faq/scripting.html - gerrit/www.eclipse.org/birt - Git at Google

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 <p class="head">BIRT FAQ</p>
 <p class="subhead">Scripting</p>

 <h1>Aggregates (Totals)</h1>

 <h2>Q: What aggregate operations does BIRT support?</div> </h2>
 <p>
 "Aggregate" is the fancy word to describe totals. BIRT suppots a wide variety
 of totals: sum, running sum, average, minimum, maximum, count, count distinct,
 and many more. See the
 <a href="../ref/ROM_Scripting_SPEC.pdf">ROM Scripting Specification</a>
 for details.

 <h2>Q: Does BIRT support look-ahead (two-pass) aggregates?</div> </h2>
 <p>
 Look-ahead aggregates are of the form "this value as a percentage of an overall
 total". For example, a customer's sales as a percentage of overall sales for a
 sales rep, sales region, and so on. These are often called two-pass aggregates
 becuase they require the reporting tool to make one pass over the data to compute
 totals, then another pass to compute the percentages for each record.
 <p>
 BIRT does provide support for such totals. Just enter the calculation and BIRT
 figures out the right way to compute it:
 <pre class="code-block">Total.percent( row.Sales, Total.sum( row.Sales ) )
 </pre>

 <h2>Q: Is an example of simple calculations like count,
 sum, max, min?</div> </h2>
 <p>TBD</div>

 <h2>Q: Does BIRT support page totals?</div> </h2>
 <p>
 Some reports may want to display totals over data
 displayed on a page of the report. For example, a count of employees on that
 page, and sum of their salaries.
 <p>
 BIRT release 1.0 delivers reports as a single web page, so the question is moot
 for this release. BIRT reports are paginated when printed as PDF, but BIRT uses
 Apache FOP to do the formatting, and so BIRT does not have visiblity into the
 pagination.
 <p>
 That said, if there is sufficient interest, the BIRT team will consider page
 totals for a future release.

 <h1>Scripting</h1>

 <h2>Q: Can I add custom logic (scripting) to my report?</div> </h2>
 <p>
 Yes. BIRT uses JavaScript (also known as EcmaScript) for expressions,
 business logic, and integration with application-specific Java classes.

 <h2>Q: JavaScript? Does that mean my code runs in the browser?</div> </h2>
 <p>
 When someone hears "JavaScript" the
 assumption is that JS is being used to script a browser. While browser
 scripting is a key use of JS, the language itself (when separated from the
 browser DOM framework) is a nice little tool that is well integrated
 with Java. Our goal in using JS is that a report developer can very quickly
 write business logic. JS tends to be easier to learn than Java for people
 who are accustomed to Visual Basic, SQL and similar scripting solutions.
 Because JS is well integrated with Java, it is easy to call from business
 logic into Java classes to do more advanced tasks, or if you prefer, to write
 your code using Java. Further, JS allows BIRT to support aggregate expression
 such as:</p>

 <pre class="code-block">sum( row.orderTotal )</pre>

 <p>This summarizes the orderTotal column over all rows. This makes aggregates
 look like other expressions, even though the BIRT report engine needs to
 "rewrite" them.

 <h2>Q: Where can I learn about JavaScript?</div> </h2>
 <p>
 JavaScript (also known as EcmaScript) is a popular language for browser scripting,
 and a wide range of books
 exist that describe JavaScript in that context. An excellent one is
 <a href="http://www.amazon.com/exec/obidos/ASIN/0596000480/qid=1110584202">
 JavaScript: the Definitive Guide</a> by David Flanagan, published by
 <a href="http://www.oreilly.com/">O'Reilly</a>. This book has two
 sections: Core JavaScript and Client-Side JavaScript. Use the Core section a
 general reference for the JavaScript language independent of whether it is in a
 client or server. VisiBone provides a useful
 <a href="http://javascript-reference.info/">on-line reference</a>.

