Javascript as domain specific language
Posted on by Wirabumi Software Posted in Domain Specific LanguageTagged , ,

JavaScript serves as an ideal choice for implementing customer-specific business logic in Java applications. By utilizing JavaScript as a domain-specific language (DSL), developers can easily tailor and customize the application’s behavior to meet the unique requirements of individual customers. JavaScript’s flexible syntax and extensive libraries provide the necessary tools to express complex business rules and workflows efficiently.

One of example is a salary formula in a Java application. For instance, let’s consider a scenario where the salary calculation varies based on factors like experience, performance, and bonus eligibility. By using JavaScript as a DSL, developers can define the salary formula in a more dynamic and customizable manner. Here’s an example of salary calculation formula written in Javascript:

function calculateSalary(experience, performance, bonusEligible) {
    let baseSalary = 50000;

    // Adjust the base salary based on experience
    if (experience >= 5) {
        baseSalary += 10000;
    } else if (experience >= 2) {
        baseSalary += 5000;
    }

    // Adjust the base salary based on performance
    if (performance === 'excellent') {
        baseSalary *= 1.1;
    } else if (performance === 'good') {
        baseSalary *= 1.05;
    }

    // Add bonus if eligible
    if (bonusEligible) {
        baseSalary += 5000;
    }

    return baseSalary;
}

calculateSalary(3, 'good', true)

Now call calculateSalary from Java application:

ScriptEngine engine = GraalJSScriptEngine.create(
		Engine.newBuilder()
			.option("engine.WarnInterpreterOnly", "false")
			.build(), 
		Context.newBuilder("js")
		.allowIO(false)
		.option(JSContextOptions.ECMASCRIPT_VERSION_NAME, "2022"));

engine.getBindings(ScriptContext.ENGINE_SCOPE).put("experience", 3);
engine.getBindings(ScriptContext.ENGINE_SCOPE).put("performance", "good");
engine.getBindings(ScriptContext.ENGINE_SCOPE).put("bonusEligible", true);
Object result = engine.eval(script);
System.out.println("result: "+result);

Result:


  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::                (v3.1.0)

2023-05-19T13:09:27.555+08:00  INFO 9500 --- [           main] com.example.demo.ConsoleBoxApplication   : Starting ConsoleBoxApplication using Java 17.0.6 with PID 9500 (C:\Users\Zaien Aji Trahutomo\eclipse\workspace\ConsoleBox\target\classes started by Zaien Aji Trahutomo in C:\Users\Zaien Aji Trahutomo\eclipse\workspace\ConsoleBox)
2023-05-19T13:09:27.557+08:00  INFO 9500 --- [           main] com.example.demo.ConsoleBoxApplication   : No active profile set, falling back to 1 default profile: "default"
2023-05-19T13:09:27.875+08:00  INFO 9500 --- [           main] com.example.demo.ConsoleBoxApplication   : Started ConsoleBoxApplication in 0.522 seconds (process running for 0.812)
test graal vm javascript enginee
result: 62750.0

In this example, the JavaScript DSL defines a calculateSalary function that takes parameters such as experience, performance, and bonus eligibility. It adjusts the base salary based on these factors and returns the calculated salary. By utilizing JavaScript as a DSL, the salary formula can be easily customized and adapted to meet the specific needs of different customers without modifying the underlying Java code.

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