Integrate PHP and Java Applications with Oracle WebLogic Server and Zend Server 5.0

Zend Server, a high-performance, enterprise-ready PHP stack, comes with a built-in "Java bridge" to connect PHP with JEE applications and services. Here's how it works.

Whether you're experienced in Java, or PHP, or both, the ability to integrate these two development environments together is a "best of both worlds" scenario for enterprise Web application developers. PHP is one of the most versatile environments for Web application development, with a wealth of extensions and add-on libraries freely available through the PECL and PEAR repositories and the Zend Framework. In the PHP environment, developers can easily perform tasks as diverse as accessing cloud services, programmatically generating PDFs and processing XML.

In the Java environment, Java developers get all the benefits of Java's security, multi-threading capability and full Unicode implementation. These benefits, together with development tools and frameworks like Java Server Pages (JSP), Enterprise JavaBeans (EJB), JavaServer Faces (JSF), Hibernate and Spring have made Java a very popular choice for application development.

So why not connect PHP with Java, and directly access Java methods and objects from within a PHP application? This is particularly handy if, say, you already have Java-based infrastructure in place and need to develop a Web interface around it. By accessing existing your Java architecture from PHP, you reduce code duplication and save time on porting and testing code; by using PHP to build the Web interface, you leverage PHP's ease of use, support for modern Web technologies and extensive add-on library.

Now, at first glance, getting PHP and Java to talk nice to each other might seem like an onerous task. However, there's an easy way to do it: Zend Server, a high-performance, enterprise-ready PHP stack that runs on both Windows and Linux and that comes with a built-in "Java bridge" to connect PHP with JEE applications and services. This article will tell you more, demonstrating just how simple it is to use Zend Server to connect PHP applications with Java classes deployed on Oracle WebLogic middleware.

Introducing the Zend Java Bridge

First up, a quick introduction. Zend Server is a ready-to-use PHP stack that makes it easy to develop and run PHP applications in both Windows and UNIX-based environments. It includes an updated version of PHP, support for a wide variety of database systems (including Oracle and MySQL), and a number of Zend-specific add-ons for improving PHP performance and diagnostics. It also comes with a built-in "Java bridge" that can be used to connect PHP applications with Java classes deployed on Oracle WebLogic middleware.

There are currently two versions of Zend Server available: a community edition and a commercial version. Both versions include the Zend Java Bridge, which allows easy integration of PHP and Java applications. This component is implemented as a daemon or background service, which instantiates its own Java Virtual Machine (JVM) and exposes an API for PHP developers to access this JVM. This API allows PHP developers to directly access Java objects and services, with the Zend Java Bridge "translating" requests and responses between the two languages. As you'll shortly see, the system is reasonably easy to configure with Zend Server's point-and-click interface, and is also quite developer-friendly.

The Zend Java Bridge offers some key advantages for enterprise or high-traffic environments:

• Single JVM instance: The Zend Java Bridge uses a single JVM for all PHP processes, resulting in a smaller memory footprint and more efficient operation.
• Loose coupling: The Zend Java Bridge is a component of Zend Server, and can be enabled or disabled without any impact on the rest of the system. Turning the component on or off is easy through Zend Server's Web-based configuration interface.
• Support and training: Each release of the Zend Java Bridge is tested and certified for use with PHP and other related tools. Developers and administrators can also access training and commercial support in deploying the Zend Java Bridge within their IT environment.

It's worth noting that the Zend Java Bridge is not the only available option. PHP's built-in support for XML and JSON formats means that even without the Zend Java Bridge, it's still possible to access Java resources exposed as Web services from PHP. PHP 4.x also included a Java extension that allowed Java classes to be instantiated directly from PHP, as well as a Java Servlet SAPI that allowed PHP to be integrated into a servlet environment.

Other open-source tools also exist to achieve the same result. For example, Quercus is a 100% Java implementation of PHP, while the PHP/Java Bridge is a Java Web application that allows two-way method invocation between PHP and Java using an XML-based protocol. Quercus and the PHP/Java Bridge are not discussed in this article; however, you can find more information on using the PHP/Java Bridge in this article by Gary Horen.

