I was searching NoSQL databases and see that Oracle provides a NoSQL database called Berkeley DB. I examined it and wrote a blog to give quick tips to start Java Edition of Berkeley DB. This blog was published in Turkish, about 1 year ago. I’ve decided to translate (in fact, re-write) and publish it in English, and this is what you are reading now.
Berkeley DB is a high-performance embedded database originated at the University of California, Berkeley. It’s fast, reliable and used in several applications such as Evolution (email client), OpenLDAP, RPM (The RPM Package Manager) and Postfix (MTA). In contrast to most other database systems, Berkeley DB provides relatively simple data access services. Berkeley DB databases are B+Trees (like indexes in Oracle RDBMS) and can store only key/value pairs (there are no columns or tables). The keys and values are byte arrays. Databases are stored as files within a single directory which is called “environment”.
There are three versions of Berkeley DB:
- Berkeley DB (the traditional database, written in C)
- Berkeley DB Java Edition (native Java version)
- Berkeley DB XML (for storing XML documents)
As a hobbyist Java programmer, I prefer Berkeley DB Java Edition (JE). Berkeley DB JE supports almost all features of traditional Berkeley DB such as replication, hot-backups, ACID and transactions. It is written in pure Java so it’s platform-independent.
Berkeley DB JE provides two interfaces:
- Traditional Berkeley DB API (with DB data abstraction of key/value pairs)
- Direct Persistence Layer (DPL) which contains “Plain Old Java Objects” (POJO)
Because I’m an old-school (ex)programmer, I’ll show how to use the traditional Berkeley DB API. Traditional Berkeley DB API will help you understand how Berkeley DB works.