ctr0 / bender

Visitor design pattern for abstract entities

Bender

Bender is a framework to apply the visitor design pattern to abstract source entities.
The default project contains the implementation for Java beans.

To apply the visitor design pattern you only need to write a visitor class for the desired abstract source.

Bender Beans

Visitor design pattern for Java beans.

For the following Java bean:

public class Person {

    private String name;
    private int age;
    private List<Person> parents;

    public String getName() {
        return name;
    }
    public int getAge() {
        return age;
    }
}

You can write a visitor like:

public class PersonVisitor implements BenderVisitor {

    @Bender("this")
    public void visitPerson(@Bender("name") String name, @Bender("this.age") int age) {
        // Do something...
    }

    @Bender("this.parents")
    public PersonVisitor visitParents(@Bender("length") int parentsLength) {
        if (parentsLength > 0) {
              return new PersonVisitor();
        }
        return null;
    }

    @Override
    public void visitEnd() {
        // Do something...
    }
}

Note that method parameters are annotated relative to the method target property.
Visitors can be stacked to accept the method target property simply returning a new visitor in that method. If this property is a primitive array or an instance of Iterable interface, each object will accept the new visitor instance.

Bender XML

Visitor design pattern for XML streams.

public class PersonXmlVisitor implements BenderVisitor {
    
    @BenderXml("/person")
    public void visitPerson(@BenderXml("name") String name, @BenderXml("age") int age) {
        // Do something...
    }
    
    @BenderXml("person/parent")
    public void visitParent(@BenderXml("name") String name, @BenderXml("age") int age) {
        // Do something...
    }

    @Override
    public void visitEnd() {
        // Do something...
    }
}

To use the XML or any other bender source you can see the following code snippet:

BenderSession session = new BenderSession();
BenderXmlSource source = new BenderXmlSource(stream);
source.accept(new PersonXmlVisitor());

For detailed info and advanced features see the wiki pages.