org.springframework.expression.spel.ast

接口 ValueRef

所有已知实现类:

ValueRef.NullValueRef, ValueRef.TypedValueHolderValueRef

public interface ValueRef

Represents a reference to a value. With a reference it is possible to get or set the value. Passing around value references rather than the values themselves can avoid incorrect duplication of operand evaluation. For example in 'list[index++]++' without a value reference for 'list[index++]' it would be necessary to evaluate list[index++] twice (once to get the value, once to determine where the value goes) and that would double increment index.

从以下版本开始:

3.2

作者:

Andy Clement

嵌套类概要

嵌套类

限定符和类型	接口和说明
static class	ValueRef.NullValueRef A ValueRef for the null value.
static class	ValueRef.TypedValueHolderValueRef A ValueRef holder for a single value, which cannot be set.

方法概要

限定符和类型	方法和说明
TypedValue	getValue() Returns the value this ValueRef points to, it should not require expression component re-evaluation.
boolean	isWritable() Indicates whether calling setValue(Object) is supported.
void	setValue(Object newValue) Sets the value this ValueRef points to, it should not require expression component re-evaluation.

方法详细资料

getValue

TypedValue getValue()

Returns the value this ValueRef points to, it should not require expression component re-evaluation.

返回:

the value

setValue

void setValue(@Nullable
              Object newValue)

Sets the value this ValueRef points to, it should not require expression component re-evaluation.

参数:

newValue - the new value

isWritable

boolean isWritable()

Indicates whether calling setValue(Object) is supported.

返回:

true if setValue() is supported for this value reference.