The Punk Image Gallery

Unlike most framework samples, PIG is a real-world application. Our social group needed a way of storing and presenting the thousands of images in our various personal archives, and none of the public services provided the right set of features. Furthermore, there are serious privacy concerns with the upload of our personal pictures to a site out of our control.

PIG was written in a whirlwind couple of weeks by Jeff Schnitzer, with some help from Scott Hernandez and Shawn Jacques. The three of us are continuing to develop new features; this is not a static example.

There were only a few requirements for PIG:

• Follow "best-practices" so that it can be published as a Maverick example.
• Run on the latest version of Orion. We use it because it supports EJB2.0 (well, mostly) and it's free for our use.
• Provide users with a wiki-like atmosphere; anyone should be able to edit just about anything.
• Users have their own accounts and passwords, but a minimal security check must be in place so that only "friends" can create accounts.
• Support for basic image types (jpg, gif, png).
• Must allow many different organizational schemes for categorizing images to coexist.

Non-requirements are:

• Scalability - PIG will be used by a relatively small friend group (maybe a few hundred people). PIG does not need to be able to service millions of hits a day or handle more than a few tens of thousands of images.
• Portability - at present time, J2EE application portability is largely a myth. While we have attempted to minimize container-specific code, PIG nevertheless currently runs only on Orion. This is discussed below in "Limitations".

PIG stores images in an entity bean (read: database) as a byte[] (read: BLOB). This means you will need to use a database and a JDBC driver that supports BLOBs. This means you will not be able to use:

• Hypersonic v1.43 (the version shipped with Orion) - BLOBs don't work.
• PostgreSQL - The database seems to be ok, but the JDBC driver is *awful*. The most recent CVS copy supposedly handles BLOBs, but it didn't work.
• The FreeTDS driver for MS SQL Server. I've never gotten this thing working with Orion, let alone with BLOBs.

The following databases are known to work:

• hsqldb v1.61 (the project continuing the development of Hypersonic), although the "server mode" seems to be broken.
• MS SQL Server with the I-Net Sprinta JDBC driver.

IMPORTANT! In order to retreive image size information, PIG makes JDBC calls which use the SQL function "datalength()". While most RDBMSes offer this facility, none seem to agree on what to name the function. MS SQL Server calls it "datalength()", but others call it "length()" or "octet-length()". If you are not using MS SQL Server, you must create a function alias or user defined function "datalength()" to map to your equivalent function.

The secret word for creating accounts is an environment context parameter set in the ejb-jar.xml deployment descriptor. The default value in the prepackaged ear is "default". You can either edit the deployment descriptor or you can rebuild the project after creating a properties file called "deployment.properties" in the same directory as the build.xml buildfile. The contents of this properties file should be "secretWord=your_secret_word"

This section is an enumeration of PIG's "warts". Some of these limitations may be removed in future revisions, but proabably not unless someone makes a request :-)

PIG requires the Orion server. Unfortunately, there are a couple good reasons for this:

• There is no J2EE standard for user management, and the authentication options are almost unusable. Since users must be able to create new accounts, we were faced with the option of either not using J2EE security or relying on Orion's UserManager and RoleManager APIs. We chose the later. If it becomes important to someone, user management facilities can be made pluggable.
• The EJB2.0 spec underwent quite a lot of change in its final days, and the Orion implementation of container-managed-relationships is lagging by a couple revisions. Consequently, our entity beans are written to pd2 rather than the released spec. As soon as the Orion team updates their server to support the final spec, we will update PIG.

There is currently a race condition in the code which generates primary keys for Members, Media, and Galleries. Primary key generation in CMP EJBland is notoriously troublesome, and we have decided to punt the issue. It is highly unlikely that this race condition will ever show up without massive loads, and the failure mode will be an exception to the user, not corrupted data. If you ever happen to meet one of the EJB spec leads, please grab them by the neck and throttle them until they consent to allow for autogenerated primary keys in the next specification revision.

PIG falls under Maverick's license; you can do pretty much anything you want with it, including use it in a commercial product.

The Maverick web page (where PIG lives) is here. Downloads are available on the SourceForge project page.

You can discuss PIG on the mav-user mailing list.