com.interface21.jdbc.object
Class MappingSqlQueryWithParameters

java.lang.Object
  |
  +--com.interface21.jdbc.object.RdbmsOperation
        |
        +--com.interface21.jdbc.object.SqlOperation
              |
              +--com.interface21.jdbc.object.SqlQuery
                    |
                    +--com.interface21.jdbc.object.MappingSqlQueryWithParameters
All Implemented Interfaces:
InitializingBean
Direct Known Subclasses:
MappingSqlQuery

public abstract class MappingSqlQueryWithParameters
extends SqlQuery

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.

Author:
Rod Johnson, Thomas Risberg
See Also:
MappingSqlQuery, SqlQuery

Fields inherited from class com.interface21.jdbc.object.RdbmsOperation
logger
 
Constructor Summary
MappingSqlQueryWithParameters()
          Constructor to allow use as a JavaBean
MappingSqlQueryWithParameters(javax.sql.DataSource ds, java.lang.String sql)
          Convenient constructor
 
Method Summary
protected abstract  java.lang.Object mapRow(java.sql.ResultSet rs, int rownum, java.lang.Object[] parameters)
          Subclasses must implement this method to convert each row of the ResultSet into an object of the result type.
protected  ResultReader newResultReader(int rowsExpected, java.lang.Object[] parameters)
          Implementation of protected abstract method.
 
Methods inherited from class com.interface21.jdbc.object.SqlQuery
execute, execute, execute, execute, execute, findObject, findObject, findObject, findObject, getRowsExpected, onCompileInternal, setRowsExpected
 
Methods inherited from class com.interface21.jdbc.object.SqlOperation
compileInternal, getJdbcTemplate, newPreparedStatementCreator
 
Methods inherited from class com.interface21.jdbc.object.RdbmsOperation
afterPropertiesSet, compile, declareParameter, getDataSource, getDeclaredParameters, getSql, isCompiled, setDataSource, setSql, setTypes, validateParameters
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

MappingSqlQueryWithParameters

public MappingSqlQueryWithParameters()
Constructor to allow use as a JavaBean

MappingSqlQueryWithParameters

public MappingSqlQueryWithParameters(javax.sql.DataSource ds,
                                     java.lang.String sql)
Convenient constructor
Parameters:
ds - DataSource to use to get connections
sql - SQL to run
Method Detail

newResultReader

protected final ResultReader newResultReader(int rowsExpected,
                                             java.lang.Object[] parameters)
Implementation of protected abstract method. This invokes the subclass's implementation of the mapRow() method.
Overrides:
newResultReader in class SqlQuery
Following copied from class: com.interface21.jdbc.object.SqlQuery
Parameters:
rowsExpected. - If 0, we don't know how many rows to expect. This parameter can be ignored, but may help some implementations choose the most efficient Collection type: e.g. ArrayList instead of LinkedList for large result sets.
parameters - parameters to the execute() method, in case subclass is interested. May be null if there were no parameters.

mapRow

protected abstract java.lang.Object mapRow(java.sql.ResultSet rs,
                                           int rownum,
                                           java.lang.Object[] parameters)
                                    throws java.sql.SQLException
Subclasses must implement this method to convert each row of the ResultSet into an object of the result type.
Parameters:
rs - RowSet 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.
Returns:
an object of the result type
Throws:
java.sql.SQLException - if there's an error extracting data. Subclasses can simply not catch SQLExceptions, relying on the framework to clean up.


Rod Johnson and Spring contributors 2001-2003.