public interface Predicate
FilteredRowSet
objects to describe their filters. Predicate
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. FilteredRowSet
. 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.
Modifier and Type | Method | Description |
---|---|---|
boolean |
evaluate |
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. |
boolean |
evaluate |
This method is called by the FilteredRowSet object to check whether the value lies between the filtering criteria set using the setFilter method. |
boolean |
evaluate |
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. |
boolean evaluate(RowSet rs)
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.rs
- The RowSet
to be evaluatedtrue
if there are more rows in the filter; false
otherwiseboolean evaluate(Object value, int column) throws SQLException
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.
value
- An Object
value which needs to be checked, whether it can be part of this FilterRowSet
object.column
- a int
object that must match the SQL index of a column in this RowSet
object. This must have been passed to Predicate
as one of the columns for filtering while initializing a Predicate
true
if row value lies within the filter; false
otherwiseSQLException
- if the column is not part of filtering criteriaboolean evaluate(Object value, String columnName) throws SQLException
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.
value
- An Object
value which needs to be checked, whether it can be part of this FilterRowSet
.columnName
- a String
object that must match the SQL name of a column in this RowSet
, ignoring case. This must have been passed to Predicate
as one of the columns for filtering while initializing a Predicate
true
if value lies within the filter; false
otherwiseSQLException
- if the column is not part of filtering criteria
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https://docs.oracle.com/en/java/javase/21/docs/api/java.sql.rowset/javax/sql/rowset/Predicate.html