Java CGI HOWTO: Using the Java CGI Classes.

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## 5. Using the Java CGI Classes.

There are currently three main classes supported -- CGI, Email and HTML. I am considering adding classes to deal with MIME-formatted input and output -- MIMEin & MIMEout, respectively.

There are also a few support and test classes. CGI_Test, Email_Test and HTML_Test are intended to be used to test your installation. They can also be used as a starting-point for your own Java programs which use this class library. The Text class is the superclass for both the `Email` and the `HTML` classes.

## 5.1 CGI

### Class Syntax

`public class CGI`

### Class Description

The CGI class holds the ``CGI Information'' -- Environment variables set by the web server and the name/value sent from a form when its submit action is selected. All information is stored in a `Properties` class object.

This class is in the ``Orbits.net'' package.

### Member Summary

            CGI()         //  Constructor.
            getNames()    //  Get the list of names.
            getValue()    //  Get form value by specifying name.

### See Also

`CGI_Test`.

### CGI()

Purpose

  Constructs an object which contains the available CGI data.

Syntax

  `public CGI()`

Description

  When a CGI object is constructed, all available CGI information is sucked-up into storage local to the new object.

### getNames()

Purpose

  List the names which are defined to have corresponding values.

Syntax

  `public Enumeration getKeys ()`

Description

  Provides the full list of names for which coresponding values are defined.

Returns

  An `Enumeration` of all the names defined.

### getValue()

Purpose

  Retrieves the value associated with the name specified.

Syntax

  `public String getValue ( String name )`

Description

  This method provides the corespondence between the `names` and `values` sent from an HTML form.

Parameter

  name

    The key by which values are selected.

Returns

  A `String` containing the value.

## 5.2 CGI_Test

This class provides both an example of how to use the `CGI` class and a test program which can be used to confirm that the Java CGI package is functioning correctly.

### Member Summary

            main()      //  Program main().

### See Also

`CGI`.

### main()

Purpose

  Provide a `main()` method.

Syntax

  `public static void main( String argv[] )`

Description

  This is the entry point for a CGI program which does nothing but return a list of the available name/value pairs and their current values.

Parameter

  argv[]

    Arguments passed to the program by the `java.cgi` script. Currently unused.

## 5.3 Email

### Class Syntax

`public class Email extends Text`

### Class Description

Messages are built up with the `Text` class `add*()` methods and the e-mail-specific methods added by this class. When complete, the message is sent to its destination.

This class is in the ``Orbits.net'' package.

### Member Summary

            Email()      //  Constructor.
            send()       //  Send the e-mail message.
            sendTo()     //  Add a destination for message.
            subject()    //  Set the Subject: for message.

### See Also

`Email_Test, Text`.

### Email()

Purpose

  Constructs an object which will contain an email message.

Syntax

  `public Email()`

Description

  Sets up an empty message to be completed by the Email methods.

See Also

  `Text`.

### send()

Purpose

  Send the e-mail message.

Syntax

  `public void send ()`

Description

  This formats and sends the message. If no destination address has been set, there is no action taken.

### sendTo()

Purpose

  Add a destination for this message.

Syntax

  `public String sendTo ( String address )`

Description

  Add `address` to the list of destinations for this method. There is no set limit to the number of destinations an e-mail message may have. I'm sure that if you build up the list large enough, you can exceed the size of the parameter list that the Mail Transport Agent can accept or use up your memory.

Parameter/

  address

    A destination to send this message to.

### subject()

Purpose

  Set the subject for this message.

Syntax

  `public void subject ( String subject )`

Description

  This method sets the text for the e-mail's `Subject:` line. If called more than once, the latest subject set is the one that is used.

Parameter

  subject

    The text of this message's `Subject:` line.

## 5.4 Email_Test

This class provides both an example of how to use the `Email` class and a test program which can be used to confirm that the Java CGI package is functioning correctly.

### Member Summary

            main()      //  Program main().

### See Also

`Email`.

### main()

Purpose

  Provide a `main()` method.

Syntax

  `public static void main( String argv[] )`

Description

  This is the entry point for a CGI program which returns a list of the available name/value pairs and their current values. It will also send this list to the address specified in the `Email` variable.

Parameter

  argv[]

    Arguments passed to the program by the `java.cgi` script. Currently unused.

## 5.5 HTML

### Class Syntax

`public class HTML extends Text`

### Class Description

Messages are built up with the `Text` class `add*()` methods and the HTML-specific methods added by this class. When complete, the message is sent to its destination.

Currently, there is no error checking to confirm that the list-building methods are being used in a correct order, so the programmer must take pains not to violate HTML syntax.

