This version must be installed on Petals ESB 5.1.0+ Feature The REST component is a Binding Component (BC) which enables to interact with external RESTful Web Services and to expose JBI services as RESTful Web Services. In provider role, when a JBI MessageExchange is sent to a ServiceEndpoint (mapped to a Web Service), it is transformed into a REST message and sent to the linked external Web Service. In consumer role, when a REST message is received on an exposed Web Service, it is transformed into a JBI MessageExchange and sent to the corresponding JBI ServiceEndpoint. The REST component is based on Jersey and Axis2 (TBD). It provides the following features: Expose Restful Web Services as JBI Services Expose Restful Web Services as JBI Services using a WADL (TBC) Expose Restful Web Services as JBI Services using a WSDL 2.0 (TBC) Expose JBI Services as Restful Web Services REST is a style of software architecture not a standard. If you want more details about REST, you can consult the Wikipedia page: http://en.wikipedia.org/wiki/Representational_State_Transfer

Table of contents Feature Exposing an external Restful Web Service as a JBI service endpoint Usage Configuration With no description of the RESTful resource With a WADL With a WSDL 2.0 Exposing an internal JBI service endpoint as a RESTful Web Service Usage Configuration Service Unit descriptor Service Unit content Configuring the component CDK parameters Interceptor Component specific parameters Parameters of the embedded REST server Parameters of the embedded REST client Logging Logging of the embedded HTTP server Logging of the embedded HTTP client Monitoring the component Using metrics Common metrics Dedicated metrics Receiving alerts Common alerts Dedicated alerts Unit testing Checking the compliance of the JBI descriptor with WSDL content Unit-testing your operation definitions Know problems Handshake error invoking external resources through HTTPS Contributors Christophe DENEUX Victor NOËL

Exposing an external Restful Web Service as a JBI service endpoint

In provide mode, the component exposes an external Web Service in the JBI environment to send REST requests to the external Web Service.

Usage

The Petals BC REST component can expose an external Web Service as a JBI service endpoint by deploying a Service Unit on it:

When a message is received on a REST linked endpoint from the JBI environment, it is transformed into a REST message and sent to the resource server.

The REST request is created like this:

• The REST URI is created from the address extension, the JBI operation and JBI message content (The JBI message content must contains the information about the path, the matrix and query parameters),
• The HTTP headers are set according to the provided configuration,
• The HTTP body is created differently according the HTTP method to used:
  • GET/DELETE: There is no HTTP body
  • POST: The HTTP body is also created differently according the JBI message content:
    • The JBI message content contains only a reference to a JBI attachment: The HTTP body is created from a JBI attachment (binary data)
    • The JBI message content does not contains a reference to a JBI attachment: The HTTP body is created from the JBI message content (form parameters)
  • PUT: The HTTP body is created from a JBI attachment.

For example the following JBI message will produces the URI http://localhost:8088/library/My+Documents/documents/6/metadata:

<consulter xmlns="http://petals.ow2.org/bc/rest/unit-test/ged">
    <library>My Documents</library>
    <reference>6</reference>
</consulter>

The external resource is called and the REST response is processed and returned to the JBI environment.

The REST response is transformed into a JBI message like this:

• In case of normal response (HTTP status as 20x), the JBI output message content and attachment are created differently according the Content-Type HTTP header:
  • XML content types: The JBI message content is created from the HTTP body. If a configuration element 'on-http-status' is defined for the HTTP status 20x, the XML of the HTTP body is transformed with the associated XSL,
  • JSON content types: The JBI message content is created from the JSON body converted into a basic XML. If a configuration element 'on-http-status' is defined for the HTTP status 20x, the basic XML is transformed with the associated XSL,
  • Non XML content types: The JBI message content is a reference (cf SOAP) to a JBI attachment which contains the HTTP body.
• In case of error (HTTP status different from 20x) a JBI error is created, the JBI output message is built according to the following rules:
  • if the HTTP status is catched by a configuration element 'on-http-status', the return depends on the message exchange pattern:
    • 'InOnly', a status DONE is returned,
    • 'RobustInOnly', a fault generated from the given XSL is returned,
    • 'InOut', a fault or normal response, both generated from the given XSL, is returned according to the value of the attribute 'as-fault',
  • if the HTTP status is not catched by a configuration element 'on-http-status', a status 'ERROR' is returned.

