1 /** 2 * 3 * Copyright 2003-2004 The Apache Software Foundation 4 * 5 * Licensed under the Apache License, Version 2.0 (the "License"); 6 * you may not use this file except in compliance with the License. 7 * You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 18 // 19 // This source code implements specifications defined by the Java 20 // Community Process. In order to remain compliant with the specification 21 // DO NOT add / change / or delete method signatures! 22 // 23 24 package javax.servlet.jsp.tagext; 25 26 import java.io.IOException; 27 import java.io.Writer; 28 29 import javax.servlet.jsp.JspContext; 30 import javax.servlet.jsp.JspException; 31 32 /** 33 * Encapsulates a portion of JSP code in an object that 34 * can be invoked as many times as needed. JSP Fragments are defined 35 * using JSP syntax as the body of a tag for an invocation to a SimpleTag 36 * handler, or as the body of a <jsp:attribute> standard action 37 * specifying the value of an attribute that is declared as a fragment, 38 * or to be of type JspFragment in the TLD. 39 * <p> 40 * The definition of the JSP fragment must only contain template 41 * text and JSP action elements. In other words, it must not contain 42 * scriptlets or scriptlet expressions. At translation time, the 43 * container generates an implementation of the JspFragment abstract class 44 * capable of executing the defined fragment. 45 * <p> 46 * A tag handler can invoke the fragment zero or more times, or 47 * pass it along to other tags, before returning. To communicate values 48 * to/from a JSP fragment, tag handlers store/retrieve values in 49 * the JspContext associated with the fragment. 50 * <p> 51 * Note that tag library developers and page authors should not generate 52 * JspFragment implementations manually. 53 * <p> 54 * <i>Implementation Note</i>: It is not necessary to generate a 55 * separate class for each fragment. One possible implementation is 56 * to generate a single helper class for each page that implements 57 * JspFragment. Upon construction, a discriminator can be passed to 58 * select which fragment that instance will execute. 59 * 60 * @since 2.0 61 */ 62 public abstract class JspFragment { 63 64 /** 65 * Executes the fragment and directs all output to the given Writer, 66 * or the JspWriter returned by the getOut() method of the JspContext 67 * associated with the fragment if out is null. 68 * 69 * @param out The Writer to output the fragment to, or null if 70 * output should be sent to JspContext.getOut(). 71 * @throws javax.servlet.jsp.JspException Thrown if an error occured 72 * while invoking this fragment. 73 * @throws javax.servlet.jsp.SkipPageException Thrown if the page 74 * that (either directly or indirectly) invoked the tag handler that 75 * invoked this fragment is to cease evaluation. The container 76 * must throw this exception if a Classic Tag EventHandler returned 77 * Tag.SKIP_PAGE or if a Simple Tag EventHandler threw SkipPageException. 78 * @throws java.io.IOException If there was an error writing to the 79 * stream. 80 */ 81 public abstract void invoke( Writer out ) 82 throws JspException, IOException; 83 84 /** 85 * Returns the JspContext that is bound to this JspFragment. 86 * 87 * @return The JspContext used by this fragment at invocation time. 88 */ 89 public abstract JspContext getJspContext(); 90 91 }