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new bfdb502 CAMEL-16861: Cleanup and update EIP docs
bfdb502 is described below
commit bfdb502cbbd743f1dfd37ab549d5f6f6bca344d4
Author: Claus Ibsen <claus.ib...@gmail.com>
AuthorDate: Fri Sep 17 14:13:32 2021 +0200
CAMEL-16861: Cleanup and update EIP docs
---
.../modules/eips/pages/dead-letter-channel.adoc | 2 +-
.../main/docs/modules/eips/pages/delay-eip.adoc | 2 +
.../main/docs/modules/eips/pages/enrich-eip.adoc | 203 ++++++++++-----------
.../pages/enterprise-integration-patterns.adoc | 12 +-
.../docs/modules/eips/pages/event-message.adoc | 65 ++++---
.../eips/pages/eventDrivenConsumer-eip.adoc | 30 +--
6 files changed, 151 insertions(+), 163 deletions(-)
diff --git
a/core/camel-core-engine/src/main/docs/modules/eips/pages/dead-letter-channel.adoc
b/core/camel-core-engine/src/main/docs/modules/eips/pages/dead-letter-channel.adoc
index 7c1131b..9a4dc19 100644
---
a/core/camel-core-engine/src/main/docs/modules/eips/pages/dead-letter-channel.adoc
+++
b/core/camel-core-engine/src/main/docs/modules/eips/pages/dead-letter-channel.adoc
@@ -454,7 +454,7 @@ The `Exchange.FAILURE_ROUTE_ID` have the constant value
`CamelFailureRouteId`.
This allows for example you to fetch this information in your dead letter
queue and use that for error reporting.
-== Control if redelivery is allowed during stopping/shutdown
+=== Control if redelivery is allowed during stopping/shutdown
The option `allowRedeliveryWhileStopping` (default is `true`) controls whether
redelivery is allowed or not,
during stopping Camel or the route. This only applies for any potential new
redelivery attempts;
diff --git
a/core/camel-core-engine/src/main/docs/modules/eips/pages/delay-eip.adoc
b/core/camel-core-engine/src/main/docs/modules/eips/pages/delay-eip.adoc
index dbd7922..c246b7f 100644
--- a/core/camel-core-engine/src/main/docs/modules/eips/pages/delay-eip.adoc
+++ b/core/camel-core-engine/src/main/docs/modules/eips/pages/delay-eip.adoc
@@ -5,6 +5,8 @@
:since:
:supportLevel: Stable
+The Delay EIP is used for delaying messages during routing.
+
== Options
// eip options: START
diff --git
a/core/camel-core-engine/src/main/docs/modules/eips/pages/enrich-eip.adoc
b/core/camel-core-engine/src/main/docs/modules/eips/pages/enrich-eip.adoc
index 467b5c0..ce377ec 100644
--- a/core/camel-core-engine/src/main/docs/modules/eips/pages/enrich-eip.adoc
+++ b/core/camel-core-engine/src/main/docs/modules/eips/pages/enrich-eip.adoc
@@ -5,11 +5,32 @@
:since:
:supportLevel: Stable
-Camel supports the Content Enricher from the EIP patterns using a Message
Translator, an arbitrary Processor in the routing logic, or using the enrich
DSL element to enrich the message.
+Camel supports the
+http://www.enterpriseintegrationpatterns.com/DataEnricher.html[Content
+Enricher] from the xref:enterprise-integration-patterns.adoc[EIP
+patterns].
image::eip/DataEnricher.gif[image]
-TIP: See the `cacheSize` option for more details on _how much cache_ to use
depending on how many or few unique endpoints are used.
+In Camel the Content Enricher can be done in several ways:
+
+* Using xref:enrich-eip.adoc[Enrich] EIP
+* Using a xref:message-translator.adoc[Message Translator]
+* Using a xref:latest@manual:ROOT:processor.adoc[Processor] with the
enrichment programmed in Java
+* Using a xref:bean-eip.adoc[Bean] EIP with the enrichment programmed in Java
+
+The most natural Camel approach is using xref:enrich-eip.adoc[Enrich] EIP,
+which comes as two kinds:
+
+* xref:enrich-eip.adoc[Enrich] EIP - This is the most common content enricher
that uses a `Producer` to obtain the data.
+It is usually used for xref:requestReply-eip.adoc[Request Reply] messaging,
for instance to invoke an external web service.
+
+* xref:pollEnrich-eip.adoc[Poll Enrich] EIP - Uses a
xref:polling-consumer.adoc[Polling
+Consumer] to obtain the additional data. It is usually used for
+xref:event-message.adoc[Event Message] messaging, for instance to read a
+file or download a xref:components::ftp-component.adoc[FTP] file.
