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 <reference id="ref.java">
  <title>PHP / Java Integration</title>
  <titleabbrev>Java</titleabbrev>
  <partintro>
   
   <section id="java.intro">
    &reftitle.intro;
    <para>
     There are two possible ways to bridge PHP and Java: you can either 
     <link linkend="java.servlet">integrate PHP into a Java Servlet
     environment</link>, which is the more stable and efficient solution,
     or integrate Java support into PHP. The former is provided by a SAPI
     module that interfaces with the Servlet server, the latter by this
     Java extension.
    </para>
    <para>
     The Java extension provides a simple and effective means for creating and
     invoking methods on Java objects from PHP. The JVM is created using JNI,
     and everything runs in-process.
    </para>
    &warn.experimental;
   </section>
   
   <section id="java.requirements">
    &reftitle.required;
    <para>
     You need a Java VM installed on your machine to use this extension.
    </para>
   </section>
   
   &reference.java.configure;

   &reference.java.ini;

   <section id="java.resources">
    &reftitle.resources;
    &no.resource;
   </section>

   <section id="java.constants">
    &reftitle.constants;
    &no.constants;
   </section>

   <section id="java.examples">
    &reftitle.examples;
    <para>
     <example>
      <title>Java Example</title>
      <programlisting role="php">
<![CDATA[
<?php
// get instance of Java class java.lang.System in PHP
$system = new Java('java.lang.System');

// demonstrate property access
echo 'Java version=' . $system->getProperty('java.version') . '<br />';
echo 'Java vendor=' . $system->getProperty('java.vendor') . '<br />';
echo 'OS=' . $system->getProperty('os.name') . ' ' .
             $system->getProperty('os.version') . ' on ' .
             $system->getProperty('os.arch') . ' <br />';

// java.util.Date example
$formatter = new Java('java.text.SimpleDateFormat',
                      "EEEE, MMMM dd, yyyy 'at' h:mm:ss a zzzz");

echo $formatter->format(new Java('java.util.Date'));
?>
]]>
      </programlisting>
     </example>
     <example>
      <title>AWT Example</title>
      <programlisting role="php">
<![CDATA[
<?php
// This example is only intended to be run as a CGI.

$frame  = new Java('java.awt.Frame', 'PHP');
$button = new Java('java.awt.Button', 'Hello Java World!');

$frame->add('North', $button);
$frame->validate();
$frame->pack();
$frame->visible = True;

$thread = new Java('java.lang.Thread');
$thread->sleep(10000);

$frame->dispose();
?>
]]>
      </programlisting>
     </example>

     Notes:

     <itemizedlist>
      <listitem>
       <simpara>
        <literal>new Java()</literal> will create an instance of a class if 
        a suitable constructor is available. If no parameters are passed and 
        the default constructor is useful as it provides access to classes 
        like <literal>java.lang.System</literal> which expose most of their 
        functionallity through static methods.
       </simpara>
      </listitem>
      <listitem>
       <simpara>
        Accessing a member of an instance will first look for bean properties
        then public fields. In other words, <literal>print $date.time</literal>
        will first attempt to be resolved as <literal>$date.getTime()</literal>,
        then as <literal>$date.time</literal>.
       </simpara>
      </listitem>
      <listitem>
       <simpara>
        Both static and instance members can be accessed on an object with
        the same syntax. Furthermore, if the java object is of type
        <literal>java.lang.Class</literal>, then static members of the class 
        (fields and methods) can be accessed.
       </simpara>
      </listitem>
      <listitem>
       <para>
        Exceptions raised result in PHP warnings, and &null; results. The
        warnings may be eliminated by prefixing the method call with an
        "@" sign. The following APIs may be used to retrieve and reset
        the last error:
        <itemizedlist>
         <listitem><simpara><function>java_last_exception_get</function></simpara></listitem>
         <listitem><simpara><function>java_last_exception_clear</function></simpara></listitem>
        </itemizedlist>
       </para>
      </listitem>
      <listitem>
       <simpara>
        Overload resolution is in general a hard problem given the
        differences in types between the two languages. The PHP Java
        extension employs a simple, but fairly effective, metric for
        determining which overload is the best match.
       </simpara>
       <simpara>
        Additionally, method names in PHP are not case sensitive, potentially
        increasing the number of overloads to select from.
       </simpara>
       <simpara>
        Once a method is selected, the parameters are coerced if necessary, 
        possibly with a loss of data (example: double precision floating point
        numbers will be converted to boolean).
        <!-- FIXME Why aren't java-doubles converted to PHP-floats? Is this
        correct? -->
       </simpara>
      </listitem>
      <listitem>
       <simpara>
        In the tradition of PHP, arrays and hashtables may pretty much
        be used interchangably. Note that hashtables in PHP may only be
        indexed by integers or strings; and that arrays of primitive types
        in Java can not be sparse. Also note that these constructs are
        passed by value, so may be expensive in terms of memory and time.
       </simpara>
      </listitem>
     </itemizedlist>
    </para>
   </section>
   
   <section id="java.servlet">
    <title>Java Servlet SAPI</title>
    <para>
     The Java Servlet SAPI builds upon the mechanism defined by the Java
     extension to enable the entire PHP processor to be run as a servlet.
     The primary advantage of this from a PHP perspective is that web servers
     which support servlets typically take great care in pooling and reusing
     JVMs. Build instructions for the Servlet SAPI module can be found in 
     <filename>php4/sapi/README</filename>.

     Notes:

     <itemizedlist>
      <listitem>
       <simpara>
        While this code is intended to be able to run on any servlet engine,
        it has only been tested on Apache's Jakarta/tomcat to date. Bug
        reports, success stories and/or patches required to get this code
        to run on other engines would be appreciated.
       </simpara>
      </listitem>
      <listitem>
       <simpara>
        PHP has a habit of changing the working directory. sapi/servlet will
        eventually change it back, but while PHP is running the servlet engine
        may not be able to load any classes from the CLASSPATH which are
        specified using a relative directory syntax, or find the work directory
        used for administration and JSP compilation tasks.
       </simpara>
      </listitem>
     </itemizedlist>
    </para>
   </section>
  </partintro>

&reference.java.functions;

 </reference>

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