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new 047264f Blog post: Command line utility with Camel Quarkus
047264f is described below
commit 047264fa3804481f2f7315d3f19e5b86da937b35
Author: Peter Palaga <ppal...@redhat.com>
AuthorDate: Wed Jul 15 12:35:13 2020 +0200
Blog post: Command line utility with Camel Quarkus
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+---
+title: "Command line utility with Camel Quarkus"
+date: 2020-07-15
+authors: ["ppalaga"]
+categories: ["Howtos", "Camel Quarkus"]
+preview: How to write a command line utility with Camel Quarkus
+---
+
+[Camel](https://camel.apache.org/) and [Camel
Quarkus](https://camel.apache.org/camel-quarkus/latest/index.html) are
+typically used to create integration applications that run as long living
processes, a.k.a. daemons or services.
+In this blog post, we are going to explain a slightly different use case:
using Camel Quarkus in programs that exit by
+themselves after performing some desired tasks.
+
+## Where can this be useful?
+
+The enterprise is full of scheduled batch processing. Say, some system exports
some sort of reports daily at 4 a.m.
+Those need to be transformed (e.g. XML -> Excel) and transferred somewhere
else (e.g. via mail, FTP or similar).
+
+Camel is a perfect match for doing the transformation and the transfer.
However, having a service running 24/7 for
+doing something useful just once a day would probably be an overkill.
Combining a
+[Cron job](https://en.wikipedia.org/wiki/Cron) (or a similar scheduling
technology) with a command line utility may suit
+much better in situations like this.
+
+## So how can I write a command line tool with Camel Quarkus?
+
+There are just two things where it would differ from a stock Camel Quarkus
application:
+
+1. Adding `camel-quarkus-main` dependency
+2. Setting an exit condition in `application.properties`
+
+The rest of the application - most notably the
[Route](https://camel.apache.org/manual/latest/routes.html) that
+performs the actual data transformation and transfer - will look the same like
with a traditional Camel service.
+
+
+## A minimal Hello World!
+
+Let's go through a minimal example that just prints `Hello World!` to the
console and exits.
+
+The route definition could look like the following:
+
+```java
+import org.apache.camel.builder.RouteBuilder;
+
+@ApplicationScoped
+public class CamelRoute extends RouteBuilder {
+
+ @Override
+ public void configure() {
+ from("timer:hello?delay=-1&repeatCount=1")
+ .setBody().constant("Hello World!")
+ .to("log:hello");
+ }
+}
+```
+
+Note that we use the
[timer](https://camel.apache.org/components/latest/timer-component.html)
component to trigger the
+route execution. The URI parameter `delay=-1` causes the timer to be triggered
with no initial delay and
+`repeatCount=1` ensures that the route is executed just once.
+
+However, doing just the above would not make our application exit by itself.
+[camel-main](https://camel.apache.org/components/latest/others/main.html) and
its `camel.main.durationMax*`
+family of configuration options offers a way to solve that. E.g. we can set
the following in
+`application.properties`
+
+```properties
+camel.main.durationMaxMessages = 1
+```
+
+to make the application exit after the route has processed a single message.
+
+For the configuration to get effective, we need to add the respective
dependency to the application. In case of Maven,
+it is
+
+```xml
+<dependency>
+ <groupId>org.apache.camel.quarkus</groupId>
+ <artifactId>camel-quarkus-main</artifactId>
+</dependency>
+```
+
+Of course, we also need to add the dependencies for `timer` and `log`
components:
+
+```xml
+<dependency>
+ <groupId>org.apache.camel.quarkus</groupId>
+ <artifactId>camel-quarkus-log</artifactId>
+</dependency>
+<dependency>
+ <groupId>org.apache.camel.quarkus</groupId>