+
+NOTE: This page documents the Enrich EIP.
// eip options: START
The Enrich EIP supports 8 options which are listed below:
@@ -28,160 +49,110 @@ The Enrich EIP supports 8 options which are listed below:
|===
// eip options: END
-== Content enrichment using a Message Translator or a Processor
-You can use Templating to consume a message from one destination, transform it
with something like Velocity or XQuery, and then send it on to another
destination. For example using InOnly (one way messaging)
+== Content enrichment using Enrich EIP
-== Samples
+Enrich EIP is the most common content enricher that uses a `Producer` to
obtain the data.
-[source,java]
-----
-from("activemq:My.Queue").
- to("velocity:com/acme/MyResponse.vm").
- to("activemq:Another.Queue");
-----
+The content enricher (`enrich`) retrieves additional data from a _resource
endpoint_ in order to enrich an incoming message (contained in the _original
exchange_).
-If you want to use InOut (request-reply) semantics to process requests on the
*My.Queue* queue on ActiveMQ with a template generated response, then sending
responses back to the JMSReplyTo Destination you could use this:
+An `AggregationStrategy` is used to combine the original exchange and the
_resource exchange_. The first parameter of the
`AggregationStrategy.aggregate(Exchange, Exchange)` method corresponds to the
original exchange, the second parameter the resource exchange.
-[source,java]
-----
-from("activemq:My.Queue").
- to("velocity:com/acme/MyResponse.vm");
-----
-
-Here is a simple example using the DSL directly to transform the message body
+Here's an example for implementing an `AggregationStrategy`, which merges the
two data together
+as a `String` with colon separator:
[source,java]
----
-from("direct:start").setBody(body().append(" World!")).to("mock:result");
-----
+public class ExampleAggregationStrategy implements AggregationStrategy {
-In this example we add our own Processor using explicit Java code
+ public Exchange aggregate(Exchange original, Exchange resource) {
+ // this is just an example, for real-world use-cases the
+ // aggregation strategy would be specific to the use-case
-[source,java]
-----
-from("direct:start").process(new Processor() {
- public void process(Exchange exchange) {
- Message in = exchange.getIn();
- in.setBody(in.getBody(String.class) + " World!");
+ if (newExchange == null) {
+ return oldExchange;
+ }
+ Object oldBody = oldExchange.getIn().getBody();
+ Object newBody = newExchange.getIn().getBody();
+ oldExchange.getIn().setBody(oldBody + ":" + newBody);
+ return oldExchange;
}
-}).to("mock:result");
-----
-
-Finally we can use Bean Integration to use any Java method on any bean to act
as the transformer
-[source,java]
-----
-from("activemq:My.Queue").
- beanRef("myBeanName", "myMethodName").
- to("activemq:Another.Queue");
-----
-
-=== Using Spring XML
-
-[source,xml]
-----
-<route>
- <from uri="activemq:Input"/>
- <bean ref="myBeanName" method="doTransform"/>
- <to uri="activemq:Output"/>
-</route>
+}
----
-== Content enrichment using the enrich DSL element
-
-Camel comes with flavor `enrich` as a choice of content enricher in the DSL.
-The other one is `pollEnrich`
-
-`enrich` uses a Producer to obtain the additional data. It is usually used for
Request Reply messaging, for instance to invoke an external web service.
-
-Both `enrich` and `pollEnrich` supports dynamic endpoints that uses an
Expression to compute the uri, which allows to use data from the current
Exchange.
-
-=== Enrich example using Java
+You then use the `AggregationStrategy` with the `enrich` in the Java DSL as
shown:
[source,java]
----
AggregationStrategy aggregationStrategy = ...
from("direct:start")
- .enrich("direct:resource", aggregationStrategy)
- .to("direct:result");
-
-from("direct:resource")
-...
+ .enrich("http:remoteserver/foo", aggregationStrategy)
+ .to("mock:result");
----
-The content enricher (`enrich`) retrieves additional data from a _resource
endpoint_ in order to enrich an incoming message (contained in the _original
exchange_).
-An aggregation strategy is used to combine the original exchange and the
_resource exchange_. The first parameter of the
`AggregationStrategy.aggregate(Exchange, Exchange)` method corresponds to the
original exchange, the second parameter the resource exchange.
-The results from the resource endpoint are stored in the resource exchange's
out-message. Here's an example template for implementing an aggregation
strategy:
+In the example Camel will call the http endpoint to collect some data, that
will then
+be merged with the original message using the `AggregationStrategy`.
