VariableInfo.java
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 jakarta.servlet.jsp.tagext;
/**
* Information on the scripting variables that are created/modified by a tag (at run-time). This information is provided
* by TagExtraInfo classes and it is used by the translation phase of JSP.
* <p>
* Scripting variables generated by a custom action have an associated scope of either AT_BEGIN, NESTED, or AT_END.
* <p>
* The class name (VariableInfo.getClassName) in the returned objects is used to determine the types of the scripting
* variables. Note that because scripting variables are assigned their values from scoped attributes which cannot be of
* primitive types, "boxed" types such as <code>java.lang.Integer</code> must be used instead of primitives.
* <p>
* The class name may be a Fully Qualified Class Name, or a short class name.
* <p>
* If a Fully Qualified Class Name is provided, it should refer to a class that should be in the CLASSPATH for the Web
* Application (see Servlet 2.4 specification - essentially it is WEB-INF/lib and WEB-INF/classes). Failure to be so
* will lead to a translation-time error.
* <p>
* If a short class name is given in the VariableInfo objects, then the class name must be that of a public class in the
* context of the import directives of the page where the custom action appears. The class must also be in the CLASSPATH
* for the Web Application (see Servlet 2.4 specification - essentially it is WEB-INF/lib and WEB-INF/classes). Failure
* to be so will lead to a translation-time error.
* <p>
* <B>Usage Comments</B>
* <p>
* Frequently a fully qualified class name will refer to a class that is known to the tag library and thus, delivered in
* the same JAR file as the tag handlers. In most other remaining cases it will refer to a class that is in the platform
* on which the JSP processor is built. Using fully qualified class names in this manner makes the usage relatively
* resistant to configuration errors.
* <p>
* A short name is usually generated by the tag library based on some attributes passed through from the custom action
* user (the author), and it is thus less robust: for instance a missing import directive in the referring JSP page will
* lead to an invalid short name class and a translation error.
* <p>
* <B>Synchronization Protocol</B>
* <p>
* The result of the invocation on getVariableInfo is an array of VariableInfo objects. Each such object describes a
* scripting variable by providing its name, its type, whether the variable is new or not, and what its scope is. Scope
* is best described through a picture:
* <p>
* <IMG src="doc-files/VariableInfo-1.gif" alt="NESTED, AT_BEGIN and AT_END Variable Scopes">
* <p>
* The JSP 2.0 specification defines the interpretation of 3 values:
* <ul>
* <li>NESTED, if the scripting variable is available between the start tag and the end tag of the action that defines
* it.
* <li>AT_BEGIN, if the scripting variable is available from the start tag of the action that defines it until the end
* of the scope.
* <li>AT_END, if the scripting variable is available after the end tag of the action that defines it until the end of
* the scope.
