Java Opener

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OpenL Objectives
Language Opener
Java Opener
OpenL Glossary

Java Opener is an OpenL-based implementation of Java called "openl.j". While covering the major features of Java 1.4, it also includes such new features like operator overloading. You may create different configurations of openl.j by adding more features or limiting an access to the existing Java features on the syntax level.

Why do we call it a Java Opener? There are three major reasons:

bulletOpenL opens Java allowing to configure different versions of Java by adding new features or limiting the existing ones
bulletOpenL opens Java introducing Java Snippets that are expressions or small fragments of Java code kept outside of traditional source files
bulletOpenL opens Java providing a direct access to different data/object sources without necessity to create special Java classes

Configuring Java

With OpenL you can built a language configuration that looks and feels like Java (any Java programmer would feel comfortable with it from the moment she sees it) but that overcomes well-known Java limitations (you can find interesting critiques of Java, C# and other similar languages at and OpenL-based Java configuration  “openl.j” includes such additional features like operator overloading allowing you to write the arithmetic expressions in a natural way understandable to a non-technical specialists.  For example, you do not want to offer your users a funny looking code like  x.add(y.abs().mul(z)) instead of the intuitive x+|y|*z. If a user wants to tell that
it should be exactly what you allow her to write instead of something strange like

      customer.getMothlyIncome().less( 3*loan.getAmount().div(loan.getTerm()))

You may also define operators that allow you to add miles to kilometers and present results in meters. So, the code like X[mi]+Y[km] or 5[h]+25[min]+30[s] presents valid OpenL expressions. You may download and analyze examples from here.

With OpenL you may also configure your Java in a way that limits some Java features (like an access to a file system) on the language level for the security purposes. If your application accepts a code from a remote machine, you do not want to jeopardize your computer and rely just on security features built-in into Internet Explorer. If you configure OpenL in the way that does not allow system calls, the code with such calls will be syntactically incorrect that will prevent it from execution.

Java Snippets

When it comes to representation of serious business logic, in most cases people still end up with languages like Java or C#. After all marketing mantras about a natural "English-like" language, you still need a real programming language with power and expressiveness of Java. But at some point, you want to present the business logic in a way that can be supported by non-programmers.  So, you actually want to open Java by distributing your business logic between different placeholders:

bulletTraditional Java/XML code maintained inside a programmer-oriented IDE like Eclipse
bulletSnippets of Java code created and maintained directly in MS Excel, Word, XML, Oracle, etc.

OpenL opens Java supporting Java Snippets for business use outside of traditional software development environment. For example, Excel-based decision tables oriented to business people can contain complex business rules whose implementation requires small pieces of Java code presented in the same Excel spreadsheet but probably hidden from a business user. See examples at

Along with the standard Java you can present logic of your business functions in Java Snippets written in “openl.j”. These snippets can use directly all Java objects defined in your application. All standard or special packages can also be used directly  from Java snippets like from a regular Java.  

The snippets can be kept in a separate file as a fragment of a Java code like in this example: 

// openl
hour = Calendar.getInstance().get(Calendar.HOUR_OF_DAY);
(hour > 0 && hour <= 12)
      greeting = "Good Morning";
(hour > 12 && hour <= 18)
      greeting = "Good Afternoon";
(hour > 18 && hour <= 21)
      greeting = "Good Evening";
(hour > 21 && hour <= 24)
      greeting = "Good Night";

System.out.println(greeting+", World!");

Note that this snippet is using the standard Java class Calendar. Thus, with OpenL, it is up to a developer to decide which business logic to keep in Java and which put in the snippets, that can be supported by non-technical or less technical users outside of a selected Java development environment.

You may define methods inside snippets and call them from a real Java code or from other snippets. Here are two snippets with methods: 

String defineCurrentGreeting()
      int hour = Calendar.getInstance().get(Calendar.HOUR_OF_DAY);
      String greeting = "?";
      if (hour > 0 && hour <= 12)
            greeting = "Good Morning";
      if (hour > 12 && hour <= 18)
            greeting = "Good Afternoon";
      if (hour > 18 && hour <= 21)
            greeting = "Good Evening";
      if (hour > 21 && hour <= 24)
            greeting = "Good Night";
      return greeting;


String definePrefix(Customer customer)
      String prefix;
      if (customer.getGender().equals("M"))
            prefix = "Mr.";
            if (customer.getMaritalStatus().equals("Married"))   
                  prefix = "Mrs.";
                  prefix = "Ms.";
      return prefix;

This following snippet will create a customer using the proper Java class Customer. It uses two previous snippets to salute her with a greeting like “Good Afternoon, Mrs. Robinson!”

int main(String[] args)
      String greeting = defineCurrentGreeting();
      Customer customer = defineCustomer();
      String prefix = definePrefix(customer);
      System.out.println(greeting+", "+prefix+customer.getName()+"!");
      return 0;  

Customer defineCustomer()
      Customer customer = new Customer();
      return customer;

The snippets can be called directly from your Java code like in this example:

// This string contains a simple OpenL code the same as a regular Java
openLcode = "System.out.println(\"Hello, World!\")";

// Get an OpenL language configuration named "org.openl.j"
language = OpenL.getInstance("org.openl.j");

//evaluate code, see result on console
language.evaluate(new StringSourceCodeModule(openLcode, null));

You can present Java snippets in regular flat files using a Notepad or your favorite text editor. You can manage large Java projects with snippets using Eclipse with the provided OpenL's plugin.  In this case, Eclipse will show you all errors in the snippets. When snippets are defined in an Excel file, double-click to an error will open the Excel with the erroneous cell selected.  You can configure OpenL in different ways to use your preferable repositories of Java snippets such as XML file, Excel’s spreadsheets, or MS Word documents.

Access To Different Data Sources

OpenL provides a direct access to objects defined in different sources such as Java, MS Office files, DB, XML including XML Schema, WSDL, RDF, etc. You may use familiar Java syntax to deal with objects defined in an XML file, in an Excel spreadsheet, or in an SQL table as if they were a described in a Java class without necessity to create such classes. No intermediate Java classes are generated either. Moreover, the same OpenL code can naturally work with objects coming from different object sources without knowing their origin. For example, in the snippets above a Customer was defines directly in the OpenL snippet using a method "defineCustomer". Below are three other ways to define a Customer:

Java Class
XML File
MS Excel






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Last updated: 01/13/05.

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