org.springframework.expression
Interface Expression

All Known Implementing Classes:

CompositeStringExpression, LiteralExpression, SpelExpression

public interface Expression

An expression capable of evaluating itself against context objects. Encapsulates the details of a previously parsed expression string. Provides a common abstraction for expression evaluation independent of any language like OGNL or the Unified EL.

Since:

3.0

Author:

Keith Donald, Andy Clement

Method Summary

String	getExpressionString() Returns the original string used to create this expression, unmodified.
Object	getValue() Evaluate this expression in the default standard context.
<T> T	getValue(Class<T> desiredResultType) Evaluate the expression in the default standard context.
Object	getValue(EvaluationContext context) Evaluate this expression in the provided context and return the result of evaluation.
<T> T	getValue(EvaluationContext context, Class<T> desiredResultType) Evaluate the expression in a specified context which can resolve references to properties, methods, types, etc - the type of the evaluation result is expected to be of a particular class and an exception will be thrown if it is not and cannot be converted to that type.
Class	getValueType() Returns the most general type that can be passed to the setValue(EvaluationContext, Object) method using the default context.
Class	getValueType(EvaluationContext context) Returns the most general type that can be passed to the setValue(EvaluationContext, Object) method for the given context.
TypeDescriptor	getValueTypeDescriptor() Returns the most general type that can be passed to the setValue(EvaluationContext, Object) method using the default context.
TypeDescriptor	getValueTypeDescriptor(EvaluationContext context) Returns the most general type that can be passed to the setValue(EvaluationContext, Object) method for the given context.
boolean	isWritable(EvaluationContext context) Determine if an expression can be written to, i.e.
void	setValue(EvaluationContext context, Object value) Set this expression in the provided context to the value provided.

Method Detail

getValue

Object getValue()
                throws EvaluationException

Evaluate this expression in the default standard context.

Returns:

the evaluation result

Throws:

EvaluationException - if there is a problem during evaluation

getValue

<T> T getValue(Class<T> desiredResultType)
           throws EvaluationException

Evaluate the expression in the default standard context. If the result of the evaluation does not match (and cannot be converted to) the expected result type then an exception will be returned.

Parameters:

desiredResultType - the class the caller would like the result to be

Returns:

the evaluation result

Throws:

EvaluationException - if there is a problem during evaluation

getValue

Object getValue(EvaluationContext context)
                throws EvaluationException

Evaluate this expression in the provided context and return the result of evaluation.

Parameters:

context - the context in which to evaluate the expression

Returns:

the evaluation result

Throws:

EvaluationException - if there is a problem during evaluation

getValue

<T> T getValue(EvaluationContext context,
               Class<T> desiredResultType)
           throws EvaluationException

Evaluate the expression in a specified context which can resolve references to properties, methods, types, etc - the type of the evaluation result is expected to be of a particular class and an exception will be thrown if it is not and cannot be converted to that type.

Parameters:

context - the context in which to evaluate the expression

desiredResultType - the class the caller would like the result to be

Returns:

the evaluation result

Throws:

EvaluationException - if there is a problem during evaluation

getValueType

Class getValueType()
                   throws EvaluationException

Returns the most general type that can be passed to the setValue(EvaluationContext, Object) method using the default context.

Returns:

the most general type of value that can be set on this context

Throws:

EvaluationException - if there is a problem determining the type

getValueType

Class getValueType(EvaluationContext context)
                   throws EvaluationException

Returns the most general type that can be passed to the setValue(EvaluationContext, Object) method for the given context.

Parameters:

context - the context in which to evaluate the expression

Returns:

the most general type of value that can be set on this context

Throws:

EvaluationException - if there is a problem determining the type

getValueTypeDescriptor

TypeDescriptor getValueTypeDescriptor()
                                      throws EvaluationException

Returns the most general type that can be passed to the setValue(EvaluationContext, Object) method using the default context.

Returns:

a type descriptor for the most general type of value that can be set on this context

Throws:

EvaluationException - if there is a problem determining the type

getValueTypeDescriptor

TypeDescriptor getValueTypeDescriptor(EvaluationContext context)
                                      throws EvaluationException

Returns the most general type that can be passed to the setValue(EvaluationContext, Object) method for the given context.

Parameters:

context - the context in which to evaluate the expression

Returns:

a type descriptor for the most general type of value that can be set on this context

Throws:

EvaluationException - if there is a problem determining the type

isWritable

boolean isWritable(EvaluationContext context)
                   throws EvaluationException

Determine if an expression can be written to, i.e. setValue() can be called.

Parameters:

context - the context in which the expression should be checked

Returns:

true if the expression is writable

Throws:

EvaluationException - if there is a problem determining if it is writable

setValue

void setValue(EvaluationContext context,
              Object value)
              throws EvaluationException

Set this expression in the provided context to the value provided.

Parameters:

context - the context in which to set the value of the expression

value - the new value

Throws:

EvaluationException - if there is a problem during evaluation

getExpressionString

String getExpressionString()

Returns the original string used to create this expression, unmodified.

Returns:

the original expression string