+ <artifactId>camel-quarkus-timer</artifactId>
+</dependency>
+```
+
+When invoking the application on the command line, you should see something
like the following:
+
+```shell
+]$ java -jar target/*-runner.jar
+2020-07-15 11:32:13,577 INFO [org.apa.cam.qua.cor.CamelBootstrapRecorder]
(main) bootstrap runtime: org.apache.camel.quarkus.main.CamelMainRuntime
+2020-07-15 11:32:13,623 INFO [org.apa.cam.mai.BaseMainSupport] (main)
Auto-configuration summary:
+2020-07-15 11:32:13,623 INFO [org.apa.cam.mai.BaseMainSupport] (main)
camel.main.durationMaxMessages=1
+2020-07-15 11:32:13,700 INFO [org.apa.cam.imp.eng.AbstractCamelContext]
(main) Apache Camel 3.4.0 (camel-1) is starting
+2020-07-15 11:32:13,701 INFO [org.apa.cam.imp.eng.AbstractCamelContext]
(main) StreamCaching is not in use. If using streams then its recommended to
enable stream caching. See more details at
http://camel.apache.org/stream-caching.html
+2020-07-15 11:32:13,709 INFO
[org.apa.cam.imp.eng.InternalRouteStartupManager] (main) Route: route1 started
and consuming from: timer://hello
+2020-07-15 11:32:13,714 INFO [org.apa.cam.imp.eng.AbstractCamelContext]
(main) Total 1 routes, of which 1 are started
+2020-07-15 11:32:13,715 INFO [org.apa.cam.imp.eng.AbstractCamelContext]
(main) Apache Camel 3.4.0 (camel-1) started in 0.014 seconds
+2020-07-15 11:32:13,718 INFO [org.apa.cam.mai.MainSupport] (camel-main)
Waiting until: 1 messages has been processed
+2020-07-15 11:32:13,719 INFO [io.quarkus] (main)
camel-quarkus-integration-test-main-command-mode 1.1.0-SNAPSHOT on JVM (powered
by Quarkus 1.6.0.Final) started in 0.592s.
+2020-07-15 11:32:13,720 INFO [io.quarkus] (main) Profile prod activated.
+2020-07-15 11:32:13,721 INFO [io.quarkus] (main) Installed features:
[camel-core, camel-log, camel-main, camel-policy, camel-support-common,
camel-timer, cdi]
+2020-07-15 11:32:13,725 INFO [hello] (Camel (camel-1) thread #0 -
timer://hello) Exchange[ExchangePattern: InOnly, BodyType: String, Body: Hello
World!]
+2020-07-15 11:32:13,729 INFO [org.apa.cam.mai.MainLifecycleStrategy] (Camel
(camel-1) thread #0 - timer://hello) Duration max messages triggering shutdown
of the JVM.
+2020-07-15 11:32:13,730 INFO [org.apa.cam.imp.eng.AbstractCamelContext]
(Camel (camel-1) thread #1 - CamelMainShutdownCamelContext) Apache Camel 3.4.0
(camel-1) is shutting down
+2020-07-15 11:32:13,740 INFO [org.apa.cam.mai.MainLifecycleStrategy] (Camel
(camel-1) thread #1 - CamelMainShutdownCamelContext) CamelContext: camel-1 has
been shutdown, triggering shutdown of the JVM.
+2020-07-15 11:32:13,741 INFO [org.apa.cam.imp.eng.AbstractCamelContext]
(Camel (camel-1) thread #1 - CamelMainShutdownCamelContext) Apache Camel 3.4.0
(camel-1) uptime 0.041 seconds
+2020-07-15 11:32:13,741 INFO [org.apa.cam.imp.eng.AbstractCamelContext]
(Camel (camel-1) thread #1 - CamelMainShutdownCamelContext) Apache Camel 3.4.0
(camel-1) is shutdown in 0.011 seconds
+2020-07-15 11:32:13,745 INFO [io.quarkus] (main)
camel-quarkus-integration-test-main-command-mode stopped in 0.005s
+```
+
+
+## Command line parameters
+
+That was really trivial. How about greeting a person whose name is passed via
a command line parameter? We can use
+[Quarkus MicroProfile Config](https://quarkus.io/guides/config) for that:
+
+```java
+import javax.enterprise.context.ApplicationScoped;
+import org.apache.camel.builder.RouteBuilder;
+import org.eclipse.microprofile.config.inject.ConfigProperty;
+
+@ApplicationScoped
+public class CamelRoute extends RouteBuilder {
+
+ @ConfigProperty(name = "greeted.subject", defaultValue = "World")
+ String greetedSubject;
+
+ @Override
+ public void configure() {
+ from("timer:hello?delay=-1")
+ .setBody().constant("Hello " + greetedSubject + "!")
+ .to("log:hello");
+ }
+}
+```
+
+For the `@ConfigProperty` annotation to work, the `CamelRoute` class needs to
be annotated with
+`@ApplicationScoped`.
