4 Developing JavaServer Pages for MapleNet

4 Developing JavaServer Pages for MapleNet

MapleNet JavaServer Pages (JSP) allow you to use HTML pages to display Maple calculations. Maple expressions can be inserted in web page sources and rendered within web browsers.

In this Chapter

Prerequisites
Creating MapleNet JSP Content
Page Setup
Using Maple Tags
Examples
Publishing JSP Content to the MapleNet Server

4.1 Prerequisites

The server must support the use of JavaServer Pages. For example, a compatible server is Tomcat 5.5.

4.2 Creating MapleNet JSP Content

To display Maple content on the web, you must add special tags to web page sources. The tags follow normal HTML tag conventions in that they are either of the single tag form
<tag ... tag parameters .../>
or matched opening and closing tags of the form
< tag ... tag parameters ...>
... data ...
</tag>
For example, in static HTML pages most of the page text is enclosed in HTML and body tags, as in the following.
<html>
<body>
This is a simple page.
</body>
</html>
To begin creating MapleNet JSP content, follow the instructions in the Page Setup and Using Maple Tags sections of this chapter.

4.3 Page Setup

The server must recognize Maple specific tags. All tags in the page are processed in the order encountered on the source pages.

Add a taglib directive before the <html> tag at the top of the document. This allows the server to recognize Maple specific tags.

<%@ taglib prefix="maple" uri="/maplemath.tld" %>

where

<%@ identifies this as a JSP directive
taglib specifies the name of the directive
prefix="maple" states that maple is the tag name, for example <maple:init ... >
uri specifies that the server use the uniform resource identifier (uri) /maplemath.tld to locate the Tag Library Descriptor

Technical Note: In the default install, the WEB-INF/web.xml file instructs the JSP engine to map the /maplenet.tld uri to the WEB-INF/tlds/maplenet.tld file.

Add a page tag following the taglib directive. This allows the server to maintain user data between pages requested by the user.

<%@ page session="true" %>

where

<%@ identifies this as a JSP directive
page specifies the name of the directive
session="true" indicates the server will store data for the entire session

4.4 Using Maple Tags

This section describes the init, statement, code, assign, plot, and release tags.

Initialization Tag

Add an init (initialization) tag to indicate how the Maple kernel is to be used. Use the following syntax.

<maple:init scope="[tag|page|request|session]" debug="[false|true]" />

where

maple:init specifies the name of the tag. This tag must occur before any other Maple tag. If not, any statement or code tags encountered before the init tag are executed as if the scope was set to page.
scope indicates how long the Maple kernel is kept active.
tag specifies that the kernel is used only for the expression(s) within the current <maple:xxx> tag. Each Maple tag has a new kernel, and no data is stored between Maple tags.
page specifies that the same kernel is used for all Maple tags encountered on this page. Once the page is sent to the user's browser, the kernel is released. Therefore multiple visits by a user to the same page result in a new kernel on each visit. This frees up the kernel for another user, but no data is stored for the same user on subsequent visits.
request specifies that the same kernel is used for all Maple tags in a single request to the server. A browser request may traverse one or more source pages.
session specifies that the same kernel is used for all Maple tags processed by the server for a particular user in a single browser session. Browser sessions are established by the <%@ page ... > directive.
If the tag <%@ page session="true" %> is encountered in a server, then the server uses the same session (not Maple session) for this user and remembers all the users server settings between visits as long as the browser is active and has not timed out. (Timeout levels are set by the server administrator).
If the page directive session is true, and the <maple:init ...> scope is set to session, then a handle to the Maple kernel is stored in the session data so that the Maple tags can share the same Maple kernel.
debug, when true, specifies that all <maple:xxx> tags add debugging information to the output HTML.

Statement Tag

The statement tag executes one or more Maple expressions, with the result of the expression(s) being inserted directly into the resultant HTML page. The form of the tag is as follows.

<maple:statement lastline="[false|true]" breakline="[true|false]" type="[text|plot]" width="value" height="value" safeHTML="[true|false]" quotes="[true|false]">

... Maple expression ...

... Maple expression ...

</maple:statement>

If the result is Maple output, it is inserted as text. If the result is a plot, the plot is converted to an image, and an HTML <img ...> tag is inserted in the page.

Important: Each line in the statement block is executed separately. Therefore, all the code for control structures, such as if/else and try/catch must be on the same line. For example:

if (x>0) then s := +1; else s:=-1; end if

A page can have more than one statement section. If the init tag sets the scope to session, all statement sections use the same kernel.
If one or more of the expressions are expected to create a static plot, set the type parameter to "plot". The kernel then generates a plot using the numeric width and height parameters. For interactive plots, see Plot Tag.
If the attribute quotes="false" is set then the string output from Maple will have the leading and trailing double quotes removed. If true then the string output is not altered. The default is true.

