Support for Guava Optional

[drekbour]

Resolution for #66

Please don't accept or reject this PR as it is not done (unless you are going to append the fix for the below after accepting!).

It is 99% complete (with test) except that, inside the processor the withOptionals directive is exposed as some horrible compiler symbol not the original enum. I remap by toString back into the OptionalSupport enum but it feels very wrong like that.

Please advise on Directives.java:35

[mkarneim]

Good point :-)

[mkarneim]

Thank you for this!
I'll merge this soon.
Just out of curiosity: can you give me some short realistic use case that uses this?

[drekbour]

1. The general gist of Optional is to avoid the need for null-defensive coding everywhere without replacing it by more code than you took out.
2. There may sometimes be a penalty to calling a setter with a null value. For instance if a property already had a default assigned at construction that you overwrite with null because a lookup fails. With the Optional support, the setter is not called for an absent value.

Assume in the following that a request may be authenticated or anonymous (no uid/pwd). It would have taken a dozen lines to do this if nothing was using Optional:

public static final Optional<String> jsonPath( String json, String path );

new RequestBuilder()
  .withUserId(jsonPath(input, "$.owner.uid")) // Invisibly passes the Optional through
  .withPassword(jsonPath(input, "$.owner.pwd").transform(decryptionFunction)) // ignores absent passwords
  .build();

[mkarneim]

Marc,

I just pushed an alternative variant of this to https://github.com/mkarneim/pojobuilder/tree/drekbour-optional-guava. Essentially I removed the OptionalSupport enum. Instead you can use the Optional class itself.

See this example (from your test case):

package net.karneim.pojobuilder.processor.with.optionals;
import net.karneim.pojobuilder.GeneratePojoBuilder;
import com.google.common.base.Optional;

@GeneratePojoBuilder(withOptionalProperties = Optional.class)
public class PojoWithGuavaOptional {

  public int primitiveInt;
  public Integer boxedInt;
  public int[] array;

}

In order to use Optional from Java 8 just replace the import:

package net.karneim.pojobuilder.processor.with.optionals;
import net.karneim.pojobuilder.GeneratePojoBuilder;
import java.util.Optional;

@GeneratePojoBuilder(withOptionalProperties = Optional.class)
public class PojoWithGuavaOptional {

  public int primitiveInt;
  public Integer boxedInt;
  public int[] array;

}

Any comments?

[drekbour]

I'd considered doing exactly that so am quite happy you found the same solution. It is also nice as it guarantees your chosen Optional is indeed available at compile time. I think we're done here.