SOAP Content Type Demo

A SOAP Content-Type demonstration by slindenau

Introduction

In SOAP web services the Content-Type header can cause some annoying problems.

The expected content types for SOAP messages are as follows:

• text/xml for SOAP v1.1
• application/soap+xml for SOAP v1.2

You can recognize the SOAP version of your project by looking at the following namespaces used:

• In the WSDL:
  • http://schemas.xmlsoap.org/wsdl/soap/ for SOAP v1.1
  • http://schemas.xmlsoap.org/wsdl/soap12/ for SOAP v1.2
• In the SOAP message envelope:
  • http://schemas.xmlsoap.org/soap/envelope/ for SOAP v1.1
  • http://www.w3.org/2003/05/soap-envelope/ for SOAP v1.2

See for reference: https://stackoverflow.com/q/736845/3756780

If there is a mismatch on this header, your Java client may respond with any of the following exceptions:

• UnsupportedMediaException: Unsupported Content-Type: text/xml; charset=utf-8 Supported ones are: [application/soap+xml]
• UnsupportedMediaException: Unsupported Content-Type: text/plain;charset=ISO-8859-1 Supported ones are: [text/xml]
• UnsupportedMediaException: Unsupported Content-Type: text/html Supported ones are: [text/xml]
• ClientTransportException: The server sent HTTP status code 200: OK
• etc

In this demonstration I have set up a SOAP v1.1 server that is responding with the content type of SOAP v1.2, and several clients to showcase the UnsupportedMediaException and possible ways to deal with this exception.

Your first action should be to inform the owner of the SOAP server, and report that there is a problem.
This project will showcase some workarounds you can apply to process the responses.
If you're looking for a solution without changing your code, a proxy server would be a good alternative.
See for reference: https://stackoverflow.com/a/65065756/18699445

The code in this project was created & tested with the following tools (unless stated otherwise):

• IntelliJ IDEA 2021.3.2 (Community Edition)
• Java jdk8u332-b09
• Maven 3.8.4

The Server

The server is set up with the following Spring guide:

• https://spring.io/guides/gs/producing-web-service/
• https://github.com/spring-guides/gs-producing-web-service

With the following modifications:

• A Servlet Filter was added in WebServiceConfig
• The content type is rewritten in ContentTypeDemoFilter

You can run the server with the following command in the server project:

• mvn spring-boot:run

The SOAP service should then be available on http://localhost:9097/ws/countries.wsdl
The code will loop through a set of different content types for the response in order.
It is the intention to leave the server running, and then you can experiment with the different clients.
On processing a request the original & rewritten content type of the response are logged to the console, see the following screenshot:

The Client - JRE

This is a basic client that uses the jaxws-maven-plugin to generate a model with the wsimport goal.
It uses the JRE internal SOAP processing code located in package com.sun.xml.internal.ws (RT.jar).

You can run the client as follows:

• Execute mvn clean package and run main class nl.slindenau.Application in project client-jre

This will result in the following exception:

Exception in thread "main" com.sun.xml.internal.ws.server.UnsupportedMediaException: Unsupported Content-Type: application/soap+xml;charset=utf-8 Supported ones are: [text/xml]
	at com.sun.xml.internal.ws.encoding.StreamSOAPCodec.decode(StreamSOAPCodec.java:220)
	at com.sun.xml.internal.ws.encoding.StreamSOAPCodec.decode(StreamSOAPCodec.java:151)
	at com.sun.xml.internal.ws.encoding.SOAPBindingCodec.decode(SOAPBindingCodec.java:299)
	at com.sun.xml.internal.ws.transport.http.client.HttpTransportPipe.createResponsePacket(HttpTransportPipe.java:268)
	at com.sun.xml.internal.ws.transport.http.client.HttpTransportPipe.process(HttpTransportPipe.java:217)
	at com.sun.xml.internal.ws.transport.http.client.HttpTransportPipe.processRequest(HttpTransportPipe.java:130)
	at com.sun.xml.internal.ws.transport.DeferredTransportPipe.processRequest(DeferredTransportPipe.java:95)

In the console the full HTTP request + response are logged, this can be disabled in CountriesSoapClient#setDebugProperties. See the following screenshot:

Note that there currently is no way to prevent this without changing the SOAP runtime, which will be shown in the next client. In theory the proposed solution in that client should be possible here as well, but that would require us to depend on- and extend internal JRE code. This is a bad practice, and maven support for system scope dependencies did not work for me.

The Client - JAXWS-RT

This client uses the exact same generated SOAP code as the client-jre (so no modifications required), but with a different JAX-WS runtime.
By depending on the following libraries we can exchange the internal runtime for jaxws-rt.
Note that this runtime should be nearly identical and fully compatible with the internal code of the JRE, but this now gives us the option to expand it.

