| /* |
| * Copyright 2004 The Apache Software Foundation |
| * |
| * 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 javax.servlet.jsp.tagext; |
| |
| import javax.servlet.jsp.*; |
| |
| /** |
| * The BodyTag interface extends IterationTag by defining additional |
| * methods that let a tag handler manipulate the content of evaluating its body. |
| * |
| * <p> |
| * It is the responsibility of the tag handler to manipulate the body |
| * content. For example the tag handler may take the body content, |
| * convert it into a String using the bodyContent.getString |
| * method and then use it. Or the tag handler may take the body |
| * content and write it out into its enclosing JspWriter using |
| * the bodyContent.writeOut method. |
| * |
| * <p> A tag handler that implements BodyTag is treated as one that |
| * implements IterationTag, except that the doStartTag method can |
| * return SKIP_BODY, EVAL_BODY_INCLUDE or EVAL_BODY_BUFFERED. |
| * |
| * <p> |
| * If EVAL_BODY_INCLUDE is returned, then evaluation happens |
| * as in IterationTag. |
| * |
| * <p> |
| * If EVAL_BODY_BUFFERED is returned, then a BodyContent object will be |
| * created (by code generated by the JSP compiler) to capture the body |
| * evaluation. |
| * The code generated by the JSP compiler obtains the BodyContent object by |
| * calling the pushBody method of the current pageContext, which |
| * additionally has the effect of saving the previous out value. |
| * The page compiler returns this object by calling the popBody |
| * method of the PageContext class; |
| * the call also restores the value of out. |
| * |
| * <p> |
| * The interface provides one new property with a setter method and one |
| * new action method. |
| * |
| * <p><B>Properties</B> |
| * <p> There is a new property: bodyContent, to contain the BodyContent |
| * object, where the JSP Page implementation object will place the |
| * evaluation (and reevaluation, if appropriate) of the body. The setter |
| * method (setBodyContent) will only be invoked if doStartTag() returns |
| * EVAL_BODY_BUFFERED and the corresponding action element does not have |
| * an empty body. |
| * |
| * <p><B>Methods</B> |
| * <p> In addition to the setter method for the bodyContent property, there |
| * is a new action method: doInitBody(), which is invoked right after |
| * setBodyContent() and before the body evaluation. This method is only |
| * invoked if doStartTag() returns EVAL_BODY_BUFFERED. |
| * |
| * <p><B>Lifecycle</B> |
| * <p> Lifecycle details are described by the transition diagram below. |
| * Exceptions that are thrown during the computation of doStartTag(), |
| * setBodyContent(), doInitBody(), BODY, doAfterBody() interrupt the |
| * execution sequence and are propagated up the stack, unless the |
| * tag handler implements the TryCatchFinally interface; see that |
| * interface for details. |
| * <p> |
| * <IMG src="doc-files/BodyTagProtocol.gif" |
| * alt="Lifecycle Details Transition Diagram for BodyTag"/> |
| * |
| * <p><B>Empty and Non-Empty Action</B> |
| * <p> If the TagLibraryDescriptor file indicates that the action must |
| * always have an empty element body, by an <body-content> entry |
| * of "empty", then the doStartTag() method must return SKIP_BODY. |
| * Otherwise, the doStartTag() method may return SKIP_BODY, |
| * EVAL_BODY_INCLUDE, or EVAL_BODY_BUFFERED. |
| * |
| * <p>Note that which methods are invoked after the doStartTag() depends on |
| * both the return value and on if the custom action element is empty |
| * or not in the JSP page, not how it's declared in the TLD. |
| * |
| * <p> |
| * If SKIP_BODY is returned the body is not evaluated, and doEndTag() is |
| * invoked. |
| * |
| * <p> |
| * If EVAL_BODY_INCLUDE is returned, and the custom action element is not |
| * empty, setBodyContent() is not invoked, |
| * doInitBody() is not invoked, the body is evaluated and |
| * "passed through" to the current out, doAfterBody() is invoked |
| * and then, after zero or more iterations, doEndTag() is invoked. |
| * If the custom action element is empty, only doStart() and |
| * doEndTag() are invoked. |
| * |
| * <p> |
| * If EVAL_BODY_BUFFERED is returned, and the custom action element is not |
| * empty, setBodyContent() is invoked, |
| * doInitBody() is invoked, the body is evaluated, doAfterBody() is |
| * invoked, and then, after zero or more iterations, doEndTag() is invoked. |
| * If the custom action element is empty, only doStart() and doEndTag() |
| * are invoked. |
| */ |
| |
| public interface BodyTag extends IterationTag { |
| |
| /** |
| * Deprecated constant that has the same value as EVAL_BODY_BUFFERED |
| * and EVAL_BODY_AGAIN. This name has been marked as deprecated |
| * to encourage the use of the two different terms, which are much |
| * more descriptive. |
| * |
| * @deprecated As of Java JSP API 1.2, use BodyTag.EVAL_BODY_BUFFERED |
| * or IterationTag.EVAL_BODY_AGAIN. |
| */ |
| |
| public final static int EVAL_BODY_TAG = 2; |
| |
| /** |
| * Request the creation of new buffer, a BodyContent on which to |
| * evaluate the body of this tag. |
| * |
| * Returned from doStartTag when it implements BodyTag. |
| * This is an illegal return value for doStartTag when the class |
| * does not implement BodyTag. |
| */ |
| |
| public final static int EVAL_BODY_BUFFERED = 2; |
| |
| |
| /** |
| * Set the bodyContent property. |
| * This method is invoked by the JSP page implementation object at |
| * most once per action invocation. |
| * This method will be invoked before doInitBody. |
| * This method will not be invoked for empty tags or for non-empty |
| * tags whose doStartTag() method returns SKIP_BODY or EVAL_BODY_INCLUDE. |
| * |
| * <p> |
| * When setBodyContent is invoked, the value of the implicit object out |
| * has already been changed in the pageContext object. The BodyContent |
| * object passed will have not data on it but may have been reused |
| * (and cleared) from some previous invocation. |
| * |
| * <p> |
| * The BodyContent object is available and with the appropriate content |
| * until after the invocation of the doEndTag method, at which case it |
| * may be reused. |
| * |
| * @param b the BodyContent |
| * @see #doInitBody |
| * @see #doAfterBody |
| */ |
| |
| void setBodyContent(BodyContent b); |
| |
| |
| /** |
| * Prepare for evaluation of the body. |
| * This method is invoked by the JSP page implementation object |
| * after setBodyContent and before the first time |
| * the body is to be evaluated. |
| * This method will not be invoked for empty tags or for non-empty |
| * tags whose doStartTag() method returns SKIP_BODY or EVAL_BODY_INCLUDE. |
| * |
| * <p> |
| * The JSP container will resynchronize the values of any AT_BEGIN and |
| * NESTED variables (defined by the associated TagExtraInfo or TLD) after |
| * the invocation of doInitBody(). |
| * |
| * @throws JspException if an error occurred while processing this tag |
| * @see #doAfterBody |
| */ |
| |
| void doInitBody() throws JspException; |
| |
| } |