Configuration

With no description of the RESTful resource

All needed information must be defined in the service-unit. See Service Unit attributes to provide services for more information :

<jbi:jbi xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:cdk5="http://petals.ow2.org/components/extensions/version-5"
   xmlns:jbi="http://java.sun.com/xml/ns/jbi" xmlns:rest="http://petals.ow2.org/components/rest/version-1"
   xmlns:ged="http://petals.ow2.org/bc/rest/unit-test/ged" version="1.0">
   <jbi:services binding-component="true">
      <jbi:provides interface-name="gerd:document" service-name="ged:documentService">
         <cdk5:timeout>30000</cdk5:timeout>
         <cdk5:wsdl>ged.wsdl</cdk5:wsdl>
         <rest:service-base-path>/sample-rest</rest:service-base-path>
         <rest:mapping>
            <rest:operation name="ged:consulter">
               <rest:http-method>GET</rest:http-method>
               <rest:http-body-type>NO_BODY</rest:http-body-type>
               <rest:uri>http://localhost:8088/library/{library}/documents/{reference}</rest:uri>
               <rest:xpath-param name="library">//*[local-name()='library']</rest:xpath-param>
               <rest:xpath-param name="reference">//*[local-name()='reference']</rest:xpath-param>
               <rest:authentication>
                  <rest:basic>
                     <rest:username><rest:constant>${username}</rest:constant></rest:username>
                     <rest:password><rest:constant>${password}</rest:constant></rest:password>
                  </rest:basic>
               </rest:authentication>
               <rest:on-http-status code="200">
                  <rest:otherwise-out>
                     <rest:transformation>
                        <rest:xsl>200-consulter.xsl</rest:xsl>
                     </rest:transformation>
                  </rest:otherwise-out>
               </rest:on-http-status>
               <rest:on-http-status code="404">
                  <rest:otherwise-fault>
                     <rest:transformation>
                        <rest:xsl>404.xsl</rest:xsl>
                     </rest:transformation>
                  </rest:otherwise-fault>
               </rest:on-http-status>
            </rest:operation>
            <rest:operation name="ged:get-metadata">
               <rest:http-method>GET</rest:http-method>
               <rest:http-body-type>NO_BODY</rest:http-body-type>
               <rest:uri>http://localhost:8088/library/{library}/documents/{reference}/metadata</rest:uri>
               <rest:xpath-param name="library">//*[local-name()='library']</rest:xpath-param>
               <rest:xpath-param name="reference">//*[local-name()='reference']</rest:xpath-param>
               <rest:authentication>
                  <rest:basic>
                     <rest:username><rest:constant>${username}</rest:constant></rest:username>
                     <rest:password><rest:constant>${password}</rest:constant></rest:password>
                  </rest:basic>
               </rest:authentication>
               <rest:headers>
                  <rest:header name="Accept">
                     <rest:constant>application/json</rest:constant>
                  </rest:header>
               </rest:headers>
               <rest:json-xml-mapping-convention>MAPPED_CONVENTION</rest:json-xml-mapping-convention>
               <rest:on-http-status code="200">
                  <rest:otherwise-out>
                     <rest:transformation>
                        <rest:xsl>200-metadata.xsl</rest:xsl>
                     </rest:transformation>
                  </rest:otherwise-out>
               </rest:on-http-status>
               <rest:on-http-status code="404">
                  <rest:otherwise-fault>
                     <rest:transformation>
                        <rest:xsl>404.xsl</rest:xsl>
                     </rest:transformation>
                  </rest:otherwise-fault>
               </rest:on-http-status>
            </rest:operation>
            <rest:operation name="edm:reset-metadatas">
               <rest:http-method>PUT</rest:http-method>
               <rest:http-body-type>JSON</rest:http-body-type>
               <rest:uri>http://localhost:8080/library/{library}/document/{reference}/metadata</rest:uri>
               <rest:xpath-param name="library">//*[local-name()='library']</rest:xpath-param>
               <rest:xpath-param name="reference">//*[local-name()='reference']</rest:xpath-param>
               <rest:authentication>
                  <rest:basic>
                     <rest:username><rest:xpath>//*[local-name()='username']</rest:xpath></rest:username>
                     <rest:password><rest:xpath>//*[local-name()='password']</rest:xpath></rest:password>
                  </rest:basic>
               </rest:authentication>
               <rest:xsl>reset-metadatas-via-json-in.xsl</rest:xsl>
               <rest:http-body-to-json-virtual-root>metadatas</rest:http-body-to-json-virtual-root>
               <rest:http-body-to-json-multiple-pi>true</rest:http-body-to-json-multiple-pi>
               <rest:http-body-to-json-auto-array>true</rest:http-body-to-json-auto-array>
               <rest:on-http-status code="404">
                  <rest:otherwise-fault>
                     <rest:transformation>
                        <rest:xsl>documentInconnu-as-fault.xsl</rest:xsl>
                     </rest:transformation>
                  </rest:otherwise-fault>
               </rest:on-http-status>
            </rest:operation>
            <rest:operation name="edm:archiver">
               <rest:http-method>POST</rest:http-method>
               <rest:http-body-type>MULTIPART_FORMDATA</rest:http-body-type>
               <rest:uri>http://localhost:8080/library/{library}/document</rest:uri>
               <rest:xpath-param name="library">//*[local-name()='library']</rest:xpath-param>
               <rest:authentication>
                  <rest:basic>
                     <rest:username><rest:xpath>//*[local-name()='username']</rest:xpath></rest:username>
                     <rest:password><rest:xpath>//*[local-name()='password']</rest:xpath></rest:password>
                  </rest:basic>
               </rest:authentication>
               <rest:form-data name="file" as-attachment="true">
                  <rest:extracted-by-xpath>
                     substring-after(//*[local-name()='document']/*[local-name()='Include']/@href, 'cid:')
                  </rest:extracted-by-xpath>
                  <rest:attachment-name>
                     <rest:xpath>//*[local-name()='document']/*[local-name()='nom']</rest:xpath>
                  </rest:attachment-name>
               </rest:form-data>
               <rest:on-http-status code="200">
                  <rest:otherwise-out>
                     <rest:transformation>
                        <rest:xsl>archiver-200.xsl</rest:xsl>
                     </rest:transformation>
                  </rest:otherwise-out>
               </rest:on-http-status>
               <rest:on-http-status code="404">
                  <rest:otherwise-fault>
                     <rest:transformation>
                        <rest:xsl>unknownLibrary-as-fault.xsl</rest:xsl>
                     </rest:transformation>
                  </rest:otherwise-fault>
               </rest:on-http-status>
            </rest:operation>
         </rest:mapping>
      </jbi:consumes>
   </jbi:services>
</jbi:jbi>

