程序包 cn.taketoday.expression.spel.support

类 SimpleEvaluationContext

java.lang.Object

cn.taketoday.expression.spel.support.SimpleEvaluationContext

所有已实现的接口:

EvaluationContext

public final class SimpleEvaluationContext
extends Object
implements EvaluationContext

A basic implementation of EvaluationContext that focuses on a subset of essential SpEL features and customization options, targeting simple condition evaluation and in particular data binding scenarios.

In many cases, the full extent of the SpEL language is not required and should be meaningfully restricted. Examples include but are not limited to data binding expressions, property-based filters, and others. To that effect, SimpleEvaluationContext is tailored to support only a subset of the SpEL language syntax, e.g. excluding references to Java types, constructors, and bean references.

When creating a SimpleEvaluationContext you need to choose the level of support that you need for property access in SpEL expressions:

• A custom PropertyAccessor (typically not reflection-based), potentially combined with a DataBindingPropertyAccessor
• Data binding properties for read-only access
• Data binding properties for read and write

Conveniently, forReadOnlyDataBinding() enables read access to properties via DataBindingPropertyAccessor; same for forReadWriteDataBinding() when write access is needed as well. Alternatively, configure custom accessors via forPropertyAccessors(cn.taketoday.expression.PropertyAccessor...), and potentially activate method resolution and/or a type converter through the builder.

Note that SimpleEvaluationContext is typically not configured with a default root object. Instead it is meant to be created once and used repeatedly through getValue calls on a pre-compiled Expression with both an EvaluationContext and a root object as arguments: Expression.getValue(EvaluationContext, Object).

In addition to support for setting and looking up variables as defined in the EvaluationContext API, SimpleEvaluationContext also provides support for registering and looking up functions as variables. Since functions share a common namespace with the variables in this evaluation context, care must be taken to ensure that function names and variable names do not overlap.

For more power and flexibility, in particular for internal configuration scenarios, consider using StandardEvaluationContext instead.

从以下版本开始:

4.0

作者:

Rossen Stoyanchev, Juergen Hoeller, Harry Yang

另请参阅:

• forPropertyAccessors(cn.taketoday.expression.PropertyAccessor...)
• forReadOnlyDataBinding()
• forReadWriteDataBinding()
• StandardEvaluationContext
• StandardTypeConverter
• DataBindingPropertyAccessor

嵌套类概要

嵌套类

修饰符和类型	类	说明
static class	SimpleEvaluationContext.Builder	Builder for SimpleEvaluationContext.

字段概要

字段

修饰符和类型	字段	说明
private final List<MethodResolver>	methodResolvers
private final List<PropertyAccessor>	propertyAccessors
private final TypedValue	rootObject
private final TypeConverter	typeConverter
private static final TypeLocator	typeNotFoundTypeLocator
private final HashMap<String,Object>	variables

构造器概要

构造器

限定符	构造器	说明
private	SimpleEvaluationContext(List<PropertyAccessor> accessors, List<MethodResolver> resolvers, TypeConverter converter, TypedValue rootObject)

方法概要

修饰符和类型	方法	说明
TypedValue	assignVariable(String name, Supplier<TypedValue> valueSupplier)	SimpleEvaluationContext does not support variable assignment within expressions.
static SimpleEvaluationContext.Builder	forPropertyAccessors(PropertyAccessor... accessors)	Create a SimpleEvaluationContext for the specified PropertyAccessor delegates: typically a custom PropertyAccessor specific to a use case (e.g. attribute resolution in a custom data structure), potentially combined with a DataBindingPropertyAccessor if property dereferences are needed as well.
static SimpleEvaluationContext.Builder	forReadOnlyDataBinding()	Create a SimpleEvaluationContext for read-only access to public properties via DataBindingPropertyAccessor.
static SimpleEvaluationContext.Builder	forReadWriteDataBinding()	Create a SimpleEvaluationContext for read-write access to public properties via DataBindingPropertyAccessor.
BeanResolver	getBeanResolver()	SimpleEvaluationContext does not support the use of bean references.
List<ConstructorResolver>	getConstructorResolvers()	Return an empty list, always, since this context does not support the use of type references.
List<MethodResolver>	getMethodResolvers()	Return the specified MethodResolver delegates, if any.
OperatorOverloader	getOperatorOverloader()	Return an instance of StandardOperatorOverloader.
List<PropertyAccessor>	getPropertyAccessors()	Return the specified PropertyAccessor delegates, if any.
TypedValue	getRootObject()	Return the specified root object, if any.
TypeComparator	getTypeComparator()	Return an instance of StandardTypeComparator.
TypeConverter	getTypeConverter()	The configured TypeConverter.
TypeLocator	getTypeLocator()	SimpleEvaluationContext does not support use of type references.
Object	lookupVariable(String name)	Look up a named variable or function within this evaluation context.
void	setVariable(String name, Object value)	Set a named variable or function in this evaluation context to the specified value.

