README

Java extension for Yellicode

Advice

This is not an official Yellicode Java Extension, I took the csharp-extension https://github.com/yellicode/csharp-extension as codebase, and I made some some changes to make it work. Right now it is only making some basic stuff I needed for my projects, later I'll be making progresive updates to have a full working Java Extension for Yellicode.

About Java extension for Yellicode

Generate Java code using powerful TypeScript code generation templates! This Yellicode extension lets you generate Java classes, interfaces, enumerations and their members from different kinds of models, using a fully typed code writer.

License: MIT

About Yellicode

Yellicode lets you build your own code generation templates with TypeScript. It consists of a Node.js CLI and extensible APIs, making it easy for developers to create, share and re-use code generators for their favorite programming languages and frameworks.

Check out our website for more.

Using the Java package

Prerequisites

In order to run a code generation template, you must have the CLI installed (@yellicode/cli) globally and have a valid codegenconfig.json file in your working directory. Please refer to the installation instructions and the quick start for more.

Installation

Open a terminal/command prompt in your working directory and install this package as a dev dependency:

npm install yellicode-java-extension --save-dev

Using the JavaWriter

The main class for generating Java code is the JavaWriter. The JavaWriter can work with 2 different model kinds as input:

A Java code definition.
A Yellicode model.

Most JavaWriter functions have 2 overloads which can be used for each different kind of input. For example, the writeClassBlock function has the following overloads:

public writeClassBlock(definition: ClassDefinition, contents: () => void): void;
public writeClassBlock(cls: elements.Class, contents: () => void, options?: opts.ClassOptions): void;

The first overload accepts a ClassDefinition, which has the following structure (comments left out for brevity):

export interface ClassDefinition extends TypeDefinition {
  isStatic?: boolean;
  isAbstract?: boolean;
  implements?: string[];
  extends?: string;
  properties?: PropertyDefinition[];
  methods?: MethodDefinition[];
}

When using this overload, you should build the definition in your code generation template. You can do this manually, but typically you would configure a JSON file as model (see the Yellicode quick start for a how-to) and transform that JSON structure to a Java definition.

The second overload accepts a class instance from a Yellicode model and accepts an optional ClassOptions object to control code generation (internally, the Yellicode class is transformed to a ClassDefinition).

Examples

Note: Check out the examples directory in the project repository for some working examples.

Generating a Class

import { TextWriter } from '@yellicode/core';
import { Generator } from '@yellicode/templating';
import { JavaWriter, ClassDefinition } from '../../src/java';

Generator.generate(
  { outputFile: '../out/HelloWold.java' },
  (output: TextWriter) => {
    const classDefinition: ClassDefinition = {
      name: 'HelloWold',
      accessModifier: 'public',
      docComment: ['A fully generated HelloWorld class'],
      properties: [
        {
          name: 'message',
          typeName: 'String',
          accessModifier: 'private',
          docComment: ['A simple message'],
          isStatic: true,
          defaultValue: 'Hi developer!',
        },
      ],
    };

    // Java code writer
    const java = new JavaWriter(output);

    java.writeClassBlock(classDefinition, () => {
      // Properties
      (classDefinition.properties || []).forEach((p) => {
        java.writeProperty(p);
        java.writeLine();
      });
      // Main method
      java.writeMainMethod(() => {
        java.writeLine('System.out.println(HelloWold.message);');
      });
    });
  }
);

The generated Java code will look as follows:

/**
 * A fully generated HelloWorld class
 */
public class HelloWold {
  /**
   * A simple message
   */
  private static String message = "Hi developer!";

  public static void main(String[] args) {
    System.out.println(HelloWold.message);
  }
}

Generating an Interface

import { TextWriter } from '@yellicode/core';
import { Generator } from '@yellicode/templating';
import { JavaWriter, InterfaceDefinition } from '../../src/java';

Generator.generate(
  { outputFile: '../out/InterfazDeclarationExample.java' },
  (output: TextWriter) => {
    const ineterfaceDefinition: InterfaceDefinition = {
      name: 'InterfazDeclarationExample',
      accessModifier: 'public',
      docComment: ['A fully generated Interface'],
    };

    // Java code writer
    const java = new JavaWriter(output);

    java.writeInterfaceBlock(ineterfaceDefinition, () => {
      java.writeLine();
      // Basic method
      java.writeMethodDeclaration({
        name: 'basicMethod',
        returnTypeName: `String`,
      });
      java.writeLine();
      // Whit parameters
      java.writeMethodDeclaration({
        name: 'withParameters',
        returnTypeName: `String`,
        parameters: [
          { name: 'param1', typeName: 'String' },
          { name: 'param2', typeName: 'Integer' },
        ],
      });
      java.writeLine();
      // Method that throws exceptions
      java.writeMethodDeclaration({
        name: 'withExecptions',
        returnTypeName: `String`,
        throws: ['Exception'],
      });
      java.writeLine();
      // Method with public modifier
      java.writeMethodDeclaration({
        isPublic: true,
        name: 'whitPublicModifier',
        returnTypeName: `String`,
      });
      java.writeLine();
      // Method with default implementation
      java.writeMethodBlock(
        {
          isDefault: true,
          name: 'whitDefultMethodImlementation',
          returnTypeName: `void`,
        },
        () => {
          java.writeLine('// Write your code here!');
        }
      );
      java.writeLine();
    });
  }
);