The Service Unit has to contain the following elements, packaged in the archive:

• the META-INF/jbi.xml descriptor file as described above,
• XSL files referenced in the JBI descriptor.

With a WADL

The address of the RESTful Web Service is found in the WADL.
The REST operation corresponding to the JBI operation is found in the WADL.
The HTTP method is defined in the WADL for the operation.

The Service Unit has to contain the following elements, packaged in the archive:

• The META-INF/jbi.xml descriptor file as described above,
• An optional imported WADL file describing the partner service.

With a WSDL 2.0

The address of the RESTful Web Service is found in the WSDL 2.0.
The REST operation corresponding to the JBI operation is found in the WSDL 2.0.
The HTTP method is defined in the WSDL 2.0 for the operation.

The Service Unit has to contain the following elements, packaged in the archive:

• The META-INF/jbi.xml descriptor file as described above,
• An optional imported WSDL 2.0 file describing the partner service.

<rest:authentication>
   <rest:basic>
      <rest:username><rest:constant>${username}</rest:constant></rest:username>
      <rest:password><rest:xpath>//*[local-name()='password']</rest:xpath></rest:password>
   </rest:basic>
</rest:authentication>

*Either uri and http-method extensions or wadl or wsdl2 must be present in a specific SU.

Exposing an internal JBI service endpoint as a RESTful Web Service

In consumer mode, the component exposes an internal JBI service outside the bus to transfer incoming REST requests to the internal service.

Usage

The petals-bc-rest component can listen incoming REST messages and send messages to a JBI service endpoint by deploying a Service Unit on it. The component consumes the JBI service:

The service-name Service Unit extension value will be used as service name.

When a REST message is handled by the component, it is transformed into a JBI Message and sent to the JBI service endpoint configured in the Service Unit.

The JBI message is created like this:

• The JBI operation is created differently from the operation present in the REST URI operation
• The JBI message content is created according to the HTTP method of the incoming REST request:
  • GET: The JBI message content is created from the REST URI path and parameters
  • POST: The JBI message content is also created differently according the Content-Type HTTP header:
    • Non XML content types: The JBI message content is a reference (cf SOAP) to a JBI attachment which contains the HTTP body
    • XML content types: The JBI message content is created from the HTTP body (there is no JBI attachment created)
  • PUT/DELETE: There is no JBI message content
• A JBI attachment is created according to the HTTP method of the incoming REST request:
  • GET/DELETE: There is no JBI attachment created
  • POST: A JBI attachment is created from the HTTP body if the Content-Type HTTP header contains a non XML content type.
  • PUT: A JBI attachment is created from the HTTP body
• The HTTP headers are added to the the protocol header JBI message property
• The MEP is defined by the petalsCDK:mep extension.

