removeAttributes() {
}
/**
* The user customised the output of the error messages - flush the
* buffered content into the main {@link javax.servlet.jsp.JspWriter}.
*/
protected void flushBufferedBodyContent(BodyContent bodyContent) throws JspException {
try {
bodyContent.writeOut(bodyContent.getEnclosingWriter());
}
catch (IOException e) {
throw new JspException("Unable to write buffered body content.", e);
}
}
protected abstract void renderDefaultContent(TagWriter tagWriter) throws JspException;
//---------------------------------------------------------------------
// BodyTag implementation
//---------------------------------------------------------------------
public void doInitBody() throws JspException {
// no op
}
public void setBodyContent(BodyContent bodyContent) {
this.bodyContent = bodyContent;
}
}