Dojo: The Definitive Guide

Chapter 9. Data Abstraction

A common bane of web development is writing routines to parse data that is returned from the server into a conveniently accessible format for the core application logic. While many good routines have been developed to parse common response types such as comma-separated values (CSV) and JSON, a lot of boilerplate is still involved in wiring it all up, issuing updates back to the server, potentially maintaining synchronicity between the local store and the server, and so forth. This chapter introduces Dojo's data APIs, which provide a uniform interface for handling data sources—regardless of where they're located, how they're accessed at the transport level, and what their format may be.

Shifting the Data Paradigm

The toolkit's machinery for managing data sources isn't exactly rocket science, but it does require shifting the paradigm ever so slightly, in that it requires that data can be treated as a local resource that is accessed via a uniform API. Traditional approaches have typically entailed treating data as a remote resource, which necessarily entails acquiring boilerplate to retrieve it, writing updates to the server, maintaining synchronicity with the server, and handling variable formats. One of the central issues, historically speaking, is that the wheel was reinvented far too many times and virtually every application used its own brittle approach to managing the burden of handling data.

Dojo gives a set of APIs via the dojo.data module that provide a standardized means for interacting with arbitrary data sources, shown in Figure 9-1. This allows application programmers to escape entanglement with retrieving, parsing, and managing it. The dojo.data API provides a standardized manner for interacting with data whether it's local or remote, which is a tremendous boon when it comes time to deal with larger and larger data sets as an application scales. Best of all, once you've implemented an interface for a specific data format, it becomes an off-the-shelf resource that you can reuse and distribute at will. Generally speaking, these kinds of off-the-shelf resources allow application developers to be more productive by allowing them to focus on far more interesting tasks at hand than I/O management.

Figure 9-1. Left: a traditional pattern for accessing arbitrary data sources from an application; right: the toolkit's dojo.data abstraction for accessing arbitrary data sources