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 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.
| Modifier and Type | Method and Description |
|---|---|
boolean |
evaluate(Object value,
int column)
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(Object value,
String columnName)
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(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. |
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.true 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 Predicatetrue ifrow 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 Predicatetrue if value lies within the filter; false otherwiseSQLException - if the column is not part of filtering criteria Submit a bug or feature
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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