If the attribute safeHTML="true" then any output from Maple that contains the characters in the table below are converted to their quoted format so as to not be misinterpreted by the browser.

Character	Quoted Format
<	<
>	>
&	&
"	"
'	'

The parameters lastline and breakline are optional. When lastline="true", all Maple expressions are evaluated within the tag but only the output generated by the last expression is inserted into the web page content. breakline="true", an HTML break tag, <br>, is inserted after the output of each expression, forcing the browser to display each expression on a new line.

When using both parameters, consider the following inserted into web page content.

<maple:statement breakline=... lastline=... >

1+1; 2+2; 3+3;
7;
8;
9;

<maple:statement>

Table 6 illustrates how the above input is displayed in a web browser based on parameter usage.

Table 6: Output in Browser

Parameter Values
breakline

true

false

lastline

true

9

9

false

2 4 6

7

8

9

2 4 6789

The following illustrates how content is processed and displayed using the examples given in Table 6.

If lastline is true and breakline is true, all lines are processed but only the result of the last line is displayed. Therefore all four lines of data

1+1; 2+2; 3+3;
7;
8;
9;

are sent to Maple, but only the last result is displayed and an HTML <br> string is appended after the line.

9<br>

If lastline is true and breakline is false, all lines are processed but only the result of the last line is displayed. Therefore all four lines of data

1+1; 2+2; 3+3;
7;
8;
9;

are sent to Maple, but only the last result is displayed.

9

If lastline is false and breakline is true, all lines are processed and displayed. Therefore all 4 lines of data

1+1; 2+2; 3+3;
7;
8;
9;

are sent to Maple, resulting in MapleNet producing

2 4 6<br>
7<br>
8<br>
9<br>

The browser displays this as

2 4 6
7
8
9

If lastline is false, and breakline is false, all lines are processed and displayed. Therefore all four lines of data

1+1; 2+2; 3+3;
7;
8;
9;

are sent to Maple, resulting in MapleNet producing

2 4 6
7
8
9

Note: browsers typically ignore white space, so the result is displayed as the following.

2 4 6789

Code Tag

The code tag is similar to the <maple:statement ...> tag, but no data is generated to the output page. This can be used to define common procedures and data for later use by expressions in the <maple:statement ...> sections. The form of the tag is as follows.

<maple:code>

... Maple expression ....

... Maple expression ....

</maple:code>

This tag has no parameters. Each expression in the tag body is evaluated by the Maple kernel.

Note: Unlike the statement block, all expressions are evaluated together. As such, control structures (if/else, try/catch) can span several lines.

Assign Tag

The assign tag allows parameters from HTML forms to be passed as variables to Maple. The form of the tag is as follows.

<maple:assign param="param name" variable="Maple variable" default="def value" />

where

**Table 6: Output in Browser**
Parameter Values	breakline
true	false
lastline	true	9	9
false	2 4 6 7 8 9	2 4 6789

assign param (required) specifies the identifier of an HTML form parameter that has an associated value.
variable (required) specifies the name of a variable in Maple. It is assigned the value of the HTML parameter.
default (optional) specifies the value to assign to a Maple variable if the parameter is not set.

Although the <maple:xxx> tags appear in the source, they do not appear in the user browser because they are converted by the Maple Tag Library into content that is consistent with web pages. The content is the output from the Maple kernel.

Plot Tag

The plot tag creates an interactive (dynamic image) plot. The form of the tag is as follows.

<maple:plot width="value" height="value"> Maple_plot_equation</maple:plot>

where

maple:plot specifies a interactive plot
width and height specify the numeric parameters to generate the plot
Maple_plot_equation specifies the plot equation, for example,

plot3d(sin(x^0.5*y^0.5), x=-Pi..Pi,y=-2*Pi..2*Pi,axes=BOXED)

For static plots, see Statement Tag.

Release Tag

The release tag terminates the JSP connection to Maple, allowing other JSP sessions to access the Maple server. The form of the tag is as follows.

<maple: release />

This tag will immediately release Maple, regardless of the scope setting in the init tag. This is the preferred method of freeing Maple for other user sessions.

4.5 Examples

To understand more about MapleNet JavaServer Pages, review the following integration.jsp and MaplePlotTest.jsp example code listings.

Integration Example

The following example is similar to the applet example (Listing 3) for performing simple integration. However, it uses only web page tags and no client-side Java.