Dependencies required to switch from internal SOAP processing to JAX-WS runtime:

<dependency>
    <groupId>javax.activation</groupId>
    <artifactId>activation</artifactId>
    <version>1.1.1</version>
</dependency>
<dependency>
    <groupId>com.sun.xml.bind</groupId>
    <artifactId>jaxb-impl</artifactId>
    <version>2.3.5</version>
</dependency>
<dependency>
    <groupId>com.sun.xml.ws</groupId>
    <artifactId>jaxws-rt</artifactId>
    <version>2.3.5</version>
</dependency>

The part that rewrites the content type on this client is implemented via a custom TransportTubeFactory that is loaded with service discovery. Keep in mind that this factory is used for every SOAP call executed by clients in the current ClassLoader (by default that is the entire application you're running in a single JRE process, unless you're using some form of container/isolation).

By using a custom HttpTransportPipe and wrapping the Codec we can rewrite the content type just before the HTTP response is passed to the SOAP codec. This works for most cases, except for text/html, which is rejected earlier in the process by JAX-WS in more recent versions of the runtime library. If you need to process HTML consider using an older version of jaxws-rt. jaxws-rt-2.1.7 is the last version that does not reject HTML right away, but beware this library is from 2009! You could also duplicate more code in the custom Transport tube or -pipe classes.
Note that the Apache CXF client (see below) does have the option to process HTML.

You can run the client as follows:

• Execute mvn clean package and run main class nl.slindenau.Application in project client-jaxws-rt

If we do not rewrite the content type in the CodecWrapper we get a similar exception as before, but note that the internal package is missing:

Exception in thread "main" com.sun.xml.ws.server.UnsupportedMediaException: Unsupported Content-Type: application/soap+xml;charset=utf-8 Supported ones are: [text/xml]
at com.sun.xml.ws.encoding.StreamSOAPCodec.decode(StreamSOAPCodec.java:205)
at com.sun.xml.ws.encoding.StreamSOAPCodec.decode(StreamSOAPCodec.java:136)
at com.sun.xml.ws.encoding.SOAPBindingCodec.decode(SOAPBindingCodec.java:289)

But with our custom HttpTransportPipe we can now access the full HTTP response body, which would otherwise be lost (or only logged to the console):

And if we enable client-side content type rewrite in the CodecWrapper, we can process the request like nothing was wrong:

The Client - Apache-CXF

This is an Apache CXF client that uses the cxf-codegen-plugin to generate a model with the wsdl2java goal.
It uses the Apache CXF custom SOAP processing code. The content-type filter of this code was inspired by https://stackoverflow.com/a/50863434/18699445

You can run the client as follows:

• Execute mvn clean package and run main class nl.slindenau.Application in project client-cxf

This client will rewrite the content type with an Interceptor, and can even process text/html:

Without this interceptor, you would encounter the following exception:

Exception in thread "main" javax.xml.ws.soap.SOAPFaultException: Response was of unexpected text/html ContentType.  Incoming portion of HTML stream: <SOAP-ENV:Envelope...
	at org.apache.cxf.jaxws.JaxWsClientProxy.mapException(JaxWsClientProxy.java:195)
	at org.apache.cxf.jaxws.JaxWsClientProxy.invoke(JaxWsClientProxy.java:145)
	at com.sun.proxy.$Proxy35.getCountry(Unknown Source)
	at nl.slindenau.soap.client.CountriesSoapClient.getCountries(CountriesSoapClient.java:23)
	at nl.slindenau.Application.main(Application.java:9)
Caused by: org.apache.cxf.interceptor.Fault: Response was of unexpected text/html ContentType.  Incoming portion of HTML stream: <SOAP-ENV:Envelope...
	at org.apache.cxf.interceptor.StaxInInterceptor.handleMessage(StaxInInterceptor.java:97)
	at org.apache.cxf.phase.PhaseInterceptorChain.doIntercept(PhaseInterceptorChain.java:307)
	at org.apache.cxf.endpoint.ClientImpl.onMessage(ClientImpl.java:829)
	at org.apache.cxf.transport.http.HTTPConduit$WrappedOutputStream.handleResponseInternal(HTTPConduit.java:1701)

Support, Disclaimer and Contributing

Be aware that all code in this project is a demonstration. It is not production ready.
Feel free to use it as the license permits, but you are fully responsible for the final product you're developing.
I am open to contributions that improve the quality of this demonstration & different client implementations that achieve the same goal.

If this helped you in any way to solve a problem, please show your support on https://stackoverflow.com/a/71734557/18699445