2015 UJUG, Servlet 4.0 portion

Servlet 4.0

Manfred Riem (@mnriem)Oracle

Copyright © 2015, Oracle and/or its affiliates. All rights reserved. |


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Agenda

Why HTTP/2?

HTTP/2 Big Features

How Servlet Might Expose These Features

Server Push and JSF/MVC

Summary and Current Status

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Why HTTP/2?A Real Life Example

index.html

style1.css

style2.css...

script1.js

script9.js

pic1.jpg

pic8.jpg

.

.

.

photo1.png

photo2.png

.

.

.


Why HTTP/2?

• HTTP Pipelining

• Head-of-Lineblocking

Problems in HTTP/1.1

style1.css

style2.css

Client Server

index.html

index.html

style1.cssstyle2.cssscript1.js

.

.

.

script2.js

.

.

.

script1.js

script2.js


Why HTTP/2?

• Inefficient use of TCP sockets

Problems in HTTP/1.1

Client ServerClient Server

Client Server

Client Server

Client Server

Client Server


Why HTTP/2?

• Much of what we do in web-apps is a hack to work around shortcomings in HTTP/1.1

– File concatenation and image sprites

– Domain sharding

– Inlined assets

What is an optimization?

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File Concatenation and Image SpritesTCP Efficiency Improves with Larger Files

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• Modern web page now consists of more than 90 resources fetched from 15 distinct hosts

• Solution:

– Just work around it by shoving more than one logical file into one physical file.

– Seminal article: A List Apart http://alistapart.com/article/sprites

– Useful tool: SpritePad http://spritepad.wearekiss.com/


File Concatenation and Image SpritesTCP Efficiency Improves with Larger Files

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.ic-AerospaceAndDefense-wht-on-gray, .ic-AerospaceAndDefense-wht-on-red, .ic-Airline-wht-on-gray, .ic-Airline-wht-on-red{

background: url(sprites.png) no-repeat;}.ic-AerospaceAndDefense-wht-on-gray{

background-position: 0 0;width: 80px;height: 80px;

}.ic-AerospaceAndDefense-wht-on-red{

background-position: -81px 0;width: 80px;height: 80px;

}.ic-Airline-wht-on-gray{

background-position: 0 -80px ;width: 80px;height: 80px;

}.ic-Airline-wht-on-red{

background-position: -81px -79px ;width: 80px;height: 80px;

}


Domain ShardingSplit page resources across several hosts to work around browser limits

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Inlined Assets

• data URLs

• <imgsrc="data:image/gif;base64,R0lGODlhEAAOALMAAOazToeHh0tLS/7LZv/0jvb29t/f3//Ub/ /ge8WSLf/rhf/3kdbW1mxsbP//mf///yH5BAAAAAAALAAAAAAQAA4…" />

Base64 Encoding Will Never Die

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Our Plan for Your Time Investment

Why HTTP/2?

HTTP/2 Big Features




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HTTP/2 is really just a new transport layer underneath HTTP/1.1

– same request/response model

– no new methods

– no new headers

– no new usage patterns from application layer

– no new usage of URL spec and other lower level specs

Network Programming Review

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The Socket Angle

• It would be like if we took the existing Servlet specification



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The Socket Angle

• It would be like if we took the existing Servlet specificationand added a new layer underneath it


Network Programming ReviewThe Socket Angle

Client ServerClient Server

Client Server

Client Server

Client Server


Network Programming ReviewSolution in HTTP/2

Client Server


HTTP/2 Request Response Multiplexing

• Fully bi-directional

• Enabled by defining some terms

– ConnectionA TCP socket

– StreamA “channel” within a connection

–MessageA logical message, such as a request or a response

– FrameThe smallest unit of communication in HTTP/2.

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Lets you do more things with a single TCP connection



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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.

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Connections, Streams, Messages, Frames

BrowserServerSingle 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 Stream Prioritization

• Stream Dependency in HEADERSFrame

• PRIORITY frame type

• An additional 40 bytes

– Stream id (31)

– Weight (8): [1, 256]

– Exclusive bit (1)

• Only a suggestion

21S

A

B C

4 12

A

B CD

4 16 12

exclusive = 0

A

B C

D

4 12

16

exclusive = 1


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).

22E


HTTP/2 Upgrade from HTTP/1.1

• Not secure

– We have to use port 80

– Use existing 101 Switching Protocols from HTTP/1.1

• Secure– Next Protocol Negotiation (NPN)

– Application Layer Protocol Negotiation (ALPN)

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Secure or not-secure?


Agenda

Why HTTP/2?

HTTP/2 Big Features




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• Existing API is designed for One Request == One Response.

• HTTP/2 destroys this assumption.

• It will be challenging to do justice to the new reality of One Request == One or More Responses.

• We must not simply bolt the “One or More Responses” concept onto some convenient part of the existing API.

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Challenges in Exposing HTTP/2 Features in Servlet API

Servlet 4.0 Big Ticket New Features


• Request/Response multiplexing

• Stream Prioritization

• Server Push

• Upgrade from HTTP/1.1

– 101 Switching Protocols

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HTTP/2 Features Potentially Exposed in Servlet API



• Add method HttpServletRequest and HttpServletResponse– int getStreamId()

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Request/Response Multiplexing



• Add a new class Priority

– boolean exclusive

– int streamId

– int weight

• Add method to HttpServletRequest

– Priority getPriority()

• Add methods to HttpServletResponse

– Priority getPriority()

– void setPriority(Priority p)

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Stream Prioritization



• 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

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Server Push


Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | 30

Server Push

Servlet 4.0Big TicketNew Features

BrowserServer Thread Aservlet.service()

GET /index.html

Server discovers

browser will need style.css and script.js

request.dispatchPushRequest("style.css")

request.dispatchPushRequest("script.js")

Server Thread Bservlet.service()

synthetic GET /style.css

synthetic GET /script.js

Server Thread Cservlet.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)) {handler.handleResourceRequest(context);

} else {lifecycle.attachWindow(context);lifecycle.execute(context);lifecycle.render(context);

}}

}

Example of Potential Use from JSF

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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

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Server Push

• The MVC EG needs to see how this will be integrated into the MVC specification so no example at the moment.

Example for MVC

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Our Plan for Your Time Investment

Why HTTP/2?

HTTP/2 Big Features




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• Servlet 4.0 brings HTTP/2 to Java EE

– 100% compliant implementation of HTTP/2

– Expose key features to the API• Server Push

• Stream Prioritization

• Request/Response multiplexing

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• JSR-369 just formed on 22 September

• Tentative Delivery Schedule

– Q3 2014: expert group formed

– Q2 2015: early draft

– Q3 2015: public review

– Q4 2015: proposed final draft

– Q3 2016: final release

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How to Get Involved

• Adopt a JSR

– http://glassfish.org/adoptajsr/

• The Aquarium

– http://blogs.oracle.com/theaquarium/

• Java EE 8 Reference Implementation– http://glassfish.org

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Technology

2015 UJUG, Servlet 4.0 portion