Using the "Input" Tag Library

The <input:text> tag displays an HTML <input type="text" ... > element. The element's name in the HTML will be fieldName. Additionally, the element's value will be drawn from the fieldName parameter in the current ServletRequest if it exists, or from defaultValue if it does not (as long as default is given a value).

Any key/value pairs in the attributeMap Map provided will be used as attribute/value pairs in the HTML <input type="text" ... > element. For instance, the key/value pair "size" -> "50" will show up as <input type="text" size="50" ... >

The <input:textarea> tag displays an HTML <textarea> element and, potentially, its body too. The element's name in the HTML will be fieldName. Additionally, the element's body (its logical "value") will be drawn from the fieldName parameter in the current ServletRequest if it exists, or from defaultValue if it does not (as long as default is given a value).

This tag does not take a body. It may produce a body in the underlying HTML if appropriate, but all of the logic is encapsulated into this single tag in order to make it easier to use.

Any key/value pairs in the attributeMap Map provided will be used as attribute/value pairs in the HTML <textarea> element. For instance, the key/value pair "rows" -> "40" will show us as <textarea rows="40" ... >

The <input:select> tag displays an HTML <select> element and its subordinate <options>. The element's name in the HTML will be fieldName. A list of <option> tags will come from the optionsMap Map, and each individual option will be marked selected if it corresponds to the fieldName parameter in the current ServletRequest if it exists, or from defaultValue if it does not (as long as default is given a value).

This tag does not take a body. It may produce a body in the underlying HTML if appropriate, but all of the logic is encapsulated into this single tag in order to make it easier to use.

Any key/value pairs in the attributeMap Map provided will be used as attribute/value pairs in the HTML <select> element. If you wish to use the attribute <multiple>, you may wish to pass a Map that allows null values; the HashMap class works nicely. Sample code for this is:

    <% HashMap attr = new HashMap(); %>
    <% attr.put("multiple", null); %>
    <input:select ... attributes="<%= attr %>" />

You might find that code like this is easier to read and maintain in bulk than tags with multiple attribute/value pairs.

This tag supports multiple selections if it retrieves them from the ServletRequest and the box is labelled as a multiple selection box (i.e., attributeMap contains multiple as a key). If there are multiple selections in the ServletRequest and the <select> box is not labelled multiple, the selections are thrown away (instead of choosing one at random).

The <input:radio> tag displays a single HTML <input type="radio" ...>. To display all buttons in a radio group, you need to use this tag multiple times with different values.

The element's name in the HTML will be buttonGroupName. (You can have as many buttons with the same buttonGroupName as you need.) Additionally, each particular button will be marked checked if its buttonValue equals the value of the fieldName parameter in the current ServletRequest if it exists, or the defaultValue if it does not (as long as default is given a value).

Any key/value pairs in the attributeMap Map provided will be used as attribute/value pairs in the HTML <input type="radio" ...> element. For instance, the key/value pair "disabled" -> null will show us as <input type="radio" disabled ... >

The <input:checkbox> tag displays a single HTML <input type="checkbox" ...>. To display all buttons in a checkbox group, you need to use this tag multiple times with different values.

The element's name in the HTML will be buttonGroupName. (You can have as many checkboxes with the same buttonGroupName as you need.) Additionally, this checkbox will be marked as checked if the tag believes it ought to be checked. The rules are as follows: if the current ServletRequest is empty (i.e., contains no parameters), then we combine the default and defaults String and String[] (respectively), and if the current checkbox's buttonValue is in that list of defaults, then the tag marks the checkbox as checked. Otherwise, the tag marks the checkbox as checked if and only if the box's buttonValue is in the list of values associated with buttonGroupName in the current ServletRequest.

Note: The rules for determining whether a checkbox is checked or not are different than the rules for other input or selection types. This is the result of underlying differences between the way CGI handles checkboxes and other fields. If a text box is empty, browsers assert, via the POST or GET to the server, an empty value; however, if all checkboxes for a given checkbox group are unchecked, the browser doesn't include any information about the checkbox group in its POST or GET. Thus, if this tag simply looked toward the parameter in the current ServletRequest, defaults would be restored on the resulting page--that is, checkboxes wouldn't necessarily stay unchecked. (As an aside, we'd have to do the same thing with radio buttons, but browsers don't let users uncheck all radio buttons, and if the default provides for no buttons to be checked, then there's, tidily enough, no problem with accepting the default in the case where all buttons remain unchecked.)

Any key/value pairs in the attributeMap Map provided will be used as attribute/value pairs in the HTML <input type="checkbox" ...> element. For instance, the key/value pair "disabled" -> null will show us as <input type="checkbox" disabled ... >