Implementing a simple OWS service¶
This section explains How to Create a Simple GeoServer OWS service for Geoserver using the following scenario. The service should supply a capabilities document which advertises a single operation called “sayHello”. The result of a sayHello operation is the simple string “Hello World”.
Contents
Setup¶
The first step in creating our plug-in is setting up a maven project for it. The project will be called “hello”.
- Create a new directory called hello anywhere on your file system.
- Add a maven pom called pom.xml to the hello directory:
<?xml version="1.0" encoding="ISO-8859-1"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<!-- set parent pom to community pom -->
<parent>
<groupId>org.geoserver</groupId>
<artifactId>community</artifactId>
<version>2.0.1</version>
</parent>
<groupId>org.geoserver</groupId>
<artifactId>hello</artifactId>
<packaging>jar</packaging>
<version>1.0</version>
<name>Hello World Service Module</name>
<!-- declare depenency on geoserver main -->
<dependencies>
<dependency>
<groupId>org.geoserver</groupId>
<artifactId>main</artifactId>
<version>2.0.1</version>
</dependency>
</dependencies>
<repositories>
<repository>
<id>opengeo</id>
<name>opengeo</name>
<url>http://repo.opengeo.org</url>
</repository>
</repositories>
</project>
Create a java source directory, src/main/java under the hello directory:
hello/ + pom.xml + src/ + main/ + java/
Creating the Plug-in¶
A plug-in is a collection of extensions realized as spring beans. In this example the extension point of interest is a HelloWorld POJO (Plain Old Java Object).
- Create a class called HelloWorld:
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class HelloWorld {
public HelloWorld() {
// Do nothing
}
public void sayHello(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.getOutputStream().write( "Hello World".getBytes() );
}
}
The service is relatively simple. It provides a method sayHello(..) which takes a HttpServletRequest, and a HttpServletResponse. The parameter list for this function is automatically discovered by the org.geoserver.ows.Dispatcher.
- Create an applicationContext.xml declaring the above class as a bean.
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans>
<!-- Spring will reference the instance of the HelloWorld class
by the id name "helloService" -->
<bean id="helloService" class="HelloWorld">
</bean>
<!-- This creates a Service descriptor, which allows the org.geoserver.ows.Dispatcher
to locate it. -->
<bean id="helloService-1.0.0" class="org.geoserver.platform.Service">
<!-- used to reference the service in the URL -->
<constructor-arg index="0" value="hello"/>
<!-- our actual service POJO defined previously -->
<constructor-arg index="1" ref="helloService"/>
<!-- a version number for this service -->
<constructor-arg index="2" value="1.0.0"/>
<!-- a list of functions for this service -->
<constructor-arg index="3">
<list>
<value>sayHello</value>
</list>
</constructor-arg>
</bean>
</beans>
At this point the hello project should look like the following:
hello/
+ pom.xml
+ src/
+ main/
+ java/
+ HelloWorld.java
+ applicationContext.xml
Trying it Out¶
- Install the hello module:
[hello]% mvn install
[hello]% mvn install
[INFO] Scanning for projects...
[INFO] ----------------------------------------------------------------------------
[INFO] Building Hello World Service Module
[INFO] task-segment: [install]
[INFO] ----------------------------------------------------------------------------
[INFO] [resources:resources]
[INFO] Using default encoding to copy filtered resources.
[INFO] [compiler:compile]
[INFO] Compiling 1 source file to /home/ak/geoserver/community/hello/target/classes
[INFO] [resources:testResources]
[INFO] Using default encoding to copy filtered resources.
[INFO] [compiler:testCompile]
[INFO] No sources to compile
[INFO] [surefire:test]
[INFO] No tests to run.
[INFO] [jar:jar]
[INFO] Building jar: /home/ak/geoserver/community/hello/target/hello-1.0.jar
[INFO] [jar:test-jar {execution: default}]
[WARNING] JAR will be empty - no content was marked for inclusion!
[INFO] Building jar: /home/ak/geoserver/community/hello/target/hello-1.0-tests.jar
[INFO] [install:install]
[INFO] Installing /home/ak/geoserver/community/hello/target/hello-1.0.jar to /home/ak/.m2/repository/org/geoserver/hello/1.0/hello-1.0.jar
[INFO] Installing /home/ak/geoserver/community/hello/target/hello-1.0-tests.jar to /home/ak/.m2/repository/org/geoserver/hello/1.0/hello-1.0-tests.jar
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESSFUL
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 6 seconds
[INFO] Finished at: Fri Sep 21 14:52:31 EDT 2007
[INFO] Final Memory: 27M/178M
[INFO] -----------------------------------------------------------------------
- Copy target/hello-1.0.jar into the WEB-INF/lib directory of your GeoServer install
- Restart GeoServer
- Visit http://<host>/geoserver/ows?request=sayHello&service=hello&version=1.0.0
- request
- the method we defined in our service
- service
- the name we passed to the Service descriptor in the applicationContext.xml
- version
- the version we passed to the Service descriptor in the applicationContext.xml
Alternative 1: Bundling with Web Module¶
An alternative is to declare a dependency from the web module on the new plugin project.
- Install the hello module as above.
- Edit web/pom.xml and add the following dependency:
<dependency> <groupId>org.geoserver</groupId> <artifactId>hello</artifactId> <version>1.0</version> </dependency>
- Install and run the web module
[web] mvn install jetty:run
Alternative 2: Running from GeoServer Source¶
As an alternative to trying the plugin:
- Install the hello module
- Change directory to the web module
- Install the web module
- Copy <hello module>/target/hello-1.0.jar to <web module>/target/geoserver/WEB-INF/lib:
[/dev/geoserver/web]% cp ~/hello/target/hello-1.0.jar target/geoserver/WEB-INF/lib
- Run the exploded war with Jetty:
[/dev/geoserver/web]% mvn jetty6:run-exploded
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