repo_zf1/documentation/manual/en/module_specs/Zend_XmlRpc_Server.xml

<?xml version="1.0" encoding="UTF-8"?>
<!-- Reviewed: no -->
<sect1 id="zend.xmlrpc.server">
    <title>Zend_XmlRpc_Server</title>

    <sect2 id="zend.xmlrpc.server.introduction">
        <title>Introduction</title>

        <para>
            <classname>Zend_XmlRpc_Server</classname> is intended as a fully-featured
            <acronym>XML-RPC</acronym> server, following <ulink url="http://www.xmlrpc.com/spec">the
                specifications outlined at www.xmlrpc.com</ulink>. Additionally, it implements the
            <command>system.multicall()</command> method, allowing boxcarring of requests.
        </para>
    </sect2>

    <sect2 id="zend.xmlrpc.server.usage">
        <title>Basic Usage</title>

        <para>
            An example of the most basic use case:
        </para>

        <programlisting language="php"><![CDATA[
$server = new Zend_XmlRpc_Server();
$server->setClass('My_Service_Class');
echo $server->handle();
]]></programlisting>
    </sect2>

    <sect2 id="zend.xmlrpc.server.structure">
        <title>Server Structure</title>

        <para>
            <classname>Zend_XmlRpc_Server</classname> is composed of a variety of components,
            ranging from the server itself to request, response, and fault objects.
        </para>

        <para>
            To bootstrap <classname>Zend_XmlRpc_Server</classname>, the developer must attach one or
            more classes or functions to the server, via the
            <methodname>setClass()</methodname> and <methodname>addFunction()</methodname> methods.
        </para>

        <para>
            Once done, you may either pass a <classname>Zend_XmlRpc_Request</classname>
            object to <methodname>Zend_XmlRpc_Server::handle()</methodname>, or it will
            instantiate a <classname>Zend_XmlRpc_Request_Http</classname> object if none
            is provided -- thus grabbing the request from
            <filename>php://input</filename>.
        </para>

        <para>
            <methodname>Zend_XmlRpc_Server::handle()</methodname> then attempts to
            dispatch to the appropriate handler based on the method
            requested. It then returns either a
            <classname>Zend_XmlRpc_Response</classname>-based object or a
            <classname>Zend_XmlRpc_Server_Fault</classname>object. These objects both have
            <methodname>__toString()</methodname> methods that create valid
            <acronym>XML-RPC</acronym> <acronym>XML</acronym> responses, allowing them to be
            directly echoed.
        </para>
    </sect2>

    <sect2 id="zend.xmlrpc.server.anatomy">
        <title>Anatomy of a webservice</title>

        <sect3 id="zend.xmlrpc.server.anatomy.general">
            <title>General considerations</title>

            <para>
                For maximum performance it is recommended to use a simple
                bootstrap file for the server component. Using
                <classname>Zend_XmlRpc_Server</classname> inside a
                <link linkend="zend.controller"><classname>Zend_Controller</classname></link>
                is strongly discouraged to avoid the overhead.
            </para>

            <para>
                Services change over time and while webservices are generally
                less change intense as code-native <acronym>APIs</acronym>, it
                is recommended to version your service. Do so to lay grounds to
                provide compatibility for clients using older versions of your
                service and manage your service lifecycle including deprecation
                timeframes.To do so just include a version number into your
                <acronym>URI</acronym>. It is also recommended to include the
                remote protocol name in the <acronym>URI</acronym> to allow easy
                integration of upcoming remoting technologies.
                http://myservice.ws/<emphasis>1.0/XMLRPC/</emphasis>.
            </para>
        </sect3>

        <sect3 id="zend.xmlrpc.server.anatomy.expose">
            <title>What to expose?</title>

            <para>
                Most of the time it is not sensible to expose business objects
                directly. Business objects are usually small and under heavy
                change, because change is cheap in this layer of your
                application. Once deployed and adopted, web services are hard to
                change. Another concern is <acronym>I/O</acronym> and latency:
                the best webservice calls are those not happening. Therefore
                service calls need to be more coarse-grained than usual business
                logic is. Often an additional layer in front of your business
                objects makes sense. This layer is sometimes referred to as <ulink
                    url="http://martinfowler.com/eaaCatalog/remoteFacade.html">Remote
                    Facade</ulink>.
                Such a service layer adds a coarse grained interface on top of
                your business logic and groups verbose operations into smaller
                ones.
            </para>
        </sect3>
    </sect2>

