javax.servlet.jsp.tagext.VariableInfo Maven / Gradle / Ivy
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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 Java EE). 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 String varName;
private String className;
private boolean declare;
private int scope;
}