LIS650 lecture 5 javascript, http and apache

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LIS650 lecture 5 javascript, http and apache

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Title: LIS650 lecture 5 javascript, http and apache


1
LIS650 lecture 5javascript, http and apache
  • Thomas Krichel
  • 2005-10-14

2
today
  • javascript
  • http
  • apache introduction

3
the ltscriptgt
  • ltscriptgt is an element that calls a script.
  • It requires a "type" attribute that gives the
    type of the script language. e.g.
    type"text/javascript".
  • It takes the src argument that gives a URI where
    the script can be found. Such a script is called
    an external script.
  • It takes a defer attribute. If set as defer"1"
    you tell the user agent that the script will
    generate no output. This helps the user agent in
    that case.

4
example
  • ltscript type"text/javascript"gt
  • document.write("hello, world")
  • lt/scriptgt
  • Interestingly enough, you can place this script
    in the head or the body.
  • This is an example of an automated script. The
    user has to do nothing to get the script to run.
  • You can also trigger a script. To do that, we
    have to study some more HTML attributes. We will
    do that later.

5
external script
  • You can also create an external file, say
    hello.js with the line
  • document.write("hello, world")
  • Then you can call it up in the html file
  • ltscript type"text/javascript"
    src"hello.js"/gt

6
default script language
  • You should set the default scripting language
    used in the document using the ltmeta/gt element in
    the ltheadgt
  • ltmeta http-equiv"content-script-type"
    content"text/javascript"/gt
  • If you don't the validator does not complain, but
    I don't see other ways to specify the language.

7
Javascript history
  • A programming language that was developed by
    Netscape for their browser in 1995.
  • To counter, Mickeysoft developed Jscript.
  • It has been standardized by the European Computer
    Manufacturers Association as ECMA 262.

8
principal features
  • It contains instructions for a user agent to
    execute. Javascript is not run by the server.
  • It resembles Java, but not the same language.
  • It is an object-oriented language.

9
object
  • In an object-oriented language, an object is the
    prime focus of attention.
  • An object has properties and methods.
  • Example from real life. Let a bus be an object.
  • color of the bus is a property
  • move to next station is a method

10
objects in javascript
  • Properties are accessed by
  • object_name.property_name
  • Methods are accessed by
  • object_name.method_name()
  • where object_name is the name of an object,
    property_name is the name of a property and
    method_name() is the name of an object. Note the
    use of the dot and the parenthesis.

11
Example
  • Syntax rules
  • Comments are started with // and go to the end of
    the line.
  • Instructions are terminated with semicolon
  • Example
  • // create a new object called bus
  • new bus Object()
  • // paint it white --- set a property
  • bus.color white
  • // move to next stop --- apply a method
  • bus.movetonextstop()

12
event attributes
  • Event attributes can be given to elements (like
    any attribute, really)
  • The name of the attributes gives a certain event
    that could happen to the element.
  • The value of the event attribute is the script to
    be executed when the event occurs on the element
    that has the event attribute.
  • Example
  • ltp onmouseover"stink"gtCow shit is ... lt/pgt
  • as the user moves the mouse over the
    paragraph, the browser fires up an imaginary
    script called stink that makes it start to stink.

13
core event attributes I
  • onclick occurs when the pointing device button
    is clicked over an element.
  • ondblclick occurs when the pointing device
    button is double clicked over an element.
  • onmousedown occurs when the pointing device
    button is pressed over an element.
  • onmouseup occurs when the pointing device button
    is released over an element.
  • onmouseover occurs when the pointing device is
    moved onto an element.

14
core events attributes II
  • onmousemove occurs when the pointing device is
    moved while it is over an element.
  • onmouseout occurs when the pointing device is
    moved away from an element.
  • onkeypress occurs when a key is pressed and
    released over an element.
  • onkeydown occurs when a key is pressed down over
    an element.
  • onkeyup occurs when a key is released over an
    element.

15
special event attributes
  • onfocus occurs when an element receives focus
    either by the pointing device or by tabbing
    navigation. This attribute may only be used with
    the ltagt element, and some form elements that we
    have not covered.
  • onblur occurs when an element loses focus either
    by the pointing device or by tabbing navigation.
    It may be used with the same elements as onfocus.