Installing and Configuring the Zend Java Bridge

For purposes of this article, I'll assume that you have a current version of Oracle WebLogic Server and JRE 1.5+, with all samples installed and the Samples domain active. In case you don't, you can download a version of Oracle WebLogic Server suitable for your development environment from the Oracle WebLogic homepage on OTN. Note that the code samples are not installed automatically; you must perform a custom installation to obtain these. The examples in this article were tested using Oracle WebLogic Server 11g (V10.3.2) with JDK 1.6 on Linux with Zend Server 5.0.1 and PHP 5.3.

I'll also assume that you have the latest version of Zend Server installed and working on a development system. In case you don't, you can download a current version; versions are available for Linux, Microsoft Windows, Mac OS X and IBM i. You'll find detailed instructions on how to install and configure Zend Server in the Zend Server Installation Guide, as well as in this OTN article.

Once Zend Server is successfully installed, you will be able to access it at the URL http://localhost:10081/ZendServer. The first time you access this URL, you will be asked to accept the software license agreement, and enter an administrator password and a license key. Remember that you can get a trial license key. In the absence of the license key, Zend Server will function in community mode, with many of its key features disabled.

Once you enter the requested information, you should see the server administration console, which provides a birds-eye view of current server status. Here's what it looks like:

On Windows systems, the Zend Server installation package includes the Zend Java Bridge and the installation routine will automatically detect the system JDK and install and activate the component. On Linux systems, the Zend Java Bridge will typically need to be downloaded and configured manually. So, navigate to the Server Setup -> Components page, and check if the Zend Java Bridge is installed and active.

If the "Status" of Zend Java Bridge is "ON" then it means Zend Java Bridge is installed. If the "Status" of Zend Java Bridge is "OFF" you can then activate it by clicking the "Turn on" link in "Action" column and restarting PHP. On some platforms you must first download and install the bridge. Subscribers to Oracle's Unbreakable Linux Network can install the zend-server-repo RPM, and then install the Zend Java Bridge with yum, as below:

shell> up2date zend-server-repo
shell> yum install php-5.3-java-bridge-zend-server

Users of Debian-based distributions can install the component with aptitude, as shown below:

In either case, the package manager will download and install the Zend Java Bridge to the /usr/local/zend/ directory hierarchy. Once the package has been installed, you will be prompted to enter the full path to the system's Java executable. In case you don't know the location of your system's JDK, you can safely use the JDK that ships with Oracle WebLogic Server. On Linux systems, you can change this path at a later date by executing the /usr/local/zend/bin/setup_jb.sh shell script.

If all goes well, the Zend Java Bridge will now start up, displaying a success message at the console. And if you navigate back to the Server Setup -> Components page, you should now see that the Zend Java Bridge is active. If this is not the case, you might need to start the Zend Java Bridge server daemon manually; the Zend Server Installation Guide has more information on how to accomplish this using the package setup and control scripts. Once the server daemon has started, you can turn on the Zend Java Bridge through the Server Setup -> Components page.

If, despite your best efforts, you're not able to activate the Zend Java Bridge, you can troubleshoot it further:

• Check that the Zend Java Bridge server daemon is running.
• Check that the JAR file required by the Java Bridge component (javamw.jar) is part of your Java CLASSPATH.
• Check that your Java CLASSPATH includes a correct version of the JRE.

Changes to Zend Java Bridge configuration can be accomplished by using the Server Setup -> Components -> Zend Java Bridge -> Directives option to display a list of available configuration options. Here's a list of available settings:

Among the things you can control: the server port on which the Java Bridge is listening for requests, the encoding used when transmitting data from PHP to Java, and whether or not Java objects should be converted to primitives. Unless you have a good reason to change them, leave these settings at their default values.

