所有已知实现类:
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.
从以下版本开始:
3.0
作者:
Keith Donald, Andy Clement, Juergen Hoeller

方法概要

所有方法实例方法抽象方法
修饰符和类型	方法	说明
`String`	`getExpressionString()`	Return 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 context.
`Object`	`getValue(Object rootObject)`	Evaluate this expression against the specified root object.
`<T> T`	`getValue(Object rootObject, Class<T> desiredResultType)`	Evaluate the expression in the default context against the specified root object.
`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.
`Object`	`getValue(EvaluationContext context, 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, Object rootObject, Class<T> desiredResultType)`	Evaluate the expression in a specified context which can resolve references to properties, methods, types, etc.
`Class<?>`	`getValueType()`	Return the most general type that can be passed to a `setValue(java.lang.Object, java.lang.Object)` method using the default context.
`Class<?>`	`getValueType(Object rootObject)`	Return the most general type that can be passed to the `setValue(Object, Object)` method using the default context.
`Class<?>`	`getValueType(EvaluationContext context)`	Return the most general type that can be passed to the `setValue(EvaluationContext, Object)` method for the given context.
`Class<?>`	`getValueType(EvaluationContext context, Object rootObject)`	Return the most general type that can be passed to the `setValue(EvaluationContext, Object, Object)` method for the given context.
`TypeDescriptor`	`getValueTypeDescriptor()`	Return the most general type that can be passed to a `setValue(java.lang.Object, java.lang.Object)` method using the default context.
`TypeDescriptor`	`getValueTypeDescriptor(Object rootObject)`	Return the most general type that can be passed to the `setValue(Object, Object)` method using the default context.
`TypeDescriptor`	`getValueTypeDescriptor(EvaluationContext context)`	Return the most general type that can be passed to the `setValue(EvaluationContext, Object)` method for the given context.
`TypeDescriptor`	`getValueTypeDescriptor(EvaluationContext context, Object rootObject)`	Return the most general type that can be passed to the `setValue(EvaluationContext, Object, Object)` method for the given context.
`boolean`	`isWritable(Object rootObject)`	Determine if an expression can be written to, i.e. setValue() can be called.
`boolean`	`isWritable(EvaluationContext context)`	Determine if an expression can be written to, i.e. setValue() can be called.
`boolean`	`isWritable(EvaluationContext context, Object rootObject)`	Determine if an expression can be written to, i.e. setValue() can be called.
`void`	`setValue(Object rootObject, Object value)`	Set this expression in the provided context to the value provided.
`void`	`setValue(EvaluationContext context, Object value)`	Set this expression in the provided context to the value provided.
`void`	`setValue(EvaluationContext context, Object rootObject, Object value)`	Set this expression in the provided context to the value provided.

