Tag.java
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上传日期:2022-07-20
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文件大小:7k
源码类别:
数据库编程
开发平台:
Java
- /*
- * The Apache Software License, Version 1.1
- *
- * Copyright (c) 1999 The Apache Software Foundation. All rights
- * reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- * 1. Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in
- * the documentation and/or other materials provided with the
- * distribution.
- *
- * 3. The end-user documentation included with the redistribution, if
- * any, must include the following acknowlegement:
- * "This product includes software developed by the
- * Apache Software Foundation (http://www.apache.org/)."
- * Alternately, this acknowlegement may appear in the software itself,
- * if and wherever such third-party acknowlegements normally appear.
- *
- * 4. The names "The Jakarta Project", "Tomcat", and "Apache Software
- * Foundation" must not be used to endorse or promote products derived
- * from this software without prior written permission. For written
- * permission, please contact apache@apache.org.
- *
- * 5. Products derived from this software may not be called "Apache"
- * nor may "Apache" appear in their names without prior written
- * permission of the Apache Group.
- *
- * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
- * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
- * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
- * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
- * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
- * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
- * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
- * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
- * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- * ====================================================================
- *
- * This software consists of voluntary contributions made by many
- * individuals on behalf of the Apache Software Foundation. For more
- * information on the Apache Software Foundation, please see
- * <http://www.apache.org/>.
- *
- */
- package javax.servlet.jsp.tagext;
- import javax.servlet.jsp.*;
- /**
- * The Tag interface defines the basic protocol between a Tag handler and JSP page
- * implementation class. It defines the life cycle and the methods to be invoked at
- * start and end tag.
- * <p>
- * There are several methods that get invoked to set the state of a Tag handler.
- * The Tag handler is required to keep this state so the page compiler can
- * choose not to reinvoke some of the state setting.
- * <p>
- * The page compiler guarantees that setPageContext and setParent
- * will all be invoked on the Tag handler, in that order, before doStartTag() or
- * doEndTag() are invoked on it.
- * The page compiler also guarantees that release will be invoked on the Tag
- * handler before the end of the page.
- * <p>
- * Here is a typical invocation sequence:
- *
- * <pre>
- * <code>
- *
- * ATag t = new ATag();
- *
- * -- need to set required information
- * t.setPageContext(...);
- * t.setParent(...);
- * t.setAttribute1(value1);
- * t.setAttribute2(value2);
- *
- * -- all ready to go
- * t.doStartTag();
- * t.doEndTag();
- *
- * ... other tags and template text
- *
- * -- say one attribute is changed, but parent and pageContext have not changed
- * t.setAttribute2(value3);
- * t.doStartTag()
- * t.doEndTag()
- *
- * ... other tags and template text
- *
- * -- assume that this new action happens to use the same attribute values
- * -- it is legal to reuse the same handler instance, with no changes...
- * t.doStartTag();
- * t.doEndTag();
- *
- * -- OK, all done
- * t.release()
- * </code>
- * </pre>
- *
- * <p>
- * The Tag interface also includes methods to set a parent chain, which is used
- * to find enclosing tag handlers.
- *
- */
- public interface Tag {
- /**
- * Skip body evaluation.
- * Valid return value for doStartTag and doAfterBody.
- */
- public final static int SKIP_BODY = 0;
- /**
- * Evaluate body into existing out stream.
- * Valid return value for doStartTag.
- * This is an illegal return value for doStartTag when the class implements
- * BodyTag, since BodyTag implies the creation of a new BodyContent.
- */
- public final static int EVAL_BODY_INCLUDE = 1;
- /**
- * Skip the rest of the page.
- * Valid return value for doEndTag.
- */
- public final static int SKIP_PAGE = 5;
- /**
- * Continue evaluating the page.
- * Valid return value for doEndTag().
- */
- public final static int EVAL_PAGE = 6;
- // Setters for Tag handler data
- /**
- * Set the current page context.
- * Called by the page implementation prior to doStartTag().
- * <p>
- * This value is *not* reset by doEndTag() and must be explicitly reset
- * by a page implementation
- */
- void setPageContext(PageContext pc);
- /**
- * Set the current nesting Tag of this Tag.
- * Called by the page implementation prior to doStartTag().
- * <p>
- * This value is *not* reset by doEndTag() and must be explicitly reset
- * by a page implementation. Code can assume that setPageContext
- * has been called with the proper values before this point.
- */
- void setParent(Tag t);
- /**
- * @return the current parent
- * @seealso TagSupport.findAncestorWithClass().
- */
- Tag getParent();
- // Actions for basic start/end processing.
- /**
- * Process the start tag for this instance.
- *
- * @returns EVAL_BODY_INCLUDE if the tag wants to process body, SKIP_BODY if it
- * does not want to process it.
- *
- * When a Tag returns EVAL_BODY_INCLUDE the body (if any) is evaluated
- * and written into the current "out" JspWriter then doEndTag() is invoked.
- *
- * @see BodyTag
- */
- int doStartTag() throws JspException;
- /**
- * Process the end tag. This method will be called on all Tag objects.
- */
- int doEndTag() throws JspException;
- /**
- * Called on a Tag handler to release state.
- * The page compiler guarantees this method will be called on all tag handlers,
- * but there may be multiple invocations on doStartTag and doEndTag in between.
- */
- void release();
- }