Integration Endpoints

This section covers the various channel adapters and messaging gateways provided by Spring Integration to support message-based communication with external systems.

Each system, from AMQP to Zookeeper, has its own integration requirements, and this section covers them.

Endpoint Quick Reference Table

As discussed in the earlier sections, Spring Integration provides a number of endpoints used to interface with external systems, file systems, and others.

For transparent dependency management Spring Integration provides a bill-of-materials POM to be imported into the Maven configuration:

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.integration</groupId>
            <artifactId>spring-integration-bom</artifactId>
            <version>5.2.0.M4</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

To recap:

Inbound channel adapters are used for one-way integration to bring data into the messaging application.
Outbound channel adapters are used for one-way integration to send data out of the messaging application.
Inbound gateways are used for a bidirectional integration flow, where some other system invokes the messaging application and receives a reply.
Outbound Gateways are used for a bidirectional integration flow, where the messaging application invokes some external service or entity and expects a result.

The following table summarizes the various endpoints with quick links to the appropriate chapter.

Table 1. Endpoint Quick Reference
Module	Inbound Adapter	Outbound Adapter	Inbound Gateway	Outbound Gateway
AMQP	Inbound Channel Adapter	Outbound Channel Adapter	Inbound Gateway	Outbound Gateway
Events	Receiving Spring Application Events	Sending Spring Application Events	N	N
Feed	Feed Inbound Channel Adapter	N	N	N
File	Reading Files and 'tail’ing Files	Writing files	N	Writing files
FTP(S)	FTP Inbound Channel Adapter	FTP Outbound Channel Adapter	N	FTP Outbound Gateway
Gemfire	Inbound Channel Adapter and Continuous Query Inbound Channel Adapter	Outbound Channel Adapter	N	N
HTTP	HTTP Namespace Support	HTTP Namespace Support	Http Inbound Components	HTTP Outbound Components
WebFlux	WebFlux Namespace Support	WebFlux Namespace Support	WebFlux Inbound Components	WebFlux Outbound Components
JDBC	Inbound Channel Adapter and Stored Procedure Inbound Channel Adapter	Outbound Channel Adapter and Stored Procedure Outbound Channel Adapter	N	Outbound Gateway and Stored Procedure Outbound Gateway
JMS	Inbound Channel Adapter and Message-driven Channel Adapter	Outbound Channel Adapter	Inbound Gateway	Outbound Gateway
JMX	Notification-listening Channel Adapter and Attribute-polling Channel Adapter and Tree-polling Channel Adapter	Notification-publishing Channel Adapter and Operation-invoking Channel Adapter	N	Operation-invoking Outbound Gateway
JPA	Inbound Channel Adapter	Outbound Channel Adapter	N	Updating Outbound Gateway and Retrieving Outbound Gateway
Mail	Mail-receiving Channel Adapter	Mail-sending Channel Adapter	N	N
MongoDB	MongoDB Inbound Channel Adapter	MongoDB Outbound Channel Adapter	N	N
MQTT	Inbound (Message-driven) Channel Adapter	Outbound Channel Adapter	N	N
Redis	Redis Inbound Channel Adapter and Redis Queue Inbound Channel Adapter and Redis Store Inbound Channel Adapter	Redis Outbound Channel Adapter and Redis Queue Outbound Channel Adapter and RedisStore Outbound Channel Adapter	Redis Queue Inbound Gateway	Redis Outbound Command Gateway and Redis Queue Outbound Gateway
Resource	Resource Inbound Channel Adapter	N	N	N
RMI	N	N	Inbound RMI	Outbound RMI
SFTP	SFTP Inbound Channel Adapter	SFTP Outbound Channel Adapter	N	SFTP Outbound Gateway
STOMP	STOMP Inbound Channel Adapter	STOMP Outbound Channel Adapter	N	N
Stream	Reading from Streams	Writing to Streams	N	N
Syslog	Syslog Inbound Channel Adapter	N	N	N
TCP	TCP Adapters	TCP Adapters	TCP Gateways	TCP Gateways
UDP	UDP Adapters	UDP Adapters	N	N
Web Services	N	N	Inbound Web Service Gateways	Outbound Web Service Gateways
Web Sockets	WebSocket Inbound Channel Adapter	WebSocket Outbound Channel Adapter	N	N
XMPP	XMPP Messages and XMPP Presence	XMPP Messages and XMPP Presence	N	N

In addition, as discussed in Core Messaging, Spring Integration provides endpoints for interfacing with Plain Old Java Objects (POJOs). As discussed in Channel Adapter, the <int:inbound-channel-adapter> element lets you poll a Java method for data. The <int:outbound-channel-adapter> element lets you send data to a void method. As discussed in Messaging Gateways, the <int:gateway> element lets any Java program invoke a messaging flow. Each of these works without requiring any source-level dependencies on Spring Integration. The equivalent of an outbound gateway in this context is using a service activator (see Service Activator) to invoke a method that returns an Object of some kind.