pyknic / reactor

An extension for Speedment that make it possible to react to changes in a database and creating Materialized Object Views (MOV).

Reactor

An extension for Speedment that make it possible to react to changes in a database and creating Materialized Object Views.

How it works

The extension consists of two classes. The Reactor polls the database at a regular interval, downloading modifications to one specific table in batches. The changes are then parsed so that a set of listeners can act on them. The second class is the MaterializedView class. It can act as a listener on a Reactor, merging the changes into one materialized view. That view can then be queried to get a current state of the database without causing additional statements to be sent.

Installation

To add reactivity to your Speedment project, simply add the following dependency to your pom.xml-file:

<dependency>
    <groupId>com.github.pyknic</groupId>
    <artifactId>reactor</artifactId>
    <version>1.0.1</version>
</dependency>

Usage

To set up a materialized view of a table article_event, do the following once (after initiating Speedment):

final MaterializedView<ArticleEvent> articlesView 
    = new MaterializedView<>(ArticleEvent.ARTICLE_ID);

final Reactor<ArticleEvent> reactor = 
    Reactor.builder(speedment.managerOf(ArticleEvent.class), ArticleEvent.ARTICLE_ID)
        .withListener(articlesView)
        .build(); // Automatically starts the reactor

A materialized view must always have a particular field that events should be merged on. This is different than the primary key. Rows that have the same value of this field, in this case ARTICLE_ID, will be considered the same entity and will be merged in the view.

License

This project is made available under the Apache 2 license.