从类继承的方法 java.lang.Object

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

字段详细资料

typeNotFoundTypeLocator

private static final TypeLocator typeNotFoundTypeLocator

rootObject

private final TypedValue rootObject

propertyAccessors

private final List<PropertyAccessor> propertyAccessors

methodResolvers

private final List<MethodResolver> methodResolvers

typeConverter

private final TypeConverter typeConverter

variables

private final HashMap<String,Object> variables

构造器详细资料

SimpleEvaluationContext

private SimpleEvaluationContext(List<PropertyAccessor> accessors,
 List<MethodResolver> resolvers,
 @Nullable
 TypeConverter converter,
 @Nullable
 TypedValue rootObject)

方法详细资料

getRootObject

public TypedValue getRootObject()

Return the specified root object, if any.

指定者:

getRootObject 在接口中 EvaluationContext

getPropertyAccessors

public List<PropertyAccessor> getPropertyAccessors()

Return the specified PropertyAccessor delegates, if any.

指定者:

getPropertyAccessors 在接口中 EvaluationContext

另请参阅:

• forPropertyAccessors(cn.taketoday.expression.PropertyAccessor...)

getConstructorResolvers

public List<ConstructorResolver> getConstructorResolvers()

Return an empty list, always, since this context does not support the use of type references.

指定者:

getConstructorResolvers 在接口中 EvaluationContext

getMethodResolvers

public List<MethodResolver> getMethodResolvers()

Return the specified MethodResolver delegates, if any.

指定者:

getMethodResolvers 在接口中 EvaluationContext

另请参阅:

• SimpleEvaluationContext.Builder.withMethodResolvers(cn.taketoday.expression.MethodResolver...)

getBeanResolver

@Nullable
public BeanResolver getBeanResolver()

SimpleEvaluationContext does not support the use of bean references.

指定者:

getBeanResolver 在接口中 EvaluationContext

返回:

always null

getTypeLocator

public TypeLocator getTypeLocator()

SimpleEvaluationContext does not support use of type references.

指定者:

getTypeLocator 在接口中 EvaluationContext

返回:

TypeLocator implementation that raises a SpelEvaluationException with SpelMessage.TYPE_NOT_FOUND.

getTypeConverter

public TypeConverter getTypeConverter()

The configured TypeConverter.

By default this is StandardTypeConverter.

指定者:

getTypeConverter 在接口中 EvaluationContext

另请参阅:

• SimpleEvaluationContext.Builder.withTypeConverter(cn.taketoday.expression.TypeConverter)
• SimpleEvaluationContext.Builder.withConversionService(cn.taketoday.core.conversion.ConversionService)

getTypeComparator

public TypeComparator getTypeComparator()

Return an instance of StandardTypeComparator.

指定者:

getTypeComparator 在接口中 EvaluationContext

getOperatorOverloader

public OperatorOverloader getOperatorOverloader()

Return an instance of StandardOperatorOverloader.

指定者:

getOperatorOverloader 在接口中 EvaluationContext

assignVariable

public TypedValue assignVariable(String name,
 Supplier<TypedValue> valueSupplier)

SimpleEvaluationContext does not support variable assignment within expressions.

指定者:

assignVariable 在接口中 EvaluationContext

参数:

name - the name of the variable to assign

valueSupplier - the supplier of the value to be assigned to the variable

返回:

a TypedValue wrapping the assigned value

抛出:

SpelEvaluationException - with SpelMessage.VARIABLE_ASSIGNMENT_NOT_SUPPORTED

setVariable

public void setVariable(String name,
 @Nullable
 Object value)

Set a named variable or function in this evaluation context to the specified value.

A function can be registered as a Method or a MethodHandle.

Note that variables and functions share a common namespace in this evaluation context. See the class-level documentation for details.

指定者:

setVariable 在接口中 EvaluationContext

参数:

name - the name of the variable or function to set

value - the value to be placed in the variable or function

另请参阅:

• lookupVariable(String)

lookupVariable

@Nullable
public Object lookupVariable(String name)

Look up a named variable or function within this evaluation context.

Note that variables and functions share a common namespace in this evaluation context. See the class-level documentation for details.

指定者:

lookupVariable 在接口中 EvaluationContext

参数:

name - the name of the variable or function to look up

返回:

the value of the variable or function, or null if not found

forPropertyAccessors

public static SimpleEvaluationContext.Builder forPropertyAccessors(PropertyAccessor... accessors)

Create a SimpleEvaluationContext for the specified PropertyAccessor delegates: typically a custom PropertyAccessor specific to a use case (e.g. attribute resolution in a custom data structure), potentially combined with a DataBindingPropertyAccessor if property dereferences are needed as well.

参数:

accessors - the accessor delegates to use

另请参阅:

• DataBindingPropertyAccessor.forReadOnlyAccess()
• DataBindingPropertyAccessor.forReadWriteAccess()

forReadOnlyDataBinding

public static SimpleEvaluationContext.Builder forReadOnlyDataBinding()

Create a SimpleEvaluationContext for read-only access to public properties via DataBindingPropertyAccessor.

另请参阅:

• DataBindingPropertyAccessor.forReadOnlyAccess()
• forPropertyAccessors(cn.taketoday.expression.PropertyAccessor...)

forReadWriteDataBinding

public static SimpleEvaluationContext.Builder forReadWriteDataBinding()

Create a SimpleEvaluationContext for read-write access to public properties via DataBindingPropertyAccessor.

另请参阅:

• DataBindingPropertyAccessor.forReadWriteAccess()
• forPropertyAccessors(cn.taketoday.expression.PropertyAccessor...)