org.apache.commons.dbutils
Class BeanProcessor

java.lang.Object
  org.apache.commons.dbutils.BeanProcessor

public class BeanProcessor
extends Object

BeanProcessor matches column names to bean property names and converts ResultSet columns into objects for those bean properties. Subclasses should override the methods in the processing chain to customize behavior.

This class is thread-safe.

Since:

DbUtils 1.1

See Also:

BasicRowProcessor

Field Summary

protected static int

PROPERTY_NOT_FOUND Special array value used by mapColumnsToProperties that indicates there is no bean property that matches a column from a ResultSet.

Constructor Summary

BeanProcessor()
Constructor for BeanProcessor.

Method Summary

protected int[]	mapColumnsToProperties(ResultSetMetaData rsmd, PropertyDescriptor[] props) The positions in the returned array represent column numbers.
protected <T> T	newInstance(Class<T> c) Factory method that returns a new instance of the given Class.
protected Object	processColumn(ResultSet rs, int index, Class<?> propType) Convert a ResultSet column into an object.
<T> T	toBean(ResultSet rs, Class<T> type) Convert a ResultSet row into a JavaBean.
<T> List<T>	toBeanList(ResultSet rs, Class<T> type) Convert a ResultSet into a List of JavaBeans.

Methods inherited from class java.lang.Object

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

Field Detail

PROPERTY_NOT_FOUND

protected static final int PROPERTY_NOT_FOUND

Special array value used by mapColumnsToProperties that indicates there is no bean property that matches a column from a ResultSet.

See Also:

Constant Field Values

Constructor Detail

BeanProcessor

public BeanProcessor()

Constructor for BeanProcessor.

Method Detail

toBean

public <T> T toBean(ResultSet rs,
                    Class<T> type)
         throws SQLException

Convert a ResultSet row into a JavaBean. This implementation uses reflection and BeanInfo classes to match column names to bean property names. Properties are matched to columns based on several factors:

1. The class has a writable property with the same name as a column. The name comparison is case insensitive.
2. The column type can be converted to the property's set method parameter type with a ResultSet.get* method. If the conversion fails (ie. the property was an int and the column was a Timestamp) an SQLException is thrown.

Primitive bean properties are set to their defaults when SQL NULL is returned from the ResultSet. Numeric fields are set to 0 and booleans are set to false. Object bean properties are set to null when SQL NULL is returned. This is the same behavior as the ResultSet get* methods.

Type Parameters:

T - The type of bean to create

Parameters:

rs - ResultSet that supplies the bean data

type - Class from which to create the bean instance

Returns:

the newly created bean

Throws:

SQLException - if a database access error occurs

toBeanList

public <T> List<T> toBeanList(ResultSet rs,
                              Class<T> type)
                   throws SQLException

Convert a ResultSet into a List of JavaBeans. This implementation uses reflection and BeanInfo classes to match column names to bean property names. Properties are matched to columns based on several factors:

1. The class has a writable property with the same name as a column. The name comparison is case insensitive.
2. The column type can be converted to the property's set method parameter type with a ResultSet.get* method. If the conversion fails (ie. the property was an int and the column was a Timestamp) an SQLException is thrown.

Primitive bean properties are set to their defaults when SQL NULL is returned from the ResultSet. Numeric fields are set to 0 and booleans are set to false. Object bean properties are set to null when SQL NULL is returned. This is the same behavior as the ResultSet get* methods.

Type Parameters:

T - The type of bean to create

Parameters:

rs - ResultSet that supplies the bean data

type - Class from which to create the bean instance

Returns:

the newly created List of beans

Throws:

SQLException - if a database access error occurs

newInstance

protected <T> T newInstance(Class<T> c)
                 throws SQLException

Factory method that returns a new instance of the given Class. This is called at the start of the bean creation process and may be overridden to provide custom behavior like returning a cached bean instance.

Type Parameters:

T - The type of object to create

Parameters:

c - The Class to create an object from.

Returns:

A newly created object of the Class.

Throws:

SQLException - if creation failed.

mapColumnsToProperties

protected int[] mapColumnsToProperties(ResultSetMetaData rsmd,
                                       PropertyDescriptor[] props)
                                throws SQLException

The positions in the returned array represent column numbers. The values stored at each position represent the index in the PropertyDescriptor[] for the bean property that matches the column name. If no bean property was found for a column, the position is set to PROPERTY_NOT_FOUND.

Parameters:

rsmd - The ResultSetMetaData containing column information.

props - The bean property descriptors.

Returns:

An int[] with column index to property index mappings. The 0th element is meaningless because JDBC column indexing starts at 1.

Throws:

SQLException - if a database access error occurs

processColumn

protected Object processColumn(ResultSet rs,
                               int index,
                               Class<?> propType)
                        throws SQLException

Convert a ResultSet column into an object. Simple implementations could just call rs.getObject(index) while more complex implementations could perform type manipulation to match the column's type to the bean property type.

This implementation calls the appropriate ResultSet getter method for the given property type to perform the type conversion. If the property type doesn't match one of the supported ResultSet types, getObject is called.

Parameters:

rs - The ResultSet currently being processed. It is positioned on a valid row before being passed into this method.

index - The current column index being processed.

propType - The bean property type that this column needs to be converted into.

Returns:

The object from the ResultSet at the given column index after optional type processing or null if the column value was SQL NULL.

Throws:

SQLException - if a database access error occurs