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From "Joe Walnes" <...@wirestation.co.uk>
Subject Re: [PROPOSAL] Integrating Struts with XML Data
Date Mon, 09 Oct 2000 16:35:10 GMT
In terms of the syntax for selecting properties, would X-Path not make
sense?

Reasons:

1) It's a W3C (proposed) standard.
http://www.w3.org/TR/xpath

2) It's very easy to perform basic selections - yet powerful enought to
select just about any node/collection.

3) Allows navigation to any child node/element/attribute or collection

4) There are many existing implementations that can easily be reused.
(Apache Xalan has a nice implementation in the org.apache.xalan.xpath
package)
http://xml.apache.org/xalan/

5) Is used in XSL to select nodes, so users of either system will not have
to 're-learn' how to use it, and transition from xsl->struts and vice-versa
will be easy.

Here's some examples of X-Path:

<blah id="12">
    Hello
    <xx>Some text</xx>
    <name first="Bob" last="Bobkins" />
    <cheeses>
        <cheese type="blue">Stilton</cheese>
        <cheese type="soft">Brie</cheese>
        <cheese type="dull">Cheddar</cheese>
        <cheese type="blue">Dorset Vinney</cheese>
    </cheeses>
</blah>

(I do not mean to offend any cheddar lovers by implying it is a dull
cheese - it's for the sake of example)

If the <blah> tag is the bean, other attributes can be access like:

. = Hello
@id = 12
xx = Some text
name/@first = Bob
cheeses/cheese[2] = Brie
cheeses/cheese[3]/@type = dull

Essentially, / seperates items in the node path, and @ represents
attributes. Collections can also be retrieved easily.

Incorporating an existing X-Path engine would be a lot easier (and probably
more powerful) than attempting to implement a proprietry expression language
from scratch.

my $0.03

-Joe Walnes


----- Original Message -----
From: "Craig R. McClanahan" <Craig.McClanahan@eng.sun.com>
To: <struts-dev@jakarta.apache.org>
Sent: Monday, October 09, 2000 7:27 AM
Subject: [PROPOSAL] Integrating Struts with XML Data


> One of the desireable goals for Struts 1.0 is a closer integration with
> XML-formatted data -- that is, a graceful way to deal with data sources
> that produce XML data and wish to have their information displayed in an
> HTML page.  One obvious candidate technology is to use for this purpose
> is XSLT transformations to convert the XML data to HTML or WML or
> whatever -- but writing XSLT stylesheets is not something that most web
> developers will be very comfortable with.  An easier solution is needed
> to deal with simple cases.
>
> Given the fact that Struts now includes some very powerful bean-related
> tags like <struts-bean:define>, wouldn't it be nice if we could extend
> those tags to deal with XML data as well?  It turns out that this is
> quite feasible ... the proposal below is an approach to extending the
> Struts bean-related tags so that, when they are presented with a bean
> that is an XML object (that is, an object of type org.w3c.dom.Document
> or some reasonable subordinate object like Element), the bean tags
> should extract property values from them similarly to the way they treat
> Java objects.  The big advantage is, a page developer would be able to
> use essentially the same tags for cases where the data was presented as
> XML as when the data was presented as JavaBeans or EJBs.  (A similar
> extension could be made later to deal with Rows and Columns in a JDBC
> result set).
>
> In the examples below, assume that a DOM object with the following
> structure is attached to the bean name "bean":
>
>     <a b="1" c="2">
>         <d e="3" f="4"/>
>         <d e="5" f="6"/>
>     </a>
>     <a b="7" c="8">
>         <d e="9" f="10"/>
>         <d e="11" f="12"/>
>     </a>
>
> Here's the proposal -- please let me know what you think:
>
> (1) Extensions to <struts-bean:define>:
>
> If the bean referenced by the "name" attribute is a DOM object, apply
> the syntax for simple, nested, and/or indexed property syntax to extract
> the appropriate element or attribute from the DOM according to the
> following rules:
>
> * If the final name in a nested property expression such as a.b.c
>   identifies an attribute of a selected XML element, return it as a
> String.
>   Otherwise, return a DOM element representing the selected
>   XML element.
>
> * If a component of a property name expression is indexed,
>   it is zero-relative in the usual way.  If it is not indexed, the
>   implied index is zero (i.e. a reference to the "a" element in
>   the example will return the first <a> element).
>
> These rules cause the following behavior given a "<struts-bean:define
> name="bean" property='xxx"/>" tag, given the following values for "xxx":
>
> Simple property names:
>
>     a --> (the first <a> element as a DOM object)
>
>     b --> 1
>
>     c --> 2
>
> Nested property names
>
>     a.b --> 1
>
>     a.c --> 2
>
>     a.d --> <d e="3" f="4"/>
>
>     a.d.e --> 3
>
>     a.d.f --> 4
>
> Indexed property names:
>
>     a[0] --> (the first <a> element as a DOM object)
>
>     a[1] --> (the second <a> element as a DOM object)
>
>     a.d --> <d e="3" f="4"/>
>
>     a[0].d --> <d e="3" f="4"/>
>
>     a[0].d[0] --> <d e="3" f="4"/>
>
>     a.d[1] = <d e="5" f="6"/>
>
> Combination property names (examples only, not exhausitive):
>
>     a.d[1].e --> 3
>
>     a[1].d[1].e --> 11
>
> (2) Extensions to <struts-bean:write>:
>
> If the object referenced by the "name" and optional "property"
> attributes is a DOM object, pretty-print it in its XML format with
> "&lt;" and "&gt" escapes for the angle brackets.  This is useful in
> debugging, and for catching property naming expression errors.  It might
> also be useful in a production application to do something similar to
> the XSL "<xsl:select>" operation.
>
> (3) Extensions to <struts-bean:iterate>:
>
> If the object referenced by the "name" and optional "property"
> attributes is a DOM object, iterate over the XML elements that are
> nested inside the specified element, exposing each iterated element as a
> DOM object:
>
>     <struts-bean:iterate name="bean"> --> Iterate over both <a> elements
>
>     <struts-bean:iterate name="bean" property="a"> --> Iterate over both
> <d> elements of the first <a> element
>
>     <struts-bean:iterate name="bean" property="a[0]"> --> Iterate over
> both <d> elements of the first <a> element
>
>     <struts-bean:iterate name="bean" property="a[1]"> --> Iterate over
> both <d> elements of the second <a> element
>
>     <struts-bean:iterate name="bean" property="a[0].d"> --> Iterate over
> a zero length collection because there are no nested elements.
>
> Note that, because the <struts-bean:write> tag can be used to extract
> appropriate properties from the individual elements being iterated over,
> you can use these tags to create reports based on a collection of
> "objects" that are in fact represented as XML elements, in the same way
> that you could create reports based on an ArrayList of Java objects that
> have properties corresponding to the attribute names of the iterated
> elements.
>
> Craig McClanahan
>
> ====================
> See you at ApacheCon Europe <http://www.apachecon.com>!
> Session VS01 (23-Oct 13h00-17h00):  Sun Technical Briefing
> Session T06  (24-Oct 14h00-15h00):  Migrating Apache JServ
>                                     Applications to Tomcat
>


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