16
more special event attributes
  • onsubmit occurs when a form is submitted. It
    only applies to the ltformgt element.
  • onreset occurs when a form is reset. It only
    applies to the ltformgt element.
  • some more are only used with other form
    elements...
  • Let us look at some examples

17
two stupid examples
  • lthtmlgtltheadgtlttitlegtjavascript testlt/titlegt
  • ltmeta http-equiv"content-script-type"
    content"text/javascript"/gtlt/headgt
  • ltbodygtltp onmouseover"alert('Today is 'Date())"
    gttimelt/pgtlthr/gt
  • ltp onmouseover
  • "document.write('not funny')"gtjokelt/pgt
    lt/bodygtlt/htmlgt

18
An even more silly example
  • lthtmlgtltheadgtlttitlegtBush in the bushlt/titlegt
  • ltmeta http-equiv"content-script-type" content
    "text/javascript"/gtltscript type"text/javascript"gt
  • prbunew Image() prbu.src"bush.jpg"
  • natbnew Image() natb.src"natgeo.jpg"
    lt/scriptgtlt/headgtltbodygtlth4gtBush in the
    bushlt/h4gtltdivgtltimg id"bush" src"bush.jpg"
    onmouseover"document.bush.srcnatb.src"
  • onmouseout"document.bush.srcprbu.src"
    alt"bush in the bush"/gtlt/divgtlt/bodygtlt/htmlgt

19
http
  • Stands for the hypertext transfer protocol. This
    is the most important application layer protocol
    on the Internet today, because it provides the
    foundation for the world wide web.
  • defined in Fielding, Roy T., James Gettys,
    Jeffrey C. Mogul, Paul J. Leach, Tim Berners-Lee
    Hypertext Transfer Protocol -- HTTP/1.1''
    (1999), RFC 2616

20
history
  • 1990 version 0.9 allows for transfer of raw
    data.
  • 1996 rfc1945 defines version 1.0. by adding
    attributevalue headers.
  • 1999 rfc 2616
  • adds support for
  • hierarchical proxies
  • caching,
  • virtual hosts and some
  • Support for persistent connections
  • is more stringent.

21
http resource identification
  • identification of resources is assumed through
    Uniform Resource Identifiers (URI).
  • As far as http is concerned, URIs are string.
  • http can use absolute'' and relative'' URIs.
  • A URL is a special case of a URI.

22
rfc about http
  • An application-level protocol for distributed,
    collaborative, hypermedia information systems.
  • HTTP is also used as a generic protocol for
    communication between user agents and
    proxies/gateways to other Internet systems,
    including those supported by the SMTP, NNTP, FTP,
    Gopher, and WAIS protocols. In this way, HTTP
    allows basic hypermedia access to resources
    available from diverse applications.

23
http assumes transport
  • http assumes that there is a reliable way to
    transport data from one host on the Internet to
    another one.
  • All http requests and responses are separate TCP
    connections. The default is TCP port 80, but
    other ports can be used.

24
use of other standards
  • http shares the same registry as the MIME
    multimedia email extensions. It is based at the
    IANA, at
  • http//www.isi.edu/innotes/iana/
  • assignments/media-types/media-types
  • The default character set is ISO-8859-1.

25
Absolute http URL
  • the absolute http URL is
  • http//hostportabs_path?query
  • If abs_path is empty, it is /.
  • The scheme name "http" and the host name are
    case-insensitive.
  • optional components are in

26
special characters in URL
  • Characters other than those in the reserved and
    unsafe character lists of RFC 2396 are
    equivalent to their HEX HEX where HEX is a
    hex number, usually the characters number in
    ASCII.
  • Example to include a blank in a URI, you write
    20, because 32 is the position of the blank in
    ASCII.

27
http messages
  • There are two types of messages.
  • Requests are sent form the client to the server.
  • Responses are sent from the server to the client.
  • The generic format is the same as for email
    messages
  • start line
  • message headers
  • empty line
  • body
  • The request's start line is called the request
    line.
  • The response start line is called the status
    line.

28
overall operation server side
  • Server sends response, required items are
  • status line
  • protocol version
  • success or error code
  • optional items are
  • server information
  • body

29
overall operation client side
  • Client sends request, required items are
  • method
  • request URI
  • protocol version
  • optional items are
  • request modifiers
  • client information
  • Let us now look at different methods

30
GET and HEAD method
  • The GET method means retrieve whatever
    information (in the form of an entity) is
    identified by the Request-URI. If the Request-URI
    refers to a data-producing process, it is the
    produced data which shall be returned as the
    entity in the response and not the source text of
    the process.
  • The HEAD method is identical to GET except that
    the server MUST NOT return a message-body in the
    response.

31
The POST method
  • The POST method is used to request that the
    origin server accept the entity enclosed in the
    request as a new subordinate of the resource
    identified by the Request-URI in the
    Request-Line. POST is designed to allow a uniform
    method to cover the following functions
  • Annotation of existing resources
  • Posting a message to a bulletin board, newsgroup,
    mailing list, or similar group of articles
  • Providing a block of data, such as the result of
    submitting a form, to a data-handling process
  • Extending a database through an append operation.

32
PUT and DELETE methods
  • The PUT method requests that the enclosed entity
    be stored under the supplied Request-URI. If the
    Request-URI refers to an already existing
    resource, the enclosed entity should be
    considered as a modified version of the one
    residing on the origin server.
  • The DELETE method requests that the origin server
    delete the resource identified by the Request-URI.

33
The request headers
  • Accept Accept-Charset
  • Accept-Encoding Accept-Language
  • Authorization Expect
  • From Host
  • If-Match If-Modified-Since
  • If-None-Match If-Range
  • If-Unmodified-Since Max-Forwards
  • Proxy-Authorization Range
  • Referer TE
  • User-Agent

34
Entity headers, common to response and request
  • Allow
  • Content-Encoding
  • Content-Language
  • Content-Length
  • Content-Location
  • Content-MD5
  • Content-Range
  • Content-Type
  • Expires
  • Last-Modified

35
The status line
  • The status line is a set of lines that are of
    the form
  • HTTP-Version Status-Code Reason-Phrase
  • The status code is a 3-digit number used by the
    computer.
  • The reason line is a friendly note for a human to
    read.

36
Status code classes
  • 1 Informational Request received, continuing
    process
  • 2 Success The action was successfully received,
    understood, and accepted
  • 3 Redirection Further action must be taken in
    order to complete the request
  • 4 Client Error The request contains bad syntax
    or cannot be understood
  • 5 Server error The request is valid but can not
    be executed by the server

37
Error codes
  • 100 Continue
  • 101 Switching Protocols
  • 200 OK
  • 201 Created
  • 202 Accepted
  • 203 Non-Authoritative Information
  • 204 No Content
  • 205 Reset Content
  • 206 Partial Content

38
Error codes II
  • 300 Multiple Choices
  • 301 Moved Permanently
  • 302 Found
  • 303 See Other
  • 304 Not Modified
  • 305 Use Proxy
  • 307 Temporary Redirect

39
Error codes III
  • 400 Bad Request
  • 401 Unauthorized
  • 402 Payment Required
  • 403 Forbidden
  • 404 Not Found
  • 405 Method Not Allowed
  • 406 Not Acceptable
  • 407 Proxy Authentication Required
  • 408 Request Time-out

40
Error codes IV
  • 409 Conflict
  • 410 Gone
  • 411 Length Required
  • 412 Precondition Failed
  • 413 Request Entity Too Large
  • 414 Request-URI Too Large
  • 415 Unsupported Media Type
  • 416 Requested range not satisfiable
  • 417 Expectation failed

41
Error codes V
  • 500 Internal Server Error
  • 501 Not Implemented
  • 502 Bad Gateway
  • 503 Service Unavailable
  • 504 Gateway Time-out
  • 505 HTTP Version not supported

42
Response headers
  • Accept-Ranges
  • Age
  • Etag
  • Location
  • Proxy-Authenticate
  • Retry-After
  • Server
  • Vary
  • WWW-Authenticate

43
example response
  • HTTP/1.1 200 OK
  • Date Fri, 14 Oct 2005 011401 GMT
  • Server Apache/2.0.54 (Debian GNU/Linux)
  • Last-Modified Fri, 07 Oct 2005 164030 GMT
  • ETag "11f711-9f1-b314bb80"
  • Accept-Ranges bytes
  • Content-Length 2545
  • Connection close
  • Content-Type text/html charsetUTF-8
  • lt!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0
    Strict//EN"
  • "http//www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd
    "gt
  • lthtmlgtltheadgtlttitlegtThomas Krichel's homepage

44
The body
  • The entity-body (if any) sent with an HTTP
    request or response is in a format and encoding
    defined by the entity-header fields.
  • When an entity-body is included with a message,
    the data type of that body is determined via the
    header fields Content-Type and Content-Encoding

45
example status redirect
  • If you use Apache, you can create a file
    .htaccess (note the dot!) with a line
  • redirect 301 old_url new_url
  • old_url must be a relative path from the top of
    your site
  • new_url can be any URL, even outside your site
  • This works on wotan by virtue of configuration
    set for apache for your home directory. Examples
  • redirect 301 /krichel http//openlib.org/home/kri
    chel
  • redirect 301 Cantcook.jpg http//www.foodtv.com

46
Apache
  • Is a free, open-source web server that is
    produced by the Apache Software Foundation, see
    http//www.apache.org
  • It has over 50 of the market share.
  • It runs best on UNX systems but can run an a
    Mickeysoft OS as well.
  • I will cover it here because it is freely
    available.
  • Wotan runs version 2.

47
Apache in debian
  • /etc/apache2/apache.conf is set main
    configuration file.
  • /etc/init.d/apache2 action, where action is one
    of
  • start
  • stop
  • restart
  • is used to fire the daemon up or down.
  • The daemon runs user www-data

48
Virtual host
  • On a single installation of Apache several web
    servers can be supported.
  • That means the server can behave in a different
    way according to how it is being addressed.
  • The easiest way to implement addressing a server
    in different was is through DNS host names.

49
directives in apache.conf
  • This file contains directives that control the
    operation of the Apache server process as a
    whole.
  • Some of them are
  • the server root, where it finds its configuration
  • the time out for requests
  • which port to listen
  • another part of apache.conf has extensive
    settings to deal with content
  • different languages
  • different character sets
  • different MIME types

50
Modules
  • To extend Apache, modules have written. The
    modules are kept in a directory modules-available
  • Modules that are enabled are listed in the
    directory modules-enabled.
  • Looking at this gives you vital information about
    what the server can do.

51
Server directives
  • User
  • Gives the user name apache runs under
  • Group
  • Gives the group name the server runs under
  • ServerAdmin
  • Email of a human who runs the default server
  • ServerName
  • The name of the default server
  • DocumentRoot
  • The top level directory of the default server

52
Directory options
  • Many options for a directory can be set with
  • ltdirectory namegt instructionsltdirectorygt
  • Name is the name of a directory.
  • Instructions can be a whole lot of stuff.

53
Directory instructions
  • Options sets global options for the directory, it
    can be
  • None
  • All
  • Or any of
  • Indexes (form directory indexes?)
  • Includes (allow server side includes?)
  • FollowSymlinks (allow to follow symbolic links)
  • ExecCGI (allow cgi-scripts?)
  • MultiViews (allow flexibility in URLs)

54
Access control
  • Can be part of ltdirectorygt to set directory level
    access control
  • Example
  • Allow from friendly.com
  • Deny from evil.com
  • Sometimes you have to set the order, example
  • Order allow, deny

55
Authentication
  • This is used to enable password access. In that
    case the authentication is handled by a file
    .htaccess in the directory.
  • The AllowOverride instruction is used to state
    what the user can do within the .htaccess file.
    Depending on its values, you can password protect
    a web site.
  • We will not discuss this further here.

56
UserDir
  • This sets the directory that is created by the
    user in her home directory to be accessed by
    requests to user.
  • On wotan, we have
  • UserDir public_html
  • That is the default, actually.

57
permissions for user directories
  • ltDirectory /home//public_htmlgt
  • AllowOverride FileInfo AuthConfig Limit
  • Options Includes
  • Options MultiViews Indexes SymLinksIfOwnerMatc
    h IncludesNoExec
  • ltLimit GET POST OPTIONS PROPFINDgt
  • Order allow,deny
  • Allow from all
  • lt/Limitgt
  • ltLimit PUT DELETE PATCH PROPPATCH MKCOL COPY
    MOVE LOCK UNLOCKgt
  • Order deny,allow
  • Deny from all
  • lt/Limitgt
  • lt/Directorygt

58
logs
  • The web server logs every transaction.
  • The are severeal types of logs that used to be
    kept separately, in early days.
  • 209.73.164.50 - - 26/Jan/2003091951 -0500
    "GET /ramon/videos/ntsc175.html
  • HTTP/1.1" 206 808
  • Additional information may be kept in the referer
    and user agent log.
  • The referer log may have some interesting
    information on who links to your pages.

59
virtual hosts
  • Most apache directive can be wrapped in a
    ltvirtualhostgt lt/virtualhostgt grouping. This
    implies that the only hold for the virtual host.
    Example
  • ltVirtualHost gt
  • ServerAdmin krichel_at_openlib.org
  • DocumentRoot /home/connect/public_html
  • ServerName connections2003.liu.edu
  • ErrorLog /var/log/apache/connections2003-erro
    r.log
  • CustomLog /var/log/apache/connectios2003-acce
    ss.log common
  • lt/VirtualHostgt

60
http//openlib.org/home/krichel
  • Thank you for your attention!
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