-[source,java]
-----
-public class ExampleAggregationStrategy implements AggregationStrategy {
-
- public Exchange aggregate(Exchange original, Exchange resource) {
- Object originalBody = original.getIn().getBody();
- Object resourceResponse = resource.getIn().getBody();
- Object mergeResult = ... // combine original body and resource response
- if (original.getPattern().isOutCapable()) {
- original.getOut().setBody(mergeResult);
- } else {
- original.getIn().setBody(mergeResult);
- }
- return original;
- }
-
-}
-----
-
-Using this template the original exchange can be of any pattern. The resource
exchange created by the enricher is always an in-out exchange.
-
-=== Enrich example using XML
+In XML DSL you use `enrich` as follows:
[source,xml]
----
+<bean id="myStrategy" class="com.foo.ExampleAggregationStrategy"/>
+
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring";>
<route>
<from uri="direct:start"/>
- <enrich strategyRef="aggregationStrategy">
- <constant>direct:resource</constant>
+ <enrich strategyRef="myStrategy">
+ <constant>http:remoteserver/foo</constant>
</enrich>
- <to uri="direct:result"/>
- </route>
- <route>
- <from uri="direct:resource"/>
- ...
+ <to uri="mock:result"/>
</route>
</camelContext>
-
-<bean id="aggregationStrategy" class="..." />
----
-== Aggregation strategy is optional
-The aggregation strategy is optional. If you do not provide it Camel will by
default just use the body obtained from the resource.
+=== Aggregation Strategy is optional
+
+The aggregation strategy is optional.
+If not provided then Camel will just use the result exchange as the result.
+
+The following example:
+
[source,java]
----
from("direct:start")
- .enrich("direct:resource")
+ .enrich("http:remoteserver/foo")
.to("direct:result");
----
-In the route above the message sent to the direct:result endpoint will contain
the output from the direct:resource as we do not use any custom aggregation.
+And in XML:
[source,xml]
----
<route>
- <from uri="direct:start"/>
- <enrich>
- <constant>direct:resource</constant>
- </enrich>
- <to uri="direct:result"/>
+ <from uri="direct:start"/>
+ <enrich>
+ <constant>http:remoteserver/foo</constant>
+ </enrich>
+ <to uri="mock:result"/>
</route>
----
-== Using dynamic uris
+
+Would be the same as using `to`:
+
+[source,java]
+----
+from("direct:start")
+ .to("http:remoteserver/foo")
+ .to("direct:result");
+----
+
+=== Using dynamic uris
Both `enrich` and `pollEnrich` supports using dynamic uris computed based on
information from the current Exchange. For example to enrich from a HTTP
endpoint where the header with key orderId is used as part of the content-path
of the HTTP url:
+
[source,java]
----
from("direct:start")
@@ -189,7 +160,8 @@ from("direct:start")
.to("direct:result");
----
-And in XML DSL
+And in XML DSL:
+
[source,xml]
----
<route>
@@ -200,3 +172,18 @@ And in XML DSL
<to uri="direct:result"/>
</route>
----
+
+=== Using out of the box Aggregation Strategies
+
+The `org.apache.camel.builder.AggregationStrategies` is a builder that can
+be used for creating commonly used aggregation strategies without having to
create a class.
+
+For example the `ExampleAggregationStrategy` from previously can be built as
follows:
+
+[source,java]
+----
+AggregationStrategy agg = AggregationStrategies.string(":");
+----
+
+There are many other possibilities with the `AggregationStrategies` builder,
and for
+more details see the
https://www.javadoc.io/static/org.apache.camel/camel-core-model/3.11.2/org/apache/camel/builder/AggregationStrategies.html[AggregationStrategies
javadoc].
diff --git
a/core/camel-core-engine/src/main/docs/modules/eips/pages/enterprise-integration-patterns.adoc
b/core/camel-core-engine/src/main/docs/modules/eips/pages/enterprise-integration-patterns.adoc
index 1dba6a8..6862c41 100644
---
a/core/camel-core-engine/src/main/docs/modules/eips/pages/enterprise-integration-patterns.adoc
+++
b/core/camel-core-engine/src/main/docs/modules/eips/pages/enterprise-integration-patterns.adoc
@@ -5,10 +5,6 @@ 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
xref:latest@manual:ROOT:getting-started.adoc[Getting Started] in the
-User Guide before attempting to implement these patterns.