A WADL is available at the following URL: (TBC)
A WSDL 2.0 is available at the following URL: (TBC)

Configuration

Service Unit descriptor

The service unit is configurable via its extensions in the jbi.xml file:

Service Unit content

The Service Unit has to contain the following elements, packaged in an archive:

• The META-INF/jbi.xml descriptor file as described above

Configuring the component

The component can be configured through the parameters of its JBI descriptor file. These parameters are divided in following groups:

• JBI parameters that have not to be changed otherwise the component will not work,
• CDK parameters that are parameters driving the processing of the CDK layer,
• and parameters dedicated to the REST part:
  • embedded REST server,
  • embedded REST client.

<jbi:jbi xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:petalsCDK="http://petals.ow2.org/components/extensions/version-5"
   xmlns:jbi="http://java.sun.com/xml/ns/jbi" version="1.0"
   xmlns:rest="http://petals.ow2.org/components/rest/version-1">

   <jbi:component type="binding-component">
      ...
      <petalsCDK:acceptor-pool-size />
      <petalsCDK:acceptor-retry-number />
      <petalsCDK:acceptor-retry-wait />
      <petalsCDK:acceptor-stop-max-wait />
      <petalsCDK:processor-pool-size />
      <petalsCDK:processor-max-pool-size />
      <petalsCDK:processor-keep-alive-time />
      <petalsCDK:processor-stop-max-wait />
      <petalsCDK:time-beetween-async-cleaner-runs />
      <petalsCDK:properties-file />
      <petalsCDK:monitoring-sampling-period />
      ...
      <rest:http-host />
      <rest:http-port>8086</rest:http-port>
      <rest:connection-timeout />
      <rest:read-timeout />
      ...
   </jbi:component>
</jbi:jbi>

CDK parameters

The component configuration includes the configuration of the CDK. The following parameters correspond to the CDK configuration.

Definition of CDK parameter scope :

• Installation: The parameter can be set during the installation of the component, by using the installation MBean (see JBI specifications for details about the installation sequence). If the parameter is optional and has not been defined during the development of the component, it is not available at installation time.
• Runtime: The paramater can be set during the installation of the component and during runtime. The runtime configuration can be changed using the CDK custom MBean named RuntimeConfiguration. If the parameter is optional and has not been defined during the development of the component, it is not available at installation and runtime times.

Interceptor

Interceptors can be defined to inject some post or pre processing in the component during service processing.

Using interceptor is very sensitive and must be manipulate only by power users. An non properly coded interceptor engaged in a component can lead to uncontrolled behaviors, out of the standard process.

Example of an interceptor configuration:

<?xml version="1.0" encoding="UTF-8"?>
<!--...-->
<petalsCDK:component-interceptors>
  <petalsCDK:interceptor active="true" class="org.ow2.petals.myInterceptor" name="myInterceptorName">
    <petalsCDK:param name="myParamName">myParamValue</petalsCDK:param>
    <petalsCDK:param name="myParamName2">myParamValue2</petalsCDK:param>
  </petalsCDK:interceptor>
</petalsCDK:component-interceptors>
<!--...-->

Component specific parameters

These parameters drive features proposed by the component and configure the REST part:

• the embedded REST server,
• the embedded REST client.

Parameters of the embedded REST server

Parameters of the embedded REST client

Logging

Logging of the embedded HTTP server

The traces of the embedded HTTP server "Jetty" are activated through the logging configuration file of Petals ESB. The root logger for Jetty is org.eclipse.jetty:

...
org.eclipse.jetty.level=INFO
...

Logging of the embedded HTTP client

The traces of the embedded HTTP client "Apache HTTP client" are activated through the logging configuration file of Petals ESB. The root logger for Apache HTTP client is org.apache.http. You will find more information about Apache HTTP client loggers here: https://hc.apache.org/httpcomponents-client-ga/logging.html

...
org.apache.http.level=INFO
...

Monitoring the component

Using metrics

Several probes providing metrics are included in the component, and are available through the JMX MBean 'org.ow2.petals:type=custom,name=monitoring_<component-id>', where <component-id> is the unique JBI identifier of the component.

Common metrics

The following metrics are provided through the Petals CDK, and are common to all components:

Dedicated metrics

No dedicated metric is available.

Receiving alerts

Several alerts are notified by the component through notification of the JMX MBean 'org.ow2.petals:type=custom,name=monitoring_<component-id>', where <component-id> is the unique JBI identifier of the component.

To integrate these alerts with Nagios, see Receiving Petals ESB defects in Nagios.

Common alerts

Dedicated alerts

No dedicated alert is available.

