Mapping the results of a BPEL process

We will need to extend the client proxy from the Calling an asynchronous BPEL process recipe, so we need to have the asynchronous BPEL process deployed and the client proxy ready.

First, we will update the response of the asynchronous BPEL process to include more XSD schema elements as follows:

<element name = "processResponse">
  <complexType>
    <sequence>
      <element name = "result" type = "string"/>
      <element name = "postalcode" type = "int"/>
      <element name = "temperature" type = "double"/>
      <element name = "person">
        <complexType>
          <sequence>
            <element name = "name" type = "string"/>
            <element name = "lastname" type = "string"/>
          </sequence>
        </complexType>
      </element>
    </sequence>
  </complexType>
</element>

If we now call an asynchronous BPEL process, we will receive more information. Also, the information is nested in the response.

The response from the BPEL process presents an XML document wrapped with the SOAP message. The XML format is not very friendly for programming in Java. That is why few implementations arise with the intent to simplify the transformation of XML to Java.

All the implementations mentioned here work with the same basic concept of serialization, deserialization, marshalling, and unmarshalling. In general, serialization and deserialization presents a way of transforming the data structures in a way that we can store them or transfer them between applications or over a network. The synonym for serialization, when we transform Java objects, is marshalling. Consequently, the synonym for the opposite operation, that is deserialization, is called unmarshalling.

The following mapping is used when we convert from XSD schema types to corresponding Java data types:

While the preceding table shows the default mapping between XML data types and Java data types, it is also possible to customize the mapping, usually through the configuration mapping file.

Applications written in Java usually do not operate with XML documents. If we want to call a BPEL process, we must also create a request. Until now, we used to build the request with the help of the XML document builder as follows:

OMFactory fac = OMAbstractFactory.getOMFactory();
OMNamespace omNs = fac.createOMNamespace("http://xmlns.oracle.com/HelloWorldAsync/HelloWordlAsync/HelloWorldAsyncProcess", "");
OMElement method = fac.createOMElement("process", omNs);
OMElement value = fac.createOMElement("input", omNs);
method.addChild(value);
//value.setText("Jurij");
value.setText("FAULT");

In the request, we have to know all the information, such as namespace, names of the XML tags, and, of course, the data itself.

To simplify the creation of a request, we can utilize the JAXB tools. First, we will take the Process.java class that we created with the wsimport tool. We include the class into the JDeveloper project. We need to add namespace info to the annotations in the class file as follows:

@XmlRootElement(name = "process", namespace = "http://xmlns.oracle.com/HelloWorldAsync/HelloWordlAsync/HelloWorldAsyncProcess")
@XmlElement(required = true, namespace = "http://xmlns.oracle.com/HelloWorldAsync/HelloWordlAsync/HelloWorldAsyncProcess")

We can now also change the createPayLoad() method in the ClientProxy.java class. We create an XML document from the DocumentBuilderFactory class as follows:

DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
dbf.setNamespaceAware(true);
Document doc = dbf.newDocumentBuilder().newDocument();

Then, we create a JAXB context with the following:

JAXBContext jc = JAXBContext.newInstance(Process.class);

Finally, we create marshaller and serialize the request class as follows:

Marshaller marshaller = jc.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, false);
marshaller.marshal(req, doc);

The difference between the previous version of createPayLoad() and the newer version is that the previous version lacks transparency and clarity in the code. We can now fill the request data in the following way:

Process req = new Process();
req.setInput("JURIJ");

And call it as follows:

createPayLoad(req)