-
-[[EnterpriseIntegrationPatterns-MessagingSystems]]
== Messaging Systems
[width="100%",cols="10%,10%,80%",]
@@ -40,7 +36,6 @@ a|image::eip/MessageEndpointIcon.gif[image]
connect to a messaging channel to send and receive messages?
|=======================================================================
-[[EnterpriseIntegrationPatterns-MessagingChannels]]
== Messaging Channels
[width="100%",cols="10%,10%,80%",]
@@ -82,7 +77,6 @@ a|image::eip/MessagingBridgeIcon.gif[image]
changes made to a database, and apply those changes to another system.
|=======================================================================
-[[EnterpriseIntegrationPatterns-MessageConstruction]]
== Message Construction
[width="100%",cols="10%,10%,80%",]
@@ -110,7 +104,6 @@ when a message should be considered stale and thus
shouldn’t be processed?
|=======================================================================
-[[EnterpriseIntegrationPatterns-MessageRouting]]
== Message Routing
[width="100%",cols="10%,10%,80%",]
@@ -211,7 +204,6 @@ a|image::eip/PollingConsumerIcon.gif[image]
|xref:loop-eip.adoc[Loop] |How can I repeat processing a message in a loop?
|=======================================================================
-[[EnterpriseIntegrationPatterns-MessageTransformation]]
== Message Transformation
[width="100%",cols="10%,10%,80%",]
@@ -244,7 +236,6 @@ a|image::eip/MessageSelectorIcon.gif[image]
|xref:validate-eip.adoc[Validate] |How can I validate a message?
|=======================================================================
-[[EnterpriseIntegrationPatterns-MessagingEndpoints]]
== Messaging Endpoints
[width="100%",cols="10%,10%,80%",]
@@ -297,7 +288,6 @@ design a service to be invoked both via various messaging
technologies
and via non-messaging techniques?
|=======================================================================
-[[EnterpriseIntegrationPatterns-SystemManagement]]
== System Management
[width="100%",cols="10%,10%,80%",]
@@ -324,7 +314,7 @@ a|image::eip/ControlBusIcon.gif[image]
|xref:log-eip.adoc[Log] |How can I log processing a message?
a|image::eip/RoutingTableIcon.gif[image]
-|xref:step-eip.adoc[Step] | Steps groups together a set of EIPs into a
composite logical unit for metrics and monitoring. |
+|xref:step-eip.adoc[Step] | Groups together a set of EIPs into a composite
logical unit for metrics and monitoring. |
|=======================================================================
diff --git
a/core/camel-core-engine/src/main/docs/modules/eips/pages/event-message.adoc
b/core/camel-core-engine/src/main/docs/modules/eips/pages/event-message.adoc
index bdbb468..24c5cd5 100644
--- a/core/camel-core-engine/src/main/docs/modules/eips/pages/event-message.adoc
+++ b/core/camel-core-engine/src/main/docs/modules/eips/pages/event-message.adoc
@@ -17,37 +17,48 @@ xref:components::seda-component.adoc[SEDA]
TIP: See the related xref:requestReply-eip.adoc[Request Reply] message.
-[[eventMessage-ExplicitlyspecifyingInOnly]]
-== Explicitly specifying InOnly
+== Using endpoint URI
-If you are using a component which defaults to InOut you can override
-the xref:latest@manual:ROOT:exchange-pattern.adoc[Exchange Pattern] for an
endpoint using
+If you are using a component which defaults to `InOut` you can override
+the xref:latest@manual:ROOT:exchange-pattern.adoc[Exchange Pattern] for a
*consumer* endpoint using
the pattern property.
-[source]
+[source,text]
----
foo:bar?exchangePattern=InOnly
----
+IMPORTANT: This is only possible on endpoints used by consumers (i.e. in
`<from>`).
-== Samples
-
-From 2.0 onwards on Camel you can specify the
-xref:latest@manual:ROOT:exchange-pattern.adoc[Exchange Pattern] using the DSL.
+In the example below the message will be forced as an event message as the
consumer
+is in `InOnly` mode.
[source,java]
----
-from("mq:someQueue").
- setExchangePattern(ExchangePattern.InOnly).
- bean(Foo.class);
+from("mq:someQueue?exchangePattern=InOnly")
+ .to("activemq:queue:one-way");
+----
+
+And with XML:
+
+[source,xml]
+----
+<route>
+ <from uri="mq:someQueue?exchangePattern=InOnly"/>
+ <to uri="activemq:queue:one-way"/>
+</route>
----
-or you can invoke an endpoint with an explicit pattern
+== Using setExchangePattern EIP
+
+You can specify the
+xref:latest@manual:ROOT:exchange-pattern.adoc[Exchange Pattern] using
`setExchangePattern` in the DSL.