Accessing Built-In Java Classes with Zend Server

Once you've got all the pieces installed, it's time to take the Zend Java Bridge out for a spin. As noted earlier, the Zend Java Bridge provides an API for PHP developers to access Java classes from within a PHP script. To illustrate, consider the following Java class, which uses the java.util.GregorianCalendar class to perform simple date addition:

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.GregorianCalendar;

class MyClass
{
    public static void main(String[] args)
    {
        SimpleDateFormat sdf = new SimpleDateFormat("d MMM yyyy hh:mm aaa");

        // set calendar to 1 Jan 2010
        Calendar calendar = new GregorianCalendar(2010,Calendar.JANUARY,1);
        String date = sdf.format(calendar.getTime());
        System.out.println("Starting date is: " + date);

        // add 4 months 3 days
        System.out.println("Adding 4 months 3 days... ");
        calendar.add(Calendar.MONTH, 4);
        calendar.add(Calendar.DAY_OF_MONTH, 3);

        // print ending date value 
        date = sdf.format(calendar.getTime());
        System.out.println("Ending date is: " + date);
    }
}

Now, try doing the same thing with PHP, by using the java.util.GregorianCalendar class through the Zend Java Bridge:

<?php
// initialize calendar object
$cal = new Java("java.util.GregorianCalendar");
$cal->set(2010,$cal->JANUARY,1);

// initialize date object
$date = new Java("java.text.SimpleDateFormat", "d MMM yyyy hh:mm aaa");

// format and print starting date
echo "Starting date is: " . $date->format($cal->getTime()) . '<br/>';

// add 4 months 3 days
echo "Adding 4 months 3 days...<br/>";
$cal->add($cal->MONTH, 4);
$cal->add($cal->DAY_OF_MONTH, 3);

// format and print ending date
echo "Ending date is: " . $date->format($cal->getTime());
?>

Save this script to the Zend Server document root, which is usually /var/www/html on Oracle Enterprise Linux and Red Hat Linux, and C:\Program Files\Zend\Apache2\htdocs\ on Windows.

1. This script begins by initializing a new Java object, passing the object constructor the name of the Java class to instantiate - in this case, an instance of the java.util.GregorianCalendar object. This request is transmitted to the JVM via the Zend Java Bridge; the JVM then creates the GregorianCalendar object and returns it to the calling PHP script. The object's set() method is then used to initialize the calendar to a specific date and time.
2. Next, a second Java object is created, this time an instance of the java.text.SimpleDateFormat class, and the date format to use is passed to the SimpleDateFormat object constructor as an additional argument. The resulting object's format() method is then used to format the date and time returned by the GregorianCalendar object's getTime() method, and the result is printed to the display using PHP's echo statement.
3. To further demonstrate the use of Java class methods in a PHP script, the next few lines of code use the GregorianCalendar object's add() method to perform simple date addition - in this case, moving the calendar ahead by 4 months and 3 days - and then again printing the revised date and time by calling Java object methods.

Here's what the output looks like:

To better understand how a request for a Java object is transferred from the PHP environment to the Java environment via the Zend Java Bridge, consider the following figure, which depicts the information flow between the two environments:

Accessing Custom Java Classes with Zend Server  

It isn't just built-in Java objects that you can access, either. The Zend Java Bridge also allows you to access user-defined Java classes from within a PHP script, so long as these are included in the Java classpath.

To see this in action, create a simple Java class as /tmp/Menu.java, as below:

public class Menu
{
  private static String[] myArray = {"eggs", "hamburgers", "tomato soup", "chicken pot pie", 
                                     "spaghetti bolognese", "ice cream", "chocolate chip cookies", 
                                     "grilled sole"};

  public static void main(String[] args)
  {
    Menu m = new Menu();
    System.out.println(m.getMenu());
  }

  public static String getMenu()
  {
    String menu = "Today's menu is: ";
    for (int i = 0; i < 3; i++) {
      int r = (int)(Math.random() * (myArray.length - 1));
      menu += myArray[r];
      if (i != 2) {
        menu += ", ";
      }
    }
    return menu;
  }
}

Nothing complicated here - the class exposes a getMenu() method, which randomly selects food items from an array and returns them to the caller. Save and compile this class using the Java compiler, as shown below:

Assuming that the compiled output is saved to /tmp/Menu.class, the next step is add the location of the compiled class to the Java classpath. You can alter the classpath used by the Zend Java Bridge by editing the corresponding configuration file, which can be found at /usr/local/zend/etc/watchdog-jb.ini file (Linux) or C:\Program Files\Zend\Zend Server\etc\java_bridge_server.ini (Windows). Here's an example of the classpath configuration:

After making the changes, restart Zend Server to have them take effect. Then, create and save the following PHP script to the Web server document root:

<?php
// initialize custom Java class and invoke class method
$m = new Java("Menu");
echo $m->getMenu();
?>

This script initializes an instance of the custom Java class, and then invokes the class' getMenu() method. When you request this script through a browser, you should see the following output:

In most cases, the Zend Java Bridge will correctly recognize Java data types and convert them to native PHP structures. Consider the following revision of the previous example, which revises the Menu.getMenu() method to return an array instead of a string:

public class Menu
{
  private static String[] myArray = {"eggs", "hamburgers", "tomato soup", "chicken pot pie", 
                                     "spaghetti bolognese", "ice cream", "chocolate chip cookies", 
                                     "grilled sole"};

  public static void main(String[] args)
  {
    Menu m = new Menu();
    System.out.println(m.getMenu());
  }

  public static String[] getMenu()
  {
    String[] menuArray;
    menuArray = new String[3];
    for (int i = 0; i < 3; i++) {
      int r = (int)(Math.random() * (myArray.length - 1));
      menuArray[i] = myArray[r];
    }
    return menuArray;
  }
}

Update the PHP script to display a dump of the return value:

<?php
// initialize custom Java class and invoke class method
$m = new Java("Menu");
print_r($m->getMenu());
?>

And here's what you'll see:

By default, the Zend Java Bridge converts Java objects to primitives. This behaviour can however be altered with the zend_jbridge.use_java_objects configuration directive in the Zend Server Web-based control panel, which can be toggled to return Java objects "as is" without first converting them to primitives.

However, it's important to note that the Zend Java Bridge will not perform dynamic data typing on your objects and values when passing them the other way, from PHP to Java. In general, if your input parameters are not correctly mapped to the data types expected by Java, the Zend Java Bridge will throw an exception. To avoid these kinds of exceptions, it's generally a good idea to explicitly specify your data types when passing data from PHP to Java. You'll find detailed examples of how to do this in the Zend Server Reference Manual, as well as in the next example.

In case things go wrong, remember that you can always use Zend Server's Code Tracing (Monitor -> Code Tracing) feature to trace the entire request and identify the source of an error. Server error logs are also useful for troubleshooting and debugging, and you can access these logs through the Monitor -> Logs tab of the Web-based control panel.

Accessing Enterprise JavaBeans with Zend Server  

In addition to allowing you to access custom Java classes, the Zend Java Bridge also makes it easy to access other resources, such as Enterprise JavaBeans, deployed on a Java application server. These beans can be accessed from a PHP script using the Java Naming and Directory Interface (JNDI).

To illustrate, consider that Oracle WebLogic Server comes with a number of sample beans that demonstrate different server capabilities. One such bean is the AccountHome bean, which provides an API to create bank accounts, deposit and withdraw funds, and retrieve current account balances. With JNDI at hand, it's a simple matter to access this bean from a PHP script via the Zend Java Bridge. Here's an example, which illustrates by accessing the deployed EJB on the Oracle WebLogic Server and using it to interactively create a new account and perform various account operations:

<html>
  <head></head>
  <body>
  <h2>Bank Account Administration</h2>
  <?php
  if (isset($_POST['submit'])) {
    // set environment
    $config = array(
       'java.naming.factory.initial' => 'weblogic.jndi.WLInitialContextFactory',
       'java.naming.provider.url' => 't3://localhost:7001'
    );

    // initialize Java class
    $context = new Java('javax.naming.InitialContext', $config);

    // look up bean using JNDI name
    $obj = $context->lookup('ejb20-beanManaged-AccountHome');

    // assume input is properly filtered and validated
    $acc = (int) $_POST['acc'];
    $amt = (int) $_POST['amt'];
    $op = $_POST['op'];

    // check if requested account is present
    // if not, create and set opening balance of $0
    try {
      $account = $obj->findByPrimaryKey($acc);
      $messages[] = 'Found account #' . $acc . ' with current balance: $' . $account->balance();
    } catch (Exception $e) {
      $account = $obj->create($acc, 0);
      $messages[] = 'Account not present, creating new account #' . $acc . ' with opening balance: $0';
    }


