Building a database front end with Jam.py

External Databases

So far I have discussed the case where the Jam.py application and the database are created together. In those cases, using SQLite spares you from installing and maintaining a separate server. However, in some situations, you might wish to build a Jam.py application for a database that already exists.

Figure 10 shows what to pass to the Builder in order to connect to a local or remote MySQL server. All the values shown in the figure must be filled in, even if they are not marked with asterisks, otherwise the connection will fail. If the connection succeeds, the next step is to import the structure of the MySQL tables and to create the necessary forms and filters. The complete procedure has its own, detailed page in the Jam.py documentation [9]. It is not complicated, but must be followed to the letter and it might change by the time you read this tutorial. The basic steps are:

Figure 10: Each database engine needs different configuration parameters. This figure shows the parameters for MySQL.
  1. Click on Project, then on the Database button and set DB manual mode to true.
  2. Click on Groups, and then select the specific group (Journals, Catalogs, etc.) in which you want to import a table.
  3. Click the Import button.

This procedure should open a form listing the tables found in the MySQL database. Click on the table you want to import, and then check if all the fields of that table were recognized with valid types. If the type of a field is empty or written in red, double click on that field, and give it the most appropriate type among those listed by the Builder. If this is not possible, or if you do not need to import the whole table, just import only the fields you really need.

If the Builder does not recognize the primary key, specify a primary key for the table. In my case, as you can see in Figure 11, all fields were properly recognized, except those of type ENUM. I have informed the developers of this issue, and it might be fixed by the time you read this.

Figure 11: A MySQL table imported by the Jam.py Builder.

System Administration Tips

If you use SQLite databases, it is easy to back up and synchronize different copies of the same application. Just include the whole jam.py folder in your backup lists and use rsync to propagate any changes made to the database to the backup computer.

Another system administration issue is how to start the application automatically – and how to shut it down cleanly when you power down your computer. Look online for a tutorial on how to start Jam.py automatically with an init script [10]. The example is based on Ubuntu, but other distributions are similar.

Last but not least, a tip about port numbers and URLs. The default way to run jam.py on a web server creates URLs that reference the port number (example.com:9000). But suppose you would prefer to access your Jam.py application at a normal address like mybookmarks.example.com. This is possible in two ways. One is to set up a standard web server like Apache or NGINX as a proxy between the application and the rest of the Internet using the WSGI interface [11]. Another way is to deploy your application on platforms like Python Anywhere [12].

Conclusion

Jam.py is quick and simple to use, and the architecture makes it easy to migrate an application to another database if the need arises. One small problem I had with Jam.py was getting used to its terminology. The Jam.py manual [2] is very rich, but I confess it took me some time to figure out what is probably the first thing you need to understand to make the best use of Jam.py: the difference between catalogs and journals.

I really like how easy it is to manage SQLite databases and move them anywhere with Jam.py. I have only implemented the most basic features of my Jam.py bookmarks manager, but I like it, and I plan to add thumbnails and maybe even statistics. Two features I would like to see added to Jam.py are bookmarklet support (to insert JavaScript-based bookmarklets from web pages) and a plugin to embed Jam.py in a NextCloud installation. All in all, I recommend Jam.py if you are looking for a nice, quick way to build browser interfaces for your databases. Finally, I would like to thank Jam.py developers Andrew Yushev and Drazen Babic for their support in the preparation of this tutorial.

The Author

Marco Fioretti (http://stop.zona-m.net) is a freelance author, trainer, and researcher based in Rome, Italy, who has worked with Free and Open Source software since 1995 and has worked on open digital standards since 2005. Marco is also a board member of the Free Knowledge Institute (http://freeknowledge.eu), and he blogs about digital rights at http://stop.zona-m.net.

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