Servlet 4.0 Adopt-a-JSR 10 Minute Infodeck

Copyright © 2015, Oracle and/or its affiliates. All rights reserved. |
Adopt-a-JSR: JSR-369
Servlet 4.0
Ed Burns and Dr. Shing-Wai Chan
Spec Leads for Servlet
Java EE Specification Team
December, 2014

Safe Harbor Statement
The following is intended to outline our general product direction. It is intended for
information purposes only, and may not be incorporated into any contract. It is not a
commitment to deliver any material, code, or functionality, and should not be relied upon
in making purchasing decisions. The development, release, and timing of any features or
functionality described for Oracle’s products remains at the sole discretion of Oracle.

• Ed Burns
– Oracle
• Long time user of Servlet technology
• Co-spec lead of JSF since 2004
Speaker Credentials

• Dr. Shing Wai Chan
– Oracle
• Servlet Spec Lead since 2013
• Expert group member on many JSRs
relating to Servlet since 2001
Speaker Credentials

Program Agenda
HTTP2 Big Features
How Servlet Might Expose These Features
Adopt-a-JSR
1
2
3

• Request/Response multiplexing
• Binary Framing
• Stream Prioritization
• Server Push
• Header Compression
• Upgrade from HTTP 1.1
• ALPN (or NPN)
• 101 Switching Protocols
8
HTTP/2 Big Ticket Feature Review

HTTP/2 Server Push
• Eliminates the need for resource inlining.
• Lets the server populate the browser’s cache in advance of the browser
asking for the resource to put in the cache.
• No corresponding JavaScript API, but can be combined with SSE
– Server pushes stuff into the browser’s cache.
– Server uses SSE to tell the browser to go fetch it (but we know it’s already in the
browser’s cache).
9
E

HTTP/2 Request Response Multiplexing
• Fully bi-directional
• Enabled by defining some terms
– Connection
A TCP socket
– Stream
A “channel” within a connection
– Message
A logical message, such as a request or a response
– Frame
The smallest unit of communication in HTTP/2.
10
Lets you do more things with a single TCP connection

11
Connections, Streams, Messages, Frames

• Once you break the communication down into frames, you can interweave
the logical streams over a single TCP connection.
• Yet another idea from the 1960s is new again.
12
Connections, Streams, Messages, Frames
Browser
ServerSingle TCP connection for HTTP 2
STREAM'4'
HEADERS'
STREAM'9'
HEADERS'
STREAM'7'
DATA'
STREAM'7'
HEADERS'
STREAM'2'
HEADERS'
STREAM'2'
DATA'

HTTP/2 Binary Framing
• Solves Head-Of-Line (HOL) blocking problem
• Type field can be DATA, HEADERS, PRIORITY, RST_STREAM, SETTINGS,
PUSH_PROMISE, PING, GOAWAY, WINDOW_UPDATE, CONTINUATION
13
Enabled by dumping newline delimited ASCII
Length (24)
Type (8) Flags (8)
R Stream Identifier (31)
Frame Payload (0 …)

• Binary Framing
• Server Push
– ALPN or (NPN)
– 101 Switching Protocols
15
HTTP/2 Features
Servlet 4.0 Big Ticket New Features

• Binary Framing
• Server Push
– ALPN or (NPN)
– 101 Switching Protocols
16
HTTP/2 Features Potentially Exposed in Servlet API

• Push resource to client for a given url and headers
• May add callback for completion or error of a push
• Not at all a replacement for WebSocket
• Really useful for frameworks that build on Servlet, such as JSF
17
Server Push

Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | 18
Server Push
Servlet 4.0
Big Ticket
New Features
Browser
Server Thread A
servlet.service()
GET /index.html
Server
discovers
browser will
need style.css
and script.js
request.dispatchPushRequest("style.css")
request.dispatchPushRequest("script.js")
Server Thread B
servlet.service()
synthetic GET /style.css
synthetic GET /script.js
Server Thread C
servlet.service()
style.css
script.js
index.html

Server Push
public class FacesServlet implements Servlet {
public void service(ServletRequest req,
ServletResponse resp) throws IOException, ServletException {
//..
HttpServletRequest request = (HttpServletRequest) req;
try {
ResourceHandler handler =
context.getApplication().getResourceHandler();
if (handler.isResourceRequest(context) || request.isPushRequest()) {
handler.handleResourceRequest(context);
} else {
lifecycle.attachWindow(context);
lifecycle.execute(context);
lifecycle.render(context);
}
}
}
Example of Potential Use from JSF
19

Server Push
public class ExternalContextImpl extends ExternalContext {
//…
public String encodeResourceURL(String url) {
if (null == url) {
String message = MessageUtils.getExceptionMessageString
(MessageUtils.NULL_PARAMETERS_ERROR_MESSAGE_ID, "url");
throw new NullPointerException(message);
}
Map attrs = getResourceAttrs();
((HttpServletRequest) request).dispatchPushRequest(url, attrs);
return ((HttpServletResponse) response).encodeURL(url);
}
//…
}
Example of Potential Use from JSF
20

Adopt-a-JSR
• Community Tab on JSR-369 page https://jcp.org/en/egc/view?id=369
– JIRA Components: currently we have none. Come up with a list of components for us!
– Use-cases for session-less applications
– List of references to async and thread safety in the spec and javadoc
– You can think of others!

Safe Harbor Statement
The preceding is intended to outline our general product direction. It is intended for
information purposes only, and may not be incorporated into any contract. It is not a
commitment to deliver any material, code, or functionality, and should not be relied upon
in making purchasing decisions. The development, release, and timing of any features or
functionality described for Oracle’s products remains at the sole discretion of Oracle.

Servlet 4.0 Adopt-a-JSR 10 Minute Infodeck

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