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Polyglot Low-Code Resource

In this tutorial, we will create a native resource for Netuno. This means we will create a Java class that will be placed in Netuno's base directory and can be used by any application inside the apps folder using the syntax _foo.methodName(args).

The example we will create, following the previous tutorials, is the _calc resource, which is a sample resource for performing simple arithmetic operations.

To begin, we first need to create the project's folder structure. In this example, we'll assume the project will be created inside a folder named Calc. We need to create the folder structure that mirrors the package name (in our example, org.netuno.addon.calc). Therefore, our folder structure will be:

  • Calc/src/main/java/org/netuno/addon/calc/resource/

Inside this structure, we'll create a Java class named CalcResource, which will define our custom native resource.

  • Calc/src/main/java/org/netuno/addon/calc/resource/CalcResource.java

The package declaration inside the class will be:

package org.netuno.addon.calc.resource;

For the class to define a custom native resource, it must be annotated with the org.netuno.tritao.Resource annotation. The name parameter defines the resource name, which can be accessed by prefixing it with an underscore (_) (in our case, _calc). The easiest way to create the resource is by extending the org.netuno.tritao.resource.ResourceBase class:

package org.netuno.addon.calc.resource;

import org.netuno.tritao.resource.Resource;
import org.netuno.tritao.resource.ResourceBase;

@Resource(name = "calc")
public class CalcResource extends ResourceBase {
    // ...
}

Extending the ResourceBase class saves us from having to initialize the resource ourselves. We only need to call super with the appropriate arguments:

package org.netuno.addon.calc.resource;

import org.netuno.proteu.Proteu;
import org.netuno.tritao.hili.Hili;
import org.netuno.tritao.resource.Resource;
import org.netuno.tritao.resource.ResourceBase;

@Resource(name = "calc")
public class CalcResource extends ResourceBase {
    // ...
    public CalcResource(Proteu proteu, Hili hili) {
        super(proteu, hili);
    }
}

The init method is required. Inside it, we initialize the resource by calling our class constructor with the getters provided by the parent class:

package org.netuno.addon.calc.resource;

import org.netuno.proteu.Proteu;
import org.netuno.tritao.hili.Hili;
import org.netuno.tritao.resource.Resource;
import org.netuno.tritao.resource.ResourceBase;

@Resource(name = "calc")
public class CalcResource extends ResourceBase {
    // ...
    public CalcResource(Proteu proteu, Hili hili) {
        super(proteu, hili);
    }

    public CalcResource init() {
        return new CalcResource(getProteu(), getHili());
    }
}

After that, we can define our own fields and methods:

package org.netuno.addon.calc.resource;

import org.netuno.proteu.Proteu;
import org.netuno.tritao.hili.Hili;
import org.netuno.tritao.resource.Resource;
import org.netuno.tritao.resource.ResourceBase;

@Resource(name = "calc")
public class CalcResource extends ResourceBase {
    public double value = 0;

    public CalcResource(Proteu proteu, Hili hili) {
        super(proteu, hili);
    }

    public CalcResource init() {
        return new CalcResource(getProteu(), getHili());
    }

    public CalcResource set(double v) {
        value = v;
        return this;
    }

    public CalcResource plus(double v) {
        value += v;
        return this;
    }

    public CalcResource minus(double v) {
        value -= v;
        return this;
    }

    public double get() {
        return value;
    }
}

Now you just need to compile the class, making sure that the CalcResource.class file is located in:

  • netuno/core/web/WEB-INF/classes/org/netuno/addon/calc/resource/

Or build a JAR file, making sure it is located in:

  • netuno/lib/

Next, let's create a test application that uses this resource:

./netuno app name=calc

We'll also create a service in this application to use the resource.

In this example, create the file netuno/apps/calc/server/services/calc-test.js:

_calc.set(10);

_calc.plus(120);

_out.println(_calc.get());

Now start the application:

./netuno server app=calc

Finally, make a request to the service:

  • http://localhost:9000/services/calc-test

The service will return the value 130.

To use a resource while coding in Java, some classes such as org.netuno.tritao.Web and org.netuno.tritao.event.EventBase provide the resource function, which initializes this resource. In the class where you want to use the calc resource, do:

import org.netuno.addon.calc.resource.CalcResource;

// ...
    CalcResource calc = resource(CalcResource.class);
    calc.set(10);
    calc.plus(120);
    System.out.println(calc.get());
// ...

You can view the complete project files in this link.