public class QueryReader
- extends Object
Helper class which keeps track of the column positions in dynamically
generated select statements so that the query user can easily get the
results correctly, especially useful where the code which generates the
query is separate from the code which uses the query.
A QueryReader may only be used for a single query generation. Also, the
Columns will not have a valid position until the query is actually
converted to a string. After that, the Columns will never change their
stored index(es), so reuse in a new query is impossible. Likewise, the
state of the QueryReader is altered by the query generation, so, it cannot
be used in a new query either. However, the QueryReader utility
is designed so that it is not modified after query generation, so it can
safely be used concurrently with the original query string as long as
desired (so it can safely be used in a static context along with the
associated query string).
// example where another class is generating the actual query
QueryReader reader = new QueryReader();
QueryReader.Column col1 = reader.getNewColumn();
QueryReader.Column col2 = reader.getNewColumn();
String queryStr = otherObj.createQuery(col1, col2);
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery(queryStr);
String col1Str = col1.getString(rs);
int col2Int = col2.getInt(rs);
// ... handle results ...
// example query generation
Column col1, col2, idCol;
String queryStr = new SelectQuery()
- James Ahlborn
Nested Class Summary
A SqlObject which outputs the passed in SqlObject, and records the
current index at the time the
appendTo method is called.
the default first index that will be assigned to a column
Creates a QueryReader with a different startIndex from the default.
|Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
public static final int DEFAULT_START_INDEX
- the default first index that will be assigned to a column
- See Also:
- Constant Field Values
public QueryReader(int startIndex)
- Creates a QueryReader with a different startIndex from the default.
This may be useful if there are other columns in the ResultSet
which are not owned by this QueryReader.
public QueryReader.Column getNewColumn()
- a new Column tied to this QueryReader. Its internal state
is not valid until the query is converted to an actual string.
Also, it can only be used in one place in the query.
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