Jooby Handlers Overview

Jooby is a web framework for Java that streamlines the development of web applications. A core feature of Jooby is the concept of handlers, which play a vital role in managing HTTP requests and responses.

What are Handlers?

• Handlers in Jooby are functions or methods that process incoming HTTP requests and generate responses.
• Each handler is typically associated with a specific route in your application.

Main Points

Key Concepts

• Route: A specific URL pattern that your application listens to.
• Request and Response: Handlers receive requests and send responses. They can read data from the request and write data to the response.

Creating Handlers

• Handlers are created using annotations or method definitions in your Jooby application.
• You can define a handler for a route using the following syntax:

get("/hello", () -> "Hello World!");

• This example defines a handler for the GET method on the /hello route, which returns "Hello World!" when accessed.

HTTP Methods

• Jooby supports various HTTP methods, including:
  • GET: Retrieve data from the server.
  • POST: Send data to the server.
  • PUT: Update existing data.
  • DELETE: Remove data.

Handling Parameters

• Handlers can also process parameters from the request URL or body. For example:

get("/greet/:name", req -> {
    String name = req.param("name").value();
    return "Hello " + name + "!";
});

• In this example, the handler extracts the name parameter from the URL and uses it to customize the greeting.

Middleware

• Middleware in Jooby is a type of handler that can run before or after your main handlers. This allows for features like logging, authentication, or error handling.

Summary

• Handlers are a fundamental part of the Jooby framework, enabling developers to define how their applications respond to various HTTP requests.
• By utilizing routes, parameters, and middleware, you can create powerful web applications with minimal complexity.

Example of a Simple Jooby Application

Here is a brief example of a simple Jooby application that utilizes handlers:

import org.jooby.Jooby;

public class MyApp extends Jooby {
    {
        get("/", () -> "Welcome to Jooby!");
        get("/hello", () -> "Hello World!");
        get("/greet/:name", req -> {
            String name = req.param("name").value();
            return "Hello " + name + "!";
        });
    }
    
    public static void main(String[] args) {
        run(MyApp::new, args);
    }
}

This example showcases an application with three routes and their respective handlers, demonstrating how simple it is to set up a web application using Jooby.