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Exposing a SOAP Endpoint as a RESTful API¶

This example demonstrates how you can expose a SOAP service over REST using an API in ESB Micro Integrator.

Synapse configuration¶

Following is a sample REST API configuration that we can used to implement this scenario. See the instructions on how to build and run this example.

<api xmlns="http://ws.apache.org/ns/synapse" name="StockQuoteAPI" context="/stockquote">
   <resource uri-template="/view/{symbol}" methods="GET">
      <inSequence>
        <payloadFactory>
          <format>
             <m0:getQuote xmlns:m0="http://services.samples">
                <m0:request>
                   <m0:symbol>$1</m0:symbol>
                </m0:request>
             </m0:getQuote>
           </format>
           <args>
            <arg expression="get-property('uri.var.symbol')"/>
           </args>
        </payloadFactory>
        <header name="Action" value="urn:getQuote"/>
        <send>
          <endpoint>
            <address uri="http://localhost:9000/services/SimpleStockQuoteService" format="soap11"/>
          </endpoint>
        </send>
      </inSequence>
      <outSequence>
        <send/>
      </outSequence>
   </resource>
   <resource url-mapping="/order/*" methods="POST">
      <inSequence>
        <property name="FORCE_SC_ACCEPTED" value="true" scope="axis2"/>
        <property name="OUT_ONLY" value="true"/>
        <header name="Action" value="urn:placeOrder"/>
        <send>
            <endpoint>
                <address uri="http://localhost:9000/services/SimpleStockQuoteService" format="soap11"/>
            </endpoint>
         </send>
      </inSequence>      
   </resource>
</api>

In this API configuration we have defined two resources. One is for the HTTP method GET and the other one is for POST. In the first resource, we have defined the uri-template as /view/{symbol} so that request will be dispatched to this resource when you invoke the API using the following URI: http://127.0.0.1:8290/stockquote/view/IBM

The context of this REST API is stockquote. The SOAP payload required for the SOAP back-end service is constructed using the payload factory mediator defined in the inSequence. The value for the <m0:symbol\> element is extracted using the following expression:

get-property('uri.var.symbol')

Here, ‘symbol’ refers to the variable we defined in the uri-template (/view/{symbol}). Therefore, for the above invocation, the 'uri.var.symbol' property will resolve to the value ‘IBM’.

After constructing the SOAP payload, the request will be sent to the SOAP back-end service from the <send\> mediator, which has an address endpoint defined inline with the format="soap11" attribute in the address element. The response received from the back-end soap service will be sent to the client in plain old XML (POX) format.

In the second resource, we have defined the URL mapping as "/order/*". Since this has POST as the HTTP method, the client has to send a payload to invoke this.

Build and run¶

Create the artifacts:

Set up ESB Integration Studio.
Create an integration project with an ESB Configs module and an Composite Exporter.
Create the rest API with the configurations given above.
Deploy the artifacts in your Micro Integrator.

Set up the back-end service:

Download the back-end service.
Extract the downloaded zip file.
Open a terminal, navigate to the axis2Server/bin/ directory inside the extracted folder.
Execute the following command to start the axis2server with the SimpleStockQuote back-end service:
On MacOS/Linux/CentOS
```
sh axis2server.sh
```
On Windows
```
axis2server.bat
```

Invoking the first resource (GET request):

Execute the following command (without query parameters):
```
curl -v http://127.0.0.1:8290/stockquote/view/IBM
```

Execute the following command with query parameters:

curl -v -X GET "http://localhost:8290/stockquote/view/IBM?param1=value1&param2=value2"

Sending a POST request:

Save the following sample place order request as placeorder.xml in your local file system and execute the command. This payload is used to invoke a SOAP service.
```
<placeOrder xmlns="http://services.samples">
  <order>
     <price>50</price>
     <quantity>10</quantity>
     <symbol>IBM</symbol>
  </order>
</placeOrder>
```

Following is a sample cURL command to invoke the second resource:

curl -v -d @placeorder.xml -H "Content-type: application/xml" http://127.0.0.1:8290/stockquote/order/

This SOAP service invocation is an OUT_ONLY invocation, so the Micro Integrator is not expecting any response back from the SOAP service. Since we have set the FORCE_SC_ACCEPTED property value to true, the Micro Integrator returns a 202 response back to the client as shown below.

< HTTP/1.1 202 Accepted
< Date: Wed, 30 Oct 2019 05:49:24 GMT
< Transfer-Encoding: chunked

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