net.sf.beanlib.spi
Interface CustomBeanTransformerSpi

All Superinterfaces:

Transformable

All Known Implementing Classes:

ChainedCustomBeanTransformer, JodaTimeTransformer, LazyHibernateCustomBeanTransformer

public interface CustomBeanTransformerSpi
extends Transformable

Custom Bean Transformer SPI.

Used to provide custom transformation that takes precedence over the default transformation.

Quick Start

For example, by default when BeanReplicator is replicating the content of a JavaBean, it would try to instantiate the target class via the no-arg constructor. If the no-arg constructor is not defined (such as in the Point class below), it would cause a NoSuchMethodException to be thrown:

public class Point {
     private final int x, y;
     
     // missing no-arg constructor 
     public Point(int x, int y) {
         this.x = x;
         this.y = y;
     }
     public int getX() { return x; }
     public int getY() { return y; }
 }
 
 public class Bean {
     private Point point;
     public Point getPoint() { return point; }
     public void setPoint(Point point) { this.point = point; }
 }
 
 ...
 // Initialize a bean
 Bean from = new Bean();
 from.setPoint(new Point(1,2));
 
 // Tries to replicate the bean using the default implementation
 BeanReplicator replicator = new BeanReplicator();
 // Will cause NoSuchMethodException, as Point does not have a no-arg constructor
 Bean to = replicator.replicateBean(from);
 

One way to get around this problem is to define a custom transformer and the respective factory:

public class MyBeanTransformer implements CustomBeanTransformerSpi {
     public  boolean isTransformable(Object from, Class toClass, PropertyInfo propertyInfo) {
         return toClass == Point.class;
     }
     
     public  T transform(Object in, Class toClass, PropertyInfo propertyInfo) {
         Point from = (Point)in;
         // Note the framework takes care of the issue of object identity,
         // so we don't need to here.
         return (T)new Point(from.getX(), from.getY());
     }
 }
 
 public class MyBeanTransformerFactory implements CustomBeanTransformerSpi.Factory {
     public CustomBeanTransformerSpi newCustomBeanTransformer(BeanTransformerSpi beanTransformer) {
         return new MyBeanTransformer();
     }
 }
 
 ...
 // Initialize a bean
 Bean from = new Bean();
 from.setPoint(new Point(1,2));
 
 // Partially overrides the default transformer behavior
 BeanTransformerSpi transformer = new BeanTransformer(new MyBeanTransformerFactory());
 BeanReplicator replicator = new BeanReplicator(transformer);
 
 // Replicates the bean
 Bean to = replicator.replicateBean(from); // now works!
 

Customizing HibernateBeanReplicator

Customizing the behavior of HibernateBeanReplicator is basically identical to that of BeanReplicator as decribed above. For example, assuming the same MyBeanTransformerFactory defined above is used,

// Partially overrides the default Hibernate bean transformer's behavior
 HibernateBeanReplicator replicator = new Hibernate3BeanReplicator();
 replicator.initCustomTransformerFactory(new MyBeanTransformerFactory());
 replicator.copy(...);
 

Author:

Joe D. Velopar

See Also:

BeanTransformerSpi

Nested Class Summary

static interface

CustomBeanTransformerSpi.Factory Custom Bean Transformer Factory SPI.

Method Summary

boolean

isTransformable(Object from, Class<?> toClass, PropertyInfo propertyInfo) Returns true if the given object is to be transformed by this transformer; false otherwise.

Methods inherited from interface net.sf.beanlib.spi.Transformable

transform

Method Detail

isTransformable

boolean isTransformable(Object from,
                        Class<?> toClass,
                        PropertyInfo propertyInfo)

Returns true if the given object is to be transformed by this transformer; false otherwise.

Parameters:

from - source object

propertyInfo - If null, it means the in object is a root level object. Otherwise, propertyInfo contains information about the input object as a java bean property value to be transformed.

toClass - target class