    <sect2 id="zend.xmlrpc.server.conventions">
        <title>Conventions</title>
        <para>
            <classname>Zend_XmlRpc_Server</classname> allows the developer to attach functions and
            class method calls as dispatchable <acronym>XML-RPC</acronym> methods. Via
            <classname>Zend_Server_Reflection</classname>, it does introspection on all attached
            methods, using the function and method docblocks to determine the
            method help text and method signatures.
        </para>

        <para>
            <acronym>XML-RPC</acronym> types do not necessarily map one-to-one to
            <acronym>PHP</acronym> types. However, the code will do its best to guess the
            appropriate type based on the values listed in @param and @return lines. Some
            <acronym>XML-RPC</acronym> types have no immediate <acronym>PHP</acronym> equivalent,
            however, and should be hinted using the <acronym>XML-RPC</acronym> type in the PHPDoc.
            These include:
        </para>

        <itemizedlist>
            <listitem>
                <para>
                    <emphasis><property>dateTime.iso8601</property></emphasis>, a string formatted
                    as '<command>YYYYMMDDTHH:mm:ss</command>'
                </para>
            </listitem>

            <listitem><para><emphasis>base64</emphasis>, base64 encoded data</para></listitem>

            <listitem><para><emphasis>struct</emphasis>, any associative array</para></listitem>
        </itemizedlist>

        <para>
            An example of how to hint follows:
        </para>

        <programlisting language="php"><![CDATA[
/**
* This is a sample function
*
* @param base64 $val1 Base64-encoded data
* @param dateTime.iso8601 $val2 An ISO date
* @param struct $val3 An associative array
* @return struct
*/
function myFunc($val1, $val2, $val3)
{
}
]]></programlisting>

        <para>
            PhpDocumentor does no validation of the types specified for params
            or return values, so this will have no impact on your <acronym>API</acronym>
            documentation. Providing the hinting is necessary, however, when the
            server is validating the parameters provided to the method call.
        </para>

        <para>
            It is perfectly valid to specify multiple types for both params and
            return values; the <acronym>XML-RPC</acronym> specification even suggests that
            system.methodSignature should return an array of all possible method
            signatures (i.e., all possible combinations of param and return
            values). You may do so just as you normally would with
            PhpDocumentor, using the '|' operator:
        </para>

        <programlisting language="php"><![CDATA[
/**
* This is a sample function
*
* @param string|base64 $val1 String or base64-encoded data
* @param string|dateTime.iso8601 $val2 String or an ISO date
* @param array|struct $val3 Normal indexed array or an associative array
* @return boolean|struct
*/
function myFunc($val1, $val2, $val3)
{
}
]]></programlisting>

        <note>
            Allowing multiple signatures can lead to confusion for developers
            using the services; to keep things simple, a <acronym>XML-RPC</acronym>
            service method should only have a single signature.
        </note>
    </sect2>

    <sect2 id="zend.xmlrpc.server.namespaces">
        <title>Utilizing Namespaces</title>

        <para>
            <acronym>XML-RPC</acronym> has a concept of namespacing; basically, it allows grouping
            <acronym>XML-RPC</acronym> methods by dot-delimited namespaces. This helps prevent
            naming collisions between methods served by different classes. As an
            example, the <acronym>XML-RPC</acronym> server is expected to server several methods in
            the 'system' namespace:
        </para>

        <itemizedlist>
            <listitem><para>system.listMethods</para></listitem>
            <listitem><para>system.methodHelp</para></listitem>
            <listitem><para>system.methodSignature</para></listitem>
        </itemizedlist>

        <para>
            Internally, these map to the methods of the same name in
            <classname>Zend_XmlRpc_Server</classname>.
        </para>

        <para>
            If you want to add namespaces to the methods you serve, simply
            provide a namespace to the appropriate method when attaching a
            function or class:
        </para>

