SOAP Binding: Difference between Document and RPC Style Web Services

SOAP
Binding: Difference between Document and RPC Style Web Services

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A Tutorial on RPC Vs Document Style WSDL SOAP binding with Example

Table of Contents

1. Basics: Document Style Vs RPC Style
2. What is SOAP Encoding and Literal?
3. Learn by doing: Document Vs RPC Web Services and Artifacts
   Examples (WSDL,Schema, SEI).
4. RPC /LITERAL SOAP Binding Example Web Service
5. Notes on RPC –ENCODED Style and JAX-WS
6. Document/Literal SOAP Binding Web service

When you create Web Services using SOAP protocol, you follow either Document or RPC SOAP messaging style. In this article, let us discuss about the difference between the Document and RPC style web services. We
use sample example programs which is developed using JAX-WS API from Java.

Basics: Document Style Vs RPC Style

The Document style indicates that the SOAP body contains a XML document which can be validated against pre-defined XML schema document.

RPC indicates that the SOAP message body contains an XML representation of a method call and uses the names of the method and its parameters to generate XML structures that represent a method’s call stack. The document/literal approach is easier because it
simply relies on XML Schema to describe exactly what the SOAP message looks like while transmission.

What is SOAP Encoding and Literal?

SOAP Encoding indicates how a data value should be encoded in an XML format. SOAP Encoding is an extension of the SOAP framework. SOAP encoding offers rules to convert any data value defined in SOAP data model
into XML format.

What is Literal?

In simplest definition, literal it means that the data is serialized according to a schema

Learn by doing: Document Vs RPC Web Services and Artifacts Examples (WSDL,Schema, SEI).

Let us create some sample programs to see the difference between the RPC and Document style web services. In Java using JAX-WS it is very easy to create web services. You can read the below article, if you are
not familiar with JAX-WS.

• Java
  JAX-WS Tutorial: Develop Web Services and Clients (Consumers) Using JAX-WS without using JEE containers.

RPC /LITERAL SOAP Binding Example Web Service

First let us see how the RPC/LITERAL/WRAPPED style web service request and response structure.

The following is a sample Java SEI (Service Endpoint Interface) to create a RPC web service.

/**
 * @author Binu George
 * Globinch.com
 * Visit  http://www.globinch.com. All rights reserved.
 */
package com.my.ws;

import javax.jws.WebMethod;
import javax.jws.WebParam;
import javax.jws.WebResult;
import javax.jws.WebService;
import javax.jws.WebParam.Mode;
import javax.jws.soap.SOAPBinding;
import javax.jws.soap.SOAPBinding.ParameterStyle;
import javax.jws.soap.SOAPBinding.Style;
import javax.jws.soap.SOAPBinding.Use;

@WebService(name = "MyJaxWSHello",
		targetNamespace = "http://globinch.com",
		wsdlLocation = "http://globinch.com/ws/MyJaxWS?wsdl")
@SOAPBinding(style=Style.RPC, use=Use.LITERAL, parameterStyle=ParameterStyle.WRAPPED)
public interface MyJaxWSSEI {

	  @WebMethod(operationName="getGreetingRequest")
	  @WebResult(targetNamespace="http://globinch.com/ws/types",
	     name="GreetingResponse")
	  public JXRes getJXWsRes(
	     @WebParam(targetNamespace="http://globinch.com/ws/types",
	               name="name",
	               mode=Mode.IN)
	               String name
	  );

}

The corresponding WSDL and XML schema definition is given below. You can the operation name still appears in the SOAP message. The type encoding info is not present since this is defined as LITERAL.

Schema Defintion

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<xs:schema version="1.0" targetNamespace="http://globinch.com" xmlns:tns="http://globinch.com" xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="jxRes" type="tns:jxRes"/>
  <xs:complexType name="jxRes">
    <xs:sequence>
      <xs:element name="message" type="xs:string" minOccurs="0"/>
      <xs:element name="name" type="xs:string" minOccurs="0"/>
    </xs:sequence>
  </xs:complexType>
</xs:schema>