 <h2>Q: Good, but most report developers don't like write code.</div> </h2>
 <p>
 In BIRT, typical tasks should require no code.
 Application-specific taks should require as little code as possible;
 preferably just a business expression when possible. For more complex logic,
 we expect a Java application developer to either create the logic, or point
 the report developer to existing Java code. The report developer then calls
 into the Java code from an expression. JavaScript allows all three:</p>
 <ol>
 <li>Simple expressions: <code>row.Price * row.Quantity</code>

 <li>Business expressions: choose a salutation (Mr., Mrs., Ms., etc.)
 depending on a database code, and concatenate the salutation, first name and
 last name.

 <li>Complex logic written in Java: Compute the recommendation rating for a
 stock based on factors in the database, and proprietary stock-rating
 algorithms.
 </ol>

 <p>Simple tasks require no code. This includes conditional formatting (make
 negative numbers red, for example), data transformations (filters, sorting,
 totals), conditional display (hide certain fields for certain types of
 customers), and so on.

 <h1>Accessing Java Classes</h1>

 <h2>Q: Can BIRT access existing Java code or objects?</div> </h2>
 <p>
 Yes. BIRT uses the
 <a href="http://www.mozilla.org/rhino/">Mozilla Rhino</a>
 JavaScript engine which provides excellent
 integration with Java. See the Mozilla Rhino
 <a href="http://www.mozilla.org/rhino/ScriptingJava.html">Scripting Java</a>
 article for information about how to call Java from JavaScript.
 <p>
 A BIRT report developer could use JavaScript to access functionality of
 pre-existing Java classes that may hold significant business logic that we
 would like to access within the report.
 <p>
 Suppose our logic is in a Java package called com.company.AppLogic.
 We'd import it into JavaScript as follows:</p>
 <pre class="code-block">importPackage( com.company.AppLogic );
 </pre>
 <p>The report's <code>initialize</code> method is the best place to put the import.
 Then, we can access objects and methods as if they were JavaScript objects. let's
 assume that MyClass is a class within the AppLogic package, and it provides business
 logic for working with, say, customer orders:
 <br>
 <pre class="code-block">obj = new MyClass( );
 result = obj.calculate( row.balance, row.dueDate );
 </pre>


 </body>
 </html>
	<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 transitional//EN">
	<html>

	<head>
	<title>BIRT FAQ</title>
	<link rel="stylesheet" href="../style/compose.css" type="text/css"/>
	<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
	</head>

	<body>

	<p class="head">BIRT FAQ</p>
	<p class="subhead">Scripting</p>

	<h1>Aggregates (Totals)</h1>

	<h2>Q: What aggregate operations does BIRT support?</div> </h2>
	<p>
	"Aggregate" is the fancy word to describe totals. BIRT suppots a wide variety
	of totals: sum, running sum, average, minimum, maximum, count, count distinct,
	and many more. See the
	<a href="../ref/ROM_Scripting_SPEC.pdf">ROM Scripting Specification</a>
	for details.

	<h2>Q: Does BIRT support look-ahead (two-pass) aggregates?</div> </h2>
	<p>
	Look-ahead aggregates are of the form "this value as a percentage of an overall
	total". For example, a customer's sales as a percentage of overall sales for a
	sales rep, sales region, and so on. These are often called two-pass aggregates
	becuase they require the reporting tool to make one pass over the data to compute
	totals, then another pass to compute the percentages for each record.
	<p>
	BIRT does provide support for such totals. Just enter the calculation and BIRT
	figures out the right way to compute it:
	<pre class="code-block">Total.percent( row.Sales, Total.sum( row.Sales ) )
	</pre>

	<h2>Q: Is an example of simple calculations like count,
	sum, max, min?</div> </h2>
	<p>TBD</div>

	<h2>Q: Does BIRT support page totals?</div> </h2>
	<p>
	Some reports may want to display totals over data
	displayed on a page of the report. For example, a count of employees on that
	page, and sum of their salaries.
	<p>
	BIRT release 1.0 delivers reports as a single web page, so the question is moot
	for this release. BIRT reports are paginated when printed as PDF, but BIRT uses
	Apache FOP to do the formatting, and so BIRT does not have visiblity into the
	pagination.
	<p>
	That said, if there is sufficient interest, the BIRT team will consider page
	totals for a future release.

