CopyFrom interface

The CopyFrom interface defines functionality similar to the clone() method with the difference that the object itself is the target of the copy operation and has to be created first. Using CopyFrom enables copying data between different implementations of a common interface without these implementations having to know about each other.

Example

public interface Foo extends CopyFrom {

    String getName();

    void setName(String name);

    Set<String> getValues();

    void setValues(Set<String> values);

}

public class FooImplA implements Foo {

    private String name;
    private Set<String> values = new HashSet<String>();

    public String getName() {
        return this.name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Set<String> getValues() {
        return this.values;
    }

    public void setValues(Set<String> values) {
        this.values = values;
    }

    public Class<? extends CopyFrom> getInterface() {
        return Foo.class;
    }

    public void copyFrom(CopyFrom obj) {
        Foo other = (Foo) obj;
        this.setName(other.getName());
        this.setValues(new HashSet<String>(other.getValues()));
    }

}

public class FooImplB implements Foo {

    private Map<String, Object> data = new HashMap<String, Object>();

    public String getName() {
        return (String) this.data.get("name");
    }

    public void setName(String name) {
        this.data.put("name", name);
    }

    public Set<String> getValues() {
        return (Set<String>) this.data.get("values");
    }

    public void setValues(Set<String> values) {
        this.data.put("values", values);
    }

    public Class<? extends CopyFrom> getInterface() {
        return Foo.class;
    }

    public void copyFrom(CopyFrom obj) {
        Foo other = (Foo) obj;
        this.setName(other.getName());
        this.setValues(new HashSet<String>(other.getValues()));
    }

}

For properties implementing the CopyFrom interface, the bean must create a property instance implementing the interface returned by the getInterface() method. This allows the bean doing the copyFrom(CopyFrom) to handle specialized subclasses of property elements properly. This is also applicable to array and collection properties. The modules property of the SyndFeed and SyndEntry beans is a use case of this feature where the copyFrom(CopyFrom) invocation must create different bean subclasses for each type of module, the getInterface() helps to find the right implementation.