Baixe PHPwith Java e outras Notas de estudo em PDF para Análise de Sistemas de Engenharia, somente na Docsity! By Harish Kamath This article copyright Melonfire 2000−2002. All rights reserved. Table of Contents Extending Yourself.............................................................................................................................................1 Getting Started....................................................................................................................................................2 Rank And File.....................................................................................................................................................3 A Custom Job......................................................................................................................................................5 Passing The Parcel..............................................................................................................................................7 An Exceptionally Clever Cow..........................................................................................................................10 Beanie Baby.......................................................................................................................................................12 Using PHP with Java i Rank And File Let's begin with a simple example to verify that everything is working as advertised. This script uses built−in Java methods to check for the existence of a particular file on your system and display its size. <?php $fp = new Java("java.io.File", "/home/john/test.txt"); if($fp−>exists()) { echo "The file ". $fp−>getAbsolutePath() . " is ". $fp−>length() . " bytes"; } else { echo "The file " . $fp−>getAbsolutePath() . " does not exist"; } ?> This is fairly simple, and should be clearly understandable to anyone who knows basic Java programming. The first line of the script instantiates an object of Java's File class, and stores it in the PHP variable $fp. $fp = new Java("java.io.File", "/home/john/test.txt"); In case you're wondering, it's possible to pass parameters to the class constructor by specifying them as arguments when creating the object. In the example above, the second argument to the class constructor contains the location of the file to be displayed. Once the object has been instantiated, it becomes possible to access the methods and properties of the Java class using regular OOP syntax. if($fp−>exists()) { echo "The file ". $fp−>getAbsolutePath() . " is ". $fp−>length() . " bytes"; } else { echo "The file " . $fp−>getAbsolutePath() . " does not exist"; } Rank And File 3 In this case, the exists(), getAbsolutePath() and length() methods are all methods of the File class; however, I've managed to use them in a PHP script by virtue of the Java connectivity built into PHP. Here's what the output of the script above looks like: The file /home/john/test.txt is 385 bytes Using PHP with Java Rank And File 4 A Custom Job Now, the example on the previous page used a built−in Java class to demonstrate PHP/Java connectivity. It's also possible to instantiate and use a custom Java class in a PHP script. I'll demonstrate this by encapsulating the functionality of the core File class in my own FileReader class. Here's the code for my custom class: import java.io.*; public class FileReader { public File LocalFile; // set file location public void loadFile(String FileName) { LocalFile = new File(FileName); } // return file size public long getFileSize() { return LocalFile.length(); } // check if file exists public boolean FileExists() { return LocalFile.exists(); } // return file path public String getFilePath() { return LocalFile.getAbsolutePath(); } } There's no rocket science here − this class is only a wrapper for core File class methods. However, it will serve to demonstrate the basics of using a custom Java class in a PHP script. Now, compile the class, copy the compiled code to your Java CLASSPATH, and write a script to use it. A Custom Job 5 } This class uses a Writer object for script communication; this Writer object is instantiated via the setWriter() class method. public void setWriter(Writer out) { this.out = out; } Next, the class method reverse() accepts a string, reverses it and returns it via the Writer object. public void reverse(String string) throws Exception { try { // reverse the string here char tempArray[] = new char[string.length()]; for (int i = 0; i < string.length(); i++) tempArray[i] = string.charAt(string.length() − i − 1); String reversedString = new String(tempArray); out.write(reversedString); // snip } } Compile this class, copy it to your Java CLASSPATH, and write a simple PHP script to access it. <?php // create an instance of the ReverseString object $obj = new Java("ReverseString"); // create an instance of the StringWriter object $writer = new Java("java.io.StringWriter"); $obj−>setWriter($writer); $obj−>reverse("The cow jumped over the moon"); Using PHP with Java Passing The Parcel 8 echo $writer−>toString(); $writer−>flush(); $writer−>close(); ?> In this case, I've instantiated two objects, one for the ReverseString class and the other for the StringWriter class. Next, I've passed the StringWriter object, as stored in the PHP object $writer, to the ReverseString class via the class' setWriter() method, and then used the reverse() method to reverse a string and return the result. Here's what the output looks like: noom eht revo depmuj woc ehT Using PHP with Java Passing The Parcel 9 An Exceptionally Clever Cow Next, let's look at exception handling. If you go back to the example on the previous page, you'll see that the Java class includes a couple of exception handlers, one for IOExceptions and one for everything else. Let's now modify the PHP script so that it includes some basic exception handling. <?php // create an instance of the ReverseString object $obj = new Java("ReverseString"); // create an instance of the StringWriter object $writer = new Java("java.io.StringWriter"); $obj−>setWriter($writer); $obj−>reverse("The cow jumped over the moon"); // get the last exception $e = java_last_exception_get(); if ($e) { // print error echo $e−>toString(); } else { echo $writer−>toString(); $writer−>flush(); $writer−>close(); } // clear the exception java_last_exception_clear(); ?> This version of the script uses two built−in PHP functions to check whether or not any exceptions were raised during the execution of the class methods. If any exceptions were raised, they would be stored in the $e PHP variable, and printed via a call to the toString() method. If you'd like to see how an exception is handled, modify the PHP script above to look like this: <?php // create an instance of the ReverseString object An Exceptionally Clever C... 10 <sup>o</sup> Fahrenheit."; } else if($units == "fahrenheit" &$temp != "") { // use the Fahrenheit functions $myClass−>setFahrenheit($temp); // print result echo $myClass−>getFahrenheit() , " <sup>o</sup> Fahrenheit is ", $myClass−>convertFahrenheitToCelsius($myClass−>getFahrenheit()) , " <sup>o</sup> Celsius."; } else { echo "Please enter a valid temperature and scale"; } } else { ?> <form action="<? echo $PHP_SELF; ?>" method="post"> <input type ="text" name="temp" size="4" maxlength="4"> <select name="units"> <option value="celsius">Celsius</option> <option value="fahrenheit">Fahrenheit</option> </select> <input type ="submit" name="submit" value="Convert"> </form> <? } ?> </body> </html> This script consists of two parts: the form which allows the user to select a temperature scale and enter a tempterature value, and the form processor which actually uses the Bean to perform the conversion and display the result. Here's what the form looks like: Using PHP with Java Beanie Baby 13 Once this form has been submitted, an object is instantiated from the Temperature class, and the information provided by the user is used to perform temperature conversion using the Bean methods described above. The result is then displayed to the user. Here's what the result looks like: Note that it's necessary to convert the type of the form variable $temp from string to integer in order to make it compatible with the arguments expected by the Bean − this data type conversion is one of the important issues you will face when accessing Java classes through PHP. And that's about it for the moment. In case you'd like to learn more, take a look at the following links: The PHP manual's Java pages, at http://www.php.net/manual/en/ref.java.php O'Reilly's PHP and Java tutorial on O'Reilly ONLamp.com, at http://www.onlamp.com/pub/a/php/2001/06/14/php_jav.html PHPBuilder's PHP and Java tutorial, at http://www.phpbuilder.com/columns/marknold20001221.php3 See you soon! Note: All examples in this article have been tested on Linux/i586 with JDK 1.3.0, Apache 1.3.20 and PHP 4.1.1. Examples are illustrative only, and are not meant for a production environment. Melonfire provides no warranties or support for the source code described in this article. YMMV! Using PHP with Java Beanie Baby 14