This class is in the ``Orbits.net'' package.

### Member Summary

            HTML()                  //  Constructor.
            author()                //  Set the name of the document author.
            definitionList()        //  Start a definition list.
            definitionListTerm()    //  Add a term to a definition list.
            endList()               //  End a list.
            listItem()              //  Add an entry to a list.
            send()                  //  Send the HTML message.
            title()                 //  Set the text for the document title.

### See Also

`HTML_Test, Text`.

### HTML()

Purpose

  Constructs an object which will contain an HTML message.

Syntax

  `public HTML()`

Description

  Sets up an empty message to be completed by the HTML methods.

See Also

  `Text`.

### author()

Purpose

  Set the name of the document author.

Syntax

  `public void author ( String author )`

Description

  Set the name of the document author to `author`.

Parameter/

  author

    The text to use as the author of this message.

See Also

  `title()`.

### definitionList()

Purpose

  Start a definition list.

Syntax

  `public void definitionList ()`

Description

  Start a definition list. A definition list is a list specialized so that each entry in the list is a term followed by the definition text for that term. The start of a definition list should be followed by the creation of (at least) one term/text pair and a call to the `endList()` method. Note that, currently, lists cannot be nested.

See Also

  `definitionListTerm()`, `endList()`, `listItem()`.

### definitionListTerm()

Purpose

  Add a term to a definition list.

Syntax

  `public void definitionListTerm ()`

Description

  Add a term to a definition list. The text for the term part of the current list entry should be appended to the message after this method is called and before a corresponding `listItem` method is called.

See Also

  `definitionList()`, `listItem()`.

### endList()

Purpose

  End a list.

Syntax

  `public void endList ()`

Description

  End a list. This method closes out a list. Note that, currently, lists cannot be nested.

See Also

  `definitionList()`.

### listItem()

Purpose

  Add an entry to a list.

Syntax

  `public void listItem ()`

  `public void listItem ( String item )`

  `public boolean listItem ( String term, String item )`

Description

  Add an entry to a list. If the first form is used, the text for the current list item should be appended to the message after this method is called and before any other list methods are called. In the second and third forms, the `item` text is specified as a parameter to the method instead of (or in addition to) being appended to the message. The third form is specific to definition lists and provides both the term and the definition of the list entry.

Parameters

  item

    The text of this list entry.

  term

    The text of this definition list entry's term part.

See Also

  `definitionList()`, `definitionListTerm()`, `endList()`.

### send()

Purpose

  Send the HTML message.

Syntax

  `public void send ()`

Description

  Send the HTML message.

### title()

Purpose

  Set the text for the document title.

Syntax

  `public void title ( String title )`

Description

  Set the text for the document title.

Parameter

  title

    The text of this message's title.

See Also

  `author()`.

## 5.6 HTML_Test

This class provides both an example of how to use the `HTML` class and a test program which can be used to confirm that the Java CGI package is functioning correctly.

### Member Summary

            main()      //  Program main().

### See Also

`HTML`.

### main()

Purpose

  Provide a `main()` method.

Syntax

  `public static void main( String argv[] )`

Description

  This is the entry point for a CGI program which returns a list of the available name/value pairs in an HTML document, with each name/value pair displayed in a definition list element.

Parameter

  argv[]

    Arguments passed to the program by the `java.cgi` script. Currently unused.

## 5.7 Text

### Class Syntax

`public abstract class Text`

### Class Description

This class is the superclass of the `Email` and `HTML` classes. Messages are built up with the methods in this class and completed and formatted with the methods in subclasses.

This class is in the ``Orbits.text'' package.

### Member Summary

            Text()            //  Constructor.
            add()             //  Add text to this object.
            addLineBreak()    //  Add a line break.
            addParagraph()    //  Add a paragraph break.

### See Also

`Email`, `HTML`.

### add()

Purpose

  Add text to this item.

Syntax

  `public void add ( char addition )`

  `public void add ( String addition )`

  `public void add ( StringBuffer addition )`

Description

  Add `addition` to the contents of this text item.

Parameter

  addition

    Text to be added to the text item.

See Also

  `addLineBreak()`, `addParagraph()`.

### addLineBreak()

Purpose

  Force a line break at this point in the text.

Syntax

  `public void addLineBreak ()`

Description

  Add a line break to the text at the current point.

See Also

  `add()`, `addParagraph()`.

### addParagraph()

Purpose

  Start a new paragaph.

Syntax

  `public void add ()`

Description

  Start a new paragraph at this point in the text flow.

See Also

  `add()`, `addLineBreak()`.

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