jneira / wai-servlet

Library to integrate eta wai applications with servlet api

wai-servlet

Library to integrate eta wai applications with the servlet api

Getting Started

• Visit the Getting Started eta instructions to build and install the library and the examples
• In src/Network/Wai/Servlet/Examples.hs you can find some examples of wai applications and code to generate a servlet class that can be deployed in your favorite servlet container.
• There are two options to deploy wai-servlet apps: generating a war file to be deployed in a servlet container or run it directly in a embedded one; this is the way more similar to use wai warp for haskell wai applications.

Running an application in a embedded servlet container

• You need to install and set the wai-servlet-jetty-adapter package as a dependency. Currently is the unique adapter implemented for wai-servlet.
• You have to import the module Network.Wai.Servlet.Handler.Jetty with the run function and call it with the port server and your application:

{-# LANGUAGE OverloadedStrings #-}
import Network.HTTP.Types                 (status200)
import Network.Wai
import Network.Wai.Servlet
import Network.Wai.Servlet.Handler.Jetty

appSimple :: Application
appSimple _ respond = respond $
   responseLBS status200 [("Content-Type", "text/plain")] "Hello World"

main = run 3000 appSimple

Generating a war to be deployed in a servlet container

• This option supposes some manual steps. There is plans to make etlas build automatically a war file, tracked in this issue.
• The main function to generate the servlet is Network.Wai.Servlet.makeServiceMethod for example:

{-# LANGUAGE OverloadedStrings #-}
import Java
import Network.Wai
import Network.HTTP.Types                 (status200)
import Network.Wai.Servlet

appSimple :: Application
appSimple _ respond = respond $
   responseLBS status200 [("Content-Type", "text/plain")] "Hello World"

servSimple :: DefaultWaiServletApplication
servSimple = makeServiceMethod appSimple

foreign export java "service" servSimple :: DefaultWaiServletApplication

• This code will generate a network.wai.servlet.DefaultWaiServlet java class that extends javax.servlet.GenericServlet suitable to use in a standard war file
• To generate the war you have to create the standard directory structure:
  • webApp
    • static resources (jsp,html,etc)
    • META-INF
    • WEB-INF
      • web.xml (required if you use servlets)
      • classes
      • lib
        • wai-servlet-app.jar
• The web.xml for the default wai servlet could be

<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
	<display-name>wai-servlet-test</display-name>

	<servlet>
		<servlet-name>wai-servlet</servlet-name>
		<servlet-class>network.wai.servlet.DefaultWaiServlet</servlet-class>
	</servlet>
	
	<servlet-mapping>
		<servlet-name>wai-servlet</servlet-name>
		<url-pattern>/</url-pattern>
	</servlet-mapping>
	
</web-app>

• You have to place the jar or jars generated by etlas in WEB-INF/lib and package the structure in a war file (using jar tool f.e.)
• With the war file you can deploy your wai application in a servlet container:
  • tomcat: https://tomcat.apache.org/tomcat-8.0-doc/deployer-howto.html
    • the easier way is to place the war file in $TOMCAT_INSTALL_DIR$/webapps
  • jetty: https://www.eclipse.org/jetty/documentation/9.4.x/configuring-deployment.html

wai-servlet's Issues

3-character endpoints aren't getting matched

See typelead/eta-fib-service#1 for a concrete example.

Not in scope: ‘unsafePerformJavaWith’ when attempting to build during installation

Resolving dependencies...
Configuring wai-servlet-0.1.5.0...
Building wai-servlet-0.1.5.0...
Failed to install wai-servlet-0.1.5.0
Build log ( /home/funnyusername/.etlas/logs/eta-0.7.0.2/wai-servlet-0.1.5.0-I0egAxeJrMBLj7pkRuaDXn.log ):
etlas: Entering directory '/tmp/etlas-tmp-12590'
Configuring wai-servlet-0.1.5.0...
Preprocessing library for wai-servlet-0.1.5.0..
Building library for wai-servlet-0.1.5.0..
[1 of 7] Compiling Network.Wai.Servlet.File ( src/Network/Wai/Servlet/File.hs, dist/build/Network/Wai/Servlet/File.jar )
[2 of 7] Compiling Javax.Servlet    ( src/Javax/Servlet.hs, dist/build/Javax/Servlet.jar )
[3 of 7] Compiling Network.Wai.Servlet.Settings ( src/Network/Wai/Servlet/Settings.hs, dist/build/Network/Wai/Servlet/Settings.jar )
[4 of 7] Compiling Network.Wai.Servlet.Request ( src/Network/Wai/Servlet/Request.hs, dist/build/Network/Wai/Servlet/Request.jar )

src/Network/Wai/Servlet/Request.hs:80:21:
    Not in scope: ‘unsafePerformJavaWith’
etlas: Leaving directory '/tmp/etlas-tmp-12590'
etlas: Error: some packages failed to install:
wai-servlet-0.1.5.0-I0egAxeJrMBLj7pkRuaDXn failed during the building phase.
The exception was:
ExitFailure 1
wai-servlet-handler-jetty-0.1.2.0-6kNESzjPZ1EbRxix0NIil depends on
wai-servlet-handler-jetty-0.1.2.0 which failed to install.