        <programlisting language="php"><![CDATA[
// All public methods in My_Service_Class will be accessible as
// myservice.METHODNAME
$server->setClass('My_Service_Class', 'myservice');

// Function 'somefunc' will be accessible as funcs.somefunc
$server->addFunction('somefunc', 'funcs');
]]></programlisting>
    </sect2>

    <sect2 id="zend.xmlrpc.server.request">
        <title>Custom Request Objects</title>

        <para>
            Most of the time, you'll simply use the default request type included with
            <classname>Zend_XmlRpc_Server</classname>,
            <classname>Zend_XmlRpc_Request_Http</classname>. However, there may be times when you
            need <acronym>XML-RPC</acronym> to be available via the <acronym>CLI</acronym>, a
            <acronym>GUI</acronym>, or other environment, or want to log incoming requests. To do
            so, you may create a custom request object that extends
            <classname>Zend_XmlRpc_Request</classname>. The most important thing to remember is to
            ensure that the <methodname>getMethod()</methodname> and
            <methodname>getParams()</methodname> methods are implemented so that the
            <acronym>XML-RPC</acronym> server can retrieve that information in order to dispatch the
            request.
        </para>
    </sect2>

    <sect2 id="zend.xmlrpc.server.response">
        <title>Custom Responses</title>

        <para>
            Similar to request objects, <classname>Zend_XmlRpc_Server</classname> can return custom
            response objects; by default, a <classname>Zend_XmlRpc_Response_Http</classname> object
            is returned, which sends an appropriate Content-Type <acronym>HTTP</acronym> header for
            use with <acronym>XML-RPC</acronym>. Possible uses of a custom object would be to log
            responses, or to send responses back to <constant>STDOUT</constant>.
        </para>

        <para>
            To use a custom response class, use
            <methodname>Zend_XmlRpc_Server::setResponseClass()</methodname> prior to calling
            <methodname>handle()</methodname>.
        </para>
    </sect2>

    <sect2 id="zend.xmlrpc.server.fault">
        <title>Handling Exceptions via Faults</title>

        <para>
            <classname>Zend_XmlRpc_Server</classname> catches Exceptions generated by a dispatched
            method, and generates an <acronym>XML-RPC</acronym> fault response when such an
            exception is caught. By default, however, the exception messages and
            codes are not used in a fault response. This is an intentional
            decision to protect your code; many exceptions expose more
            information about the code or environment than a developer would
            necessarily intend (a prime example includes database abstraction or
            access layer exceptions).
        </para>

        <para>
            Exception classes can be whitelisted to be used as fault responses,
            however. To do so, simply utilize
            <methodname>Zend_XmlRpc_Server_Fault::attachFaultException()</methodname> to pass an
            exception class to whitelist:
        </para>

        <programlisting language="php"><![CDATA[
Zend_XmlRpc_Server_Fault::attachFaultException('My_Project_Exception');
]]></programlisting>

        <para>
            If you utilize an exception class that your other project exceptions
            inherit, you can then whitelist a whole family of exceptions at a
            time. <classname>Zend_XmlRpc_Server_Exception</classname>s are always whitelisted, to
            allow reporting specific internal errors (undefined methods, etc.).
        </para>

        <para>
            Any exception not specifically whitelisted will generate a fault
            response with a code of '404' and a message of 'Unknown error'.
        </para>
    </sect2>

    <sect2 id="zend.xmlrpc.server.caching">
        <title>Caching Server Definitions Between Requests</title>

        <para>
            Attaching many classes to an <acronym>XML-RPC</acronym> server instance can utilize a
            lot of resources; each class must introspect using the Reflection
            <acronym>API</acronym> (via <classname>Zend_Server_Reflection</classname>), which in
            turn generates a list of all possible method signatures to provide to the server class.
        </para>

        <para>
            To reduce this performance hit somewhat, <classname>Zend_XmlRpc_Server_Cache</classname>
            can be used to cache the server definition between requests. When
            combined with <methodname>__autoload()</methodname>, this can greatly increase
            performance.
        </para>

        <para>
            An sample usage follows:
        </para>

        <programlisting language="php"><![CDATA[
function __autoload($class)
{
    Zend_Loader::loadClass($class);
}

