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new 1e793ef CAMEL-14191: EIP docs - Add links to last EIP patterns and
add new pages if missing content
1e793ef is described below
commit 1e793ef2efefa88089b2446de77ed50a3737d516
Author: Claus Ibsen <claus.ib...@gmail.com>
AuthorDate: Wed Nov 20 06:50:33 2019 +0100
CAMEL-14191: EIP docs - Add links to last EIP patterns and add new pages if
missing content
---
.../ROOT/assets/images/eip/BroadcastAggregate.gif | Bin 0 -> 4005 bytes
.../ROOT/pages/composed-message-processor.adoc | 6 +-
.../pages/enterprise-integration-patterns.adoc | 22 ++--
.../modules/ROOT/pages/getting-started.adoc | 35 ++----
.../modules/ROOT/pages/scatter-gather.adoc | 136 +++++++++++++++++++++
5 files changed, 162 insertions(+), 37 deletions(-)
diff --git
a/docs/user-manual/modules/ROOT/assets/images/eip/BroadcastAggregate.gif
b/docs/user-manual/modules/ROOT/assets/images/eip/BroadcastAggregate.gif
new file mode 100644
index 0000000..9387cc4
Binary files /dev/null and
b/docs/user-manual/modules/ROOT/assets/images/eip/BroadcastAggregate.gif differ
diff --git
a/docs/user-manual/modules/ROOT/pages/composed-message-processor.adoc
b/docs/user-manual/modules/ROOT/pages/composed-message-processor.adoc
index 15c17b9..7571b58 100644
--- a/docs/user-manual/modules/ROOT/pages/composed-message-processor.adoc
+++ b/docs/user-manual/modules/ROOT/pages/composed-message-processor.adoc
@@ -1,9 +1,9 @@
[[Composed-Message-Processor]]
= Composed Message Processor
-The
-http://www.enterpriseintegrationpatterns.com/MessageRouter.html[Composed
-Message Processor] from the xref:enterprise-integration-patterns.adoc[EIP
patterns]
+Camel supports the
+https://www.enterpriseintegrationpatterns.com/patterns/messaging/DistributionAggregate.html[Composed
Message Processor]
+from the xref:enterprise-integration-patterns.adoc[EIP patterns] book.
How can you maintain the overall message flow when processing a message
consisting of multiple elements, each of which may require different processing?
diff --git
a/docs/user-manual/modules/ROOT/pages/enterprise-integration-patterns.adoc
b/docs/user-manual/modules/ROOT/pages/enterprise-integration-patterns.adoc
index 9046138..393abf5 100644
--- a/docs/user-manual/modules/ROOT/pages/enterprise-integration-patterns.adoc
+++ b/docs/user-manual/modules/ROOT/pages/enterprise-integration-patterns.adoc
@@ -5,10 +5,8 @@ Camel supports most of the
http://www.eaipatterns.com/toc.html[Enterprise Integration Patterns]
from the excellent book by Gregor Hohpe and Bobby Woolf.
-If you are new to Camel you might want to try the
-Getting Started in the
-User Guide before attempting to implement these
-patterns.
+If you are new to Camel you might want to try the xref:getting-started[Getting
Started] in the
+User Guide before attempting to implement these patterns.
[[EnterpriseIntegrationPatterns-MessagingSystems]]
== Messaging Systems
@@ -139,7 +137,7 @@ consisting of multiple elements, each of which may require
different
processing?
|
-|Scatter-Gather |How do you maintain the
+|xref:scatter-gather.adoc[Scatter-Gather] |How do you maintain the
overall message flow when a message needs to be sent to multiple
recipients, each of which may send a reply?
@@ -302,11 +300,11 @@ analyze and debug the flow of messages in a loosely
coupled system?
=== EIP Icons
The EIP icons library is available as a Visio stencil file adapted to
-render the icons with the Camel color : sand. Download it
+render the icons with the Camel color. Download it
link:{attachmentsdir}/Hohpe_EIP_camel_20150622.zip[here]
-for your presentation, functional and technical analysis documents. The
-original EIP stencil is also available in
-link:{attachmentsdir}/Hohpe_EIP_camel_OpenOffice.zip[OpenOffice
-3.x Draw] (thanks to Marco Garbelini) ,
-http://www.eaipatterns.com/download/EIP_Visio_stencil.zip[Microsoft
-Visio], or http://www.graffletopia.com/stencils/137[Omnigraffle].
