With SOAP it is possible to return multiple values in a single request. This is impossible in Java as a method can only return one object.
JAX-WS solves this problem with the concept of Holders. A javax.xml.ws.Holder is a simple wrapper object that can be passed into the @WebService method as a parameter. The application sets the value of the holder during the request and the server will send the value back as an OUT parameter.
The @WebParam annotation allows us to declare the sum and multiply Holders as WebParam.Mode.OUT parameters. As mentioned, these holders are simply empty buckets the application can fill in with data to have sent to the client. The server will pass them in uninitialized.
@Stateless
@WebService(
portName = "CalculatorPort",
serviceName = "CalculatorService",
targetNamespace = "http://superbiz.org/wsdl",
endpointInterface = "org.superbiz.ws.out.CalculatorWs")
public class Calculator implements CalculatorWs {
public void sumAndMultiply(int a, int b,
@WebParam(name = "sum", mode = WebParam.Mode.OUT) Holder<Integer> sum,
@WebParam(name = "multiply", mode = WebParam.Mode.OUT) Holder<Integer> multiply) {
sum.value = a + b;
multiply.value = a * b;
}
}
If the Holders were specified as WebParam.Mode.INOUT params, then the client could use them to send data and the application as well. The Holder instances would then be initialized with the data from the client request. The application could check the data before eventually overriting it with the response values.
The above JAX-WS @WebService component results in the folliwing WSDL that will be created automatically. Note the sumAndMultiplyResponse complext type returns two elements. These match the @WebParam declarations and our two Holder<Integer> params.
<?xml version="1.0" encoding="UTF-8"?>
<wsdl:definitions xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/"
name="CalculatorService"
targetNamespace="http://superbiz.org/wsdl"
xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
xmlns:tns="http://superbiz.org/wsdl"
xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<wsdl:types>
<xsd:schema attributeFormDefault="unqualified" elementFormDefault="unqualified"
targetNamespace="http://superbiz.org/wsdl"
xmlns:tns="http://superbiz.org/wsdl"
xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<xsd:element name="sumAndMultiply" type="tns:sumAndMultiply"/>
<xsd:complexType name="sumAndMultiply">
<xsd:sequence>
<xsd:element name="arg0" type="xsd:int"/>
<xsd:element name="arg1" type="xsd:int"/>
</xsd:sequence>
</xsd:complexType>
<xsd:element name="sumAndMultiplyResponse" type="tns:sumAndMultiplyResponse"/>
<xsd:complexType name="sumAndMultiplyResponse">
<xsd:sequence>
<xsd:element minOccurs="0" name="sum" type="xsd:int"/>
<xsd:element minOccurs="0" name="multiply" type="xsd:int"/>
</xsd:sequence>
</xsd:complexType>
</xsd:schema>
</wsdl:types>
<wsdl:message name="sumAndMultiplyResponse">
<wsdl:part element="tns:sumAndMultiplyResponse" name="parameters"/>
</wsdl:message>
<wsdl:message name="sumAndMultiply">
<wsdl:part element="tns:sumAndMultiply" name="parameters"/>
</wsdl:message>
<wsdl:portType name="CalculatorWs">
<wsdl:operation name="sumAndMultiply">
<wsdl:input message="tns:sumAndMultiply" name="sumAndMultiply"/>
<wsdl:output message="tns:sumAndMultiplyResponse" name="sumAndMultiplyResponse"/>
</wsdl:operation>
</wsdl:portType>
<wsdl:binding name="CalculatorServiceSoapBinding" type="tns:CalculatorWs">
<soap:binding style="document" transport="http://schemas.xmlsoap.org/soap/http"/>
<wsdl:operation name="sumAndMultiply">
<soap:operation soapAction="" style="document"/>
<wsdl:input name="sumAndMultiply">
<soap:body use="literal"/>
</wsdl:input>
<wsdl:output name="sumAndMultiplyResponse">
<soap:body use="literal"/>
</wsdl:output>
</wsdl:operation>
</wsdl:binding>
<wsdl:service name="CalculatorService">
<wsdl:port binding="tns:CalculatorServiceSoapBinding" name="CalculatorPort">
<soap:address location="http://127.0.0.1:4204/Calculator?wsdl"/>
</wsdl:port>
</wsdl:service>
</wsdl:definitions>
Here we see a JAX-WS client executing the sumAndMultiply operation. Two empty Holder instances are created and passed in as parameters. The data from the sumAndMultiplyResponse is placed in the Holder instances and is then available to the client after the operation completes.
The holders themselves are not actually sent in the request unless they are configured as INOUT params via WebParam.Mode.INOUT on @WebParam
import org.junit.BeforeClass;
import org.junit.Test;
import javax.ejb.embeddable.EJBContainer;
import javax.xml.namespace.QName;
import javax.xml.ws.Holder;
import javax.xml.ws.Service;
import java.net.URL;
import java.util.Properties;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;
public class CalculatorTest {
@BeforeClass
public static void setUp() throws Exception {
Properties properties = new Properties();
properties.setProperty("openejb.embedded.remotable", "true");
//properties.setProperty("httpejbd.print", "true");
//properties.setProperty("httpejbd.indent.xml", "true");
EJBContainer.createEJBContainer(properties);
}
@Test
public void outParams() throws Exception {
final Service calculatorService = Service.create(
new URL("http://127.0.0.1:4204/Calculator?wsdl"),
new QName("http://superbiz.org/wsdl", "CalculatorService"));
assertNotNull(calculatorService);
final CalculatorWs calculator = calculatorService.getPort(CalculatorWs.class);
final Holder<Integer> sum = new Holder<Integer>();
final Holder<Integer> multiply = new Holder<Integer>();
calculator.sumAndMultiply(4, 6, sum, multiply);
assertEquals(10, (int) sum.value);
assertEquals(24, (int) multiply.value);
}
}
The above execution results in the following SOAP message.
<?xml version="1.0" encoding="UTF-8"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<ns1:sumAndMultiply xmlns:ns1="http://superbiz.org/wsdl">
<arg0>4</arg0>
<arg1>6</arg1>
</ns1:sumAndMultiply>
</soap:Body>
</soap:Envelope>
<?xml version="1.0" encoding="UTF-8"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<ns1:sumAndMultiplyResponse xmlns:ns1="http://superbiz.org/wsdl">
<sum>10</sum>
<multiply>24</multiply>
</ns1:sumAndMultiplyResponse>
</soap:Body>
</soap:Envelope>
svn co http://svn.apache.org/repos/asf/tomee/tomee/trunk/examples/webservice-holder cd webservice-holder mvn clean install