org.springframework.expression.spel.standard

Class SpelExpression

java.lang.Object

org.springframework.expression.spel.standard.SpelExpression

All Implemented Interfaces:

Expression

public class SpelExpression
extends java.lang.Object
implements Expression

A SpelExpression represents a parsed (valid) expression that is ready to be evaluated in a specified context. An expression can be evaluated standalone or in a specified context. During expression evaluation the context may be asked to resolve references to types, beans, properties, and methods.

Since:

3.0

Author:

Andy Clement

Field Summary

Fields

Modifier and Type	Field and Description
private SpelNodeImpl	ast
private CompiledExpression	compiledAst
private SpelParserConfiguration	configuration
private EvaluationContext	evaluationContext
private java.lang.String	expression
private static int	FAILED_ATTEMPTS_THRESHOLD
private int	failedAttempts
private static int	INTERPRETED_COUNT_THRESHOLD
private int	interpretedCount

Constructor Summary

Constructors

Constructor and Description
SpelExpression(java.lang.String expression, SpelNodeImpl ast, SpelParserConfiguration configuration) Construct an expression, only used by the parser.

Method Summary

Modifier and Type	Method and Description
private void	checkCompile(ExpressionState expressionState) Compile the expression if it has been evaluated more than the threshold number of times to trigger compilation.
boolean	compileExpression() Perform expression compilation.
SpelNode	getAST() Return the Abstract Syntax Tree for the expression.
EvaluationContext	getEvaluationContext() Return the default evaluation context that will be used if none is supplied on an evaluation call.
java.lang.String	getExpressionString() Returns the original string used to create this expression, unmodified.
java.lang.Object	getValue() Evaluate this expression in the default standard context.
<T> T	getValue(java.lang.Class<T> expectedResultType) Evaluate the expression in the default context.
java.lang.Object	getValue(EvaluationContext context) Evaluate this expression in the provided context and return the result of evaluation.
<T> T	getValue(EvaluationContext context, java.lang.Class<T> expectedResultType) 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.
java.lang.Object	getValue(EvaluationContext context, java.lang.Object rootObject) Evaluate this expression in the provided context and return the result of evaluation, but use the supplied root context as an override for any default root object specified in the context.
<T> T	getValue(EvaluationContext context, java.lang.Object rootObject, java.lang.Class<T> expectedResultType) 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.
java.lang.Object	getValue(java.lang.Object rootObject) Evaluate this expression against the specified root object
<T> T	getValue(java.lang.Object rootObject, java.lang.Class<T> expectedResultType) Evaluate the expression in the default context against the specified root object.
java.lang.Class<?>	getValueType() Returns the most general type that can be passed to the Expression.setValue(EvaluationContext, Object) method using the default context.
java.lang.Class<?>	getValueType(EvaluationContext context) Returns the most general type that can be passed to the Expression.setValue(EvaluationContext, Object) method for the given context.
java.lang.Class<?>	getValueType(EvaluationContext context, java.lang.Object rootObject) Returns the most general type that can be passed to the Expression.setValue(EvaluationContext, Object) method for the given context.
java.lang.Class<?>	getValueType(java.lang.Object rootObject) Returns the most general type that can be passed to the Expression.setValue(EvaluationContext, Object) method using the default context.
TypeDescriptor	getValueTypeDescriptor() Returns the most general type that can be passed to the Expression.setValue(EvaluationContext, Object) method using the default context.
TypeDescriptor	getValueTypeDescriptor(EvaluationContext context) Returns the most general type that can be passed to the Expression.setValue(EvaluationContext, Object) method for the given context.
TypeDescriptor	getValueTypeDescriptor(EvaluationContext context, java.lang.Object rootObject) Returns the most general type that can be passed to the Expression.setValue(EvaluationContext, Object) method for the given context.
TypeDescriptor	getValueTypeDescriptor(java.lang.Object rootObject) Returns the most general type that can be passed to the Expression.setValue(EvaluationContext, Object) method using the default context.
boolean	isWritable(EvaluationContext context) Determine if an expression can be written to, i.e.
boolean	isWritable(EvaluationContext context, java.lang.Object rootObject) Determine if an expression can be written to, i.e.
boolean	isWritable(java.lang.Object rootObject) Determine if an expression can be written to, i.e.
void	revertToInterpreted() Cause an expression to revert to being interpreted if it has been using a compiled form.
void	setEvaluationContext(EvaluationContext evaluationContext) Set the evaluation context that will be used if none is specified on an evaluation call.
void	setValue(EvaluationContext context, java.lang.Object value) Set this expression in the provided context to the value provided.
void	setValue(EvaluationContext context, java.lang.Object rootObject, java.lang.Object value) Set this expression in the provided context to the value provided.
void	setValue(java.lang.Object rootObject, java.lang.Object value) Set this expression in the provided context to the value provided.
java.lang.String	toStringAST() Produce a string representation of the Abstract Syntax Tree for the expression.
private TypedValue	toTypedValue(java.lang.Object object)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

