Mixing scala and java in Play Framework

问题:

I have a Java file that looks like this:

package AuthorizeNetFingerprint;


class Fingerprint {
    private static Log logger = LogFactory.getLog(Fingerprint.class);

    private long sequence;
    private long timeStamp;
    private String fingerprintHash;

    private Fingerprint() {
    }

    /**
     * Creates a fingerprint with raw data fields.
     * 
     * @param loginID
     * @param transactionKey
     * @param sequence : this number will be concatenated with a random value
     * @param amount
     * @return A Fingerprint object.
     */
    public static String createFingerprint(String loginID,
                    String transactionKey, long sequence, String amount) {
         return transactionKey;
    }
}

And I am trying to access it like this scala:

val fingerprint = new AuthorizeNetFingerprint.Fingerprint
val x_fp_hash = fingerprint.createFingerprint(x_api_login_id,
                  transaction_key, x_fp_sequence, x_amount)

And it gives me this error:

object Fingerprint in package AuthorizeNetFingerprint cannot be accessed in package AuthorizeNetFingerprint

Is it possible to mix scala and java in Play Framework?

What I am doing wrong?

EDIT

I needed: public class Fingerprint

instead of

class Fingerprint

回答1:

Three things:

1. As you've already figured out, your Fingerprint class needs to be public.
2. You've made Fingerprint's constructor private; you can't instantiate it.
3. Any static methods in a Java class should be accessed through the class' companion object in Scala.

All the Scala code in your example should be replaced by:

val x_fp_hash = AuthorizeNetFingerprint.Fingerprint.createFingerprint(…)

This works in the Scala (2.9.1) console, compiled with sbt (0.11.3).

Yes, you can mix Java and Scala in a Play2 application, just put the Java code in the app directory. Note that Java classes need to be in their corresponding package directories, which is not the case for Scala classes.

回答2:

I am not familiar with the Play framework, but the first line in your Scala sample code should instantiate the class AuthorizeNetFingerprint.Fingerprint, which only has a private constructor and is not a public class (i.e., it can only be accessed from the same package).

Maybe a call to AuthorizeNetFingerprint.Fingerprint.createFingerprint(...) works, after making the class public?

回答3:

In theory this should work just fine. Check out this blog Re Java and Scala interop. http://www.codecommit.com/blog/java/interop-between-java-and-scala

When creating the project did you specify Java, Scala or None (1,2 or 3)

回答4:

It's conventional to name Java packages in all lower case.

It also appears that Scala gets confused if you try to use a Java package that starts with upper case. If you use authorize as the package name instead of AuthorizeNetFingerprint, it will compile.

Also, there's no need for this:

val fingerprint = new AuthorizeNetFingerprint.Fingerprint 

createFingerprint is a static method, so just call

val x_fp_hash = Fingerprint.createFingerprint

(after importing authorize.Fingerprint).