+for your presentation, functional and technical analysis documents.
+
+The original EIP stencil is also available in
+link:{attachmentsdir}/Hohpe_EIP_camel_OpenOffice.zip[OpenOffice 3.x Draw],
+http://www.eaipatterns.com/download/EIP_Visio_stencil.zip[Microsoft Visio],
+or http://www.graffletopia.com/stencils/137[Omnigraffle].
diff --git a/docs/user-manual/modules/ROOT/pages/getting-started.adoc
b/docs/user-manual/modules/ROOT/pages/getting-started.adoc
index 92cf3ce..53e0a03 100644
--- a/docs/user-manual/modules/ROOT/pages/getting-started.adoc
+++ b/docs/user-manual/modules/ROOT/pages/getting-started.adoc
@@ -9,34 +9,25 @@ Then come back here and you might want to read the following
documentation before continuing:
* Longer Getting Started Guide
-* Find out about xref:enterprise-integration-patterns.adoc[Enterprise
-Integration Patterns] and how to implement them with Camel
-* Review the Architecture guide to see how to
-build Routes using the Java DSL or
-Spring based xref:xml-configuration.adoc[Xml
-Configuration]
+* Find out about xref:enterprise-integration-patterns.adoc[Enterprise
Integration Patterns]
+ and how to implement them with Camel
+* Review the Architecture guide to see how to build Routes using the
xref:java-dsl[Java DSL]
+ or xref:xml-configuration.adoc[XML DSL]
[[GettingStarted-WorkingwithCamelContextsandRouteBuilders]]
== Working with CamelContexts and RouteBuilders
To get started with Camel:
-1. Create a CamelContext.
-2. Optionally, xref:configuring-camel.adoc[configure components or
-endpoints].
-3. Add whatever routing rules you wish using the DSL and
-RouteBuilder or using
-XML Configuration.
-4. Start the context.
-
-When your application is closing you may wish to
-stop the context
-
-When you are ready, why not xref:walk-through-an-example.adoc[Walk
-through an Example]? +
- And then continue the walk xref:walk-through-another-example.adoc[Walk
-through another example] +
- And after the walks head over to the tutorials.
+1. Create a `CamelContext`.
+2. Optionally, xref:configuring-camel.adoc[configure components or endpoints].
+3. Add whatever routing rules you wish using the DSL and `RouteBuilder` or
using XML DSL.
+4. Start the Camel context.
+
+When your application is closing you may wish to stop the context
+
+When you are ready, why not xref:walk-through-an-example.adoc[Walk through an
Example]?
+And then continue the walk xref:walk-through-another-example.adoc[Walk through
another example].
[[GettingStarted-WorkingwithSpring]]
== Working with Spring
diff --git a/docs/user-manual/modules/ROOT/pages/scatter-gather.adoc
b/docs/user-manual/modules/ROOT/pages/scatter-gather.adoc
new file mode 100644
index 0000000..3cb5d30
--- /dev/null
+++ b/docs/user-manual/modules/ROOT/pages/scatter-gather.adoc
@@ -0,0 +1,136 @@
+[[Scatter-Gather]]
+= Scatter Gather
+
+Camel supports the
+https://www.enterpriseintegrationpatterns.com/patterns/messaging/BroadcastAggregate.html[Scatter
Gather]
+from the xref:enterprise-integration-patterns.adoc[EIP patterns] book.
+
+The Scatter Gather from the EIP patterns allows you to route messages to a
number of dynamically
+specified recipients and re-aggregate the responses back into a single message.
+
+image::eip/BroadcastAggregate.gif[image]
+
+With Camel this pattern is implemented by using the
xref:recipientList-eip.adoc[Recipient List]
+and the xref:aggregate-eip[Aggregate] patterns.
+
+== Sample
+
+In this example we want to get the best quote for beer from several different
vendors.