WSDL Document

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<!-- Generated by JAX-WS RI at http://jax-ws.dev.java.net. RI's version is JAX-WS RI 2.1.1 in JDK 6. -->
<definitions targetNamespace="http://globinch.com" name="MyJaxWSHelloService" xmlns="http://schemas.xmlsoap.org/wsdl/" xmlns:tns="http://globinch.com" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/">
  <types>
    <xsd:schema>
      <xsd:import namespace="http://globinch.com" schemaLocation="MyJaxWSHelloService_schema1.xsd"/>
    </xsd:schema>
  </types>
  <message name="getGreetingRequest">
    <part name="name" type="xsd:string"/>
  </message>
  <message name="getGreetingRequestResponse">
    <part name="GreetingResponse" type="tns:jxRes"/>
  </message>
  <portType name="MyJaxWSHello">
    <operation name="getGreetingRequest" parameterOrder="name">
      <input message="tns:getGreetingRequest"/>
      <output message="tns:getGreetingRequestResponse"/>
    </operation>
  </portType>
  <binding name="MyJaxWSSEIPortBinding" type="tns:MyJaxWSHello">
    <soap:binding transport="http://schemas.xmlsoap.org/soap/http" style="rpc"/>
    <operation name="getGreetingRequest">
      <soap:operation soapAction=""/>
      <input>
        <soap:body use="literal" namespace="http://globinch.com"/>
      </input>
      <output>
        <soap:body use="literal" namespace="http://globinch.com"/>
      </output>
    </operation>
  </binding>
  <service name="MyJaxWSHelloService">
    <port name="MyJaxWSSEIPort" binding="tns:MyJaxWSSEIPortBinding">
      <soap:address location="REPLACE_WITH_ACTUAL_URL"/>
    </port>
  </service>
</definitions>

SOAP Request Message

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:glob="http://globinch.com">
   <soapenv:Header/>
   <soapenv:Body>
      <glob:getGreetingRequest>
         <name>Binu George</name>
      </glob:getGreetingRequest>
   </soapenv:Body>
</soapenv:Envelope>

SOAP Response Message

<S:Envelope xmlns:S="http://schemas.xmlsoap.org/soap/envelope/">
   <S:Body>
      <ns2:getGreetingRequestResponse xmlns:ns2="http://globinch.com">
         <GreetingResponse>
            <message>Hello</message>
            <name>Binu George</name>
         </GreetingResponse>
      </ns2:getGreetingRequestResponse>
   </S:Body>
</S:Envelope>

From the above you can see that the WSDL is not so complex. It is not very easy to validate the messages since there is no complete schema defined for it. This means the schema alone does not tell you what the
message body Info set contains because some of the soap:body contents comes from WSDL definitions. Because of this , schema describing an RPC/literal message is not sufficient to validate that message.

From the above request and response you can see that the Soap:Body contains one element which has the name of the WSDL operation and the namespace specified on the soap:body element in the WSDL binding. Inside
this element, there’s an element for each part of the message and its name is name of the part. Inside each part element are the contents of that part, as defined by the schema type that the part references in WSDL.

For example see the above response. The

<ns2:getGreetingRequestResponse xmlns:ns2="http://globinch.com">

has the name of the WSDL operation and the namespace specified on the soap:body element in the WSDL binding. Inside this you can see the part element “GreetingResponse” and its content is as per the defined
schema.

Notes on RPC –ENCODED Style and JAX-WS

In JAX-WS RPC/encoded is not supported as a messaging mode. In JAX-WS the “encoded” encoding style isn’t supported and only the “literal” encoding style used.

If you use wsimport/wsgen on wsdl documents/SEI that has use=”encoded” attribute/SOAP binding you may get the following error,

“….. invalid SOAP Binding annotation. Rpc/encoded SOAPBinding is not supported”

Or

“ rpc/encoded wsdls are not supported in JAXWS 2.0.  “

You can use JAX-RPC or Apache Axis V1 , f you want to send SOAP encoded messages or create RPC/encoded style WSDL.

Document/Literal SOAP Binding Web service

Let us now change the style to Document and see the generated schema files and WSDL files. There are two schema files generated and are included in the WSDLfile.

The SEI

/**
 * @author Binu George
 * Globinch.com
 * Visit  http://www.globinch.com. All rights reserved.
 */
package com.my.ws;

import javax.jws.WebMethod;
import javax.jws.WebParam;
import javax.jws.WebResult;
import javax.jws.WebService;
import javax.jws.WebParam.Mode;
import javax.jws.soap.SOAPBinding;
import javax.jws.soap.SOAPBinding.ParameterStyle;
import javax.jws.soap.SOAPBinding.Style;
import javax.jws.soap.SOAPBinding.Use;
import javax.xml.ws.RequestWrapper;
import javax.xml.ws.ResponseWrapper;

@WebService(name = "MyJaxWSHello",
		targetNamespace = "http://globinch.com",
		wsdlLocation = "http://globinch.com/ws/MyJaxWS?wsdl")
@SOAPBinding(style=Style.DOCUMENT, use=Use.LITERAL, parameterStyle=ParameterStyle.BARE)
public interface MyJaxWSSEI {

