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<title>12.4. Debugging SOAP Web Services</title>
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<h2 class="title"><a name="soap.debug"></a>12.4. Debugging <span class="acronym">SOAP</span> Web Services
</h2>
</div>
</div>
<div></div>
</div>
<div class="abstract">
<p>The <span class="acronym">SOAP</span> libraries provide an easy way to see what's going on behind the scenes.
</p>
</div>
<p>Turning on debugging is a simple matter of setting two flags in the <tt class="classname">SOAPProxy</tt>'s configuration.
</p>
<div class="example"><a name="d0e30423"></a><h3 class="title">Example 12.7. Debugging <span class="acronym">SOAP</span> Web Services
</h3><pre class="screen">
<tt class="prompt">>>> </tt><span class="userinput"><span class='pykeyword'>from</span> SOAPpy <span class='pykeyword'>import</span> SOAPProxy</span>
<tt class="prompt">>>> </tt><span class="userinput">url = <span class='pystring'>'http://services.xmethods.net:80/soap/servlet/rpcrouter'</span></span>
<tt class="prompt">>>> </tt><span class="userinput">n = <span class='pystring'>'urn:xmethods-Temperature'</span></span>
<tt class="prompt">>>> </tt><span class="userinput">server = SOAPProxy(url, namespace=n)</span> <a name="soap.debug.1.1"></a><img src="../images/callouts/1.png" alt="1" border="0" width="12" height="12">
<tt class="prompt">>>> </tt><span class="userinput">server.config.dumpSOAPOut = 1</span> <a name="soap.debug.1.2"></a><img src="../images/callouts/2.png" alt="2" border="0" width="12" height="12">
<tt class="prompt">>>> </tt><span class="userinput">server.config.dumpSOAPIn = 1</span>
<tt class="prompt">>>> </tt><span class="userinput">temperature = server.getTemp(<span class='pystring'>'27502'</span>)</span> <a name="soap.debug.1.3"></a><img src="../images/callouts/3.png" alt="3" border="0" width="12" height="12">
<span class="computeroutput">*** Outgoing SOAP ******************************************************
<?xml version="1.0" encoding="UTF-8"?>
<SOAP-ENV:Envelope SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"
xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/"
xmlns:xsi="http://www.w3.org/1999/XMLSchema-instance"
xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:xsd="http://www.w3.org/1999/XMLSchema">
<SOAP-ENV:Body>
<ns1:getTemp xmlns:ns1="urn:xmethods-Temperature" SOAP-ENC:root="1">
<v1 xsi:type="xsd:string">27502</v1>
</ns1:getTemp>
</SOAP-ENV:Body>
</SOAP-ENV:Envelope>
************************************************************************
*** Incoming SOAP ******************************************************
<?xml version='1.0' encoding='UTF-8'?>
<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<SOAP-ENV:Body>
<ns1:getTempResponse xmlns:ns1="urn:xmethods-Temperature"
SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
<return xsi:type="xsd:float">80.0</return>
</ns1:getTempResponse>
</SOAP-ENV:Body>
</SOAP-ENV:Envelope>
************************************************************************
</span>
<tt class="prompt">>>> </tt><span class="userinput">temperature</span>
<span class="computeroutput">80.0</span>
</pre><div class="calloutlist">
<table border="0" summary="Callout list">
<tr>
<td width="12" valign="top" align="left"><a href="#soap.debug.1.1"><img src="../images/callouts/1.png" alt="1" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">First, create the <tt class="classname">SOAPProxy</tt> like normal, with the service <span class="acronym">URL</span> and the namespace.
</td>
</tr>
<tr>
<td width="12" valign="top" align="left"><a href="#soap.debug.1.2"><img src="../images/callouts/2.png" alt="2" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">Second, turn on debugging by setting <tt class="varname">server.config.dumpSOAPIn</tt> and <tt class="varname">server.config.dumpSOAPOut</tt>.
</td>
</tr>
<tr>
<td width="12" valign="top" align="left"><a href="#soap.debug.1.3"><img src="../images/callouts/3.png" alt="3" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">Third, call the remote <span class="acronym">SOAP</span> method as usual. The <span class="acronym">SOAP</span> library will print out both the outgoing XML request document, and the incoming XML response document. This is all the hard
work that <tt class="classname">SOAPProxy</tt> is doing for you. Intimidating, isn't it? Let's break it down.