INTERPRETED_COUNT_THRESHOLD

private static final int INTERPRETED_COUNT_THRESHOLD

See Also:

Constant Field Values

FAILED_ATTEMPTS_THRESHOLD

private static final int FAILED_ATTEMPTS_THRESHOLD

See Also:

Constant Field Values

expression

private final java.lang.String expression

ast

private final SpelNodeImpl ast

configuration

private final SpelParserConfiguration configuration

evaluationContext

private EvaluationContext evaluationContext

compiledAst

private CompiledExpression compiledAst

interpretedCount

private volatile int interpretedCount

failedAttempts

private volatile int failedAttempts

Constructor Detail

SpelExpression

public SpelExpression(java.lang.String expression,
                      SpelNodeImpl ast,
                      SpelParserConfiguration configuration)

Construct an expression, only used by the parser.

Method Detail

setEvaluationContext

public void setEvaluationContext(EvaluationContext evaluationContext)

Set the evaluation context that will be used if none is specified on an evaluation call.

Parameters:

evaluationContext - the evaluation context to use

getEvaluationContext

public EvaluationContext getEvaluationContext()

Return the default evaluation context that will be used if none is supplied on an evaluation call.

Returns:

the default evaluation context

getValue

public java.lang.Object getValue()
                          throws EvaluationException

Description copied from interface: Expression

Evaluate this expression in the default standard context.

Specified by:

getValue in interface Expression

Returns:

the evaluation result

Throws:

EvaluationException - if there is a problem during evaluation

getValue

public java.lang.Object getValue(java.lang.Object rootObject)
                          throws EvaluationException

Description copied from interface: Expression

Evaluate this expression against the specified root object

Specified by:

getValue in interface Expression

Parameters:

rootObject - the root object against which properties/etc will be resolved

Returns:

the evaluation result

Throws:

EvaluationException - if there is a problem during evaluation

getValue

public <T> T getValue(java.lang.Class<T> expectedResultType)
               throws EvaluationException

Description copied from interface: Expression

Evaluate the expression in the default 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.

Specified by:

getValue in interface Expression

Parameters:

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

Returns:

the evaluation result

Throws:

EvaluationException - if there is a problem during evaluation

getValue

public <T> T getValue(java.lang.Object rootObject,
                      java.lang.Class<T> expectedResultType)
               throws EvaluationException

Description copied from interface: Expression

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

Specified by:

getValue in interface Expression

Parameters:

rootObject - the root object against which properties/etc will be resolved

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

Returns:

the evaluation result

Throws:

EvaluationException - if there is a problem during evaluation

getValue

public java.lang.Object getValue(EvaluationContext context)
                          throws EvaluationException

Description copied from interface: Expression

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

Specified by:

getValue in interface Expression

Parameters:

context - the context in which to evaluate the expression

Returns:

the evaluation result

Throws:

EvaluationException - if there is a problem during evaluation

getValue

public java.lang.Object getValue(EvaluationContext context,
                                 java.lang.Object rootObject)
                          throws EvaluationException

Description copied from interface: Expression

Evaluate this expression in the provided context and return the result of evaluation, but use the supplied root context as an override for any default root object specified in the context.

Specified by:

getValue in interface Expression

Parameters:

context - the context in which to evaluate the expression

rootObject - the root object against which properties/etc will be resolved

Returns:

the evaluation result

Throws:

EvaluationException - if there is a problem during evaluation

getValue

public <T> T getValue(EvaluationContext context,
                      java.lang.Class<T> expectedResultType)
               throws EvaluationException

Description copied from interface: Expression

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.

Specified by:

getValue in interface Expression

Parameters:

context - the context in which to evaluate the expression

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

Returns:

the evaluation result

Throws:

EvaluationException - if there is a problem during evaluation

getValue

public <T> T getValue(EvaluationContext context,
                      java.lang.Object rootObject,
                      java.lang.Class<T> expectedResultType)
               throws EvaluationException

Description copied from interface: Expression

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. The supplied root object overrides any default specified on the supplied context.

Specified by:

getValue in interface Expression

Parameters:

context - the context in which to evaluate the expression

rootObject - the root object against which properties/etc will be resolved

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

Returns:

the evaluation result

Throws:

EvaluationException - if there is a problem during evaluation

getValueType

public java.lang.Class<?> getValueType()
                                throws EvaluationException

Description copied from interface: Expression

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

Specified by:

getValueType in interface 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

getValueType

public java.lang.Class<?> getValueType(java.lang.Object rootObject)
                                throws EvaluationException

Description copied from interface: Expression

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

Specified by:

getValueType in interface Expression

Parameters:

rootObject - the root object against 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

getValueType

public java.lang.Class<?> getValueType(EvaluationContext context)
                                throws EvaluationException

Description copied from interface: Expression

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

Specified by:

getValueType in interface Expression

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

getValueType

public java.lang.Class<?> getValueType(EvaluationContext context,
                                       java.lang.Object rootObject)
                                throws EvaluationException

Description copied from interface: Expression

Returns the most general type that can be passed to the Expression.setValue(EvaluationContext, Object) method for the given context. The supplied root object overrides any specified in the context.

