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public interface Predicate
The standard interface that provides the framework for allFilteredRowSet
objects to describe their filters.1.0 Background
ThePredicate
interface is a standard interface that applications can implement to define the filter they wish to apply to a aFilteredRowSet
object. AFilteredRowSet
object consumes implementations of this interface and enforces the constraints defined in the implementation of the methodevaluate
. AFilteredRowSet
object enforces the filter constraints in a bi-directional manner: It outputs only rows that are within the constraints of the filter; and conversely, it inserts, modifies, or updates only rows that are within the constraints of the filter.2.0 Implementation Guidelines
In order to supply a predicate for theFilteredRowSet
. this interface must be implemented. At this time, the JDBC RowSet Implementations (JSR-114) does not specify any standard filters definitions. By specifying a standard means and mechanism for a range of filters to be defined and deployed with both the reference and vendor implementations of theFilteredRowSet
interface, this allows for a flexible and application motivated implementations ofPredicate
to emerge.A sample implementation would look something like this:
public class Range implements Predicate { private Object lo[]; private Object hi[]; private int idx[]; public Range(Object[] lo, Object[] hi, int[] idx) { this.lo = lo; this.hi = hi; this.idx = idx; } public boolean evaluate(RowSet rs) { CachedRowSet crs = (CachedRowSet)rs; boolean bool1,bool2; // Check the present row determine if it lies // within the filtering criteria. for (int i = 0; i < idx.length; i++) { if ((rs.getObject(idx[i]) >= lo[i]) && (rs.getObject(idx[i]) >= hi[i]) { bool1 = true; // within filter constraints } else { bool2 = true; // outside of filter constraints } } if (bool2) { return false; } else { return true; } }
The example above implements a simple range predicate. Note, that implementations should but are not required to provider
String
and integer index based constructors to provide for JDBC RowSet Implementation applications that use both column identification conventions.
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Method Summary
Methods Modifier and Type Method and Description boolean
evaluate(Object value, int column)
This method is called by aFilteredRowSet
object to check whether the value lies between the filtering criterion (or criteria if multiple constraints exist) set using thesetFilter()
method.boolean
evaluate(Object value, String columnName)
This method is called by theFilteredRowSet
object to check whether the value lies between the filtering criteria set using the setFilter method.boolean
evaluate(RowSet rs)
This method is typically called aFilteredRowSet
object internal methods (not public) that control theRowSet
object's cursor moving from row to the next.
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Method Detail
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evaluate
boolean evaluate(RowSet rs)
This method is typically called aFilteredRowSet
object internal methods (not public) that control theRowSet
object's cursor moving from row to the next. In addition, if this internal method moves the cursor onto a row that has been deleted, the internal method will continue to ove the cursor until a valid row is found.- Returns:
true
if there are more rows in the filter;false
otherwise
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evaluate
boolean evaluate(Object value, int column) throws SQLException
This method is called by aFilteredRowSet
object to check whether the value lies between the filtering criterion (or criteria if multiple constraints exist) set using thesetFilter()
method.The
FilteredRowSet
object will use this method internally while inserting new rows to aFilteredRowSet
instance.- Parameters:
value
- AnObject
value which needs to be checked, whether it can be part of thisFilterRowSet
object.column
- aint
object that must match the SQL index of a column in thisRowSet
object. This must have been passed toPredicate
as one of the columns for filtering while initializing aPredicate
- Returns:
true
ifrow value lies within the filter;false
otherwise- Throws:
SQLException
- if the column is not part of filtering criteria
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evaluate
boolean evaluate(Object value, String columnName) throws SQLException
This method is called by theFilteredRowSet
object to check whether the value lies between the filtering criteria set using the setFilter method.The
FilteredRowSet
object will use this method internally while inserting new rows to aFilteredRowSet
instance.- Parameters:
value
- AnObject
value which needs to be checked, whether it can be part of thisFilterRowSet
.columnName
- aString
object that must match the SQL name of a column in thisRowSet
, ignoring case. This must have been passed toPredicate
as one of the columns for filtering while initializing aPredicate
- Returns:
true
if value lies within the filter;false
otherwise- Throws:
SQLException
- if the column is not part of filtering criteria
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