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mozilla/js/rhino/org is now distributed between mozilla/js/rhino/src and mozilla/js/rhino/toolsrc. The build.xml has been split in three. Docs now live in the project directory. These changes mean that the cvs directories mirror the distribution and thus a distribution will build the same way as a cvs build.
279 lines
17 KiB
HTML
279 lines
17 KiB
HTML
<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<meta name="Generator" content="Microsoft Word 97">
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<meta name="GENERATOR" content="Mozilla/4.7 [en] (WinNT; U) [Netscape]">
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<title>Embedding ‘Scripting Host’ in Business Applications</title>
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</head>
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<body link="#0000FF">
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<b><font face="Arial"><font size=-1>Embedding
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‘Scripting Host’ in Business Applications</font></font></b>
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<p><b><font face="Arial"><font size=-1>Madhukumar Seshadri, <a href="http://www.cognizant.com)/">www.cognizant.com</a></font></font></b>
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<br>
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<br>
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<p><font face="Arial"><font size=-1>With web browsers, continuing to rule
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the human interface for applications, creating value by being ubiquitous,
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few adoptions of rich technology that’s getting brewed underneath, will
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help designing business applications even though most of the current ones
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are made with bird’s eye of the underlying technologies.</font></font>
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<p><font face="Arial"><font size=-1>JavaScript is a scripting language
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invented and developed by Netscape. The language was primarily designed
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for creating lightweight programming for web browser extensions by exposing
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the Document Object Model of an HTML page to the scripts. JavaScript is
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becoming object oriented and getting adopted for server-side scripting.</font></font>
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<p><font face="Arial"><font size=-1>JavaScript is also becoming a standard
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in the scripting world as Netscape is working closely with ECMA (European
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Computer Manufacturers Association) to make it as a standard scripting
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language for the script world. The standards are published as ECMA Script.</font></font>
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<p><font face="Arial"><font size=-1>JavaScript originally designed for
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exposing the DOM (Document Object Model) standardized by World Wide Web
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consortium (W3C), to help web page designers to control and manipulate
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the pages dynamically. ‘JavaScript’ engines were embedded in the browsers
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and they execute those portions of the code embedded in the HTML pages.</font></font>
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<p><font face="Arial"><font size=-1>In short, JavaScript engine embedded
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in the browser allowed extensions or manipulations for DOM Object run time
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for the HTML page by executing the ‘scripts’ associated with them. In other
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words, browser exposes its DOM object for the page to scripts for extensions
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and dynamic manipulations of the same, using a language that the script
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interpreter understands.</font></font>
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<p><font face="Arial"><font size=-1>Can I do the same for my application
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by exposing my custom business objects written in my middle-tier? Can I
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allow user to my write JavaScript extensions for my objects and also be
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host for executing those scripts?</font></font>
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<p><font face="Arial"><font size=-1>JavaScript host runs times are available
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as binaries written in major languages. Check out <a href="http://www.mozilla.org/js">www.mozilla.org/js</a>.
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Spider Monkey and Rhino are open source JavaScripting engines available
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from mozilla.</font></font>
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<p><font face="Arial"><font size=-1>Microsoft implementation of ECMA Script
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(ECMA Script is based on core JavaScript, created by Netscape) is called
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JScript. Microsoft binaries of jscript engine can be downloaded from http://msdn.microsoft.com/scripting/.</font></font>
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<p><font face="Arial"><font size=-1>This document doesn’t explain the JavaScript
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language in detail but explains how these scripting engines can be used
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as host to expose business objects in the middle-tier and how the user
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of these applications can extend it if needed using JavaScript.</font></font>
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<p><font face="Arial"><font size=-1>The scripting engine Rhino (<a href="http://www.mozilla.org/js)">www.mozilla.org/rhino)</a>,
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a javascript engine purely written in Java is one that I am going to use
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for the testing the above.</font></font>
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<p><font face="Arial"><font size=-1>Let us set some simple goals,</font></font>
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<ul>
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<li>
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<font face="Arial"><font size=-1>Execute a plain ‘JavaScript’ code and
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use static Java object</font></font></li>
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<li>
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<font face="Arial"><font size=-1>Instantiate external objects (written
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in Java) from the script and use them within the script</font></font></li>
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</ul>
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<br>