* </ul>
* The scope value for a variable implies what methods may affect its value and thus where synchronization is needed as
* illustrated by the table below. <b>Note:</b> the synchronization of the variable(s) will occur <em>after</em> the
* respective method has been called. <blockquote>
* <table style="background-color:#999999">
* <caption>Variable Synchronization Points</caption> <tbody>
* <tr>
* <td colspan="6" style="background-color:#999999"><u><b>Variable Synchronization Points</b></u><br>
* </td>
* </tr>
* <tr>
* <th style="background-color:#c0c0c0"> </th>
* <th style="background-color:#c0c0c0">doStartTag()</th>
* <th style="background-color:#c0c0c0">doInitBody()</th>
* <th style="background-color:#c0c0c0">doAfterBody()</th>
* <th style="background-color:#c0c0c0">doEndTag()</th>
* <th style="background-color:#c0c0c0">doTag()</th>
* </tr>
* <tr>
* <td style="background-color:#c0c0c0"><b>Tag<br>
* </b></td>
* <td style="background-color:#ffffff">AT_BEGIN, NESTED<br>
* </td>
* <td style="background-color:#ffffff"><br>
* </td>
* <td style="background-color:#ffffff"><br>
* </td>
* <td style="background-color:#ffffff">AT_BEGIN, AT_END<br>
* </td>
* <td style="background-color:#ffffff"><br>
* </td>
* </tr>
* <tr>
* <td style="background-color:#c0c0c0"><b>IterationTag<br>
* </b></td>
* <td style="background-color:#ffffff">AT_BEGIN, NESTED<br>
* </td>
* <td style="background-color:#ffffff"><br>
* </td>
* <td style="background-color:#ffffff">AT_BEGIN, NESTED<br>
* </td>
* <td style="background-color:#ffffff">AT_BEGIN, AT_END<br>
* </td>
* <td style="background-color:#ffffff"><br>
* </td>
* </tr>
* <tr>
* <td style="background-color:#c0c0c0"><b>BodyTag<br>
* </b></td>
* <td style="background-color:#ffffff">AT_BEGIN, NESTED<sup>1</sup><br>
* </td>
* <td style="background-color:#ffffff">AT_BEGIN, NESTED<sup>1</sup><br>
* </td>
* <td style="background-color:#ffffff">AT_BEGIN, NESTED<br>
* </td>
* <td style="background-color:#ffffff">AT_BEGIN, AT_END<br>
* </td>
* <td style="background-color:#ffffff"><br>
* </td>
* </tr>
* <tr>
* <td style="background-color:#c0c0c0"><b>SimpleTag<br>
* </b></td>
* <td style="background-color:#ffffff"><br>
* </td>
* <td style="background-color:#ffffff"><br>
* </td>
* <td style="background-color:#ffffff"><br>
* </td>
* <td style="background-color:#ffffff"><br>
* </td>
* <td style="background-color:#ffffff">AT_BEGIN, AT_END<br>
* </td>
* </tr>
* </tbody>
* </table>
* <sup>1</sup> Called after <code>doStartTag()</code> if <code>EVAL_BODY_INCLUDE</code> is returned, or after
* <code>doInitBody()</code> otherwise. </blockquote>
* <p>
* <B>Variable Information in the TLD</B>
* <p>
* Scripting variable information can also be encoded directly for most cases into the Tag Library Descriptor using the
* <variable> subelement of the <tag> element. See the JSP specification.
*/
public class VariableInfo {
/**
* Scope information that scripting variable is visible only within the start/end tags.
*/
public static final int NESTED = 0;
/**
* Scope information that scripting variable is visible after start tag.
*/
public static final int AT_BEGIN = 1;
/**
* Scope information that scripting variable is visible after end tag.
*/
public static final int AT_END = 2;
/**
* Constructor These objects can be created (at translation time) by the TagExtraInfo instances.
*
* @param varName The name of the scripting variable
* @param className The type of this variable
* @param declare If true, it is a new variable (in some languages this will require a declaration)
* @param scope Indication on the lexical scope of the variable
*/
public VariableInfo(String varName, String className, boolean declare, int scope) {
this.varName = varName;
this.className = className;
this.declare = declare;
this.scope = scope;
}
// Accessor methods
/**
* Returns the name of the scripting variable.
*
* @return the name of the scripting variable
*/
public String getVarName() {
return varName;
}
/**
* Returns the type of this variable.
*
* @return the type of this variable
*/
public String getClassName() {
return className;
}
/**
* Returns whether this is a new variable. If so, in some languages this will require a declaration.
*
* @return whether this is a new variable.
*/
public boolean getDeclare() {
return declare;
}
/**
* Returns the lexical scope of the variable.
*
* @return the lexical scope of the variable, either AT_BEGIN, AT_END, or NESTED.
*
* @see #AT_BEGIN
* @see #AT_END
* @see #NESTED
*/
public int getScope() {
return scope;
}
// == private data
private final String varName;
private final String className;
private final boolean declare;
private final int scope;
}