de.odysseus.el

Class TreeMethodExpression

java.lang.Object

javax.el.Expression

javax.el.MethodExpression

de.odysseus.el.TreeMethodExpression

All Implemented Interfaces:

java.io.Serializable

public final class TreeMethodExpression
extends MethodExpression

A method expression is ready to be evaluated (by calling either invoke(ELContext, Object[]) or getMethodInfo(ELContext)). Instances of this class are usually created using an ExpressionFactoryImpl.

Author:

Christoph Beck

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
TreeMethodExpression(TreeStore store, FunctionMapper functions, VariableMapper variables, java.lang.String expr, java.lang.Class<?> returnType, java.lang.Class<?>[] paramTypes) Create a new method expression.

Method Summary

Methods

Modifier and Type	Method and Description
void	dump(java.io.PrintWriter writer) Print the parse tree.
boolean	equals(java.lang.Object obj) Expressions are compared using the concept of a structural id: variable and function names are anonymized such that two expressions with same tree structure will also have the same structural id and vice versa.
java.lang.String	getExpressionString() Returns the original String used to create this Expression, unmodified.
MethodInfo	getMethodInfo(ELContext context) Evaluates the expression and answers information about the method
int	hashCode() Returns the hash code for this Expression.
java.lang.Object	invoke(ELContext context, java.lang.Object[] paramValues) Evaluates the expression and invokes the method.
boolean	isDeferred() Answer true if this is a deferred expression (starting with #{)
boolean	isLiteralText() Returns whether this expression was created from only literal text.
java.lang.String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

TreeMethodExpression

public TreeMethodExpression(TreeStore store,
                    FunctionMapper functions,
                    VariableMapper variables,
                    java.lang.String expr,
                    java.lang.Class<?> returnType,
                    java.lang.Class<?>[] paramTypes)

Create a new method expression. The expression must be an lvalue expression or literal text. The expected return type may be null, meaning "don't care". If it is an lvalue expression, the parameter types must not be null. If it is literal text, the expected return type must not be void.

Parameters:

store - used to get the parse tree from.

functions - the function mapper used to bind functions

variables - the variable mapper used to bind variables

expr - the expression string

returnType - the expected return type (may be null)

paramTypes - the expected parameter types (must not be null for lvalues)

Method Detail

getMethodInfo

public MethodInfo getMethodInfo(ELContext context)
                         throws ELException

Evaluates the expression and answers information about the method

Specified by:

getMethodInfo in class MethodExpression

Parameters:

context - used to resolve properties (base.property and base[property])

Returns:

method information or null for literal expressions

Throws:

ELException - if evaluation fails (e.g. suitable method not found)

getExpressionString

public java.lang.String getExpressionString()

Description copied from class: Expression

Returns the original String used to create this Expression, unmodified.

This is used for debugging purposes but also for the purposes of comparison (e.g. to ensure the expression in a configuration file has not changed).

This method does not provide sufficient information to re-create an expression. Two different expressions can have exactly the same expression string but different function mappings. Serialization should be used to save and restore the state of an Expression.

Specified by:

getExpressionString in class Expression

Returns:

The original expression String.

invoke

public java.lang.Object invoke(ELContext context,
                      java.lang.Object[] paramValues)
                        throws ELException

Evaluates the expression and invokes the method.

Specified by:

invoke in class MethodExpression

Parameters:

context - used to resolve properties (base.property and base[property])

paramValues - The parameters to pass to the method, or null if no parameters.

Returns:

method result or null if this is a literal text expression

Throws:

ELException - if evaluation fails (e.g. suitable method not found)

isLiteralText

public boolean isLiteralText()

Description copied from class: Expression

Returns whether this expression was created from only literal text.

This method must return true if and only if the expression string this expression was created from contained no unescaped EL delimeters (${...} or #{...}).

Specified by:

isLiteralText in class Expression

Returns:

true if this is a literal text expression

isDeferred

public boolean isDeferred()

Answer true if this is a deferred expression (starting with #{)

equals

public boolean equals(java.lang.Object obj)

Expressions are compared using the concept of a structural id: variable and function names are anonymized such that two expressions with same tree structure will also have the same structural id and vice versa. Two method expressions are equal if

1. their builders are equal
2. their structural id's are equal
3. their bindings are equal
4. their expected types match (see below)
5. their parameter types are equal (no-text method expressions only)

For text method expressions, the two expected types match if both types are the same or one of them is null and the other is Object.class. For non-text method expressions, the expected types match if both types are the same or one of them is null.

Specified by:

equals in class Expression

Parameters:

obj - the Object to test for equality.

Returns:

true if obj equals this Expression; false otherwise.

See Also:

Hashtable, Object.equals(java.lang.Object)

hashCode

public int hashCode()

Description copied from class: Expression

Returns the hash code for this Expression.

See the note in the Expression.equals(java.lang.Object) method on how two expressions can be equal if their expression Strings are different. Recall that if two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result. Implementations must take special note and implement hashCode correctly.

Specified by:

hashCode in class Expression

Returns:

The hash code for this Expression.

See Also:

Expression.equals(java.lang.Object), Hashtable, Object.hashCode()

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

dump

public void dump(java.io.PrintWriter writer)

Print the parse tree.

Parameters:

writer -