</td>
</tr>
</table>
</div>
</div>
<p>Most of the XML request document that gets sent to the server is just boilerplate. Ignore all the namespace declarations;
they're going to be the same (or similar) for all <span class="acronym">SOAP</span> calls. The heart of the “<span class="quote">function call</span>” is this fragment within the <tt class="sgmltag-element"><Body></tt> element:
</p>
<div class="informalexample"><pre class="programlisting">
<ns1:getTemp <a name="soap.debug.2.1"></a><img src="../images/callouts/1.png" alt="1" border="0" width="12" height="12">
xmlns:ns1=<span class='pystring'>"urn:xmethods-Temperature"</span> <a name="soap.debug.2.2"></a><img src="../images/callouts/2.png" alt="2" border="0" width="12" height="12">
SOAP-ENC:root=<span class='pystring'>"1"</span>>
<v1 xsi:type=<span class='pystring'>"xsd:string"</span>>27502</v1> <a name="soap.debug.2.3"></a><img src="../images/callouts/3.png" alt="3" border="0" width="12" height="12">
</ns1:getTemp>
</pre><div class="calloutlist">
<table border="0" summary="Callout list">
<tr>
<td width="12" valign="top" align="left"><a href="#soap.debug.2.1"><img src="../images/callouts/1.png" alt="1" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">The element name is the function name, <tt class="function">getTemp</tt>. <tt class="classname">SOAPProxy</tt> uses <a href="../scripts_and_streams/handlers_by_node_type.html" title="10.5. Creating separate handlers by node type"><tt class="function">getattr</tt> as a dispatcher</a>. Instead of calling separate local methods based on the method name, it actually uses the method name to construct the XML
request document.
</td>
</tr>
<tr>
<td width="12" valign="top" align="left"><a href="#soap.debug.2.2"><img src="../images/callouts/2.png" alt="2" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">The function's XML element is contained in a specific namespace, which is the namespace you specified when you created the
<tt class="classname">SOAPProxy</tt> object. Don't worry about the <tt class="literal">SOAP-ENC:root</tt>; that's boilerplate too.
</td>
</tr>
<tr>
<td width="12" valign="top" align="left"><a href="#soap.debug.2.3"><img src="../images/callouts/3.png" alt="3" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">The arguments of the function also got translated into XML. <tt class="classname">SOAPProxy</tt> introspects each argument to determine its datatype (in this case it's a string). The argument datatype goes into the <tt class="literal">xsi:type</tt> attribute, followed by the actual string value.
</td>
</tr>
</table>
</div>
</div>
<p>The XML return document is equally easy to understand, once you know what to ignore. Focus on this fragment within the <tt class="sgmltag-element"><Body></tt>:
</p>
<div class="informalexample"><pre class="programlisting">
<ns1:getTempResponse <a name="soap.debug.3.1"></a><img src="../images/callouts/1.png" alt="1" border="0" width="12" height="12">
xmlns:ns1=<span class='pystring'>"urn:xmethods-Temperature"</span> <a name="soap.debug.3.2"></a><img src="../images/callouts/2.png" alt="2" border="0" width="12" height="12">
SOAP-ENV:encodingStyle=<span class='pystring'>"http://schemas.xmlsoap.org/soap/encoding/"</span>>
<<span class='pykeyword'>return</span> xsi:type=<span class='pystring'>"xsd:float"</span>>80.0</<span class='pykeyword'>return</span>> <a name="soap.debug.3.3"></a><img src="../images/callouts/3.png" alt="3" border="0" width="12" height="12">
</ns1:getTempResponse>
</pre><div class="calloutlist">
<table border="0" summary="Callout list">
<tr>
<td width="12" valign="top" align="left"><a href="#soap.debug.3.1"><img src="../images/callouts/1.png" alt="1" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">The server wraps the function return value within a <tt class="sgmltag-element"><getTempResponse></tt> element. By convention, this wrapper element is the name of the function, plus <tt class="literal">Response</tt>. But it could really be almost anything; the important thing that <tt class="classname">SOAPProxy</tt> notices is not the element name, but the namespace.
</td>
</tr>
<tr>
<td width="12" valign="top" align="left"><a href="#soap.debug.3.2"><img src="../images/callouts/2.png" alt="2" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">The server returns the response in the same namespace we used in the request, the same namespace we specified when we first
create the <tt class="classname">SOAPProxy</tt>. Later in this chapter we'll see what happens if you forget to specify the namespace when creating the <tt class="classname">SOAPProxy</tt>.
</td>
</tr>
<tr>
<td width="12" valign="top" align="left"><a href="#soap.debug.3.3"><img src="../images/callouts/3.png" alt="3" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">The return value is specified, along with its datatype (it's a float). <tt class="classname">SOAPProxy</tt> uses this explicit datatype to create a <span class="application">Python</span> object of the correct native datatype and return it.
</td>
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