Package org.springframework.data.cassandra.core.cql

Class SingleColumnRowMapper<T>

java.lang.Object
org.springframework.data.cassandra.core.cql.SingleColumnRowMapper<T>
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 Row 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 a Row and converted into the specified target type.

Since:
2.0
Author:
Mark Paluch
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.

      Consider using the newInstance(java.lang.Class<T>) factory method instead, which allows for specifying the required type once only.

      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 Row.

    • mapRow

      public T mapRow(com.datastax.oss.driver.api.core.cql.Row row, int rowNum) throws com.datastax.oss.driver.api.core.DriverException
      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:
      row - the Row to map, must not be null.
      rowNum - the number of the current row.
      Returns:
      the result object for the current row.
      Throws:
      com.datastax.oss.driver.api.core.DriverException - if a DriverException is encountered getting column values (that is, there's no need to catch DriverException)
      See Also:

    • getColumnValue

      @Nullable protected Object getColumnValue(com.datastax.oss.driver.api.core.cql.Row row, int index, @Nullable Class<?> requiredType) throws com.datastax.oss.driver.api.core.DriverException
      Retrieve a CQL object value for the specified column.

      The default implementation calls RowUtils.getRowValue(Row, int, Class). If no required type has been specified, this method delegates to getColumnValue(rs, index), which basically calls GettableByIndex.getObject(int) but applies some additional default conversion to appropriate value types.

      Parameters:
      row - is the Row holding the data, must not be null.
      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:
      com.datastax.oss.driver.api.core.DriverException - in case of extraction failure
      See Also:

    • getColumnValue

      @Nullable protected Object getColumnValue(com.datastax.oss.driver.api.core.cql.Row row, int index)
      Retrieve a 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 RowUtils.getRowValue(Row, int, Class), which uses the GettableByIndex.getObject(int) method.

      Parameters:
      row - is the Row holding the data, must not be null.
      index - is the column index
      Returns:
      the Object value.
      Throws:
      com.datastax.oss.driver.api.core.DriverException - in case of extraction failure.
      See Also:

    • convertValueToRequiredType

      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).

      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 (with the required type specified only once).
      Parameters:
      requiredType - the type that each result object is expected to match