public class SingleColumnRowMapper<T> extends Object implements RowMapper<T>
RowMapper
implementation that converts a single column into a single
result value per row. Expects to operate on a java.sql.ResultSet
that just contains a single column.
The type of the result value for each row can be specified. The value
for the single column will be extracted from the ResultSet
and converted into the specified target type.
JdbcTemplate.queryForList(String, Class)
,
JdbcTemplate.queryForObject(String, Class)
Constructor and Description |
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SingleColumnRowMapper()
Create a new SingleColumnRowMapper.
|
SingleColumnRowMapper(Class<T> requiredType)
Create a new SingleColumnRowMapper.
|
Modifier and Type | Method and Description |
---|---|
protected Object |
convertValueToRequiredType(Object value,
Class requiredType)
Convert the given column value to the specified required type.
|
protected Object |
getColumnValue(ResultSet rs,
int index)
Retrieve a JDBC object value for the specified column, using the most
appropriate value type.
|
protected Object |
getColumnValue(ResultSet rs,
int index,
Class requiredType)
Retrieve a JDBC object value for the specified column.
|
T |
mapRow(ResultSet rs,
int rowNum)
Extract a value for the single column in the current row.
|
void |
setRequiredType(Class<T> requiredType)
Set the type that each result object is expected to match.
|
public SingleColumnRowMapper()
setRequiredType(java.lang.Class<T>)
public void setRequiredType(Class<T> requiredType)
If not specified, the column value will be exposed as returned by the JDBC driver.
public T mapRow(ResultSet rs, int rowNum) throws SQLException
Validates that there is only one column selected,
then delegates to getColumnValue()
and also
convertValueToRequiredType
, if necessary.
mapRow
in interface RowMapper<T>
rs
- the ResultSet to map (pre-initialized for the current row)rowNum
- the number of the current rowSQLException
- if a SQLException is encountered getting
column values (that is, there's no need to catch SQLException)ResultSetMetaData.getColumnCount()
,
getColumnValue(java.sql.ResultSet, int, Class)
,
convertValueToRequiredType(Object, Class)
protected Object getColumnValue(ResultSet rs, int index, Class requiredType) throws SQLException
The default implementation calls
JdbcUtils.getResultSetValue(java.sql.ResultSet, int, Class)
.
If no required type has been specified, this method delegates to
getColumnValue(rs, index)
, which basically calls
ResultSet.getObject(index)
but applies some additional
default conversion to appropriate value types.
rs
- is the ResultSet holding the dataindex
- is the column indexrequiredType
- the type that each result object is expected to match
(or null
if none specified)SQLException
- in case of extraction failureJdbcUtils.getResultSetValue(java.sql.ResultSet, int, Class)
,
getColumnValue(java.sql.ResultSet, int)
protected Object getColumnValue(ResultSet rs, int index) throws SQLException
The default implementation delegates to JdbcUtils.getResultSetValue()
,
which uses the ResultSet.getObject(index)
method. Additionally,
it includes a "hack" to get around Oracle returning a non-standard object for
their TIMESTAMP datatype. See the JdbcUtils#getResultSetValue()
javadoc for details.
rs
- is the ResultSet holding the dataindex
- is the column indexSQLException
- in case of extraction failureJdbcUtils.getResultSetValue(java.sql.ResultSet, int)
protected Object convertValueToRequiredType(Object value, Class requiredType)
If the required type is String, the value will simply get stringified
via toString()
. In case of a Number, the value will be
converted into a Number, either through number conversion or through
String parsing (depending on the value type).
value
- the column value as extracted from getColumnValue()
(never null
)requiredType
- the type that each result object is expected to match
(never null
)getColumnValue(java.sql.ResultSet, int, Class)