Package org.jfree.report.expressions
Interface Expression
- All Superinterfaces:
Cloneable
,Serializable
- All Known Subinterfaces:
Function
- All Known Implementing Classes:
AbstractExpression
,ColumnAggregationExpression
,FormulaExpression
,FormulaFunction
,GetValueExpression
,GroupByExpression
,IsEmptyDataExpression
,IsEmptyExpression
,IsEndOfDataExpression
,IsExportTypeExpression
,IsNullExpression
,SurveyScaleExpression
An expression is a lightweight computation that does not maintain a state.
Expressions are used to calculate values within a single row of a report.
Expressions can use a dataRow to access other fields, expressions or
functions within the current row in the report.
Statefull computations can be implemented using functions.
- Author:
- Thomas Morgner
- See Also:
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Method Summary
Modifier and TypeMethodDescriptionclone()
Clones the expression, expression should be reinitialized after the cloning.Return the current expression value.Return a new instance of this expression.getName()
Returns the name of the expression.boolean
A deep-traversing expression declares that it should receive updates from all subreports.boolean
Returns, whether the expression will be precomputed.boolean
Checks, whether the expression's result should be preserved in the precomputed value registry.void
setDeepTraversing
(boolean deepTraversing) Defines, whether the expression is deep-traversing.void
Sets the name of the expression.void
setPrecompute
(boolean precompute) Defines, whether the expression will be precomputed.void
setPreserve
(boolean preserve) Defines, whether the expression's result should be preserved in the precomputed value registry.void
setRuntime
(ExpressionRuntime runtime) Defines the DataRow used in this expression.
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Method Details
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getName
String getName()Returns the name of the expression. An expression without a name cannot be referenced from outside the element.- Returns:
- the function name.
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setName
Sets the name of the expression.- Parameters:
name
- the name.
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computeValue
Return the current expression value.The value depends (obviously) on the expression implementation.
- Returns:
- the value of the function.
- Throws:
DataSourceException
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clone
Clones the expression, expression should be reinitialized after the cloning.Expression maintain no state, cloning is done at the beginning of the report processing to disconnect the used expression from any other object space.
- Returns:
- A clone of this expression.
- Throws:
CloneNotSupportedException
- this should never happen.
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getInstance
Expression getInstance()Return a new instance of this expression. The copy is initialized and uses the same parameters as the original, but does not share any objects.- Returns:
- a copy of this function.
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setRuntime
Defines the DataRow used in this expression. The dataRow is set when the report processing starts and can be used to access the values of functions, expressions and the reports datasource.- Parameters:
runtime
- the runtime information for the expression
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isDeepTraversing
boolean isDeepTraversing()A deep-traversing expression declares that it should receive updates from all subreports. This mode should be activated if the expression's result depends on values contained in the subreport.- Returns:
- true, if the expression is deep-traversing, false otherwise.
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setDeepTraversing
void setDeepTraversing(boolean deepTraversing) Defines, whether the expression is deep-traversing.- Parameters:
deepTraversing
- true, if the expression is deep-traversing, false otherwise.
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isPrecompute
boolean isPrecompute()Returns, whether the expression will be precomputed. For precomputed expressions a parallel evaluation process is started and the result to which the expression evaluates before it gets out of scope will be used whenever an other expression queries this expression's value.- Returns:
- true, if the expression is precomputed, false otherwise.
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setPrecompute
void setPrecompute(boolean precompute) Defines, whether the expression will be precomputed. For precomputed expressions a parallel evaluation process is started and the result to which the expression evaluates before it gets out of scope will be used whenever an other expression queries this expression's value.- Parameters:
precompute
- true, if the expression is precomputed, false otherwise.
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isPreserve
boolean isPreserve()Checks, whether the expression's result should be preserved in the precomputed value registry. This way, the last value for that expression can be retrieved after the report has been finished. The preserve-function will only preserve the last value that has been evaluated before the expression went out of scope.- Returns:
- true, if the expression's results should be preserved, false otherwise.
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setPreserve
void setPreserve(boolean preserve) Defines, whether the expression's result should be preserved in the precomputed value registry. This way, the last value for that expression can be retrieved after the report has been finished.- Parameters:
preserve
- true, if the expression's results should be preserved, false otherwise.
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