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<br>
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<p><font face="Arial"><font size=-1>Let us write a simple Javscript to
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test the above set goals,</font></font>
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<p><font face="Arial"><font size=-1><b>Fig 1</b> – jshosttest.js</font></font>
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<p><b><i><font face="Arial"><font size=-1>/* Test 1 */</font></font></i></b>
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<br><b><i><font face="Arial"><font size=-1>/* Use a static Java Object
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in the script */</font></font></i></b>
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<p><font face="Arial"><font size=-1>function test1() {</font></font>
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<br><font face="Arial"><font size=-1> var str;</font></font>
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<br><font face="Arial"><font size=-1> str = '"Hello World";</font></font>
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<br><font face="Arial"><font size=-1> return str;</font></font>
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<br><font face="Arial"><font size=-1>}</font></font>
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<p><font face="Arial"><font size=-1>var str = test1( );</font></font>
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<br><font face="Arial"><font size=-1>//out is expected to be Java Object
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exposed to the script scope</font></font>
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<br><font face="Arial"><font size=-1>out.println ("JavaScript - Test 1
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- " + str);</font></font>
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<p><b><i><font face="Arial"><font size=-1>/* Test 2 */</font></font></i></b>
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<p><b><i><font face="Arial"><font size=-1>/* Instantiate a Javaobject for
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this scope and use it */</font></font></i></b>
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<p><font face="Arial"><font size=-1>function test2(){</font></font>
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<br><font face="Arial"><font size=-1> // create a Java
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string buffer object from JavaScript and use its java instance</font></font>
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<br><font face="Arial"><font size=-1> // This uses an
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another Java object created for creating new objects within Java and</font></font>
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<br><font face="Arial"><font size=-1> // brings the same
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for JavaScript execution scope</font></font>
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<br><font face="Arial"><font size=-1> // Refer _create.java
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for more information</font></font>
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<br><font face="Arial"><font size=-1> create.getInstance("java.lang.StringBuffer","buffer");</font></font>
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<br><font face="Arial"><font size=-1> //JavaScript refers
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the java object instance as ‘buffer’</font></font>
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<br><font face="Arial"><font size=-1> out.println(buffer.toString());</font></font>
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<br> <font face="Arial"><font size=-1>buffer.append("I
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am a javaobject dynamically created and executed in JavaScript");</font></font>
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<br> <font face="Arial"><font size=-1>return buffer.toString();</font></font>
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<br><font face="Arial"><font size=-1>}</font></font>
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<p><font face="Arial"><font size=-1>var str = test2();</font></font>
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<br><font face="Arial"><font size=-1>out.println("From JavaScript - Test
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2 " + str);</font></font>
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<p><font face="Arial"><font size=-1>Let us write a simple Javahost Object
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using the Rhino engine to execute the above script,</font></font>
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<p><b><font face="Arial"><font size=-1>Fig 2.1 - JSHost.java</font></font></b>
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<p><font face="Arial"><font size=-1>/**</font></font>
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<br><font face="Arial"><font size=-1>* @author Madhukumar Seshadri</font></font>
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<br><font face="Arial"><font size=-1>* @version</font></font>
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<br><font face="Arial"><font size=-1>*/</font></font>
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<p><font face="Arial"><font size=-1>import org.mozilla.javascript.*;</font></font>
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<br><font face="Arial"><font size=-1>import java.io.*;</font></font>
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<br><font face="Arial"><font size=-1>import java.lang.*;</font></font>
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<br><i><font face="Arial"><font size=-1>// import com.xxx.xxx.*;</font></font></i>
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<p><font face="Arial"><font size=-1>public class JSHost extends Object
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{</font></font>
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<br><font face="Arial"><font size=-1> /** Creates new
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JSHost */</font></font>
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<br><font face="Arial"><font size=-1> public JSHost()
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{</font></font>
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<br><font face="Arial"><font size=-1> }</font></font>
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<p><i><font face="Arial"><font size=-1> /*** Executes
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.js file ***/</font></font></i>
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<br><font face="Arial"><font size=-1> public Object executeJS
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(String jsfname){</font></font>
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<br><font face="Arial"><font size=-1> //You can also
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use evaluateReader</font></font>
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<br><font face="Arial"><font size=-1> File fp = new File(jsfname);</font></font>
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<br><font face="Arial"><font size=-1> String str_buff
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=null;</font></font>
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<br><font face="Arial"><font size=-1> try {</font></font>
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<br><font face="Arial"><font size=-1>
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FileReader fr = new FileReader(jsfname);</font></font>