+We use a dynamic Recipient List to get the request for a quote to all vendors
and an Aggregator
+to pick the best quote out of all the responses. The routes for this are
defined as:
+
+[source,xml]
+----
+<camelContext xmlns="http://camel.apache.org/schema/spring";>
+ <route>
+ <from uri="direct:start"/>
+ <recipientList>
+ <header>listOfVendors</header>
+ </recipientList>
+ </route>
+
+ <route>
+ <from uri="seda:quoteAggregator"/>
+ <aggregate strategyRef="aggregatorStrategy" completionTimeout="1000">
+ <correlationExpression>
+ <header>quoteRequestId</header>
+ </correlationExpression>
+ <to uri="mock:result"/>
+ </aggregate>
+ </route>
+</camelContext>
+----
+
+So in the first route you see that the Recipient List is looking at the
listOfVendors header
+for the list of recipients. So, we need to send a message like
+
+[source,java]
+----
+Map<String, Object> headers = new HashMap<>();
+headers.put("listOfVendors", "bean:vendor1, bean:vendor2, bean:vendor3");
+headers.put("quoteRequestId", "quoteRequest-1");
+template.sendBodyAndHeaders("direct:start", "<quote_request item=\"beer\"/>",
headers);
+----
+
+This message will be distributed to the following Endpoints: bean:vendor1,
bean:vendor2, and bean:vendor3.
+These are all beans which look like:
+
+[source,java]
+----
+public class MyVendor {
+ private int beerPrice;
+
+ @Produce("seda:quoteAggregator")
+ private ProducerTemplate quoteAggregator;
+
+ public MyVendor(int beerPrice) {
+ this.beerPrice = beerPrice;
+ }
+
+ public void quote(@XPath("/quote_request/@item") String item, Exchange
exchange) {
+ if ("beer".equals(item)) {
+ exchange.getIn().setBody(beerPrice);
+ quoteAggregator.send(exchange);
+ } else {
+ // ignore no quote
+ }
+ }
+}
+----
+
+And are loaded up in Spring XML like:
+
+[source,xml]
+----
+<bean id="aggregatorStrategy"
class="org.apache.camel.spring.processor.scattergather.LowestQuoteAggregationStrategy"/>
+
+<bean id="vendor1"
class="org.apache.camel.spring.processor.scattergather.MyVendor">
+ <constructor-arg>
+ <value>1</value>
+ </constructor-arg>
+</bean>
+
+<bean id="vendor2"
class="org.apache.camel.spring.processor.scattergather.MyVendor">
+ <constructor-arg>
+ <value>2</value>
+ </constructor-arg>
+</bean>
+
+<bean id="vendor3"
class="org.apache.camel.spring.processor.scattergather.MyVendor">
+ <constructor-arg>
+ <value>3</value>
+ </constructor-arg>
+</bean>
+----
+
+Each bean is loaded with a different price for beer. When the message is sent
to each bean endpoint,
+it will arrive at the `MyVendor.quote` method. This method does a simple check
whether this quote
+request is for beer and then sets the price of beer on the exchange for
retrieval at a later step.
+The message is forwarded on to the next step using POJO Producing (see the
`@Produce` annotation).
+
+At the next step we want to take the beer quotes from all vendors and find out
which one was the best
+(i.e. the lowest!). To do this we use an Aggregator with a custom aggregation
strategy.
+The Aggregator needs to be able to compare only the messages from this
particular quote;
+this is easily done by specifying a correlationExpression equal to the value
of the quoteRequestId header.
+As shown above in the message sending snippet, we set this header to
quoteRequest-1.
+This correlation value should be unique or you may include responses that are
not part of this quote.
+To pick the lowest quote out of the set, we use a custom aggregation strategy
like
+
+[source,java]
+----
+public class LowestQuoteAggregationStrategy implements AggregationStrategy {
+ public Exchange aggregate(Exchange oldExchange, Exchange newExchange) {
+ // the first time we only have the new exchange
+ if (oldExchange == null) {
+ return newExchange;
+ }
+
+ if (oldExchange.getIn().getBody(int.class) <
newExchange.getIn().getBody(int.class)) {
+ return oldExchange;
+ } else {
+ return newExchange;
+ }
+ }
+}
+----
+