[source,java]
----
-from("mq:someQueue").
- inOnly("mq:anotherQueue");
+from("mq:someQueue")
+ .setExchangePattern(ExchangePattern.InOnly)
+ .to("activemq:queue:one-way");
----
And with XML:
@@ -56,15 +67,27 @@ And with XML:
----
<route>
<from uri="mq:someQueue"/>
- <inOnly uri="bean:foo"/>
+ <setExchangePattern pattern="InOnly"/>
+ <to uri="activemq:queue:one-way"/>
</route>
----
-[source,xml]
+When using `setExchangePattern` then the
xref:latest@manual:ROOT:exchange-pattern.adoc[Exchange Pattern]
+on the xref:latest@manual:ROOT:exchange.adoc[Exchange] is changed from this
point onwards in the route.
+
+This means you can change the pattern back again at a later point:
+
+[source,java]
----
-<route>
- <from uri="mq:someQueue"/>
- <inOnly uri="mq:anotherQueue"/>
-</route>
+from("mq:someQueue")
+ .setExchangePattern(ExchangePattern.InOnly)
+ .to("activemq:queue:one-way");
+ .setExchangePattern(ExchangePattern.InOut)
+ .to("activemq:queue:in-and-out")
+ .log("InOut MEP received ${body}")
----
+NOTE: Using `setExchangePattern` to change the
xref:latest@manual:ROOT:exchange-pattern.adoc[Exchange Pattern]
+is often only used in special use-cases where you must
+force to be using either `InOnly` or `InOut` mode when using components that
support both modes (such as messaging components like ActiveMQ, JMS, RabbitMQ
etc.)
+
diff --git
a/core/camel-core-engine/src/main/docs/modules/eips/pages/eventDrivenConsumer-eip.adoc
b/core/camel-core-engine/src/main/docs/modules/eips/pages/eventDrivenConsumer-eip.adoc
index aa3e086..e8a4af0 100644
---
a/core/camel-core-engine/src/main/docs/modules/eips/pages/eventDrivenConsumer-eip.adoc
+++
b/core/camel-core-engine/src/main/docs/modules/eips/pages/eventDrivenConsumer-eip.adoc
@@ -5,10 +5,13 @@ Camel supports the
http://www.enterpriseintegrationpatterns.com/EventDrivenConsumer.html[Event
Driven Consumer]
from the
xref:enterprise-integration-patterns.adoc[EIP patterns].
+
The default consumer model is event based (i.e. asynchronous)
as this means that the Camel container can then manage pooling,
threading and concurrency for you in a declarative manner.
+TIP: The alternative consumer mode is xref:pollEnrich-eip.adoc[Polling
Consumer].
+
image::eip/EventDrivenConsumerSolution.gif[image]
The Event Driven Consumer is implemented by consumers implementing the
@@ -16,41 +19,24 @@
http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/Proces
interface which is invoked by the xref:message-endpoint.adoc[Message Endpoint]
when a xref:message.adoc[Message] is available for processing.
-[[eventDrivenConsumer-Example]]
== Example
-The following demonstrates a
-http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/Processor.html[Processor]
-defined in the Camel xref:latest@manual:ROOT:registry.adoc[Registry] which is
-invoked when an event occurs from a xref:components::jms-component.adoc[JMS]
queue.
+The following demonstrates a xref:bean-eip.adoc[Bean] being invoked when
+an event occurs from a xref:components::jms-component.adoc[JMS] queue.
[source,java]
----
from("jms:queue:foo")
- .processRef("processor");
+ .bean(MyBean.class);
----
-**Using the xref:latest@manual:ROOT:spring-xml-extensions.adoc[Spring XML
Extensions]**
+And in XML:
[source,xml]
----
<route>
<from uri="jms:queue:foo"/>
- <to uri="processor"/>
+ <bean beanType="com.foo.MyBean"/>
</route>
----
-For more details see:
-
-* xref:message.adoc[Message]
-* xref:message-endpoint.adoc[Message Endpoint]
-
-[[eventDrivenConsumer-UsingThisPattern]]
-== Using This Pattern
-
-If you would like to use this EIP Pattern then please read the
-xref:latest@manual:ROOT:getting-started.adoc[Getting Started], you may also
find the
-xref:latest@manual:ROOT:architecture.adoc[Architecture] useful particularly
the description
-of xref:latest@manual:ROOT:endpoint.adoc[Endpoint] and
xref:latest@manual:ROOT:uris.adoc[URIs]. Then you could
-try out some of the xref:latest@manual:ROOT:examples.adoc[Examples] first
before trying
-this pattern out.
