/*
* 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.
Scripting variables generated by a custom action have an associated scope of
either AT_BEGIN, NESTED, or AT_END.
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
java.lang.Integer must be used instead of primitives.
The class name may be a Fully Qualified Class Name, or a short class name.
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.
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.
Usage Comments
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.
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.
Synchronization Protocol
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:
The JSP 2.0 specification defines the interpretation of 3 values:
- NESTED, if the scripting variable is available between the start tag and
the end tag of the action that defines it.
- AT_BEGIN, if the scripting variable is available from the start tag of
the action that defines it until the end of the scope.
- AT_END, if the scripting variable is available after the end tag of the
action that defines it until the end of the scope.
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.
Note: the synchronization of the variable(s) will occur after
the respective method has been called.
Variable Synchronization Points
Variable Synchronization Points
doStartTag()
doInitBody()
doAfterBody()
doEndTag()
doTag()
Tag
AT_BEGIN, NESTED
AT_BEGIN, AT_END
IterationTag
AT_BEGIN, NESTED
AT_BEGIN, NESTED
AT_BEGIN, AT_END
BodyTag
AT_BEGIN,
NESTED1
AT_BEGIN,
NESTED1
AT_BEGIN, NESTED
AT_BEGIN, AT_END
SimpleTag
AT_BEGIN, AT_END
1 Called after doStartTag() if
EVAL_BODY_INCLUDE is returned, or after
doInitBody() otherwise.
Variable Information in the TLD
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.
/**
* 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 (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>
* <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 valign="top" colspan="6" style="background-color:#999999">
* <u><b>Variable Synchronization Points</b></u><br>
* </td>
* </tr>
* <tr>
* <th valign="top" style="background-color:#c0c0c0"> </th>
* <th valign="top" style="background-color:#c0c0c0">doStartTag()</th>
* <th valign="top" style="background-color:#c0c0c0">doInitBody()</th>
* <th valign="top" style="background-color:#c0c0c0">doAfterBody()</th>
* <th valign="top" style="background-color:#c0c0c0">doEndTag()</th>
* <th valign="top" style="background-color:#c0c0c0">doTag()</th>
* </tr>
* <tr>
* <td valign="top" style="background-color:#c0c0c0"><b>Tag<br>
* </b></td>
* <td valign="top" style="background-color:#ffffff">AT_BEGIN, NESTED<br>
* </td>
* <td valign="top" style="background-color:#ffffff"><br>
* </td>
* <td valign="top" style="background-color:#ffffff"><br>
* </td>
* <td valign="top" style="background-color:#ffffff">AT_BEGIN, AT_END<br>
* </td>
* <td valign="top" style="background-color:#ffffff"><br>
* </td>
* </tr>
* <tr>
* <td valign="top" style="background-color:#c0c0c0"><b>IterationTag<br>
* </b></td>
* <td valign="top" style="background-color:#ffffff">AT_BEGIN, NESTED<br>
* </td>
* <td valign="top" style="background-color:#ffffff"><br>
* </td>
* <td valign="top" style="background-color:#ffffff">AT_BEGIN, NESTED<br>
* </td>
* <td valign="top" style="background-color:#ffffff">AT_BEGIN, AT_END<br>
* </td>
* <td valign="top" style="background-color:#ffffff"><br>
* </td>
* </tr>
* <tr>
* <td valign="top" style="background-color:#c0c0c0"><b>BodyTag<br>
* </b></td>
* <td valign="top" style="background-color:#ffffff">AT_BEGIN,
* NESTED<sup>1</sup><br>
* </td>
* <td valign="top" style="background-color:#ffffff">AT_BEGIN,
* NESTED<sup>1</sup><br>
* </td>
* <td valign="top" style="background-color:#ffffff">AT_BEGIN, NESTED<br>
* </td>
* <td valign="top" style="background-color:#ffffff">AT_BEGIN, AT_END<br>
* </td>
* <td valign="top" style="background-color:#ffffff"><br>
* </td>
* </tr>
* <tr>
* <td valign="top" style="background-color:#c0c0c0"><b>SimpleTag<br>
* </b></td>
* <td valign="top" style="background-color:#ffffff"><br>
* </td>
* <td valign="top" style="background-color:#ffffff"><br>
* </td>
* <td valign="top" style="background-color:#ffffff"><br>
* </td>
* <td valign="top" style="background-color:#ffffff"><br>
* </td>
* <td valign="top" 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.
/**
* 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.
/**
* 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.
/**
* 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.
Params: - varName –
The name of the scripting variable
- className –
The type of this variable
- declare –
If true, it is a new variable (in some languages this will
require a declaration)
- scope –
Indication on the lexical scope of the variable
/**
* 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.
Returns: the name of the scripting variable
/**
* 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.
Returns: the type of this variable
/**
* 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.
Returns: whether this is a new variable.
/**
* 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.
See Also: Returns: the lexical scope of the variable, either AT_BEGIN, AT_END, or
NESTED.
/**
* 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;
}