wiki:WebServiceClientSelection
Last modified 4 years ago

docx4all web services client

Context

docx4all needs a web services client, so that it can interact with a plutext-server during a collaboration session.

There are a number to choose from, including:

  • Axis 1.4
  • Axis 2 - 1.3
  • CXF
  • Java SE 6 built-in functionality

This page explains why we are currently using Axis 1.4.

Selection Criteria

  • Interoperates with Alfresco web services
  • - support for WS Security
  • Small footprint
  • Can be used in a Java Web Start application (no need to put stuff in endorsed dirs)

WS Security

To use the plutext-server web services running in Alfresco, you first have to get a ticket from the Alfresco authentication service.

See  http://wiki.alfresco.com/wiki/Web_Service_Samples_for_Java

So we need support for OASIS Web Services Security (WS-Security), as is provided by Apache WSS4J.  http://ws.apache.org/wss4j/axis.html

Axis 1.4

Axis 1.4 is getting old, and it is superseded by Axis 2.

But Alfresco use this (and WSS4J) server-side and client-side.

So if we use this, we can use Alfresco's existing client-side authentication stuff. There's no reason we couldn't generate a client-side binding to suit one of the other web service client libraries, but this way, we can leverage the community.

So, here is what I did:

  1. Generated a WSDL from org.plutext.server.PlutextWebService?

plutext-server/build.xml contains a target 'generate.wsdl.axis1'

Note that the style must be WRAPPED, not RPC. Without WRAPPED, you get:

org.xml.sax.SAXException: Found character data inside an array element while deserializing

at org.apache.axis.encoding.ser.ArrayDeserializer?.characters(ArrayDeserializer?.java:502)
at org.apache.axis.encoding.DeserializationContext?.characters(DeserializationContext?.java:966)

Setting WRAPPED also changed things from ENCODED to LITERAL (not sure whether this matters).

  1. Generate client code

axis-1_4/lib$ java -cp axis.jar:commons-logging-1.0.4.jar:commons-discovery-0.2.jar:jaxrpc.jar:wsdl4j-1.5.1.jar org.apache.axis.wsdl.WSDL2Java -p org.plutext.client.webservice ../../axis1-out.wsdl

  1. Add that code to docx4all, together with alfresco-web-service-client.jar and axis-1.4.jar and dependencies

To build alfresco-web-service-client.jar, use target 'package-webserviceclient'. There's a fair bit of stuff in there we can remove to make the footprint smaller.

Axis 1.4 dependencies

To make it all work, here are the jars that need to be on docx4all's classpath:

  • axis.jar (1.6 MB)
  • commons-discovery-0.2.jar
  • jaxrpc.jar
  • wsdl4j-1.5.1.jar
  • wss4j.jar
  • bcprov-jdk15-137.jar (1.5 MB)
  • opensaml-1.0.1.jar
  • xmlsec-1.4.1.jar (415 KB)

All these are in the main public maven repositories, except xmlsec-1.4.1 and opensaml-1.0.1.

The maven dependency:tree looks like this:

axis:axis:jar:1.4:compile

axis:axis-jaxrpc:jar:1.4:compile
axis:axis-saaj:jar:1.4:compile
axis:axis-wsdl4j:jar:1.5.1:runtime
commons-discovery:commons-discovery:jar:0.2:runtime

wss4j:wss4j:jar:1.5.0:compile
bouncycastle:bcprov-jdk16:jar:136:compile

Axis 2

I tried to generate classes using our existing wsdl:

sh wsdl2java.sh -uri ../../PlutextWebService.wsdl -p org.docx4all -d jaxbri -o tmp -S tmp

I wanted to use jaxb, since we're already using that extensively.

But it didn't work.

(Iirc, it did work if I didn't use jaxb).

So I thought I'd generate a new WSDL, and work from that. See plutext-server/build.xml target 'generate.wsdl.axis2'. But that failed as well.

I guess I could try to generate classes using the WSDL which worked for Axis 1, but there is no immediate need to move from Axis 1. Mayeb we'll move if/when Alfresco does.

There are some posts about the size of the footprint:  May 2006,  March 2007, but Axis 1 is not exactly small either!

Java SE 6 web service client

The idea of using stuff already built in to Java SE 6 is appealing, from a footprint point of view.

However, the instructions for  getting security to work suggest you need a different version of SAAJ RI to the one packaged in Java 6, and this rings alarm bells - can a Java Web Start application be easily made to use it?

The XWSS mailing list also has very little traffic.

In all, Axis is an easier approach for now. But we should revist Java SE 6 web service client again further down the track.

CXF

This is just coming out of incubation. Something to keep an eye on.