+
+Having the above in place, we can call the application with the
`-Dgreeted.subject=Joe` parameter at the command
+line and voilà
+
+```shell
+$ $ java -Dgreeted.subject=Joe -jar target/*-runner.jar
+2020-07-15 11:42:18,770 INFO [org.apa.cam.qua.cor.CamelBootstrapRecorder]
(main) bootstrap runtime: org.apache.camel.quarkus.main.CamelMainRuntime
+2020-07-15 11:42:18,816 INFO [org.apa.cam.mai.BaseMainSupport] (main)
Auto-configuration summary:
+2020-07-15 11:42:18,816 INFO [org.apa.cam.mai.BaseMainSupport] (main)
camel.main.durationMaxMessages=1
+2020-07-15 11:42:18,892 INFO [org.apa.cam.imp.eng.AbstractCamelContext]
(main) Apache Camel 3.4.0 (camel-1) is starting
+2020-07-15 11:42:18,893 INFO [org.apa.cam.imp.eng.AbstractCamelContext]
(main) StreamCaching is not in use. If using streams then its recommended to
enable stream caching. See more details at
http://camel.apache.org/stream-caching.html
+2020-07-15 11:42:18,902 INFO
[org.apa.cam.imp.eng.InternalRouteStartupManager] (main) Route: route1 started
and consuming from: timer://hello
+2020-07-15 11:42:18,907 INFO [org.apa.cam.imp.eng.AbstractCamelContext]
(main) Total 1 routes, of which 1 are started
+2020-07-15 11:42:18,908 INFO [org.apa.cam.imp.eng.AbstractCamelContext]
(main) Apache Camel 3.4.0 (camel-1) started in 0.015 seconds
+2020-07-15 11:42:18,911 INFO [org.apa.cam.mai.MainSupport] (camel-main)
Waiting until: 1 messages has been processed
+2020-07-15 11:42:18,914 INFO [io.quarkus] (main)
camel-quarkus-integration-test-main-command-mode 1.1.0-SNAPSHOT on JVM (powered
by Quarkus 1.6.0.Final) started in 0.569s.
+2020-07-15 11:42:18,915 INFO [io.quarkus] (main) Profile prod activated.
+2020-07-15 11:42:18,915 INFO [io.quarkus] (main) Installed features:
[camel-core, camel-log, camel-main, camel-policy, camel-support-common,
camel-timer, cdi]
+2020-07-15 11:42:18,919 INFO [hello] (Camel (camel-1) thread #0 -
timer://hello) Exchange[ExchangePattern: InOnly, BodyType: String, Body: Hello
Joe!]
+2020-07-15 11:42:18,921 INFO [org.apa.cam.mai.MainLifecycleStrategy] (Camel
(camel-1) thread #0 - timer://hello) Duration max messages triggering shutdown
of the JVM.
+2020-07-15 11:42:18,922 INFO [org.apa.cam.imp.eng.AbstractCamelContext]
(Camel (camel-1) thread #1 - CamelMainShutdownCamelContext) Apache Camel 3.4.0
(camel-1) is shutting down
+2020-07-15 11:42:18,931 INFO [org.apa.cam.mai.MainLifecycleStrategy] (Camel
(camel-1) thread #1 - CamelMainShutdownCamelContext) CamelContext: camel-1 has
been shutdown, triggering shutdown of the JVM.
+2020-07-15 11:42:18,933 INFO [org.apa.cam.imp.eng.AbstractCamelContext]
(Camel (camel-1) thread #1 - CamelMainShutdownCamelContext) Apache Camel 3.4.0
(camel-1) uptime 0.040 seconds
+2020-07-15 11:42:18,933 INFO [org.apa.cam.imp.eng.AbstractCamelContext]
(Camel (camel-1) thread #1 - CamelMainShutdownCamelContext) Apache Camel 3.4.0
(camel-1) is shutdown in 0.011 seconds
+2020-07-15 11:42:18,937 INFO [io.quarkus] (main)
camel-quarkus-integration-test-main-command-mode stopped in 0.005s
+```
+
+## Compiling the command line utility to a native executable
+
+[As usual with Camel
Quarkus](https://camel.apache.org/camel-quarkus/latest/user-guide/first-steps.html#_native_mode),
+the application can be compiled to native executable by activating the
`native` profile.
+GraalVM with `native-image` command installed and `GRAALVM_HOME` environment
variable set is required for that,
+see [Building a native
executable](https://quarkus.io/guides/building-native-image) section of the
Quarkus
+documentation.
+
+```shell
+$ export GRAALVM_HOME=...
+$ mvn clean package -Pnative
+...
+$ ls -lh target
+...
