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Building Web Applications With Building Web Applications With WebjectsWebjects

Michael D. Barker

The MIT Educational Media Creation Center

September 2001

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What's a Webject?What's a Webject? A set of servlets, allowing handling of several

"standard" operations on data over the web by setting up the correct forms and configuration files. Notice that I did not say writing code – the servlets are deliberately designed to be generic, so that changes are made in the forms and configuration files, not the code.

At this point in time, there are five webject servlets: Capture, Lister, Displayer, Revise, and Deleter.

Webject as a one set of data.

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CaptureCapture

HTML Form

Capture Servlet Webject

List

Capture is used to collect information from a web form for ONE webject. Often, the web form is just a simple html page, with form action posting to capture.

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ListerLister

HTML Form

Lister ServletWebject

List

Lister generates a web form displaying information from all the webjects in a list.

HTMX Form

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DisplayerDisplayer

HTML Form

Displayer ServletWebject

List

Displayer generates a web form displaying information from a single webject.

HTMX Form

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ReviseRevise

HTML Form

Revise Servlet Webject

List

Revise is used to collect information from a web form to make changes for ONE webject. Often, the web form is generated by displayer.

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DeleterDeleter

HTML Form

Deleter Servlet Webject

List

Deleter is used to remove one webject from the list. Often, it is invoked from a form generated by lister.

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Typical ApplicationTypical Application

Collect information (using Capture) Display a list of results (using Lister) With edit buttons (using Displayer) that

bring up forms whose submit changes the information (using Revise)

And delete buttons (that bring up a form and confirm, then invoke Deleter)

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Parameters, XML files, and Parameters, XML files, and suchsuch

Every servlet has some parameters. webject specification file webject list file Configuration in servlet zone properties

file page templates (htmx files)

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Webject Specification FileWebject Specification File<?xml version="1.0" encoding="UTF-8"?> <defnspec docclass="edu.mit.emcc.webject.XMLObjectSpecFile" > <parameter name="term" required="1" errorRequired="You must provide a term to be defined." />  <parameter name="definition" required="1" errorRequired="You must provide a definition for the term." />

  <parameter name="SUBMIT" ignored="1"/>

<parameter name="Submit" ignored="1"/> </defnspec>

Replace the parameter definitions with your data fields.

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Possible AttributesPossible Attributes

Among the attributes that can be specified for a parameter are: name="name" The name of the parameter. Required. required="1" errorRequired="message" optional="1" (default) ignored="1" (discard even if value present – good for discarding

submit) multiple="1" May have multiple values default="value" equals="name" use value of name defaultequals="name" use value of name as default

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Webject List FileWebject List File

<?xml version="1.0" encoding="UTF-8"?>

<iplist type="iprange"

specfile="../conf/iplistspec.xml"

docclass="edu.mit.emcc.webject.WebjectList"

webjectclass="edu.mit.emcc.webject.Webject">

<lastid>1</lastid>

</iplist>

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HTMX FileHTMX File

Normal HTML plus(Displayer and Lister) <WEBJECTDATA name> : the value of name <WEBJECTDATACHECK name>: CHECKED if

non-blank value <WEBJECTDATASELECT name=value> :

SELECTED if value(Lister only) <WEBJECTLIST count>: number of items in list <FRAGREPEAT WEBJECT>...</WEBJECT>: repeat

for all elements in list

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Capture ParametersCapture ParametersMinimum: servlet.AddTicket.code=edu.mit.emcc.webject.Capture

(alias) servlet.AddTicket.initArgs=root=/development (root

directory to prepend to all other file names) servlet.AddTicket.initArgs=capturepage=ListTickets or

servlet.Register.initArgs=capturepage=../lobby/register.html (html form, allows gets to servlet to redirect to form)

servlet.AddTicket.initArgs=webjectlist=data/ccoach/accessinfo/tickets.xml (the webject list)

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Capture ParametersCapture ParametersAdditional: servlet. SomeName.initArgs=templatedir=<filename>

Directory where HTML templates are stored servlet. SomeName.initArgs=successtemplate=<filename>

for successful submissions (default: capturesuccess.htmx) servlet. SomeName.initArgs=errortemplate=<filename> for

validation errors (captureerror.htmx) servlet. SomeName.initArgs=duplicatetemplate=<filename>

for duplicate keys (captureduplicate.htmx) There is also a set of parameters to generate email – read

the code for details (list follows)

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Capture Parameters (email)Capture Parameters (email) servlet.SomeName.initArgs=mailserver=(address) servlet.SomeName.initArgs=partialemailtemplate=(filename) servlet.SomeName.initArgs=partialto=(address) servlet.SomeName.initArgs=partialsubject=(subject) servlet.SomeName.initArgs=partialfrom=(address) servlet.SomeName.initArgs=completeemailtemplate=(filename) servlet.SomeName.initArgs=completeto=(address) servlet.SomeName.initArgs=completesubject=(subject) servlet.SomeName.initArgs=completefrom=(address)

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Lister ParametersLister ParametersMinimal servlet.SomeName.code=edu.mit.emcc.webject.Lister

(alias) servlet. SomeName.initArgs=projectroot=<directory>

(root of files) servlet. SomeName.initArgs=webjectlist=<filename>

(data list) servlet. SomeName.initArgs=templatedir=<filename>

(where are the templates)

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Lister ParametersLister ParametersOptional servlet. SomeName.initArgs=listtemplate=<filename>Defaults to listtemplate.htmx servlet. SomeName.initArgs=mimetype=<mime-type>Defaults to text/html servlet. SomeName.initArgs=sortby=<date|title>Defaults to date servlet. SomeName.initArgs=daysback=<number>How many days back to include (defaults to all) Often

entered in url (servlet name?daysback=5 for example)

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Displayer ParametersDisplayer Parameters

Minimal servlet.SomeName.code=edu.mit.emcc.webject.Displayer

(alias) servlet.SoName.initArgs=projectroot=<directory> (root

for files) servlet.SoName.initArgs=webjectlist=<filename> (data

list) servlet.SoName.initArgs=templatedir=<filename>

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Displayer ParametersDisplayer ParametersOptional servlet.SoName.initArgs=webjecttemplate=<filename>

Defaults to webjecttemplate.htmx servlet.SoName.initArgs=notfoundtemplate=<filename>

Defaults to notfoundtemplate.htmx servlet.SoName.initArgs=idsource=<param|auth|username>

How to get id of webject. Defaults to parameter (ID=xxx).

Also accepts auth (look up user in webject list) and

username (a username parameter will be supplied)

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Revise ParametersRevise Parameters

Minimal servlet.SomeName.code=edu.mit.emcc.webject.Revise

(alias) servlet.SoName.initArgs=projectroot=<directory> servlet. SoName.initArgs=editpage=<URL> servlet. SoName.initArgs=webjectlist=<filename> servlet. SoName.initArgs=templatedir=<filename>

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Revise ParametersRevise Parameters

Optional servlet. SoName.initArgs=successtemplate=<filename>

Defaults to revisesucess.htmx servlet. SoName.initArgs=errortemplate=<filename>

Defaults to reviseerror.htmx

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Deleter ParametersDeleter Parameters

Minimal servlet.SomeName.code=edu.mit.emcc.webject.Deleter (alias) servlet.SoName.initArgs=projectroot=<directory> servlet.SoName.initArgs=webjectlist=<filename> servlet.SoName.initArgs=templatedir=<filename>

Runtime SomeName?ID=xxxxx

Or

SomeName?id=xxxxxx

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Deleter ParametersDeleter Parameters

Optional servlet. SoName.initArgs=deletedtemplate=<filename>

Defaults to deletedtemplate.htmx

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Likely Future Additions to the Likely Future Additions to the Webject LibraryWebject Library

"archive" – put a class of webjects into another file and remove from the "active" file

Conversion to use mySQL, Oracle, or other database

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For Additional InformationFor Additional Information

<https://web.mit.edu/emcc/Private/library/webjects.html>

Brian Bermack's original documentation

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You Can Reach Us...You Can Reach Us...

Michael Barker– mbarker@mit.edu

– 617/253-0119

EMCC website: http://web.mit.edu/emcc/