- 方法详细资料
  - getExpressionString
```
String getExpressionString()
```
    Return the original string used to create this expression (unmodified).
    返回:
    the original expression string
  - getValue
```
@Nullable
Object getValue()
         throws EvaluationException
```
    Evaluate this expression in the default standard context.
    返回:
    the evaluation result
    抛出:
    EvaluationException - if there is a problem during evaluation
  - getValue
```
@Nullable
<T> T getValue(@Nullable
               Class<T> desiredResultType)
        throws EvaluationException
```
    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.
    参数:
    desiredResultType - the class the caller would like the result to be
    返回:
    the evaluation result
    抛出:
    EvaluationException - if there is a problem during evaluation
  - getValue
```
@Nullable
Object getValue(@Nullable
                Object rootObject)
         throws EvaluationException
```
    Evaluate this expression against the specified root object.
    参数:
    rootObject - the root object against which to evaluate the expression
    返回:
    the evaluation result
    抛出:
    EvaluationException - if there is a problem during evaluation
  - getValue
```
@Nullable
<T> T getValue(@Nullable
               Object rootObject,
               @Nullable
               Class<T> desiredResultType)
        throws EvaluationException
```
    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.
    参数:
    rootObject - the root object against which to evaluate the expression
    desiredResultType - the class the caller would like the result to be
    返回:
    the evaluation result
    抛出:
    EvaluationException - if there is a problem during evaluation
  - getValue
```
@Nullable
Object getValue(EvaluationContext context)
         throws EvaluationException
```
    Evaluate this expression in the provided context and return the result of evaluation.
    参数:
    context - the context in which to evaluate the expression
    返回:
    the evaluation result
    抛出:
    EvaluationException - if there is a problem during evaluation
  - getValue
```
@Nullable
Object getValue(EvaluationContext context,
                @Nullable
                Object rootObject)
         throws EvaluationException
```
    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.
    参数:
    context - the context in which to evaluate the expression
    rootObject - the root object against which to evaluate the expression
    返回:
    the evaluation result
    抛出:
    EvaluationException - if there is a problem during evaluation
  - getValue
```
@Nullable
<T> T getValue(EvaluationContext context,
               @Nullable
               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.
    参数:
    context - the context in which to evaluate the expression
    desiredResultType - the class the caller would like the result to be
    返回:
    the evaluation result
    抛出:
    EvaluationException - if there is a problem during evaluation
  - getValue
```
@Nullable
<T> T getValue(EvaluationContext context,
               @Nullable
               Object rootObject,
               @Nullable
               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. The supplied root object overrides any default specified on the supplied context.
    参数:
    context - the context in which to evaluate the expression
    rootObject - the root object against which to evaluate the expression
    desiredResultType - the class the caller would like the result to be
    返回:
    the evaluation result
    抛出:
    EvaluationException - if there is a problem during evaluation
  - getValueType
```
@Nullable
Class<?> getValueType()
               throws EvaluationException
```
    Return the most general type that can be passed to a setValue(java.lang.Object, java.lang.Object) method using the default context.
    返回:
    the most general type of value that can be set on this context
    抛出:
    EvaluationException - if there is a problem determining the type
  - getValueType
```
@Nullable
Class<?> getValueType(@Nullable
                      Object rootObject)
               throws EvaluationException
```
    Return the most general type that can be passed to the setValue(Object, Object) method using the default context.
    参数:
    rootObject - the root object against which to evaluate the expression
    返回:
    the most general type of value that can be set on this context
    抛出:
    EvaluationException - if there is a problem determining the type
  - getValueType
```
@Nullable
Class<?> getValueType(EvaluationContext context)
               throws EvaluationException
```
    Return the most general type that can be passed to the setValue(EvaluationContext, Object) method for the given context.
    参数:
    context - the context in which to evaluate the expression
    返回:
    the most general type of value that can be set on this context
    抛出:
    EvaluationException - if there is a problem determining the type
  - getValueType
```
@Nullable
Class<?> getValueType(EvaluationContext context,
                      @Nullable
                      Object rootObject)
               throws EvaluationException
```
    Return the most general type that can be passed to the setValue(EvaluationContext, Object, Object) method for the given context. The supplied root object overrides any specified in the context.
    参数:
    context - the context in which to evaluate the expression
    rootObject - the root object against which to evaluate the expression
    返回:
    the most general type of value that can be set on this context
    抛出:
    EvaluationException - if there is a problem determining the type
  - getValueTypeDescriptor
```
@Nullable
TypeDescriptor getValueTypeDescriptor()
                               throws EvaluationException
```
    Return the most general type that can be passed to a setValue(java.lang.Object, java.lang.Object) method using the default context.
    返回:
    a type descriptor for values that can be set on this context
    抛出:
    EvaluationException - if there is a problem determining the type
  - getValueTypeDescriptor
```
@Nullable
TypeDescriptor getValueTypeDescriptor(@Nullable
                                      Object rootObject)
                               throws EvaluationException
```
    Return the most general type that can be passed to the setValue(Object, Object) method using the default context.
    参数:
    rootObject - the root object against which to evaluate the expression
    返回:
    a type descriptor for values that can be set on this context
    抛出:
    EvaluationException - if there is a problem determining the type
  - getValueTypeDescriptor
```
@Nullable
TypeDescriptor getValueTypeDescriptor(EvaluationContext context)
                               throws EvaluationException
```
    Return the most general type that can be passed to the setValue(EvaluationContext, Object) method for the given context.
    参数:
    context - the context in which to evaluate the expression
    返回:
    a type descriptor for values that can be set on this context
    抛出:
    EvaluationException - if there is a problem determining the type
  - getValueTypeDescriptor
```
@Nullable
TypeDescriptor getValueTypeDescriptor(EvaluationContext context,
                                      @Nullable
                                      Object rootObject)
                               throws EvaluationException
```
    Return the most general type that can be passed to the setValue(EvaluationContext, Object, Object) method for the given context. The supplied root object overrides any specified in the context.
    参数:
    context - the context in which to evaluate the expression
    rootObject - the root object against which to evaluate the expression
    返回:
    a type descriptor for values that can be set on this context
    抛出:
    EvaluationException - if there is a problem determining the type
  - isWritable
```
boolean isWritable(@Nullable
                   Object rootObject)
            throws EvaluationException
```
    Determine if an expression can be written to, i.e. setValue() can be called.
    参数:
    rootObject - the root object against which to evaluate the expression
    返回:
    true if the expression is writable; false otherwise
    抛出:
    EvaluationException - if there is a problem determining if it is writable
  - isWritable
```
boolean isWritable(EvaluationContext context)
            throws EvaluationException
```
    Determine if an expression can be written to, i.e. setValue() can be called.
    参数:
    context - the context in which the expression should be checked
    返回:
    true if the expression is writable; false otherwise
    抛出:
    EvaluationException - if there is a problem determining if it is writable
  - isWritable
```
boolean isWritable(EvaluationContext context,
                   @Nullable
                   Object rootObject)
            throws EvaluationException
```
    Determine if an expression can be written to, i.e. setValue() can be called. The supplied root object overrides any specified in the context.
    参数:
    context - the context in which the expression should be checked
    rootObject - the root object against which to evaluate the expression
    返回:
    true if the expression is writable; false otherwise
    抛出:
    EvaluationException - if there is a problem determining if it is writable
  - setValue
```
void setValue(@Nullable
              Object rootObject,
              @Nullable
              Object value)
       throws EvaluationException
```
    Set this expression in the provided context to the value provided.
    参数:
    rootObject - the root object against which to evaluate the expression
    value - the new value
    抛出:
    EvaluationException - if there is a problem during evaluation
  - setValue
```
void setValue(EvaluationContext context,
              @Nullable
              Object value)
       throws EvaluationException
```
    Set this expression in the provided context to the value provided.
    参数:
    context - the context in which to set the value of the expression
    value - the new value
    抛出:
    EvaluationException - if there is a problem during evaluation
  - setValue
```
void setValue(EvaluationContext context,
              @Nullable
              Object rootObject,
              @Nullable
              Object value)
       throws EvaluationException
```
    Set this expression in the provided context to the value provided. The supplied root object overrides any specified in the context.
    参数:
    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
    抛出:
    EvaluationException - if there is a problem during evaluation

接口 Expression

方法概要

方法详细资料

getExpressionString

getValue

getValue

getValue

getValue

getValue

getValue

getValue

getValue

getValueType

getValueType

getValueType

getValueType

getValueTypeDescriptor

getValueTypeDescriptor

getValueTypeDescriptor

getValueTypeDescriptor

isWritable

isWritable

isWritable

setValue

setValue

setValue