Listing 7 Integration.jsp
<%@ taglib prefix="maple" uri="/maplemath.tld" %>

<%@ page session="true" %>

<maple:init scope="session" debug="false" />

<maple:assign param="expr001" variable="eqn" default="sin(x)" />

<maple:code>

  doInt := proc()

    global eqn;

    int(eqn, x);

  end proc;

</maple:code>



<html>

  <head>

    <title>

      Sample Integration

    </title>

  </head>

  <body>

    <center>

      <h1>Sample Integration</h1>

      <form method="post"

            action="Integration.jsp" >

        <table width="50%" >

          <tr>

            <td width="35%">Enter Expression : </td>

            <td width="65%">

              <input type="text"

                     size="40"

                     name="expr001"

                     value="<maple:statement>eqn</maple:statement>" >

            </td>

          </tr>

          <tr>

            <td width="35%">Result : </td>

            <td width="65%">

              <input type="text"

                     size="40"

                     name="result001"

                     value="<maple:statement>doInt()</maple:statement>" >

            </td>

          </tr>

        </table>

        <input type="submit"

               name="Calculate"

               value="Submit">

      </form>

    </center>

    <maple:statement type="plot" height="200" width="400"> plot(eqn, x=0..10)</maple:statement>

  </body>

  <maple:release />

</html>
The following discussion refers to Listing 7.

The first tag, <%@ taglib ...%>, establishes that "maple" is the tag prefix for Maple calculations.
The <%@ page ...%> tag sets the server to remember this user for a session.
The <maple:init ...> tag specifies that the same kernel is used for this session and that debugging is off.

Note: If an error arises on the server side while processing the Maple tags, the current kernel is released and any state information is lost.
The <maple:assign ...> tag takes the form parameter, expr001, and assigns it to the Maple variable, eqn. The first time this page is loaded, the form has not yet been processed and expr001 is undefined. Therefore the default value, sin(x), is assigned to the variable, eqn.
Following this is a <maple:code ...> block. The server passes the included Maple code directly to the Maple kernel. This block defines a simple procedure, doInt(), that integrates the expression assigned to eqn. This procedure is referenced later in the web page.
The remainder of the example is an HTML document that has two input fields inside a <form ...> tag. The action of the form is to invoke the same web page, Integration.jsp. The expr001 input field is filled using a <maple:statement ...> tag to output the value of eqn. The result001 field is filled using a <maple:statement ...> to evaluate the doInt() procedure that is defined by the code block.
The release tag terminates the JSP connection to the Maple server.

When the Calculate button is clicked, the form is submitted to the server to be processed again by Integration.jsp. This time the <maple:assign ...> tag takes the user input from the expr001 field and assigns it to eqn. The new value of eqn is integrated and placed in the output page in the result001 field.

Plot Example

The following code provides an example of static and interactive plots.

Listing 8 MaplePlotTest.jsp
<%@ taglib prefix="maple" uri="/maplemath.tld" %>

<%@ page session="true" %>

<maple:init scope="page" debug="true" />

<maple:assign param="eqn001" variable="plt_eqn" default="plot3d(sin(x^0.5*y^0.5), x=-Pi..Pi, y=-2*Pi..2*Pi,axes=BOXED)" />

<html>

  <head>

    <title>MaplePlotTest</title>

  </head>

  <body bgcolor="#ffffc0">

    <h1>Test of Maple Plot Tag</h1>

    Time is <%= new java.util.Date().toString() %>

    <br>

    <center>

      <b> Static Image plot</b>

      <br>

      <maple:statement type="plot" width="250" height="200" >plot(cos(4*x),x=0..10)</maple:statement>

    </center>

    <br>

    <center>

      <b>Dynamic Image plot</b>

      <br>

      <maple:plot width="500" height="300" >plt_eqn</maple:plot>

    </center>

    <br>

    <center>

      <form method="post">

        <br>

        <input type="text"

               size="50"

               name="eqn001"

               value="plot3d(sin(x^0.5*y^0.5), x=-Pi..Pi, y=-2*Pi..2*Pi,axes=BOXED)" >

        <br>

        <input type="submit"

               name="Submit"

               value="Submit">

        <input type="reset"

               value="Reset">

      </form>

    </center>

    <maple:release/>

  </body>

</html>
A static plot is displayed above an interactive plot. The user can submit new values for the interactive plot in an input field.

4.6 Publishing JSP Content to the MapleNet Server

Publishing a JSP to the MapleNet server requires copying the JSP file to the appropriate directory on the server. The file can be copied to the server using any network file transfer tool, such as FTP, SSH, or WebDAV.

Consult your site administrator for specific details on where your files should be placed and what method should be used to transfer them.

Once the file is copied to the server, your content will be available by accessing the appropriate URL. For example, if your JSP is mypage.jsp, then assuming the MapleNet server is myserver.com and that your worksheet was transferred to the jsp directory of the MapleNet web application, the worksheet can be accessed by pointing your browser to http://myserver.com/maplenet/jsp/mypage.jsp.

Consult your site administrator for the exact URL to access your content.