$cacheFile = dirname(__FILE__) . '/xmlrpc.cache';
$server = new Zend_XmlRpc_Server();

if (!Zend_XmlRpc_Server_Cache::get($cacheFile, $server)) {
    require_once 'My/Services/Glue.php';
    require_once 'My/Services/Paste.php';
    require_once 'My/Services/Tape.php';

    $server->setClass('My_Services_Glue', 'glue');   // glue. namespace
    $server->setClass('My_Services_Paste', 'paste'); // paste. namespace
    $server->setClass('My_Services_Tape', 'tape');   // tape. namespace

    Zend_XmlRpc_Server_Cache::save($cacheFile, $server);
}

echo $server->handle();
]]></programlisting>

        <para>
            The above example attempts to retrieve a server definition from
            <property>xmlrpc.cache</property> in the same directory as the script. If unsuccessful,
            it loads the service classes it needs, attaches them to the server
            instance, and then attempts to create a new cache file with the
            server definition.
        </para>
    </sect2>

    <sect2 id="zend.xmlrpc.server.use">
        <title>Usage Examples</title>

        <para>
            Below are several usage examples, showing the full spectrum of
            options available to developers. Usage examples will each build
            on the previous example provided.
        </para>

        <example id="zend.xmlrpc.server.use.attach-function">
            <title>Basic Usage</title>

            <para>
                The example below attaches a function as a dispatchable <acronym>XML-RPC</acronym>
                method and handles incoming calls.
            </para>

            <programlisting language="php"><![CDATA[
/**
 * Return the MD5 sum of a value
 *
 * @param string $value Value to md5sum
 * @return string MD5 sum of value
 */
function md5Value($value)
{
    return md5($value);
}

$server = new Zend_XmlRpc_Server();
$server->addFunction('md5Value');
echo $server->handle();
]]></programlisting>
        </example>

        <example id="zend.xmlrpc.server.use.attach-class">
            <title>Attaching a class</title>

            <para>
                The example below illustrates attaching a class' public methods
                as dispatchable <acronym>XML-RPC</acronym> methods.
            </para>

            <programlisting language="php"><![CDATA[
require_once 'Services/Comb.php';

$server = new Zend_XmlRpc_Server();
$server->setClass('Services_Comb');
echo $server->handle();
]]></programlisting>
        </example>

        <example id="zend.xmlrpc.server.use.attach-class-with-arguments">
            <title>Attaching a class with arguments</title>

            <para>
                The following example illustrates how to attach a class' public
                methods and passing arguments to its methods. This can be used to specify certain
                defaults when registering service classes.
            </para>

            <programlisting language="php"><![CDATA[
class Services_PricingService
{
    /**
     * Calculate current price of product with $productId
     *
     * @param ProductRepository $productRepository
     * @param PurchaseRepository $purchaseRepository
     * @param integer $productId
     */
    public function calculate(ProductRepository $productRepository,
                              PurchaseRepository $purchaseRepository,
                              $productId)
    {
        ...
    }
}

$server = new Zend_XmlRpc_Server();
$server->setClass('Services_PricingService', 'pricing', new ProductRepository(), new PurchaseRepository());
]]></programlisting>

            <para>
                The arguments passed at <methodname>setClass()</methodname> at server construction time are
                injected into the method call <command>pricing.calculate()</command> on remote invokation.
                In the example above, only the argument <code>$purchaseId</code> is expected from the client.
            </para>
        </example>

        <example id="zend.xmlrpc.server.use.attach-class-with-arguments-constructor">
            <title>Passing arguments only to constructor</title>

            <para>
                <classname>Zend_XmlRpc_Server</classname> allows to restrict argument passing to
                constructors only. This can be used for constructor dependency injection.
                To limit injection to constructors, call <methodname>sendArgumentsToAllMethods</methodname>
                and pass <code>false</code> as an argument. This disables the default behavior of all arguments
                being injected into the remote method. In the example below the instance of
                <classname>ProductRepository</classname> and <classname>PurchaseRepository</classname> is only
                injected into the constructor of <classname>Services_PricingService2</classname>.
            </para>