	<h1>Scripting</h1>

	<h2>Q: Can I add custom logic (scripting) to my report?</div> </h2>
	<p>
	Yes. BIRT uses JavaScript (also known as EcmaScript) for expressions,
	business logic, and integration with application-specific Java classes.

	<h2>Q: JavaScript? Does that mean my code runs in the browser?</div> </h2>
	<p>
	When someone hears "JavaScript" the
	assumption is that JS is being used to script a browser. While browser
	scripting is a key use of JS, the language itself (when separated from the
	browser DOM framework) is a nice little tool that is well integrated
	with Java. Our goal in using JS is that a report developer can very quickly
	write business logic. JS tends to be easier to learn than Java for people
	who are accustomed to Visual Basic, SQL and similar scripting solutions.
	Because JS is well integrated with Java, it is easy to call from business
	logic into Java classes to do more advanced tasks, or if you prefer, to write
	your code using Java. Further, JS allows BIRT to support aggregate expression
	such as:</p>

	<pre class="code-block">sum( row.orderTotal )</pre>

	<p>This summarizes the orderTotal column over all rows. This makes aggregates
	look like other expressions, even though the BIRT report engine needs to
	"rewrite" them.

	<h2>Q: Where can I learn about JavaScript?</div> </h2>
	<p>
	JavaScript (also known as EcmaScript) is a popular language for browser scripting,
	and a wide range of books
	exist that describe JavaScript in that context. An excellent one is
	<a href="http://www.amazon.com/exec/obidos/ASIN/0596000480/qid=1110584202">
	JavaScript: the Definitive Guide</a> by David Flanagan, published by
	<a href="http://www.oreilly.com/">O'Reilly</a>. This book has two
	sections: Core JavaScript and Client-Side JavaScript. Use the Core section a
	general reference for the JavaScript language independent of whether it is in a
	client or server. VisiBone provides a useful
	<a href="http://javascript-reference.info/">on-line reference</a>.

	<h2>Q: Good, but most report developers don't like write code.</div> </h2>
	<p>
	In BIRT, typical tasks should require no code.
	Application-specific taks should require as little code as possible;
	preferably just a business expression when possible. For more complex logic,
	we expect a Java application developer to either create the logic, or point
	the report developer to existing Java code. The report developer then calls
	into the Java code from an expression. JavaScript allows all three:</p>
	<ol>
	<li>Simple expressions: <code>row.Price * row.Quantity</code>

	<li>Business expressions: choose a salutation (Mr., Mrs., Ms., etc.)
	depending on a database code, and concatenate the salutation, first name and
	last name.

	<li>Complex logic written in Java: Compute the recommendation rating for a
	stock based on factors in the database, and proprietary stock-rating
	algorithms.
	</ol>

	<p>Simple tasks require no code. This includes conditional formatting (make
	negative numbers red, for example), data transformations (filters, sorting,
	totals), conditional display (hide certain fields for certain types of
	customers), and so on.

	<h1>Accessing Java Classes</h1>

	<h2>Q: Can BIRT access existing Java code or objects?</div> </h2>
	<p>
	Yes. BIRT uses the
	<a href="http://www.mozilla.org/rhino/">Mozilla Rhino</a>
	JavaScript engine which provides excellent
	integration with Java. See the Mozilla Rhino
	<a href="http://www.mozilla.org/rhino/ScriptingJava.html">Scripting Java</a>
	article for information about how to call Java from JavaScript.
	<p>
	A BIRT report developer could use JavaScript to access functionality of
	pre-existing Java classes that may hold significant business logic that we
	would like to access within the report.
	<p>
	Suppose our logic is in a Java package called com.company.AppLogic.
	We'd import it into JavaScript as follows:</p>
	<pre class="code-block">importPackage( com.company.AppLogic );
	</pre>
	<p>The report's <code>initialize</code> method is the best place to put the import.
	Then, we can access objects and methods as if they were JavaScript objects. let's
	assume that MyClass is a class within the AppLogic package, and it provides business
	logic for working with, say, customer orders:
	<br>
	<pre class="code-block">obj = new MyClass( );
	result = obj.calculate( row.balance, row.dueDate );
	</pre>


	</body>
	</html>