javax.servlet.jsp.tagext.VariableInfo Maven / Gradle / Ivy
/*
* 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
*
*
*
*
* 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.
*/
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;
}