[jira] Commented: (AXIS-616) MessageElement is not for mortals

["Robert J Weber (JIRA)" <ax...@ws.apache.org>]

    [ https://issues.apache.org/jira/browse/AXIS-616?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12590065#action_12590065 ] 

Robert J Weber commented on AXIS-616:
-------------------------------------

I know it's been a long time, but might someone link to the means of leveraging this "[other] approach"?

Thanks!

> MessageElement is not for mortals
> ---------------------------------
>
>                 Key: AXIS-616
>                 URL: https://issues.apache.org/jira/browse/AXIS-616
>             Project: Axis
>          Issue Type: Bug
>          Components: Serialization/Deserialization
>    Affects Versions: future (enh)
>         Environment: Operating System: Other
> Platform: Other
>            Reporter: James Snell
>         Attachments: MessageElementHelper.java
>
>
> The purpose of this note is to document issues I encountered during the 
> development of the WSRP WSTK demo with respect to Axis and the 
> org.apache.axis.message.MessageElement class.  I suspect the MessageElement 
> class is not meant for programmers to use directly, but this is a requirement 
> in our case.
> Background:
> The WSDL for the demo makes use of "any" in several places in order to allow 
> user defined xml data to be passed in messages.  Here is an example of its use 
> in defining the Property type:
>       <complexType name="Property">
>         <sequence>
>           <any namespace="##other" minOccurs="0" maxOccurs="unbounded"/>
>         </sequence>
>         <attribute name="name"         type="xsd:string" use="required"/>
>         <attribute name="lang"         type="xsd:string" use="required"/>
>       <!--
>         Would prefer this form, but Axis tools ignore the definition
>         <attribute ref="xml:lang"      use="required"/>
>       -->
>         <attribute name="resourceName" type="xsd:string"/>
>       </complexType>
> The WSDL2Java tool generates the type for this as a Property class that 
> contains an array of MessageElements like so:
> public class Property  implements java.io.Serializable {
>     private org.apache.axis.message.MessageElement [] _any;
>     private java.lang.String name;  // attribute
>     private java.lang.String lang;  // attribute
>     private java.lang.String resourceName;  // attribute
>     public Property() {
>     }
>     public org.apache.axis.message.MessageElement [] get_any() {
>         return _any;
>     }
>     public void set_any(org.apache.axis.message.MessageElement [] _any) {
>         this._any = _any;
>     }
> 	.
> 	.
> 	.
> In order to use the Property class, the programmer must create MessageElements 
> and MessageElement arrays as well as try to obtain the contents of a 
> MessageElement instance.
> Issues:
> 1.  Constructing a MessageElement:
> 	If I want to create a Property, I must construct a MessageElement.   
> There are 9 constructors in the MessageElement class.  The Javadoc does not 
> describe any of the them.  It matters which one is chosen. After a lot of 
> experimentation,  I ended up using the MessageElement(org.w3c.Element) 
> constructor.   Under the covers, the MessageElement class has several member 
> variables for holding value information.  The constructor you use determines 
> which member variable gets used (e.g. Text vs Element vs children), and also 
> determines how you try to "get" the value later.   There are also many 
> possibilities for using the no-argument constructor and the calling one of the 
> multitude of set methods. The setObjectValue method is tempting, but the value 
> doesn't make it across the network connection.
> 2. Retrieving the value:
> 	There is no usable "get" method on a MessageElement.   Even if you knew 
> how it was created and where the data was stored in the MessageElement (e.g. 
> textRep, elementRep), there is no corresponding get method.  There is a method 
> called  getAsDOM, but this method calls getAsString and then parses the 
> result.  The protected method getAsString() method requires a MessageContext 
> which is used to obtain a SerializationContext.  Since I created the 
> MessageElement myself, there is no MessageContext.  If you call toString(), it 
> just calls getAsString() .
> Workarounds:
> I ended up creating a class called MessageElementHelper which has methods to 
> create a MessageElement, to clone a MessageElement and to fetch its content.  
> It implements SerializationContext so I can use the output() method and fake 
> out the serialization context.   Note that I had to inspect the source code for 
> MessageElement in order to derive this solution.
> Here it is:
> Conclusions:
> I hope I described the problem well enough without going in to too much 
> detail.  Folks using "any" in their messages are going to have to use 
> MessageElement and it's painful.  I have a couple of suggestions going forward.
> 	1. change the WSDL2Java program to generate something more useable than 
> MessageElement arrays.
> 	2. document MessageElement more precisely, specifically for this use 
> case
> 	3. wrap MessageElement in a more usable form and change WSDL2Java 
> correspondingly. It would be nice to have setElement(w3c.dom.Element) and 
> w3c.dom.Element getElement() .  
> Please feel free to contact me for more information or to discuss my 
> experiences.  My ultimate goal is to improve the product and help other users.
> Thanks.
>  
> Julie E.MacNaught
> IBM Research

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