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<br><font face="Arial"><font size=-1>
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int length = (int) fp.length();</font></font>
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<br><font face="Arial"><font size=-1>
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char cbuff[] = new char[(char)length];</font></font>
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<br><font face="Arial"><font size=-1>
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fr.read(cbuff);</font></font>
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<br><font face="Arial"><font size=-1>
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str_buff = new String(cbuff);</font></font>
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<br><font face="Arial"><font size=-1> } catch(Exception
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e) {</font></font>
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<br><font face="Arial"><font size=-1>
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e.printStackTrace();</font></font>
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<br><font face="Arial"><font size=-1> }</font></font>
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<p><font face="Arial"><font size=-1> //Execute the .js
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file content</font></font>
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<br><font face="Arial"><font size=-1> return executeJSSource(str_buff);</font></font>
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<br><font face="Arial"><font size=-1>}</font></font>
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<p><i><font face="Arial"><font size=-1>/*** Executes javascript source
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***/</font></font></i>
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<br><font face="Arial"><font size=-1>public Object executeJSSource (String
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jsbuff){</font></font>
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<br><font face="Arial"><font size=-1>Object any=null;</font></font>
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<br><font face="Arial"><font size=-1>try{</font></font>
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<br><i><font face="Arial"><font size=-1>//Enter the Context</font></font></i>
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<br><font face="Arial"><font size=-1><i>// Refer </i><u><font color="#0000FF">http://www.mozilla.org/js/rhino/tutorial.html</font></u></font></font>
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<br><font face="Arial"><font size=-1>Context context = Context.enter();</font></font>
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<br><i><font face="Arial"><font size=-1>// Get the execution scope</font></font></i>
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<br><font face="Arial"><font size=-1>Scriptable scope = context.initStandardObjects(null);</font></font>
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<p><i><font face="Arial"><font size=-1>//----------- For Test 1 - Get System.out
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in scope</font></font></i>
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<br><font face="Arial"><font size=-1>//Scriptable jObj1 = Context.toObject(System.out,
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scope);</font></font>
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<br><font face="Arial"><font size=-1>scope.put("out", scope, jObj1);</font></font>
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<p><i><font face="Arial"><font size=-1>//------------ For Test 2 - Instantiate
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Create Object and get that in scope</font></font></i>
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<br><i><font face="Arial"><font size=-1>//Allow JScript to create Java
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Objects</font></font></i>
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<br><i><font face="Arial"><font size=-1>//Bring the _create object to context</font></font></i>
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<br><font face="Arial"><font size=-1>_create create = new _create( );</font></font>
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<br><i><font face="Arial"><font size=-1>//Register this context and scope
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to this create object instance</font></font></i>
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<br><font face="Arial"><font size=-1>create.registerContext(context,scope);</font></font>
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<br><font face="Arial"><font size=-1>//Scriptable jObj2 = Context.toObject(_create,
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scope);</font></font>
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<br><font face="Arial"><font size=-1>scope.put("create",scope,create);</font></font>
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<br><i><font face="Arial"><font size=-1>//Evaluate (or execute js)</font></font></i>
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<br><font face="Arial"><font size=-1><i>//Refer </i><u><font color="#0000FF">http://www.mozilla.org/js/rhino/tutorial.html</font></u></font></font>
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<br><font face="Arial"><font size=-1>any = context.evaluateString(scope,
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jsbuff, "", 1, null);</font></font>
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<br><i><font face="Arial"><font size=-1>//Exit the Context</font></font></i>
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<br><font face="Arial"><font size=-1>context.exit( );</font></font>
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<br><font face="Arial"><font size=-1>}</font></font>
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<p><font face="Arial"><font size=-1>catch ( JavaScriptException jse) {</font></font>
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<br><font face="Arial"><font size=-1>jse.printStackTrace();</font></font>
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<br><font face="Arial"><font size=-1>}</font></font>
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<p><font face="Arial"><font size=-1>return any;</font></font>
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<p><font face="Arial"><font size=-1>}</font></font>
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<p><font face="Arial"><font size=-1>}</font></font>
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<br>
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<br>
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<p><font face="Arial"><font size=-1>Let us write a class for creating new
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Java objects and bringing them to this script execution scope,</font></font>
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<p><b><font face="Arial"><font size=-1>Fig 2.2 – _create.java</font></font></b>
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<p><i><font face="Arial"><font size=-1>/**</font></font></i>
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<p><i><font face="Arial"><font size=-1>* @author Madhukumar</font></font></i>
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<p><i><font face="Arial"><font size=-1>*/</font></font></i>
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<p><font face="Arial"><font size=-1>import java.lang.Class;</font></font>
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<p><font face="Arial"><font size=-1>import org.mozilla.javascript.*;</font></font>