Specified by:

getValueType in interface Expression

Parameters:

context - the context in which to evaluate the expression

rootObject - the root object against 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

public TypeDescriptor getValueTypeDescriptor()
                                      throws EvaluationException

Description copied from interface: Expression

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

Specified by:

getValueTypeDescriptor in interface 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

getValueTypeDescriptor

public TypeDescriptor getValueTypeDescriptor(java.lang.Object rootObject)
                                      throws EvaluationException

Description copied from interface: Expression

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

Specified by:

getValueTypeDescriptor in interface Expression

Parameters:

rootObject - the root object against 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

getValueTypeDescriptor

public TypeDescriptor getValueTypeDescriptor(EvaluationContext context)
                                      throws EvaluationException

Description copied from interface: Expression

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

Specified by:

getValueTypeDescriptor in interface Expression

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

getValueTypeDescriptor

public TypeDescriptor getValueTypeDescriptor(EvaluationContext context,
                                             java.lang.Object rootObject)
                                      throws EvaluationException

Description copied from interface: Expression

Returns the most general type that can be passed to the Expression.setValue(EvaluationContext, Object) method for the given context. The supplied root object overrides any specified in the context.

Specified by:

getValueTypeDescriptor in interface Expression

Parameters:

context - the context in which to evaluate the expression

rootObject - the root object against 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

getExpressionString

public java.lang.String getExpressionString()

Description copied from interface: Expression

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

Specified by:

getExpressionString in interface Expression

Returns:

the original expression string

isWritable

public boolean isWritable(EvaluationContext context)
                   throws EvaluationException

Description copied from interface: Expression

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

Specified by:

isWritable in interface Expression

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

isWritable

public boolean isWritable(java.lang.Object rootObject)
                   throws EvaluationException

Description copied from interface: Expression

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

Specified by:

isWritable in interface Expression

Parameters:

rootObject - the root object against which to evaluate the expression

Returns:

true if the expression is writable

Throws:

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

isWritable

public boolean isWritable(EvaluationContext context,
                          java.lang.Object rootObject)
                   throws EvaluationException

Description copied from interface: Expression

Determine if an expression can be written to, i.e. setValue() can be called. The supplied root object overrides any specified in the context.

Specified by:

isWritable in interface Expression

Parameters:

context - the context in which the expression should be checked

rootObject - the root object against which to evaluate the expression

Returns:

true if the expression is writable

Throws:

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

setValue

public void setValue(EvaluationContext context,
                     java.lang.Object value)
              throws EvaluationException

Description copied from interface: Expression

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

Specified by:

setValue in interface Expression

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

setValue

public void setValue(java.lang.Object rootObject,
                     java.lang.Object value)
              throws EvaluationException

Description copied from interface: Expression

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

Specified by:

setValue in interface Expression

Parameters:

rootObject - the root object against which to evaluate the expression

value - the new value

Throws:

EvaluationException - if there is a problem during evaluation

setValue

public void setValue(EvaluationContext context,
                     java.lang.Object rootObject,
                     java.lang.Object value)
              throws EvaluationException

Description copied from interface: Expression

Set this expression in the provided context to the value provided. The supplied root object overrides any specified in the context.

Specified by:

setValue in interface Expression

Parameters:

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

rootObject - the root object against which to evaluate the expression

value - the new value

Throws:

EvaluationException - if there is a problem during evaluation

checkCompile

private void checkCompile(ExpressionState expressionState)

Compile the expression if it has been evaluated more than the threshold number of times to trigger compilation.

Parameters:

expressionState - the expression state used to determine compilation mode

compileExpression

public boolean compileExpression()

Perform expression compilation. This will only succeed once exit descriptors for all nodes have been determined. If the compilation fails and has failed more than 100 times the expression is no longer considered suitable for compilation.

revertToInterpreted

public void revertToInterpreted()

Cause an expression to revert to being interpreted if it has been using a compiled form. It also resets the compilation attempt failure count (an expression is normally no longer considered compilable if it cannot be compiled after 100 attempts).

getAST

public SpelNode getAST()

Return the Abstract Syntax Tree for the expression.

toStringAST

public java.lang.String toStringAST()

Produce a string representation of the Abstract Syntax Tree for the expression. This should ideally look like the input expression, but properly formatted since any unnecessary whitespace will have been discarded during the parse of the expression.

Returns:

the string representation of the AST

toTypedValue

private TypedValue toTypedValue(java.lang.Object object)