Class MappingSqlQueryWithParameters<T>

Type Parameters:
T - the result type
All Implemented Interfaces:
Direct Known Subclasses:

public abstract class MappingSqlQueryWithParameters<T> extends SqlQuery<T>
Reusable RDBMS query in which concrete subclasses must implement the abstract mapRow(ResultSet, int) method to map each row of the JDBC ResultSet into an object.

Such manual mapping is usually preferable to "automatic" mapping using reflection, which can become complex in non-trivial cases. For example, the present class allows different objects to be used for different rows (for example, if a subclass is indicated). It allows computed fields to be set. And there's no need for ResultSet columns to have the same names as bean properties. The Pareto Principle in action: going the extra mile to automate the extraction process makes the framework much more complex and delivers little real benefit.

Subclasses can be constructed providing SQL, parameter types and a DataSource. SQL will often vary between subclasses.

Rod Johnson, Thomas Risberg, Jean-Pierre Pawlak
See Also:
  • Constructor Details

    • MappingSqlQueryWithParameters

      public MappingSqlQueryWithParameters()
      Constructor to allow use as a JavaBean.
    • MappingSqlQueryWithParameters

      public MappingSqlQueryWithParameters(DataSource ds, String sql)
      Convenient constructor with DataSource and SQL string.
      ds - the DataSource to use to get connections
      sql - the SQL to run
  • Method Details

    • newRowMapper

      protected RowMapper<T> newRowMapper(@Nullable Object[] parameters, @Nullable Map<?,?> context)
      Implementation of protected abstract method. This invokes the subclass's implementation of the mapRow() method.
      Specified by:
      newRowMapper in class SqlQuery<T>
      parameters - the parameters to the execute() method, in case subclass is interested; may be null if there were no parameters.
      context - the contextual information passed to the mapRow callback method. The JDBC operation itself doesn't rely on this parameter, but it can be useful for creating the objects of the result list.
      See Also:
    • mapRow

      @Nullable protected abstract T mapRow(ResultSet rs, int rowNum, @Nullable Object[] parameters, @Nullable Map<?,?> context) throws SQLException
      Subclasses must implement this method to convert each row of the ResultSet into an object of the result type.
      rs - the ResultSet we're working through
      rowNum - row number (from 0) we're up to
      parameters - to the query (passed to the execute() method). Subclasses are rarely interested in these. It can be null if there are no parameters.
      context - passed to the execute() method. It can be null if no contextual information is need.
      an object of the result type
      SQLException - if there's an error extracting data. Subclasses can simply not catch SQLExceptions, relying on the framework to clean up.