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micra

get("/", (req, resp) -> "Java, sans fluff.");

Inspired by Java 8 which introduced lambdas, Micra is a proof-of-concept for a Sinatra-inspired micro Web framework. It allows you to map URLs to lambdas. The routing syntax is derived from both Sinatra and Golang's Gorilla library.

Running it

You'll need Gradle to build this project. To run this example project, just type:

$ gradle jettyRun

To stop the server, press CTRL+C

Making your own

You can start your own project by removing HelloWorldServlet.java and creating your own class that inherits from MicraServlet:

public class YourServlet extends MicraServlet

Then, update the WEB-INF/web.xml file with the name of your class.

You can then use the helper functions to route requests to your new app:

post("/user/", (req, resp) -> {/* Do some database work here.. */ "Got it!" });

There are four helper functions: get, post, put, delete.

Routes

There are four types of routes: a Gorilla-inspired route (called a parameterized route), a plain Regex route, and a lambda route.

A parameterized route can be:

  1. "/"
  2. "/foo"
  3. "/foo/bar"
  4. "/foo/{bar}" where bar will match everything
  5. "/foo/{bar:[0-9]{0,2}} where bar will match all two-digit numbers

Any parameters (those parts of the routes in {}) can be used by the handler lambda:

get("/helloworld/{name}",
    (req, resp) -> {
        String name = "world";
        if (req.getRouteParameter("name") != null)
            name = req.getRouteParameter("name")
            
    }
    "Hello, " + name + "!"
);

A regex route is exactly how it sounds: a regex that checks agains the URL.

A lambda route takes a MicraRequest object (currently a wrapper around HTTPServletRequest) and returns a boolean:

put((req) -> req.getUrl().equals("/"), ...);

Route Condition

You can specify a route condition if you want to use other information besides the URL to route:

put("/foo",
    (req) -> req.getParameter("User-Agent").contains("Trident"),
    (req, resp) -> "Get chrome!"
);

Gradle Goodness

I've included a plugin that watches the src/ folder and it will recompiles the webapp if there's a change. To use it, open two command windows, and run this in the first:

gradle watch

You need to start that first to prevent it from being locked by the other process. Run this command in the other command window:

gradle jettyRun

Jetty is set to reload when it see's that you've recompiled. On my machine, this is fast enough that the change is reflected as soon as I tab over to refresh.