compact3
javax.sql.rowset
Interface Predicate
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public interface PredicateThe standard interface that provides the framework for allFilteredRowSetobjects to describe their filters.1.0 Background
ThePredicateinterface is a standard interface that applications can implement to define the filter they wish to apply to a aFilteredRowSetobject. AFilteredRowSetobject consumes implementations of this interface and enforces the constraints defined in the implementation of the methodevaluate. AFilteredRowSetobject 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 theFilteredRowSetinterface, this allows for a flexible and application motivated implementations ofPredicateto 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
Stringand integer index based constructors to provide for JDBC RowSet Implementation applications that use both column identification conventions.
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Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method and Description booleanevaluate(Object value, int column)This method is called by aFilteredRowSetobject to check whether the value lies between the filtering criterion (or criteria if multiple constraints exist) set using thesetFilter()method.booleanevaluate(Object value, String columnName)This method is called by theFilteredRowSetobject to check whether the value lies between the filtering criteria set using the setFilter method.booleanevaluate(RowSet rs)This method is typically called aFilteredRowSetobject internal methods (not public) that control theRowSetobject's cursor moving from row to the next.
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Method Detail
evaluate
boolean evaluate(RowSet rs)
This method is typically called aFilteredRowSetobject internal methods (not public) that control theRowSetobject'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:
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rs- TheRowSetto be evaluated - Returns:
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trueif there are more rows in the filter;falseotherwise
evaluate
boolean evaluate(Object value, int column) throws SQLException
This method is called by aFilteredRowSetobject to check whether the value lies between the filtering criterion (or criteria if multiple constraints exist) set using thesetFilter()method.The
FilteredRowSetobject will use this method internally while inserting new rows to aFilteredRowSetinstance.- Parameters:
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value- AnObjectvalue which needs to be checked, whether it can be part of thisFilterRowSetobject. -
column- aintobject that must match the SQL index of a column in thisRowSetobject. This must have been passed toPredicateas one of the columns for filtering while initializing aPredicate - Returns:
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trueif row value lies within the filter;falseotherwise - Throws:
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SQLException- if the column is not part of filtering criteria
evaluate
boolean evaluate(Object value, String columnName) throws SQLException
This method is called by theFilteredRowSetobject to check whether the value lies between the filtering criteria set using the setFilter method.The
FilteredRowSetobject will use this method internally while inserting new rows to aFilteredRowSetinstance.- Parameters:
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value- AnObjectvalue which needs to be checked, whether it can be part of thisFilterRowSet. -
columnName- aStringobject that must match the SQL name of a column in thisRowSet, ignoring case. This must have been passed toPredicateas one of the columns for filtering while initializing aPredicate - Returns:
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trueif value lies within the filter;falseotherwise - Throws:
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SQLException- if the column is not part of filtering criteria
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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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