    // check requested operation
    // withdraw or deposit funds as required
    switch ($op) {
      case 'D':
        $account->deposit($amt);
        $messages[] = 'Added: $' . $amt;
        break;
      case 'W':
        $account->withdraw($amt);
        $messages[] = 'Subtracted: $' . $amt;
        break;
    }

    // get new account balance
    $messages[] = 'New account balance is: $' . $account->balance();

    // print messages
    echo 'MESSAGES <br/>';
    echo implode($messages, '<br/>');
  }
  ?>
  <form method="post">
    <select name="op">
      <option value="D">Deposit</option>
      <option value="W">Withdraw</option>
    </select>
     amount:
    <input type="text" size="4" name="amt" />
     to/from account #:
    <input type="text" size="10" name="acc" />
    <input type="submit" name="submit" value="Go!" />
    </form>
  </body>
</html>

This script generates a Web form asking the user to enter an account number and the amount of money to deposit or withdraw into that account. Once the form is submitted, the script creates a new initial context by specifying the WebLogic implementation and provider URL. This context is used to look up the JNDI name for the bean, and return it as an object. It now becomes possible to access the methods of this object as though they were native PHP methods, with the Zend Java Bridge taking care of transmitting arguments and return values between the PHP script and Oracle WebLogic Server.

The first step, once the bean becomes available to PHP, is to look up the specified account number to see if it exists in the database. All account data is maintained in a database; this database is automatically started when you activate the Oracle WebLogic Server Samples domain. The bean exposes a findByPrimaryKey() method which can be used to look up the account and return an object representing it; if this method fails, indicating that the requested account does not exist, the script uses the bean's create() method to create a new account with the specified number and set its opening balance to 0.

The next step is to add or remove funds from the account, depending on the operation selected by the user. This is accomplished with the account object's withdraw() and deposit() methods, both of which are called by the PHP script with the amount specified as a method argument. The revised account balance can now be obtained with a call to the account object's balance() method, and the result is printed to the output device with PHP's echo statement.

This example also demonstrates how to handle data types when passing data from a PHP script to a Java object via the Zend Java Bridge. When the form values in this example are submitted to the PHP script, they are submitted as string data. However, the bean's create(), withdraw() and deposit() methods all expect integer values, and so it is necessary to cast the account number and amount as integers before using them in bean methods.

Here's a figure that depicts how the request is handled by the Zend Java Bridge:

Before you can run this example, you must ensure that the WebLogic class files, particularly weblogic.jar, are present in the classpath specified in the Zend Java Bridge configuration file. If this is not the case, make the changes to the classpath and restart Zend Server for your changes to take effect.

Here's an example of the initial form:

And here's an example of the data presented after performing some account operations:

Understanding Performance Issues and Best Practices

The Zend Java Bridge is an extremely robust implementation, using a single JVM instance to reduce overhead and thereby produce more efficient system architecture. This centralized implementation also makes debugging easier, and allows developers to focus their performance optimizations efforts on a single point.

Additionally, the same tuning parameters that are available to any Java application can also be applied to the Zend Java Bridge. For example, unused memory from the single JVM instance is automatically handled by Java's regular garbage collection mechanism.

To optimize Zend Java Bridge performance, the Zend team suggests monitoring the performance of the Zend Java Bridge under different usage scenarios and adjusting the number of worker threads upwards or downwards based on concurrent load analysis. Alternatively, if available use cases exist to predict the likely load on the server, it's also possible to aggressively configure the Zend Java Bridge for a high level of load, to ensure that performance meets expectations. The number of worker threads can be set in the Zend Java Bridge configuration file, using the zend.javamw.threads variable. There are several monitoring tools out in the market e.g jconsole that can help you in monitoring and managing the JVM.

Conclusion

As the examples in this article demonstrate, Zend Server comes with a high-performance, loosely-coupled JVM implementation, a robust and secure PHP stack, built-in caching and job queuing, and browser-based administration. All of these features make it a good choice for developers looking to integrate PHP applications with existing Oracle WebLogic Server environments.

Vikram Vaswani is the founder and CEO of Melonfire, a consultancy firm with special expertise in open-source tools and technologies. He is the author of four books on PHP and MySQL, and a frequent contributor to Zend Developer Zone, IBM DeveloperWorks, and other community sites.

Copyright Zend Technologies, 2010.