«Spring Integration as Integration Patterns Provider»

April 12, 2023

Spring Integrationas Integration Patterns provider

Blynov Viacheslav

Dnepropetrovsk

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Introduction

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Spring Integration Goals Provide a simple model for implementing complex enterprise

integration solutions.

Facilitate asynchronous, message-driven behavior within a Spring-based application.

Promote intuitive, incremental adoption for existing Spring users.

Spring Integration Introduction

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Spring Integration Features Implementation of most of the Enterprise Integration Patterns

– Endpoint

– Channel

– Aggregator

– Filter

– …

Integration with External Systems

– REST/HTTP

– FTP

– Twitter

– JMS

– …

The framework has extensive JMX support

– exposing framework components as MBeans

– adapters to obtain attributes from MBeans, invoke operations, send/receive notifications


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Spring Integration Endpoints

AMQP

Spring Application Events

File System

FTP

Gemfire

HTTP/REST

JDBC

JMX

JPA

Mail

MongoDB

Redis

RMI

TCP

Twitter

UDP

XMPP


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Main Components

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Main Components Message Message Channel Message Endpoint

– Transformer

– Filter

– Router

– Splitter

– Aggregator

– Service Activator

– Channel Adapter

– Gateway

Spring Integration Main Components

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Message Message is a generic

wrapper for any Java object combined with metadata used by the framework while handling that object

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Message Channel Point-To-Point Channel Publish/Subscribe Channel Pollable Channels Message-Driven Channels

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Message Endpoint

Encapsulates communication-specific details:

converts/extracts business data to/from message

sends/receives messages to/from message channel

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Transformer Message Transformer is

responsible for converting a Message's content or structure and returning the modified Message

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Filter Message Filter determines

whether a Message should be passed to an output channel at all

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Splitter Splitter is another type of

Message Endpoint whose responsibility is to accept a Message from its input channel, split that Message into multiple Messages, and then send each of those to its output channel.

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Service Activator

Service Activator is a generic endpoint for connecting a service instance to the messaging system.

The input Message Channel must be configured, and if the service method to be invoked is capable of returning a value, an output Message Channel may also be provided.

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Gateway

The Gateway encapsulates messaging-specific code (e.g., the code required to send or receive a message) and separates it from the rest of the application code. The Messaging Gateway exposes a business function to the rest of the application so that instead of requiring the application to set properties like Message.

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Example

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Task We receive JMS messages with some CompoundObject in JSON format

CompoundObject is-a list of some Objects

We need to extract all Objects from CompoundObject and save them to database (possibly performing some other business logic)

Those Objects which are considered “good” (verified against some rule) should be sent via JMS to another queue in JSON format

Spring Integration Example

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We need to add the following dependencies in pom.xml

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Specify JMS connection factory

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Configure Spring Integration context

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CompObjectDTO parseCompoundObject(String payload)

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List<ObjectDTO> splitCompound(CompObjectDTO dto)

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Object convertToEntity(ObjectDTO dto)

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Object saveEntity(Object obj)

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boolean isGoodObject(Object obj)

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ObjectDTO convertToDTO(Object obj)

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ObjectDTO convertToDTO(Object obj)

String serializeObjectDTO(ObjectDTO obj)

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Receiving messages via HTTP REST

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Another option: JMS backed message channels

Channel adapter are intended for applications that are integrating with other external systems. There are cases where both the producer and consumer for a given JMS Destination are intended to be part of the same application, running within the same process.

<int-jms:channel id="jmsChannel" queue="exampleQueue"/>

<int-jms:publish-subscribe-channel id="jmsChannel" topic="exampleTopic"/>

Support of transactions (“transaction-manager” atrribute) Support for connection (session, consumer) cache Concurrency (number of concurrent sessions/consumers to start for

each listener)


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Task 2 An exteranl system feeds us with stream of JSON objects putting them

to JMS queue

We need to make some calculations (business logic) using these objects in the order as they come

Depending on calculationd results we could change the persistent state of our domain objects

Incoming objects should be saved to our DB

Finally, the results of calculation should be sent in JSON format to another JMS queue


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Basic FlowSpring Integration Example

Receive objects

Validationconvertion to entity

Calculation

Analyze and save results

Send to outbound JMS

Save entities to DB

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RouterSpring Integration Example

• Payload Type Router• Header Value Router• Recipient List Router• XPath Router (Part of the XML Module)• Error Message Exception Type Router• (Generic) Router

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ProblemSpring Integration Example

The incoming messages could arrive very frequently

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AggregatorSpring Integration Example

• Message Store• Correlation Strategy (delaults to grouping be MessageHeader.CORRELATION_ID)• Release Strategy• Expiration policy

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Back to task 2: receive and aggregateSpring Integration Example

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Back to task 2: receive and aggregateSpring Integration Example

boolean canReleaseMessages(List<IncObject>)

List<IncObject> aggregate(List<IncObject>)

Object getCorrelationKey(IncObject)

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Back to task 2: routingSpring Integration Example

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Back to task 2: via publish-subscribe channelSpring Integration Example

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Task summary Built on the top of other Spring modules (e. g. Spring JMS)

Every element of the chain – just a simple POJO

High cohesion

Easy to cover with unit-tests

“Convention over configuration” – bean with name “connectionFactory” will be found automatically

Change the whole business flow only by configuration


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Spring Integration VS Apache Camel

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Both projects aim to fill similar need: light-weight integration library with full implementations of EIP

Apache Camel introduces DSL (Java, Scala, Groovy). Spring Integration - only XML

Apache Camel supports longer list of technologies

Apache Camel offers rich support for both integration and unit-testing. Spring Integration supports just generic Spring Test

Apache Camel Community is larger, documentation is better

Spring Integration Spring Integration VS Apache Camel

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Apache Camel Java DSL Example

final JaxbDataFormat jaxbDataFormat = new JaxbDataFormat();

jaxbDataFormat.setContextPath(“test.ns.oxm");

jaxbDataFormat.setPartClass(“test.ns.oxm.ABSPartnerChangesEventType");

from("activemq:incoming.partner")

.log("log:test.log")

.choice() .when(header("EVENTTYPE").isEqualTo(“TESTVALUE")).to("direct:createPartner“) .when(header("EVENTTYPE").isEqualTo(“TESTVALUE2")).to("direct:updatePartner");

from("direct:createPartner")

.errorHandler(noErrorHandler())

.unmarshal(jaxbDataFormat)

.beanRef(“partnerChangeHandler", "createPartner");

from("direct:updatePartner")

.errorHandler(noErrorHandler())

.unmarshal(jaxbDataFormat)

.beanRef(“partnerChangeHandler", "updatePartner");

Spring Integration Spring Integration VS Apache Camel

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Recent changes Spring EL support (3.0.2)

HTTP request mapping (based on Spring MVC infrastructure) (3.0.2)

Enhanced support for MongoDB, Redis and JPA (3.0.2)

@EnableIntegration, @IntegrationComponentScan (4.0.2)

Requires Spring 4.0 (4.0.2)


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Questions?

Technology

«Spring Integration as Integration Patterns Provider»