This could be linked to typelead/eta#678, most likely unreleased
But I also do see

wai-servlet/src/Network/Wai/Servlet/Request.hs

Lines 36 to 42 in f0e2322

	doJavaWith :: (Class c) => c -> Java c a -> a
	#ifdef PURE_JAVA_WITH
	doJavaWith = pureJavaWith
	#else
	doJavaWith = unsafePerformJavaWith
	#endif

which might be in place for backward compatibility?

Create a test suite for the library

• To be launched in some integration tool like CircleCI (see #9)
• We could use as model the test suite of wai and warp

Enable logging for wai-servlet apps

• Currently there is no an easy, tested way to log from wai-servlet apps
• The appropriate features could be
  • work with the minimum possible configuration
  • integration with java logging, specially within servers
    • but avoiding the madness of java log frameworks
  • use of existing haskell libraries
• The options could be:
  • Make any of the existent haskell libraries work, maybe through a wrapper that integrates java logging
    • @NickSeagull has tested Network.Wai.Middleware.RequestLogger in wai-extra, that uses in turn fast-logger and it works if you use logStdOut
  • Create a new library, specific for eta to fulfill the features, in the spirit of clojure timbre
    • This could be a long time task
• Other useful links
  • https://stackoverflow.com/questions/6310961/how-do-i-do-logging-in-haskell
  • https://github.com/wdanilo/haskell-logger
  • http://hackage.haskell.org/package/hslogger
    • it can output Log4j's XMLLayout
  • https://hackage.haskell.org/package/katip

Add reference to how to run apps with wai-servlet-handler-jetty

Fix memory leak

There's a memory leak when allocating a foreign ptr to store the request body contents. We can get around this by using finalizerFree, but that currently triggers a bug with Eta v0.7.0b1, so I have kept it commented until we fix that bug.

Setup CircleCI

At minimum, there should be a build that runs a simple etlas build for basic verification.

Add gradle support

• If possible we'll try to keep etlas installation
• Using the eta plugin
• Not sure if a special war goal could be added in this project

Implement sendFile using java NIO

The new Java NIO channels API provides a very efficient way to transfer data avoiding copying through an intermediate buffer. The sendFile java method used through FFI should be implemented using transferTo or transferFrom, with care for Windows:

https://stackoverflow.com/questions/7379469/filechannel-transferto-for-large-file-in-windows

Make a 1.1.0.0 release for Eta v0.0.9

Can you make a wai-servlet-1.1.0.0 release? I just tested the servant example with Eta v0.0.9 and it's working pretty well with the changes I just made. If you can upload the new version, users can seamlessly try the example without any breakage. Thanks!

Incorrect handling of uris with non ascii chars

Actually, wai-servlet handle incorrectly (and differently than wai) uris containing non ascii chars. For example:

• For /caña it gives us: rawPathInfo = "ca%F1a" and pathInfo = ["ca\65533"]
• With Wai: rawPathInfo = "/ca%C3%B1a and pathInfo = ["ca\241a"]

httpVersion is partial

httpVersion ::  (a <: ServletRequest) => a -> H.HttpVersion
httpVersion req = pureJavaWith req $ do 
  httpVer <- getProtocol
  return $ case httpVer of
    "HTTP/0.9" -> H.http09
    "HTTP/1.0" -> H.http10
    "HTTP/1.1" -> H.http11

This is the current definition of httpVersion. Is there a way to smoothly handle the situation when a newer version of HTTP is used?

Implement the wai ResponseFile type handling in Network.Wai.Servlet.Response.updateHttpServletResponse

The main goals to provide an implementation that is efficient and takes into account the client cache and the header byte-range
Resources:

• File server using java servlets:
  • https://gist.github.com/jneira/cf33844230f1ae4c22bf4a82d28d12c0
  • http://www.nurkiewicz.com/2015/06/writing-download-server-part-ii-headers.html
• WAI related links:
  • https://github.com/yesodweb/wai/blob/master/warp/Network/Wai/Handler/Warp/Response.hs#L265-L322
  • https://github.com/yesodweb/wai/blob/master/warp/Network/Wai/Handler/Warp/File.hs
  • https://github.com/yesodweb/wai/blob/master/warp/Network/Wai/Handler/Warp/SendFile.hs
  • https://github.com/yesodweb/wai/blob/master/wai-app-static/Network/Wai/Application/Static.hs

Incorrect handling of request body

• The example app that shows the request body behaves incorrectly
• It shows incorrect additional content after the actual body request
• With the example app running doing curl http://localhost:3000 -method post -body "hola" i get:
  hola Content/Type text/plain" instead hola
• It seems the handling of the body request servlet input stream with foreign pointers is not workinkg correctly