php-doc-en/reference/sam/functions/SAM-Message-header.xml

<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.3 $ -->
<refentry id='function.SAM-Message-header'>
 <refnamediv>
  <refname>SAMMessage::header</refname>
  <refpurpose>
   The header properties of the message.
  </refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
  <para>
  The "header" property is a container for any system or user properties that area associated with the message.
  Properties may be assigned by the sender of a message to control the way the messaging systems handles it or
  may be assigned by the messaging system itself to tell the recipient extra information about the message or
  the way in which it has been handled.
  </para>
  <para>
  Some properties are understood by SAM in which case constants have been defined for them. The majority of properties
  however are ignored by the SAM implementation and simply passed through to the underlying messaging systems allowing
  the application to use messaging specific property names or to define its own "user" properties.
  </para>
  <para>
  The SAM defined properties are as follows:
  <informaltable>
    <tgroup cols="2">
      <thead>
        <row>
          <entry>Property name</entry>
          <entry>Possible values</entry>
        </row>
      </thead>
      <tbody>
        <row>
          <entry>SAM_MESSAGEID</entry>
          <entry>
           When a message is received this field contains the unique identifier of the message as allocated
           by the underlying messaging system. When sending a message this field is ignored.
          </entry>
        </row>
        <row>
          <entry>SAM_REPLY_TO</entry>
          <entry>
           A string providing the identity of the queue on to which responses to this message should be posted.
          </entry>
        </row>
        <row>
          <entry>SAM_TYPE</entry>
          <entry>
           <para>
           An indication of the type of message to be sent. The value may be SAM_TEXT indicating the contents of
           the message body is a text string, or SAM_BYTES indicating the contents of the message body are some
           application defined format.
           </para>
           <para>
           The way in which this property is used may depend on the underlying messaging server. For instance
           a messaging server that supports the JMS (Java Message Service) specification may interpret this value
           and send messages of type "jms_text" and "jms_bytes". In addition, if the SAM_TYPE property is set to
           SAM_TEXT the data provided for the message body is expected to be a UTF8 encoded string.
           </para>
          </entry>
        </row>
      </tbody>
    </tgroup>
  </informaltable>
  </para>
  <para>
   When setting the values of properties it is often useful to give a hint as to the format in which the property
   should be delivered to the messaging system.  By default property values are delivered as text and the
   following simple syntax may be used to set a value:
  </para>
  <para>
   <example>
    <title>Setting a text format property using the default syntax</title>
    <programlisting role="php">
<![CDATA[
<?php
   $msg = new SAMMessage();

   $msg->header->myPropertyName = 'textData';
?>
]]>
    </programlisting>
   </example>
  </para>
  <para>
   If it is desired to pass type information an alternative syntax may be used where the value and the
   type hint are passed in an associative array:
  </para>
  <para>
   <example>
    <title>Setting a text format property using a type hint</title>
    <programlisting role="php">
<![CDATA[
<?php
   $msg = new SAMMessage();