            <programlisting language="php"><![CDATA[
class Services_PricingService2
{
    /**
     * @param ProductRepository $productRepository
     * @param PurchaseRepository $purchaseRepository
     */
    public function __construct(ProductRepository $productRepository,
                                PurchaseRepository $purchaseRepository)
    {
        ...
    }

    /**
     * Calculate current price of product with $productId
     *
     * @param integer $productId
     * @return double
     */
    public function calculate($productId)
    {
        ...
    }
}

$server = new Zend_XmlRpc_Server();
$server->sendArgumentsToAllMethods(false);
$server->setClass('Services_PricingService2', 'pricing', new ProductRepository(), new PurchaseRepository());


]]></programlisting>
        </example>

        <example id="zend.xmlrpc.server.use.attach-instance">
            <title>Attaching a class instance</title>

            <para>
                <methodname>setClass()</methodname> allows to register a previously instantiated
                object at the server. Just pass an instance instead of the class name. Obviously
                passing arguments to the constructor is not possible with pre-instantiated
                objects.
            </para>
        </example>

        <example id="zend.xmlrpc.server.use.attach-several-classes-namespaces">
            <title>Attaching several classes using namespaces</title>

            <para>
                The example below illustrates attaching several classes, each
                with their own namespace.
            </para>

            <programlisting language="php"><![CDATA[
require_once 'Services/Comb.php';
require_once 'Services/Brush.php';
require_once 'Services/Pick.php';

$server = new Zend_XmlRpc_Server();
$server->setClass('Services_Comb', 'comb');   // methods called as comb.*
$server->setClass('Services_Brush', 'brush'); // methods called as brush.*
$server->setClass('Services_Pick', 'pick');   // methods called as pick.*
echo $server->handle();
]]></programlisting>
        </example>

        <example id="zend.xmlrpc.server.use.exceptions-faults">
            <title>Specifying exceptions to use as valid fault responses</title>

            <para>
                The example below allows any <classname>Services_Exception</classname>-derived
                class to report its code and message in the fault response.
            </para>

            <programlisting language="php"><![CDATA[
require_once 'Services/Exception.php';
require_once 'Services/Comb.php';
require_once 'Services/Brush.php';
require_once 'Services/Pick.php';

// Allow Services_Exceptions to report as fault responses
Zend_XmlRpc_Server_Fault::attachFaultException('Services_Exception');

$server = new Zend_XmlRpc_Server();
$server->setClass('Services_Comb', 'comb');   // methods called as comb.*
$server->setClass('Services_Brush', 'brush'); // methods called as brush.*
$server->setClass('Services_Pick', 'pick');   // methods called as pick.*
echo $server->handle();
]]></programlisting>
        </example>

        <example id="zend.xmlrpc.server.use.custom-request-object">
            <title>Utilizing custom request and response objects</title>

            <para>
                Some use cases require to utilize a custom request object.
                For example, <acronym>XML/RPC</acronym> is not bound to
                <acronym>HTTP</acronym> as a transfer protocol. It is possible to use
                other transfer protocols like <acronym>SSH</acronym> or telnet to send
                the request and response data over the wire. Another use case is
                authentication and authorization. In case of a different transfer
                protocol, one need to change the implementation to read request data.
            </para>

            <para>
                The example below instantiates a custom request object and
                passes it to the server to handle.
            </para>

            <programlisting language="php"><![CDATA[
require_once 'Services/Request.php';
require_once 'Services/Exception.php';
require_once 'Services/Comb.php';
require_once 'Services/Brush.php';
require_once 'Services/Pick.php';

// Allow Services_Exceptions to report as fault responses
Zend_XmlRpc_Server_Fault::attachFaultException('Services_Exception');

$server = new Zend_XmlRpc_Server();
$server->setClass('Services_Comb', 'comb');   // methods called as comb.*
$server->setClass('Services_Brush', 'brush'); // methods called as brush.*
$server->setClass('Services_Pick', 'pick');   // methods called as pick.*

// Create a request object
$request = new Services_Request();

echo $server->handle($request);
]]></programlisting>
        </example>

        <example id="zend.xmlrpc.server.use.custom-response-object">
            <title>Specifying a custom response class</title>

