Experiment with minimal HttpHandler creation in java

http4k-core/src/main/kotlin/org/http4k/core/Status.kt

@@ -7,6 +7,7 @@ data class Status(val code: Int, val description: String) {
         val SWITCHING_PROTOCOLS = status(101, "Switching Protocols")
 
         private val SUCCESSFUL = 200..299
+        @JvmField
         val OK = status(200, "OK")
         val CREATED = status(201, "Created")
         val ACCEPTED = status(202, "Accepted")

http4k-core/src/main/kotlin/org/http4k/core/Uri.kt

@@ -7,6 +7,7 @@ data class Uri(val scheme: String, val userInfo: String, val host: String, val p
     companion object {
         private val AUTHORITY = Regex("(?:([^@]+)@)?([^:]+)(?::([\\d]+))?")
         private val RFC3986 = Regex("^(?:([^:/?#]+):)?(?://([^/?#]*))?([^?#]*)(?:\\?([^#]*))?(?:#(.*))?")
+        @JvmStatic
         fun of(value: String): Uri {
             val result = RFC3986.matchEntire(value) ?: throw RuntimeException("Invalid Uri: $value")
             val (scheme, authority, path, query, fragment) = result.destructured

src/test/java/org/http4k/java/Http4kJavaCompatibilityTest.java

@@ -0,0 +1,44 @@
+package org.http4k.java;
+
+import com.google.common.base.Function;
+import org.http4k.core.*;
+import org.junit.Test;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.http4k.core.Method.GET;
+import static org.http4k.core.Status.OK;
+import static org.http4k.java.RequestFactory.request;
+import static org.http4k.java.ResponseFactory.response;
+import static org.junit.Assert.assertThat;
+
+public class Http4kJavaCompatibilityTest {
+
+    @Test
+    public void handler_function() {
+        HttpHandler handler = request -> response(OK).body("test");
+
+        Response response = handler.handle(request(GET, Uri.of("/test")));
+
+        assertThat(response.getStatus(), equalTo(OK));
+        assertThat(response.bodyString(), equalTo("test"));
+    }
+
+}
+
+interface HttpHandler extends Function<Request, Response> {
+    default Response handle(Request request) {
+        return apply(request);
+    }
+}
+
+class RequestFactory {
+    static Request request(Method method, Uri uri) {
+        return Request.Companion.invoke(method, uri);
+    }
+}
+
+class ResponseFactory {
+    static Response response(Status status) {
+        return Response.Companion.invoke(status);
+    }
+}