Package org.springframework.jdbc.core

Class SingleColumnRowMapper<T>

java.lang.Object

org.springframework.jdbc.core.SingleColumnRowMapper<T>

Type Parameters:

T - the result type

All Implemented Interfaces:

RowMapper<T>

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.

Since:

1.2

Author:

Juergen Hoeller, Kazuki Shimizu

See Also:

• JdbcTemplate.queryForList(String, Class)
• JdbcTemplate.queryForObject(String, Class)

Constructor Summary

Constructors

Constructor	Description
SingleColumnRowMapper()	Create a new SingleColumnRowMapper for bean-style configuration.
SingleColumnRowMapper(Class<T> requiredType)	Create a new SingleColumnRowMapper.

Method Summary

Modifier and Type	Method	Description
protected @Nullable Object	convertValueToRequiredType(Object value, Class<?> requiredType)	Convert the given column value to the specified required type.
protected @Nullable Object	getColumnValue(ResultSet rs, int index)	Retrieve a JDBC object value for the specified column, using the most appropriate value type.
protected @Nullable Object	getColumnValue(ResultSet rs, int index, @Nullable Class<?> requiredType)	Retrieve a JDBC object value for the specified column.
@Nullable T	mapRow(ResultSet rs, int rowNum)	Extract a value for the single column in the current row.
static <T> SingleColumnRowMapper<T>	newInstance(Class<T> requiredType)	Static factory method to create a new SingleColumnRowMapper.
static <T> SingleColumnRowMapper<T>	newInstance(Class<T> requiredType, @Nullable ConversionService conversionService)	Static factory method to create a new SingleColumnRowMapper.
void	setConversionService(@Nullable ConversionService conversionService)	Set a ConversionService for converting a fetched value.
void	setRequiredType(Class<T> requiredType)	Set the type that each result object is expected to match.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

SingleColumnRowMapper

public SingleColumnRowMapper()

Create a new SingleColumnRowMapper for bean-style configuration.

See Also:

• setRequiredType(java.lang.Class<T>)

SingleColumnRowMapper

public SingleColumnRowMapper(Class<T> requiredType)

Create a new SingleColumnRowMapper.

Parameters:

requiredType - the type that each result object is expected to match

Method Details

setRequiredType

public void setRequiredType(Class<T> requiredType)

Set the type that each result object is expected to match.

If not specified, the column value will be exposed as returned by the JDBC driver.

setConversionService

public void setConversionService(@Nullable ConversionService conversionService)

Set a ConversionService for converting a fetched value.

Default is the DefaultConversionService.

Since:

5.0.4

See Also:

• DefaultConversionService.getSharedInstance()

mapRow

public @Nullable T mapRow(ResultSet rs,
 int rowNum)
                   throws SQLException

Extract a value for the single column in the current row.

Validates that there is only one column selected, then delegates to getColumnValue() and also convertValueToRequiredType, if necessary.

Specified by:

mapRow in interface RowMapper<T>

Parameters:

rs - the ResultSet to map (pre-initialized for the current row)

rowNum - the number of the current row

Returns:

the result object for the current row (may be null)

Throws:

SQLException - if an SQLException is encountered while getting column values (that is, there's no need to catch SQLException)

See Also:

• ResultSetMetaData.getColumnCount()
• getColumnValue(java.sql.ResultSet, int, Class)
• convertValueToRequiredType(Object, Class)

getColumnValue

protected @Nullable Object getColumnValue(ResultSet rs,
 int index,
 @Nullable Class<?> requiredType)
                                   throws SQLException

Retrieve a JDBC object value for the specified column.

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.

Parameters:

rs - is the ResultSet holding the data

index - is the column index

requiredType - the type that each result object is expected to match (or null if none specified)

Returns:

the Object value

Throws:

SQLException - in case of extraction failure

See Also:

• JdbcUtils.getResultSetValue(java.sql.ResultSet, int, Class)
• getColumnValue(java.sql.ResultSet, int)

getColumnValue

protected @Nullable Object getColumnValue(ResultSet rs,
 int index)
                                   throws SQLException

Retrieve a JDBC object value for the specified column, using the most appropriate value type. Called if no required type has been specified.

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.

Parameters:

rs - is the ResultSet holding the data

index - is the column index

Returns:

the Object value

Throws:

SQLException - in case of extraction failure

See Also:

• JdbcUtils.getResultSetValue(java.sql.ResultSet, int)

convertValueToRequiredType

protected @Nullable Object convertValueToRequiredType(Object value,
 Class<?> requiredType)

Convert the given column value to the specified required type. Only called if the extracted column value does not match already.

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). Otherwise, the value will be converted to a required type using the ConversionService.

Parameters:

value - the column value as extracted from getColumnValue() (never null)

requiredType - the type that each result object is expected to match (never null)

Returns:

the converted value

See Also:

• getColumnValue(java.sql.ResultSet, int, Class)

newInstance

public static <T> SingleColumnRowMapper<T> newInstance(Class<T> requiredType)

Static factory method to create a new SingleColumnRowMapper.

Parameters:

requiredType - the type that each result object is expected to match

Since:

4.1

See Also:

• newInstance(Class, ConversionService)

newInstance

public static <T> SingleColumnRowMapper<T> newInstance(Class<T> requiredType,
 @Nullable ConversionService conversionService)

Static factory method to create a new SingleColumnRowMapper.

Parameters:

requiredType - the type that each result object is expected to match

conversionService - the ConversionService for converting a fetched value, or null for none

Since:

5.0.4

See Also:

• newInstance(Class)
• setConversionService(org.springframework.core.convert.ConversionService)