Unit testing

The unit testing can occur at several levels in your Rest service unit:

• on the provider side:
  • to check the operation definition in the JBI descriptor
  • to check the compliance of the JBI descriptor with the WSDL content,
  • to unit test your XSL transformations.

A dedicated framework is available as an extension of JUnit providing facilities:

• to validate your WSDL:
  • in a WSDL point of view,
  • checking the compliance of the JBI descriptor with the WSDL content,
• to validate your JBI descriptor:
  • checking syntax of the XPath expressions,
• to verify generated response from HTTP response.

This dedicated framework is provided by the Maven artifact org.ow2.petals:petals-bc-rest-junit:

<project>
   ...
   <dependencies>
      ...
      <dependency>
         <groupId>org.ow2.petals</groupId>
         <artifactId>petals-bc-rest-junit</artifactId>
         <version>1.0.0</version>
         <scope>test</scope>
      </dependency>
      ...
   </dependencies>
   ...
</project>

The version 1.0.0+ of the framework is compliant with the Petals BC REST 1.1.0+.

Checking the compliance of the JBI descriptor with WSDL content

The unit test framework contains an assertion 'assertWsdlCompliance' to verify easily the compliance of your JBI descriptor with the WSDL content. As the WSDL is parsed, it's syntax is also verified:

import static org.ow2.petals.binding.rest.junit.Assert.assertWsdlCompliance;

public class WsdlValidatorTest {

    @Test
    public void validateJbiAgainstWsdl() throws Exception {

        assertWsdlCompliance();
    }

}

The WSDL file to verify is extracted from the JBI descriptor content.

Unit-testing your operation definitions

The unit test framework contains several assertions to verify transformation of HTTP response:

• assertJBIOutResponse: The result of the HTTP response is expected as an OUT message similar to the given resource,
• assertJBIFault: The result of the HTTP response is expected as a fault similar to the given resource,
• assertJBIStatus: The result of the HTTP response is expected as the given status,
• assertJBIRequestJSON: The result of the transformation from JBI to an HTTP request is expected as a JSON body similar to the given resource,
• assertJBIRequestXML: The result of the transformation from JBI to an HTTP request is expected as a XML body similar to the given resource,

import static org.ow2.petals.binding.rest.junit.Assert.assertJBIFault;
import static org.ow2.petals.binding.rest.junit.Assert.assertJBIOutResponse;
...
import org.ow2.petals.binding.rest.junit.rule.ServiceOperationUnderTest;
...

    @ClassRule
    public static final ServiceOperationUnderTest OPERATION_UNDER_TEST = new ServiceOperationUnderTest(
            OP_GET_METADATA_BY_JSON);

    @Test
    public void nominal() throws Exception {
        assertJBIOutResponse("get-metadata-expected-nominal-response.xml", OPERATION_UNDER_TEST,
                HttpStatus.SC_OK, null, "get-metadata-nominal-http-body.json",
                MediaType.APPLICATION_JSON_TYPE, null);
    }

    @Test
    public void nometadata() throws Exception {
        assertJBIOutResponse("get-metadata-expected-no-metadata-response.xml", OPERATION_UNDER_TEST,
                HttpStatus.SC_OK, null, "get-metadata-no-metadata-http-body.json",
                MediaType.APPLICATION_JSON_TYPE, null);
    }

    @Test
    public void unexistingDocument() throws Exception {

        assertJBIFault("get-metadata-expected-fault-unexisting-document.xml", OPERATION_UNDER_TEST,
                HttpStatus.SC_NOT_FOUND, null, null, null, "get-metadata-by-json-request.xml", null);
    }
}

In the service unit JBI descriptor, the response transformations are described for each operation. The JUnit rule ServiceOperationUnderTest represents one of these operations, and the response transformation processing is the same than the one of the component. This JUnit rule is used to execute the transformation on a given HTTP response through assertions assertJBIOutResponse or assertJBIFault. For each assertion, the transformation result is compared to the content of the given resource. Following part of the HTTP response used as input of the transformation can be set:

• the HTTP status,
• a resource name containing the HTTP body,
• the content type of the HTTP body,
• a resource name containing the JBI IN message payload,
• URI parameters.

See the Javadoc for more details on parameters.

Know problems

Handshake error invoking external resources through HTTPS

Problem:
In some cases, invoking external resources through HTTPS, you can get a connection reset by peer because of a handshake error. This problem can occur on Java 7 (previous to 1.7.0_91-b15) with a SSL certificate with a key size upper to 1024 bits.

Solution:
Run Petals ESB with a more recent Java 7 version (1.7.0_91-b15 or upper) or with Java 8 (any version).