Spring Utils Properties

Properties

Contains classes to work with properties and integratie with the Spring Environment abstraction.

JdbcPropertySourceInitializer

This is an implementation of an ApplicationContextInitializer which registers an additional PropertySource with the Environment. The properties in that PropertySource are loaded from a database. It by default expects a table named Configuration with 2 columns name and value. The default query that is being executed is select NAME, VALUE from CONFIGURATION.

As this is an ApplicationContextInitializer it has to be added to the web.xml or WebApplicationInitializer to have it registered with the context.

Note: The properties are loaded at startup, updates to the properties in the database aren't propagated as with using property files a restart of the application is required!

XML

You can either use a context-param or init-param (for the DispatcherServlet) to register the initializer. Create a param with the name contextInitializerClasses.

For the ContextLoaderListener.

<context-param>
    <param-name>contextInitializerClasses</param-name>
    <param-value>biz.deinum.core.env.JdbcPropertySourceInitializer</param-value>
</context-param>

For the DispatcherServlet

<servlet>
    <servlet-name>dispatcher</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
    <context-param>
        <param-name>contextInitializerClasses</param-name>
        <param-value>biz.deinum.core.env.JdbcPropertySourceInitializer</param-value>
    </context-param>    
</servlet>

or globally (both ContextLoaderListener and DispatcherServlet).

<context-param>
    <param-name> globalInitializerClasses </param-name>
    <param-value>biz.deinum.core.env.JdbcPropertySourceInitializer</param-value>
</context-param>

Java

Assuming one uses the AbstractAnnotationConfigDispatcherServletInitializer or one of the other classes in the hierarchy you can use the getServletApplicationContextInitializers to register it for the DispatcherServlet or getRootApplicationContextInitializers to register it for the ContextLoaderListener being used.

public class MyInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {

   	protected ApplicationContextInitializer<?>[] getServletApplicationContextInitializers() {
        return new ApplicationContextInitializer[] { new JdbcPropertySourceInitializer()}
    }

    protected ApplicationContextInitializer<?>[] getRootApplicationContextInitializers() {
        return new ApplicationContextInitializer[] { new JdbcPropertySourceInitializer()}
    }
}

After registration Spring will invoke the defined callback methods and the initialized PropertySource will be added to the Environment.

Configuration

DataSource

The JdbcPropertySourceInitializer needs a few properties so that it knows which DataSource to use. It can either use a DataSource from JNDI or create one using a URL, username and password property.

The properties can be set as environment variables, system properties (-D) or when using a web application the Servlet Context as well.

DataSource using JNDI

When the property config.jdbc.jndi-name is set in the Environment that will be used to do a lookup for the datasource.

DataSource using URL

When setting the config.jdbc.url property that is used to construct a temporary DataSource based on the DriverManagerDataSource for Spring. Optionally a config.jdbc.username and config.jdbc.password property can also be specified.

Query

By default the query that is being executed is select NAME, VALUE from CONFIGURATION this can be overriden using the config.jdbc.query property. Note: When overriding the query make sure that it returns 2 columns, the first the name of the property the second the value of the property.