Enumerated Type

[Akram Moncer]

hello ;

can someone tell me how can i use the Enumerated Type in JPA, and how can i persist it

thanks

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Akram MONCER
Personne

[Brandon Donnelson]

What type of Datastore?

[Akram Moncer]

google app engine datastore

2012/5/8 Brandon Donnelson <branfl...@gmail.com>

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What type of Datastore?

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Akram MONCER
Personne

[Brandon Donnelson]

If you can serialize the object it can be persisted to the datastore.

If TaskType is an enum:

public class Task {

  @Persistent   

  private TaskType taskType; 

}

public enum TaskType {

  MYTASK; 

  public String value() {

    return name().toLowerCase();

  }

  public static TaskType fromValue(String v) {

    return valueOf(v.toUpperCase());

  }

}

Hope that helps,

Brandon Donnelson

http://c.gwt-examples.com

[Patrick Julien]

Just use JPA's @Enumerated


use @Enumerated(EnumType.ORDINAL) to only store a number or @Enumerated(EnumType.String) to get the textual representation of your enum

[Joseph Lust]

Patrick's suggest is how I usually achieve this, but think for a few minutes on your choice of EnumType.STRING vs EnumType.ORDINAL. How do you think you're application will change with time? Generally I prefer STRING since reordering of your enumeration or removal of values will leave you in a bind (say for an API that you don't control). Either way you're subject to change, but STRING is more versatile in my mind. I all depends on the volatility of your project schema.

Just don't worry about a few bytes here and there since you're now in the cloud and bytes are not what they seem. For example a boolean is a 4 bytes in GAE DataStore due to word size issues. That's right, 32 bits to store 1 bit (note you can store 2 bools in 4 bytes, but if you have just 1, it's 4 bytes).

Sincerely,

Joseph