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<p><font face="Arial"><font size=-1>public class _create extends Object
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{</font></font>
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<p><font face="Arial"><font size=-1>static Context ptr = null;</font></font>
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<p><font face="Arial"><font size=-1>static Scriptable scope =null;</font></font>
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<p><font face="Arial"><font size=-1>public _create () { }</font></font>
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<p><font face="Arial"><font size=-1>public void registerContext(Context
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cptr, Scriptable sc){</font></font>
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<p><font face="Arial"><font size=-1>ptr = cptr;</font></font>
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<p><font face="Arial"><font size=-1>scope = sc;</font></font>
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<p><font face="Arial"><font size=-1>}</font></font>
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<p><font face="Arial"><font size=-1>public void getInstance(String classname,String
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jsclassname) {</font></font>
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<p><font face="Arial"><font size=-1>Object any=null;</font></font>
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<p><font face="Arial"><font size=-1>try {</font></font>
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<p><font face="Arial"><font size=-1>Class thisclass = Class.forName(classname);</font></font>
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<p><font face="Arial"><font size=-1>any = thisclass.newInstance();</font></font>
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<p><font face="Arial"><font size=-1>}</font></font>
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<p><font face="Arial"><font size=-1>catch(Exception e){</font></font>
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<p><font face="Arial"><font size=-1>e.printStackTrace();</font></font>
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<p><font face="Arial"><font size=-1>}</font></font>
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<p><font face="Arial"><font size=-1>if( ptr != null) {</font></font>
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<p><font face="Arial"><font size=-1>if (scope !=null) {</font></font>
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<p><i><font face="Arial"><font size=-1>//register created object for this
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execution scope</font></font></i>
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<p><font face="Arial"><font size=-1>scope.put(jsclassname,scope,any);</font></font>
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<p><font face="Arial"><font size=-1>}</font></font>
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<p><font face="Arial"><font size=-1>}</font></font>
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<p><font face="Arial"><font size=-1>}</font></font>
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<p><font face="Arial"><font size=-1>}</font></font>
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<br>
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<br>
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<p><font face="Arial"><font size=-1>It is time to test the code, so let
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us write a small object that will use the JSHost object,</font></font>
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<p><b><font face="Arial"><font size=-1>Fig 3 - JSHosttest.java</font></font></b>
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<p><font face="Arial"><font size=-1>/**</font></font>
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<p><font face="Arial"><font size=-1>* @author Madhukumar</font></font>
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<p><font face="Arial"><font size=-1>* @version</font></font>
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<p><font face="Arial"><font size=-1>*/</font></font>
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<p><font face="Arial"><font size=-1>public class JSHosttest extends Object
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{</font></font>
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<p><font face="Arial"><font size=-1>/** Creates new JSHostTest*/</font></font>
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<p><font face="Arial"><font size=-1>public JSHosttest() {</font></font>
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<p><font face="Arial"><font size=-1>}</font></font>
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<p><font face="Arial"><font size=-1>public static void main (String args[]){</font></font>
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<p><font face="Arial"><font size=-1>if (args.length < 1) {</font></font>
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<p><font face="Arial"><font size=-1>System.out.println("Usage - Java JSHosttest.class
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<js source file>");</font></font>
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<p><font face="Arial"><font size=-1>return;</font></font>
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<p><font face="Arial"><font size=-1>}</font></font>
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<p><font face="Arial"><font size=-1>JSHost jsh = new JSHost();</font></font>
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<p><font face="Arial"><font size=-1>System.out.println("Executing JavaScript
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file - " + args[0]);</font></font>
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<p><font face="Arial"><font size=-1>Object result = jsh.executeJS(args[0]);</font></font>
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<p><font face="Arial"><font size=-1>if (result instanceof String){</font></font>
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<p><font face="Arial"><font size=-1>System.out.println("Results - " + result);</font></font>
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<p><font face="Arial"><font size=-1>}</font></font>
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<p><font face="Arial"><font size=-1>}</font></font>
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<p><font face="Arial"><font size=-1>}</font></font>
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<br>
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<br>
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<p><font face="Arial"><font size=-1>For more explanations on the code execution,
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please refer embedding tutorial <a href="http://www.mozilla.org/js/rhino/tutorial.html">http://www.mozilla.org/js/rhino/tutorial.html</a>
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and for all documentation and examples on Rhino visit <a href="http://www.mozilla.org/rhino/doc.html">http://www.mozilla.org/rhino/doc.html</a>.</font></font>
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<br>
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<br>
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<br>
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<br>
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<br>
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<br>
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</body>
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</html>
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