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java.lang.Object | +--gnu.jel.Library
A namespace for JEL expressions.
There are two types of members in the library, those which are stateless (i.e. their value depends only on their arguments, if there are any) and stateful (also called here dynamic). The result of evaluation of stateful members may depend on other factors besides their arguments.
Examples of possible stateless members are : Math.sin(double), Math.PI.
Examples of possible stateful members are : Math.random(), System.currentTimeMillis().
Stateless members of this library are always static members of the classes, which define them. The inverse is generally not true. However, this library goes as far as assuming that static members are stateless, if this assumption does not hold for some of Your members it is possible to mark them as stateful using the markStateDependent() method of this class.
The most crucial difference between the two kind of members of this library is that evaluation of stateless methods is attempted by JEL at a compile time during the constants folding phase.
Field Summary | |
java.util.Hashtable |
cnmap
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DVResolver |
resolver
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Constructor Summary | |
Library(java.lang.Class[] staticLib,
java.lang.Class[] dynamicLib)
Deprecated. Please us 5 argument constructor with unused arguments set to null. This constructor is scheduled for removal in JEL 1.0. |
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Library(java.lang.Class[] staticLib,
java.lang.Class[] dynamicLib,
java.lang.Class[] dotClasses)
Deprecated. Please us 5 argument constructor with unused arguments set to null. This constructor is scheduled for removal in JEL 1.0. |
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Library(java.lang.Class[] staticLib,
java.lang.Class[] dynamicLib,
java.lang.Class[] dotClasses,
DVResolver resolver)
Deprecated. Please us 5 argument constructor with unused arguments set to null. This constructor is scheduled for removal in JEL 1.0. |
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Library(java.lang.Class[] staticLib,
java.lang.Class[] dynamicLib,
java.lang.Class[] dotClasses,
DVResolver resolver,
java.util.Hashtable cnmap)
Creates a library for JEL. |
Method Summary | |
protected static java.lang.String |
describe(java.lang.String name,
java.lang.Class[] params)
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int |
getDynamicMethodClassID(java.lang.reflect.Member m)
Returns ID(position in the object array) of the dynamic Method. |
java.lang.reflect.Member |
getMember(java.lang.Class container,
java.lang.String name,
java.lang.Class[] params)
Searches the namespace defined by this library object for method or field. |
boolean |
isStateless(java.lang.reflect.Member o)
Used to check if the given method is stateless. |
void |
markStateDependent(java.lang.String name,
java.lang.Class[] params)
This method marks a static member as having the internal state. |
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
public DVResolver resolver
public java.util.Hashtable cnmap
Constructor Detail |
public Library(java.lang.Class[] staticLib, java.lang.Class[] dynamicLib)
See the three argument constructor for more info.
staticLib
- is the array of classes, whose public static
methods are exported.dynamicLib
- is the array of classes, whose public virutal
methods are exported.public Library(java.lang.Class[] staticLib, java.lang.Class[] dynamicLib, java.lang.Class[] dotClasses)
See the three argument constructor for more info.
staticLib
- is the array of classes, whose public static
methods are exported.dynamicLib
- is the array of classes, whose public virutal
methods are exported.dotClasses
- Controls access to the "dot" operator on classes.public Library(java.lang.Class[] staticLib, java.lang.Class[] dynamicLib, java.lang.Class[] dotClasses, DVResolver resolver)
See the three argument constructor for more info.
staticLib
- is the array of classes, whose public static
methods are exported.dynamicLib
- is the array of classes, whose public virutal
methods are exported.dotClasses
- Controls access to the "dot" operator on classes.resolver
- Controls resolution of dynamic variables.public Library(java.lang.Class[] staticLib, java.lang.Class[] dynamicLib, java.lang.Class[] dotClasses, DVResolver resolver, java.util.Hashtable cnmap)
The following should be kept in mind when constructing a library:
The array (dotClasses), which is the third argument of this constructor determines how (and whether) to compile the dot operators encountered in expressions. These operators are of the form
Method Detail |
public void markStateDependent(java.lang.String name, java.lang.Class[] params) throws CompilationException
If You include java.lang.Math into the library it is necessary to mark java.lang.random() as having the state. This can be done by calling markStateDependent("random",null)
Please specify parameters as close as possible, otherwise You can accidentally mark another function.
name
- is the function name.params
- are the possible invocation parameters of the function.CompilationException
- if the method can't be resolvedpublic boolean isStateless(java.lang.reflect.Member o)
m
- is method or field to check.public java.lang.reflect.Member getMember(java.lang.Class container, java.lang.String name, java.lang.Class[] params) throws CompilationException
The method with the same name, and closest (convertible) parameter types is returned. If there are several methods the most specific one is used.
Ambiguities are detected. Example of detectable ambiguity:
You want to call : someName(int, int)
There are two applicable methods : someName(int, double),
someName(double, int) , requirements to parameter types of each
of those can be satisfied by _widening_ conversions.
Those methods are same specific, there is no most specific method in
terms of Java Language Specification (15.11.2.2). Thus there is ambiguity
and null will be returned.
Java compiler normally would not allow to define such ambiguous methods in the same class. However, as this library is assembled from several Java classes such ambiguities can happen, and should be detected.
container
- the class to search the method within, if null
the root namespace is searched.name
- is the name of the method to find.params
- are the types of formal parameters in the method invocation.CompilationException
- if the method can't be resolvedprotected static java.lang.String describe(java.lang.String name, java.lang.Class[] params)
public int getDynamicMethodClassID(java.lang.reflect.Member m)
ID's are used to locate the pointers to the objects, implementing dynamic methods, in the array, argument of evaluate(Object[]) function.
m
- method to get an ID of.NullPointerException
- if method is not a dynamic method of
this library.
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