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:

  • Constructor Details

    • SingleColumnRowMapper

      public SingleColumnRowMapper()
      Create a new SingleColumnRowMapper for bean-style configuration.
      See Also:

    • 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 org.springframework.core.convert.ConversionService conversionService)
      Set a ConversionService for converting a fetched value.

      Default is the DefaultConversionService.

      Since:
      5.0.4
      See Also:
      • DefaultConversionService.getSharedInstance()

    • mapRow

      @Nullable public 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 getting column values (that is, there's no need to catch SQLException)
      See Also:

    • getColumnValue

      @Nullable protected 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:

    • getColumnValue

      @Nullable protected 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:

    • convertValueToRequiredType

      @Nullable protected 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:

    • 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

      public static <T> SingleColumnRowMapper<T> newInstance(Class<T> requiredType, @Nullable org.springframework.core.convert.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: