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HTTPCore, Cookies

Managing Data on the World Wide-Web

Elad Kravi

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Overview

HttpCore – handlers4

HttpCore - connections2

HttpCore - basics1

HttpCore - demo5

6 Cookies

HttpCore - processors3

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• Apache Software Foundation

• HttpCore is a set of components implementing the most fundamental aspects of the HTTP protocol that are nonetheless sufficient to develop full-featured client-side and server-side HTTP services with a minimal footprint.

• blocking I/O model and and non-blocking I/O.

HttpCore - Intro

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• Manipulate http properties:– Client– Server– Proxy– 236369 home work…

• My example of downloading data from the web– Messages from Social Networks (Twitter)

When would you use HttpCore

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Generic-message = start-line *(message-header CRLF) CRLF [ message-body ]

Start-line = Request-Line | Status-Line

Request = Request-Line *(( general-header | request-header | entity-

header ) CRLF) CRLF [ message-body ]

Response = Status-Line *(( general-header | response-header | entity-

header ) CRLF) CRLF [ message-body ]

HttpMessage, HttpRequest, HttpResponse

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• AbstractHttpMessage – base class– Handle headers: setHeader, getHeaders, etc..– More elegant – use Interceptors (in the following)

• BasicHttpRequest HttpRequest request = new BasicHttpRequest("GET", "/",

HttpVersion.HTTP_1_1);

• BasicHttpResponseHttpRequest request = new BasicHttpRequest("GET", "/",

HttpVersion.HTTP_1_1);

AbstractHttpMessage, BasicHttpRequest, BasicHttpResponse

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• Setting a headerresponse.addHeader("Set-Cookie", "c1=a; path=/; domain=localhost");

• Reading the headers1) Header h1 = response.getFirstHeader("Set-Cookie");2) HeaderIterator it = response.headerIterator("Set-Cookie");

while (it.hasNext()) { System.out.println(it.next());

}

• HTTP headers can be tokenized into individual header elements.– Header elements are properties of the header, e.g.

response.addHeader("Set-Cookie", "c2=b; path=\"/\", c3=c; domain=\"localhost\"");– Parameters can be parsed as name-value pairs.

Setting headers - explicitly

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• HTTP messages can carry a content entity associated with the request or response. – Responses are usually expected to enclose a content entity

• Repeatable Entity - its content can be read more than once– only possible with self contained entities (ByteArrayEntity &

StringEntity)

• Streamed Entity: The content is received from a stream, or generated on the fly.

Http Entities - message payload

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Http Entities (cont)

Http entities that stream out their content from the input stream of the underlying connection, must ensure that the content of the message body is fully consumed for that connection to be potentially re-usable

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• BasicHttpEntity - A generic streamed, non-repeatable entity that obtains its content from an InputStream.

• ByteArrayEntity - A self contained, repeatable entity that obtains its content from a byte array

String myData = "Hello world on the other side!!";ByteArrayEntity myEntity = new ByteArrayEntity(myData.getBytes());

• StringEntity - A self contained, repeatable entity that obtains its

content from java.lang.String object• FileEntity - a self contained, repeatable entity that obtains its content

from a file– for instance, sending a zip file with content type application/zipHttpEntity entity = new FileEntity(staticFile,

"application/java-archive");

(Some) Types of Entities

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Overview

HttpCore – handlers4

HttpCore - connections2

HttpCore - basics1

HttpCore - demo5

6 Cookies

HttpCore - processors3

HttpCore - connections

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• A generic HTTP connection, useful on client and server side.– AbstractHttpClientConnection

• sendRequestHeader, sendRequestEntity, receiveResponseHeader, flush

– AbstractHttpServerConnection• receiveRequestHeader, receiveRequestEntity, sendResponseHeader,

sendResponseEntity, flush

– Which kind a proxy should have?

• Concrete types define ‘bind’ method to bind a socket.

HttpConnection (extends closable)

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• Terminating HTTP connections– Gracefully by calling HttpConnection#close()– Forcibly by calling HttpConnection#shutdown()

• HTTP exception handling– IOException in case of an I/O failure such as socket timeout or an

socket reset– HttpException that signals an Http failure such as a violation of the

Http protocol

Closing connection and Exceptions

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Overview

HttpCore – handlers4

HttpCore - connections2

HttpCore - basics1

HttpCore - demo5

6 Cookies

HttpCore - processors3

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• A routine that implements a specific aspect of the Http protocol using protocol interceptors– protocol interceptors act upon specific header(s) of the incoming or

outgoing message.– http protocol processor is a collection of protocol interceptors that

implements the 'Chain of Responsibility' pattern• each individual protocol interceptor is expected to work on the particular

aspect of the Http protocol it is responsible for.

– If the interceptors must be executed in a particular order, they should be added to the processor in the same sequence.

HttpProcessor

void process(HttpRequest request, HttpContext context) throws HttpException, IOException

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• RequestContent / ResponseContent – important interceptors for outgoing requests / responses. – Responsible for delimiting content length by adding Content-Length

or Transfer-Content headers based on the properties of the enclosed entity and the protocol version.

• RequestConnControl / ResponseConnControl –– responsible for adding Connection header to the outgoing requests /

responses.

• RequestTargetHost – required for client side protocol– responsible for adding Host header

• RequestUserAgent – recommended for client side protocol– responsible for adding User-Agent header

(Some) Protocol interceptors

e.g. Connection : close

content-length, content-type…

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Using Protocol Processors

Send the request to the target host and get a response.

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• Protocol interceptors collaborate by sharing information such as processing state through an Http execution context.– HttpContext is a structure that can be used to map an attribute

name to an attribute value.

Http Context

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Overview

HttpCore – handlers4

HttpCore - connections2

HttpCore - basics1

HttpCore - demo5

6 Cookies

HttpCore - processors3

HttpCore - handlers

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• a client side HTTP protocol handler based on the blocking I/O model

• relies on HttpProcessor to generate mandatory protocol headers for all outgoing messages

• apply common, cross-cutting message transformations to all incoming and outgoing messages

HttpRequestExecutor httpexecutor = new HttpRequestExecutor();…httpexecutor.preProcess(request, httpproc, context);HttpResponse response = httpexecutor.execute(request, conn, context);…httpexecutor.postProcess(response, httpproc, context);

HttpRequestExecutor

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• a server side HTTP protocol handler based on the blocking I/O model

• relies on HttpProcessor to generate mandatory protocol headers for all outgoing messages

• apply common, cross-cutting message transformations to all incoming and outgoing messages– whereas individual HttpRequestHandlers are expected to take care

of application specific content generation and processing– relies on HttpRequestHandler to resolve matching request handler

for a particular request URI of an incoming HTTP request

HttpService

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Overview

HttpCore – c & s handlers4

HttpCore - headers2

HttpCore - basics1

HttpCore - demo5

6 Cookies

HttpCore - entities3

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• A client implemented using HttpCore– Configuration

• HttpRequestExecutor• HttpProcessor• HttpContext• HttpRequest

– Main logic – “GET” some files from the server• Using HttpRequestExecutor

– preProcess, execute and postProcess

• Print some usefull information from the response

What we will see in this example?

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• A server implemented using HttpCore– Configuration

• HttpService• HttpProcessor• HttpContext• HttpRequest

What we will see in this example?

sd Sequence

RequestListenerThread

WorkerThread

loop ForEveryNewRequest

configurations()

.(HttpService, Socket)

handle(request, response, context)

– Main logic – Upon receiving a new request• Create a working thread

– Handles the request

• Wait for the next request

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• HttpClient is a HTTP/1.1 compliant Http agent implementation based on HttpCore. It also provides reusable components for client-side authentication, Http state management, and Http connection management.– e.g., parsing cookies

• Self learning

HttpClient

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Overview

HttpCore – c & s handlers4

HttpCore - headers2

HttpCore - basics1

HttpCore - demo5

6 Cookies

HttpCore - entities3

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• An Http cookie is a token or short packet of state information that the Http agent (e.g. browser) and the target server can exchange to maintain a session.

• In its simplest form an Http cookie is merely a name / value pair.– Usually a cookie also contains a number of

attributes such as: version, a domain for which is valid, a path that specifies the subset of URLs on the origin server to which this cookie applies, and the maximum period of time for which the cookie is valid

Http Cookies

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• Cookies allow to save state using stateless http protocol.

• Usefull scenario: a shopping cart• Privacy hazzard:

– Consider the following scenario:• A cookie is set on the user’s browser• Every site the user visits the cookie is sent to the server

• Cookies can help monitoring your browsing history

Are they really ‘fortune cookies’?