	  @WebMethod(operationName="getGreetingRequest")
	  /*@RequestWrapper(targetNamespace="http://globinch.com/ws/types",
	     className="java.lang.String")
	  @ResponseWrapper(targetNamespace="http://globinch.com/ws/types",
	     className="com.my.ws.JXRes")
	  @WebResult(targetNamespace="http://globinch.com/ws/types",
	     name="JXWsRes")*/
	    @WebResult(targetNamespace="http://globinch.com/ws/types",
	     name="GreetingResponse")
	  public JXRes getJXWsRes(
	     @WebParam(targetNamespace="http://globinch.com/ws/types",
	               name="name",
	               mode=Mode.IN)
	               String name
	  );

}

Schema defintion document1

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<xs:schema version="1.0" targetNamespace="http://globinch.com/ws/types" xmlns:ns1="http://globinch.com" xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:import namespace="http://globinch.com" schemaLocation="MyJaxWSHelloService_schema2.xsd"/>
  <xs:element name="GreetingResponse" nillable="true" type="ns1:jxRes"/>
  <xs:element name="name" nillable="true" type="xs:string"/>
</xs:schema>

Schema defintion document 2

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<xs:schema version="1.0" targetNamespace="http://globinch.com" xmlns:tns="http://globinch.com" xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="jxRes" type="tns:jxRes"/>
  <xs:complexType name="jxRes">
    <xs:sequence>
      <xs:element name="message" type="xs:string" minOccurs="0"/>
      <xs:element name="name" type="xs:string" minOccurs="0"/>
    </xs:sequence>
  </xs:complexType>
</xs:schema>

The WSDL Document

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<!-- Generated by JAX-WS RI at http://jax-ws.dev.java.net. RI's version is JAX-WS RI 2.1.1 in JDK 6. -->
<definitions targetNamespace="http://globinch.com" name="MyJaxWSHelloService" xmlns="http://schemas.xmlsoap.org/wsdl/" xmlns:tns="http://globinch.com" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/">
  <types>
    <xsd:schema>
      <xsd:import namespace="http://globinch.com/ws/types" schemaLocation="MyJaxWSHelloService_schema1.xsd"/>
    </xsd:schema>
    <xsd:schema>
      <xsd:import namespace="http://globinch.com" schemaLocation="MyJaxWSHelloService_schema2.xsd"/>
    </xsd:schema>
  </types>
  <message name="getGreetingRequest">
    <part name="name" element="ns1:name" xmlns:ns1="http://globinch.com/ws/types"/>
  </message>
  <message name="getGreetingRequestResponse">
    <part name="GreetingResponse" element="ns2:GreetingResponse" xmlns:ns2="http://globinch.com/ws/types"/>
  </message>
  <portType name="MyJaxWSHello">
    <operation name="getGreetingRequest">
      <input message="tns:getGreetingRequest"/>
      <output message="tns:getGreetingRequestResponse"/>
    </operation>
  </portType>
  <binding name="MyJaxWSSEIPortBinding" type="tns:MyJaxWSHello">
    <soap:binding transport="http://schemas.xmlsoap.org/soap/http" style="document"/>
    <operation name="getGreetingRequest">
      <soap:operation soapAction=""/>
      <input>
        <soap:body use="literal"/>
      </input>
      <output>
        <soap:body use="literal"/>
      </output>
    </operation>
  </binding>
  <service name="MyJaxWSHelloService">
    <port name="MyJaxWSSEIPort" binding="tns:MyJaxWSSEIPortBinding">
      <soap:address location="REPLACE_WITH_ACTUAL_URL"/>
    </port>
  </service>
</definitions>

You can see from the schema and wsdl files that all the elements are defined. The following request and response SOAP messages are following the schema definitions.

Sample SOAP Request

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:typ="http://globinch.com/ws/types">
   <soapenv:Header/>
   <soapenv:Body>
      <typ:name>Binu George</typ:name>
   </soapenv:Body>
</soapenv:Envelope>

Sample SOAP Response

<S:Envelope xmlns:S="http://schemas.xmlsoap.org/soap/envelope/">
   <S:Body>
      <ns3:GreetingResponse xmlns:ns2="http://globinch.com" xmlns:ns3="http://globinch.com/ws/types">
         <message>Hello</message>
         <name>Binu George</name>
      </ns3:GreetingResponse>
   </S:Body>
</S:Envelope>

In the above SOAP request and response messages, all the elements are defined in the XML schema definition files. But if you use the parameter style as WRAPPED you will see the operation name element in SOAP messages.
Still the definition will be complaint to the XSD. Document style requires extra classes to run the application. You can use “wsgen” to generate all required Java artifacts including mapping classes, wsdl or xsd schema. Read more below

• Using
  wsgen tool to generate WSDL and required XML Schema documents

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