   $msg->header->myPropertyName = array('textData', SAM_STRING);
?>
]]>
    </programlisting>
   </example>
  </para>
  <para>
   When passing a type hint the type entry should be one of the SAM defined constant values as defined by the
   following table:
  <informaltable>
    <tgroup cols="2">
      <thead>
        <row>
          <entry>Constant</entry>
          <entry>Type description</entry>
        </row>
      </thead>
      <tbody>
        <row>
          <entry>SAM_BOOLEAN</entry>
          <entry>
           Any value passed will be interpreted as logical true or false. If the value cannot be interpreted
           as a PHP boolean value the value passed to the messaging system is undefined.
          </entry>
        </row>
        <row>
          <entry>SAM_BYTE</entry>
          <entry>
           An 8-bit signed integer value. SAM will attempt to convert the property value specified into a
           single byte value to pass to the messaging system. If a string value is passed an attempt will
           be made to interpret the string as a numeric value. If the numeric value cannot be expressed as
           an 8-bit signed binary value data may be lost in the conversion.
          </entry>
        </row>
        <row>
          <entry>SAM_DOUBLE</entry>
          <entry>
           A long floating point value. SAM will attempt to convert the property value specified into a
           floating point value with 15 digits of precision. If a string value is passed an attempt will
           be made to interpret the string as a numeric value. If the passed value cannot be expressed as
           a 15 digit floating point value data may be lost in the conversion.
          </entry>
        </row>
        <row>
          <entry>SAM_FLOAT</entry>
          <entry>
           A short floating point value. SAM will attempt to convert the property value specified into a
           floating point value with 7 digits of precision. If a string value is passed an attempt will
           be made to interpret the string as a numeric value. If the passed value cannot be expressed as
           a 7 digit floating point value data may be lost in the conversion.
          </entry>
        </row>
        <row>
          <entry>SAM_INT</entry>
          <entry>
           An 32-bit signed integer value. SAM will attempt to convert the property value specified into a
           32-bit value to pass to the messaging system. If a string value is passed an attempt will
           be made to interpret the string as a numeric value. If the numeric value cannot be expressed as
           an 32-bit signed binary value data may be lost in the conversion.
          </entry>
        </row>
        <row>
          <entry>SAM_LONG</entry>
          <entry>
           An 64-bit signed integer value. SAM will attempt to convert the property value specified into a
           64-bit value to pass to the messaging system. If a string value is passed an attempt will
           be made to interpret the string as a numeric value. If the numeric value cannot be expressed as
           an 64-bit signed binary value data may be lost in the conversion.
          </entry>
        </row>
        <row>
          <entry>SAM_STRING</entry>
          <entry>
           SAM will interpret the property value specified as a string and pass it to the messaging system
           accordingly.
          </entry>
        </row>
      </tbody>
    </tgroup>
  </informaltable>
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title>Setting properties as the sender of a message</title>
    <programlisting role="php">
<![CDATA[
<?php
   $msg = new SAMMessage('This is a test message');

   // defining SAM specific properties...
   $msg->header->SAM_REPLY_TO = 'queue://test/replyQueue';

   // defining arbitrary properties...
   //
   // a default string property
   $msg->header->myStringProp1 = 'a string property';
   // a string property with a type hint
   $msg->header->myStringProp2 = array('another string property', SAM_STRING);

   // a boolean property
   $msg->header->myBoolProp = array(FALSE, SAM_BOOL);

   // numeric format properties
   $msg->header->myIntProp = array(32768, SAM_INT);
   $msg->header->myLongProp = array(9876543, SAM_LONG);
   $msg->header->myByteProp1 = array(123, SAM_BYTE);
   $msg->header->myByteProp2 = array('12', SAM_BYTE);
   $msg->header->myFloatProp = array(3.141592, SAM_FLOAT);
   $msg->header->myDoubleProp = array(3.14159265358979, SAM_DOUBLE);
?>
]]>
    </programlisting>
   </example>
  </para>
  <para>
   <example>
    <title>Retreiving property values from a message</title>
    <programlisting role="php">
<![CDATA[
<?php

   // accessing an application specific property
   $intProp = $msg->header->'MyIntProp';

   // accessing a messaging system specific property
   $encoding = $msg->header->'JMS_IBM_Msgtype';

?>
]]>
    </programlisting>
   </example>
  </para>
 </refsect1>

</refentry>

<!-- Keep this comment at the end of the file
Local variables:
mode: sgml
sgml-omittag:t
sgml-shorttag:t
sgml-minimize-attributes:nil
sgml-always-quote-attributes:t
sgml-indent-step:1
sgml-indent-data:t
indent-tabs-mode:nil
sgml-parent-document:nil
sgml-default-dtd-file:"../../../../manual.ced"
sgml-exposed-tags:nil
sgml-local-catalogs:nil
sgml-local-ecat-files:nil
End:
vim600: syn=xml fen fdm=syntax fdl=2 si
vim: et tw=78 syn=sgml
vi: ts=1 sw=1
-->