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 TypeMethodDescriptionboolean
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
This method is called by theFilteredRowSet
object to check whether the value lies between the filtering criteria set using the setFilter method.boolean
This method is typically called aFilteredRowSet
object internal methods (not public) that control theRowSet
object's cursor moving from row to the next.
-
Method Details
-
evaluate
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.- Parameters:
rs
- TheRowSet
to be evaluated- Returns:
true
if there are more rows in the filter;false
otherwise
-
evaluate
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
if row value lies within the filter;false
otherwise- Throws:
SQLException
- if the column is not part of filtering criteria
-
evaluate
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
-