            <para>
                The example below illustrates specifying a custom response class
                for the returned response.
            </para>

            <programlisting language="php"><![CDATA[
require_once 'Services/Request.php';
require_once 'Services/Response.php';
require_once 'Services/Exception.php';
require_once 'Services/Comb.php';
require_once 'Services/Brush.php';
require_once 'Services/Pick.php';

// Allow Services_Exceptions to report as fault responses
Zend_XmlRpc_Server_Fault::attachFaultException('Services_Exception');

$server = new Zend_XmlRpc_Server();
$server->setClass('Services_Comb', 'comb');   // methods called as comb.*
$server->setClass('Services_Brush', 'brush'); // methods called as brush.*
$server->setClass('Services_Pick', 'pick');   // methods called as pick.*

// Create a request object
$request = new Services_Request();

// Utilize a custom response
$server->setResponseClass('Services_Response');

echo $server->handle($request);
]]></programlisting>
        </example>
    </sect2>

    <sect2 id="zend.xmlrpc.server.performance">
        <title>Performance optimization</title>

        <example id="zend.xmlrpc.server.performance.caching">
            <title>Cache server definitions between requests</title>

            <para>
                The example below illustrates caching server definitions
                between requests.
            </para>

            <programlisting language="php"><![CDATA[
// Specify a cache file
$cacheFile = dirname(__FILE__) . '/xmlrpc.cache';

// Allow Services_Exceptions to report as fault responses
Zend_XmlRpc_Server_Fault::attachFaultException('Services_Exception');

$server = new Zend_XmlRpc_Server();

// Attempt to retrieve server definition from cache
if (!Zend_XmlRpc_Server_Cache::get($cacheFile, $server)) {
    $server->setClass('Services_Comb', 'comb');   // methods called as comb.*
    $server->setClass('Services_Brush', 'brush'); // methods called as brush.*
    $server->setClass('Services_Pick', 'pick');   // methods called as pick.*

    // Save cache
    Zend_XmlRpc_Server_Cache::save($cacheFile, $server);
}

// Create a request object
$request = new Services_Request();

// Utilize a custom response
$server->setResponseClass('Services_Response');

echo $server->handle($request);
]]></programlisting>

            <note>
                The server cache file should be located outside the document root.
            </note>
        </example>

        <example id="zend.xmlrpc.server.performance.xmlgen">

            <title>Optimizing XML generation</title>

            <para>
                <classname>Zend_XmlRpc_Server</classname> uses
                <classname>DOMDocument</classname> of <acronym>PHP</acronym>
                extension <code>ext/dom</code> to generate it's
                <acronym>XML</acronym> output. While <code>ext/dom</code> is
                available on a lot of hosts it is is not exactly the fastest.
                Benchmarks have shown, that <classname>XMLWriter</classname>
                from <code>ext/xmlwriter</code> performs better.
            </para>

            <para>
                If <code>ext/xmlwriter</code> is available on your host, you can
                select a the <classname>XMLWriter</classname>-based generator
                to leaverage the performance differences.
            </para>

            <programlisting language="php"><![CDATA[
<?php
require_once 'Zend/XmlRpc/Server.php';
require_once 'Zend/XmlRpc/Generator/XMLWriter.php';

Zend_XmlRpc_Value::setGenerator(new Zend_XmlRpc_Generator_XMLWriter());

$server = new Zend_XmlRpc_Server();
...
]]></programlisting>

            <note>
                <title>Benchmark your application</title>

                <para>
                    Performance is determined by a lot of parameters and
                    benchmarks only apply for the specific test case. Differences
                    come from PHP version, installed extensions, webserver and
                    operating system just to name a few. Please make sure to
                    benchmark your application on your own and decide which
                    generator to use based on <emphasis>your</emphasis> numbers.
                </para>
            </note>

            <note>
                <title>Benchmark your client</title>

                <para>
                    This optimization makes sense for the client side too. Just
                    select the alternate <acronym>XML</acronym> generator before
                    doing any work with <classname>Zend_XmlRpc_Client</classname>.
                </para>
            </note>

        </example>
    </sect2>
</sect1>
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