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 }