Expression

All Known Implementing Classes:

AbstractAlertExpressionContext.AlertVariableExpression, AbstractExpression, AlarmEventPropertyExpression, ArithmeticExpression, BitwiseExpression, BitwiseNot, BoundPropertyExpression, BoundPropertyExpression, BoundTagExpression, BoundVariableExpression, ComparisonExpression, ConstantExpression, EqualityExpression, FormattedExpression, FunctionExpression, LikeExpression, LocaleAwareMessageParseContext.LocaleStringExpression, LogicalExpression, NonLocalizedToStringExpression, NotExpression, PropertyBasedExpressionParseContext.PropertyReferenceExpression, SubscriptExpression, TagPathReadExpression, TagReferenceBinder.SubscribedTagExpression, TagReferenceBinder.TagReadExpression, ToStringExpression, UMinusExpression
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public interface Expression
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An expression is something that can be executed to compute a result. Each instance of expression is typically some node in what amounts to a parse tree. Many expressions such as operators and function calls have child expressions.

Method Summary

All Methods Instance Methods Abstract Methods Default Methods
Modifier and Type	Method	Description
`void`	`connect(CommonContext context, InteractionListener updateListener)`	Gives the expression a chance to connect itself to things, if necessary.
`void`	`disconnect()`	Tells the expression to disconnect from anything it was connected to.
`QualifiedValue`	`execute()`	Compute and return the value of this expression
`Expression[]`	`getChildren()`	The children (if any) that this expression is dependent on for its execution
`java.lang.String`	`getOpName()`	Return a human-readable name for the operation that this expression performs
`default java.lang.Class<?>`	`getType()`	Return the type that this expression will return
`void`	`shutdown()`	Tells the expression to shutdown any polling operations.
`void`	`startup()`	Tells the expression to startup any polling operations.

- Method Detail
  - execute
```
@Nonnull
QualifiedValue execute()
                throws ExpressionException
```
    Compute and return the value of this expression
    
    Throws:
    
    ExpressionException
  - getType
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default java.lang.Class<?> getType()
```
    Return the type that this expression will return
  - getOpName
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java.lang.String getOpName()
```
    Return a human-readable name for the operation that this expression performs
  - getChildren
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Expression[] getChildren()
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    The children (if any) that this expression is dependent on for its execution
  - connect
```
void connect(CommonContext context,
             InteractionListener updateListener)
```
    Gives the expression a chance to connect itself to things, if necessary. Most expressions do not have any connections. An expression should notify the updateListener if they change.
  - disconnect
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void disconnect()
```
    Tells the expression to disconnect from anything it was connected to.
  - startup
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void startup()
```
    Tells the expression to startup any polling operations. Expressions that use this can remember the updateListener from connect() to feed update notification to.
  - shutdown
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void shutdown()
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    Tells the expression to shutdown any polling operations.