Basic REST Service with Apache CXF

Let’s build a basic REST service, that will serve as a basis for all the following posts.

The complete source code is available here.

Technologies used :

Java SE Development Kit 8u66
Eclipse IDE for Java Developers Version: Mars.1 Release (4.5.1)
Maven 3.3.3 (comes with Eclipse)
Spring Framework 4.2.3 (as Maven dependency)
Apache CXF 3.1.4 (as Maven dependency)

pom.xml

	<dependency>
		<groupId>javax.ws.rs</groupId>
		<artifactId>jsr311-api</artifactId>
		<version>1.1.1</version>
	</dependency>
	<dependency>
		<groupId>org.apache.cxf</groupId>
		<artifactId>cxf-rt-frontend-jaxrs</artifactId>
		<version>3.1.4</version>
	</dependency>
	<dependency>
		<groupId>org.springframework</groupId>
		<artifactId>spring-beans</artifactId>
		<version>4.2.3.RELEASE</version>
		<scope>runtime</scope>
	</dependency>
	<dependency>
		<groupId>org.springframework</groupId>
		<artifactId>spring-web</artifactId>
		<version>4.2.3.RELEASE</version>
		<scope>runtime</scope>
	</dependency>
	<dependency>
		<groupId>org.codehaus.jackson</groupId>
		<artifactId>jackson-jaxrs</artifactId>
		<version>1.9.0</version>
		<scope>runtime</scope>
	</dependency>
	<dependency>
		<groupId>org.codehaus.jackson</groupId>
		<artifactId>jackson-xc</artifactId>
		<version>1.9.13</version>
		<scope>runtime</scope>
	</dependency>

Resource

The fundamental concept in REST is the resource. Let us start with that :

public class PersonResource {

    private String id;
    private String lastName;
    private String firstName;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    @Override
    public String toString() {
        return "PersonResource [id=" + id + ", lastName=" + lastName + ", firstName=" + firstName + "]";
    }

}

Service

Now we would like to do something with these resources, for example typical CRUD operations: list all the resources, return a single resource, create a resource, update or delete it…

One good point of CXF is that you can define all the REST relevant annotations on you interface, as opposed to Spring REST Services where you must annotate the controller.

@Path("/persons")
public interface PersonService {

    @GET
    @Produces(APPLICATION_JSON)
    Collection<PersonResource> getAll();

    @GET
    @Path("/{id}")
    @Produces(APPLICATION_JSON)
    PersonResource get(@PathParam(value = "id") String id);

    @POST
    @Consumes(APPLICATION_JSON)
    @Produces(APPLICATION_JSON)
    PersonResource create(PersonResource person);

    @PUT
    @Path("/{id}")
    @Consumes(APPLICATION_JSON)
    @Produces(APPLICATION_JSON)
    PersonResource update(@PathParam(value = "id") String id, PersonResource person);

    @DELETE
    @Path("/{id}")
    void delete(@PathParam(value = "id") String id);

}

The implementations simply uses a map to store the resources.

public class PersonServiceImpl implements PersonService {

    private Map<String, PersonResource> persons;

    public PersonServiceImpl() {
        persons = new HashMap<String, PersonResource>();
    }

    public Collection<PersonResource> getAll() {
        return persons.values();
    }

    public PersonResource get(String id) {
        return persons.get(id);
    }

    public PersonResource create(PersonResource person) {
        String id = UUID.randomUUID().toString();
        person.setId(id);
        persons.put(id, person);
        return person;
    }

    public PersonResource update(String id, PersonResource person) {
        if (persons.containsKey(id)) {
            person.setId(id);
            persons.put(id, person);
            return person;
        }
        return null;
    }

    public void delete(String id) {
        persons.remove(id);
    }

}

Spring configuration

To publish the service under /rest and be able to serialize / deserialize JSON messages :

<jaxrs:server address="/rest">
    <jaxrs:serviceBeans>
        <ref bean="personService" />
    </jaxrs:serviceBeans>
    <jaxrs:providers>
        <bean class="org.codehaus.jackson.jaxrs.JacksonJaxbJsonProvider" />
    </jaxrs:providers>
</jaxrs:server>

<bean id="personService" class="de.griesser.rest.services.PersonServiceImpl" />

web.xml

Every request is delegated to CXFServlet.

<web-app>

    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>WEB-INF/beans.xml</param-value>
    </context-param>

    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>

    <servlet>
        <servlet-name>CXFServlet</servlet-name>
        <display-name>CXF Servlet</display-name>
        <servlet-class>org.apache.cxf.transport.servlet.CXFServlet</servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <servlet-mapping>
        <servlet-name>CXFServlet</servlet-name>
        <url-pattern>/*</url-pattern>
    </servlet-mapping>

</web-app>

Launch

To run the example, we can use the Jetty plugin, no need to download and install an application server.

Add this plugin configuration to the pom.xml

<plugin>
	<groupId>org.eclipse.jetty</groupId>
	<artifactId>jetty-maven-plugin</artifactId>
	<version>9.3.6.v20151106</version>
</plugin>

The following command line will let the application run under http://localhost:8080/rest

mvn clean install jetty:run-war

Open http://localhost:8080/rest/persons in you favorite browser, it should display [], as no resources have been created yet.

Written on December 5, 2015