+-rwxr-xr-x. 1 ppalaga ppalaga 33M Jul 15 11:48 command-mode-runner
+...
+```
+
+The basic command line application compiled into a Linux native executable has
about 33 Megabytes.
+
+Running it is easy:
+
+```shell
+$ target/*runner -Dgreeted.subject=Joe
+2020-07-15 12:19:22,810 INFO [org.apa.cam.qua.cor.CamelBootstrapRecorder]
(main) bootstrap runtime: org.apache.camel.quarkus.main.CamelMainRuntime
+2020-07-15 12:19:22,811 INFO [org.apa.cam.mai.BaseMainSupport] (main)
Auto-configuration summary:
+2020-07-15 12:19:22,811 INFO [org.apa.cam.mai.BaseMainSupport] (main)
camel.main.durationMaxMessages=1
+2020-07-15 12:19:22,812 INFO [org.apa.cam.imp.eng.AbstractCamelContext]
(main) Apache Camel 3.4.0 (camel-1) is starting
+2020-07-15 12:19:22,812 INFO [org.apa.cam.imp.eng.AbstractCamelContext]
(main) StreamCaching is not in use. If using streams then its recommended to
enable stream caching. See more details at
http://camel.apache.org/stream-caching.html
+2020-07-15 12:19:22,812 INFO
[org.apa.cam.imp.eng.InternalRouteStartupManager] (main) Route: route1 started
and consuming from: timer://hello
+2020-07-15 12:19:22,812 INFO [org.apa.cam.imp.eng.AbstractCamelContext]
(main) Total 1 routes, of which 1 are started
+2020-07-15 12:19:22,812 INFO [org.apa.cam.imp.eng.AbstractCamelContext]
(main) Apache Camel 3.4.0 (camel-1) started in 0.000 seconds
+2020-07-15 12:19:22,812 INFO [io.quarkus] (main)
camel-quarkus-integration-test-main-command-mode 1.1.0-SNAPSHOT native (powered
by Quarkus 1.6.0.Final) started in 0.007s.
+2020-07-15 12:19:22,813 INFO [io.quarkus] (main) Profile prod activated.
+2020-07-15 12:19:22,812 INFO [hello] (Camel (camel-1) thread #0 -
timer://hello) Exchange[ExchangePattern: InOnly, BodyType: String, Body: Hello
Joe!]
+2020-07-15 12:19:22,813 INFO [io.quarkus] (main) Installed features:
[camel-core, camel-log, camel-main, camel-policy, camel-support-common,
camel-timer, cdi]
+2020-07-15 12:19:22,813 INFO [org.apa.cam.mai.MainSupport] (camel-main)
Waiting until: 1 messages has been processed
+2020-07-15 12:19:22,813 INFO [org.apa.cam.mai.MainLifecycleStrategy] (Camel
(camel-1) thread #0 - timer://hello) Duration max messages triggering shutdown
of the JVM.
+2020-07-15 12:19:22,813 INFO [org.apa.cam.imp.eng.AbstractCamelContext]
(Camel (camel-1) thread #1 - CamelMainShutdownCamelContext) Apache Camel 3.4.0
(camel-1) is shutting down
+2020-07-15 12:19:22,813 INFO [org.apa.cam.mai.MainLifecycleStrategy] (Camel
(camel-1) thread #1 - CamelMainShutdownCamelContext) CamelContext: camel-1 has
been shutdown, triggering shutdown of the JVM.
+2020-07-15 12:19:22,813 INFO [org.apa.cam.imp.eng.AbstractCamelContext]
(Camel (camel-1) thread #1 - CamelMainShutdownCamelContext) Apache Camel 3.4.0
(camel-1) uptime 0.001 seconds
+2020-07-15 12:19:22,813 INFO [org.apa.cam.imp.eng.AbstractCamelContext]
(Camel (camel-1) thread #1 - CamelMainShutdownCamelContext) Apache Camel 3.4.0
(camel-1) is shutdown in 0.000 seconds
+2020-07-15 12:19:22,813 INFO [io.quarkus] (main)
camel-quarkus-integration-test-main-command-mode stopped in 0.000s
+```
+
+## Show me the code!
+
+The sources of the application used in this blog post are based on the
`main-command-mode` integration test in
+the Camel Quarkus source tree:
https://github.com/apache/camel-quarkus/tree/master/integration-tests/main-command-mode
+
+Bonus: The integration test module shows a way how to test command line
applications.
+
+Have a lot of fun!
