Interface Predicate
public interface Predicate
The standard interface that provides the framework for all FilteredRowSet
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 a FilteredRowSet
object. A FilteredRowSet
object consumes implementations of this interface and enforces the constraints defined in the implementation of the method evaluate
. A FilteredRowSet
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 the FilteredRowSet
interface, this allows for a flexible and application motivated implementations of Predicate
to emerge.
A sample implementation would look something like this:
public class Range implements Predicate { private int[] lo; private int[] hi; private int[] idx; public Range(int[] lo, int[] hi, int[] idx) { this.lo = lo; this.hi = hi; this.idx = idx; } public boolean evaluate(RowSet rs) { // Check the present row determine if it lies // within the filtering criteria. for (int i = 0; i < idx.length; i++) { int value; try { value = (Integer) rs.getObject(idx[i]); } catch (SQLException ex) { Logger.getLogger(Range.class.getName()).log(Level.SEVERE, null, ex); return false; } if (value < lo[i] && value > hi[i]) { // outside of filter constraints return false; } } // Within filter constraints return true; } }
The example above implements a simple range predicate. Note, that implementations should but are not required to provide String
and integer index based constructors to provide for JDBC RowSet Implementation applications that use both column identification conventions.
- Since:
- 1.5
Method Summary
Modifier and Type | Method | Description |
---|---|---|
boolean | evaluate(Object value,
int column) | This method is called by a |
boolean | evaluate(Object value,
String columnName) | This method is called by the |
boolean | evaluate(RowSet rs) | This method is typically called a |
Method Detail
evaluate
boolean evaluate(RowSet rs)
This method is typically called a FilteredRowSet
object internal methods (not public) that control the RowSet
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.
- Parameters:
-
rs
- TheRowSet
to be evaluated - Returns:
-
true
if there are more rows in the filter;false
otherwise
evaluate
boolean evaluate(Object value, int column) throws SQLException
This method is called by a FilteredRowSet
object to check whether the value lies between the filtering criterion (or criteria if multiple constraints exist) set using the setFilter()
method.
The FilteredRowSet
object will use this method internally while inserting new rows to a FilteredRowSet
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
if row value lies within the filter;false
otherwise - Throws:
-
SQLException
- if the column is not part of filtering criteria
evaluate
boolean evaluate(Object value, String columnName) throws SQLException
This method is called by the FilteredRowSet
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 a FilteredRowSet
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