Using Java Commands

The set command is written in Java, so you have already seen how to use Java commands. There are a few more things that bear mentioning, though.

commands are case sensitive - if you mistype a command, the rendered version of your WELD page will only output: invalid command name "cmd"
commands often have a specific number of parameters (WELD calls these "args" as in "arguments") - use grouping as necessary to be sure that the right parameters are set - if you have this wrong, the rendered version of your WELD page will only output: wrong # args: should be "a list of parameters"
multiple commands may be placed inside of a single pair of square brackets, but must be separated by a semicolon - the result which is placed into the rendered page will be the result of the last command in the set.
square brackets nest, so that command execution can be invoked within command execution to provide parameters
sometimes you may only want to execute the commands, but not get the results output into the page - this can be done by using HTML comments (i.e. )

Joining results

A very useful command is join - which takes two parameters: a list of strings and a string to join them with. Often the list of strings will be output from another command. A command that results in a list of values, for example, can be joined with <tr><td> to define a table row. The same list could be joined with <li> to make list items, or with <option> to make a selection list for a form.

A good simple example of this is to get a list of all WELD commands. To do this, make a WELD file that looks something like this:

  <html><head><title>[set pagetitle "WELD commands"]</title></head>
  <body><center><h1>$pagetitle</h1>
  <table border=3><tr><td>[join [lsort [info commands]] <tr><td>]</table>
  </body></html>

The nested commands may need a little explanation. As with other forms of nesting, command nesting should be read from the inside out instead of left-to-right. Here, the "info" Java command takes "commands" as it's only parameter and returns a list of valid commands. This list of commands is sorted by lsort (which means "list sort") and then joined with join.

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Using Java Commands

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Modified: Tue Apr 18 15:49:05 EDT 2000