Tomcat example source code file (VariableInfo.java)

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Java - Tomcat tags/keywords

at_begin, at_begin, at_end, at_end, nested, string, string, variableinfo, variableinfo

The Tomcat VariableInfo.java source code

/*
* 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 javax.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 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>Usage Comments
 * <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 (like J2EE). 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>Synchronization Protocol
 *
 * <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: the synchronization of the variable(s)
 * will occur <em>after the respective method has been called.
 *
 * <blockquote>
 * <table cellpadding="2" cellspacing="2" border="0" width="55%"
 *        bgcolor="#999999" summary="Variable Synchronization Points">
 * <tbody>
 *   <tr align="center">
 *     <td valign="top" colspan="6" bgcolor="#999999">Variable Synchronization
 *     Points</b>

 *     </td>
 *   </tr>
 *   <tr>
 *     <th valign="top" bgcolor="#c0c0c0"> 
 *     <th valign="top" bgcolor="#c0c0c0" align="center">doStartTag()
 *     <th valign="top" bgcolor="#c0c0c0" align="center">doInitBody()
 *     <th valign="top" bgcolor="#c0c0c0" align="center">doAfterBody()
 *     <th valign="top" bgcolor="#c0c0c0" align="center">doEndTag()
 *     <th valign="top" bgcolor="#c0c0c0" align="center">doTag()
 *   </tr>
 *   <tr>
 *     <td valign="top" bgcolor="#c0c0c0">Tag

 *     </b>