Database Resource Bundle

Database backed implementation of java.util.ResourceBundle. With this implementation resource bundle contents are loaded from a database table instead of .properties files.

Usage

First you need to have a database table which can be created by /resources/create.sql. In this case you can use DefaultBundleContentLoaderStrategy without any customization.

You can normally use default implementation of java.util.ResourceBundle which uses .properties files by default as following static methods of ResourceBundle class:

// Static methods of `java.util.ResourceBundle`
static ResourceBundle getBundle​(String baseName)
static ResourceBundle getBundle(String baseName, Locale locale)
static ResourceBundle getBundle(String baseName, Locale locale, ClassLoader loader)
static ResourceBundle getBundle(String baseName, Locale targetLocale, ClassLoader loader, ResourceBundle.Control control)
static ResourceBundle getBundle(String baseName, Locale targetLocale, ResourceBundle.Control control)
static ResourceBundle getBundle(String baseName, ResourceBundle.Control control)

To get an instance of DatabaseResourceBundle you can use static methods above which has ResourceBundle.Control as an argument because ResourceBundle.Control class is responsible of content loading.

In other words you can create DatabaseResourceBundle instances via following static methods if you supply a DatabaseResourceBundleControl instance as ResourceBundle.Control parameter.

// Static methods of `java.util.ResourceBundle`
static ResourceBundle getBundle(String baseName, Locale targetLocale, ClassLoader loader, ResourceBundle.Control control)
static ResourceBundle getBundle(String baseName, Locale targetLocale, ResourceBundle.Control control)
static ResourceBundle getBundle(String baseName, ResourceBundle.Control control)

There are also two static methods to load DatabaseResourceBundle instances in DatabaseResourceBundle class:

// Static methods of `DatabaseResourceBundle`
public static ResourceBundle getBundle(String baseName, DataSource dataSource)
public static ResourceBundle getBundle(String baseName, Locale locale, DataSource dataSource)

Above two methods creates DatabaseResourceBundle without DatabaseResourceBundleControl parameters. Those methods create DatabaseResourceBundleControl implicitly and eventually return DatabaseResourceBundle instances.

Code Example

ResourceBundle.Control control = new DatabaseResourceBundleControl(new DefaultBundleContentLoaderStrategy(dataSource));
ResourceBundle rb = ResourceBundle.getBundle("messages", locale, control);
rb.getString("demo.username")

Using DefaultBundleContentLoaderStrategy

DefaultBundleContentLoaderStrategy uses a prepared statement to load resource content.

By default it assumes you have a table in your database which is created via database-resource-bundle.jar/create.sql. Hence uses following queries:

DEFAULT_LOAD_QUERY = "SELECT DISTINCT b.key, b.value FROM " + DEFAULT_TABLE_NAME + " b WHERE name = ? AND language = ? AND country = ? AND variant = ? ;"
DEFAULT_NEEDS_RELOAD_QUERY = "SELECT MAX(last_modified) FROM " + DEFAULT_TABLE_NAME + " b WHERE name = ? ;";

DEFAULT_TABLE_NAME is Bundle and coming from BundleContentLoaderStrategy.DEFAULT_TABLE_NAME.

Customizations: Using a different Table name or completely different Table structure

You can override those queries by using DefaultBundleContentLoaderStrategy's 3-parameter constructor. When you do this, you can use any database table structure or name as you like as long as you conform to expected return values of the queries.

Expected return values of the load query is a key-value string pair.

Expected return values of the needs reload query is a long value which represents the epoch milliseconds of latest change on the table.

Usage in Spring Boot

There is a Spring Boot starter which configures a message source backed by DatabaseResourceBundle. You can find it here.

LICENSE

© Copyright 2018 Kod Gemisi Ltd.

Mozilla Public License 2.0 (MPL-2.0)

https://tldrlegal.com/license/mozilla-public-license-2.0-(mpl-2)

MPL is a copyleft license that is easy to comply with. You must make the source code for any of your changes available under MPL, but you can combine the MPL software with proprietary code, as long as you keep the MPL code in separate files. Version 2.0 is, by default, compatible with LGPL and GPL version 2 or greater. You can distribute binaries under a proprietary license, as long as you make the source available under MPL.

See Full License Here