Introducing Spring Framework

Chapter 20 ■ Your First Spring XD Application
Spring XD
Spring XD can work in two different modes, single and multi-mode. The single mode can be used for all processing
and administration. The multi-mode is a distributed mode that can spread some jobs and tasks across a cluster of
multiple nodes.
Spring XD has some key components, the XD Admin and the XD Container Servers, where the XD Admin
will take a DSL command task and send it over to the XD container servers for processing using different types of
transports (that can be specified at start time) such as in-memory (default), Redis, and RabbitMQ. Figure 20-1 shows a
general Spring XD architecture.
Data Processing DSL
XD Admin
Message Queue
Redis
RabbitMQ
XD Container
XD Container
Module
Module
Figure 20-1. Spring XD Runtime Architecture (DIRT – Distributed Integration Runtime)
Modules
Spring XD supports three types of modules:
Taps
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• Source: This module polls from an external resource or can be triggered by an event and only
provides an output. This module is always a stream. Out of the box, Spring XD provides several
sources: file, gemfire, rabbit, http, mail, jms, etc. You can see the complete list by
executing the command module list on the XD shell (that you run later).
• Processor: This module provides some processing (business logic) or transforming; by
providing an input and one or more outputs. Out of the box, Spring XD provides several
processors such as aggregator, http-client, bridge, filter, json-field-extractor,
json-field-value-filter, object-to-json, script, splitter, transform, etc.
• Sink: This module only provides one input and outputs the data to an external resource
to terminate the stream. Out of the box, Spring XD provides several sinks such as hdfs
(Hadoop), file, gemfire-json-server, jdbc, mail, splunk, tcp, aggregatecounter,
counter gauge, rabbit, etc.
Spring XD provides taps that listen to data while it is being processed by a stream. This is the implementation of the
WireTap pattern (enterprise integration patterns) on the Spring Integration module and it is one of the features you
are going to use in your Spring application.