Create README.md

Author: rbygrave

README.md

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+# javalin-generator
+Java annotation processor for generating web route to Controller adapters
+
+## Define a Controller
+```java
+package org.example.hello
+
+import io.dinject.controller.Controller
+import io.dinject.controller.Get
+import io.dinject.controller.Path
+
+@Path("/widgets")
+@Controller
+class WidgetController(private val hello: HelloComponent) {
+
+  @Get("/:id")
+  fun getById(id : Int): Widget {
+    return Widget(id, "you got it${hello.hello()}")
+  }
+
+  @Get
+  fun getAll(): MutableList<Widget> {
+
+    val list = mutableListOf<Widget>()
+    list.add(Widget(1, "Rob"))
+    list.add(Widget(2, "Fi"))
+
+    return list
+  }
+
+  data class Widget(var id: Int, var name: String)
+}
+
+```
+
+## Generated source
+
+The annotation processor will generate a `$route` for the controller like below.
+
+Note that this class implements the WebRoutes interface, which means we can
+get all the WebRoutes and register them with Javalin using.
+
+```java
+fun main(args: Array<String>) {
+
+  // get all the webRoutes
+  val webRoutes = SystemContext.getBeans(WebRoutes::class.java)
+  
+  val javalin = Javalin.create()
+
+  javalin.routes {
+    // register all the routes with Javalin
+    webRoutes.forEach { it.registerRoutes() }
+
+    // other routes etc as desired
+    ApiBuilder.get("/foo") { ctx ->
+      ctx.html("bar")
+      ctx.status(200)
+    }
+    ...
+  }
+
+  javalin.start(7000)
+}
+
+```
+
+### The generated WidgetController$route.java is:
+
+
+```java
+package org.example.hello;
+
+import static io.dinject.controller.PathTypeConversion.*;
+import io.dinject.controller.WebRoutes;
+import io.javalin.apibuilder.ApiBuilder;
+import javax.annotation.Generated;
+import javax.inject.Singleton;
+import org.example.hello.WidgetController;
+
+@Generated("io.dinject.web.javlin")
+@Singleton
+public class WidgetController$route implements WebRoutes {
+
+ private final WidgetController controller;
+
+ public WidgetController$route(WidgetController controller) {
+   this.controller = controller;
+ }
+
+  @Override
+  public void registerRoutes() {
+
+    ApiBuilder.get("/widgets/:id", ctx -> {
+      int id = asInt(ctx.pathParam("id"));
+      ctx.json(controller.getById(id));
+      ctx.status(200);
+    });
+
+    ApiBuilder.get("/widgets", ctx -> {
+      ctx.json(controller.getAll());
+      ctx.status(200);
+    });
+
+  }
+}
+```