MACROMEDIA COLDFUSION 4.5-CFML LANGUAGE Manuel d'utilisateur télécharger pdf (Page 15)

15Writing CFX Tags with Java

Yo u can even catch exceptions thrown by a CFX and handle them intelligently, using <cftry> and

<cfcatch>, like so:

<cftry>

<CFX_HelloWorld

NAME=”#SESSION.FirstName#”

AGE=”#FORM.Age#”>

...error handling code goes here...

</cfcatch>

</cftry>

Returning Query Objects

Now that you’ve seen how to create a simple CFX tag with Java, it’s time to move on to something a

bit more complicated and useful. Our next project will be a CFX tag called

<CFX_DatabaseMetaData>,

which can be used to inspect the structure of a database on the ﬂy. To use the tag in a ColdFusion

page, you will specify the type of information you want (a list of tables, columns, indexes, or the

like), and the tag will return a query object ﬁlled with items like column names, table names, data

types, and so on.

Table 30.11 shows the syntax that will be supported by the completed tag.

Table 30.11 <CFX_DatabaseMetaData> Tag Syntax

ATTRIBUTE DESCRIPTION

action Required. A string indicating the type of information you are interested

in, such as

GetTables or GetColumns. You can provide any of the

actions listed in Table 30.12.

driver Required. The name of the JDBC driver to use. For ODBC databases,

you can use Sun’s ODBC Bridge driver, as in

driver=”sun.jdbc.odbc.

JdbcOdbcDriver.”

connect

Required. Whatever connection information the driver needs to connect

to the database. In the case of ODBC datasources, you can use a string

in the form

jdbc:odbc:dsn_name, as in connect=”jdbc:odbc:ows”

for the Orange Whip Studios example database.

username Required. The username for the data source (may be case sensitive).

password Required. The password for the data source (may be case sensitive).

name Required. Like the name attribute for <cfquery>, a name for the query

object that the tag returns. The returned query will contain different

columns depending on the

action you choose, as listed in Table 30.12.

dbcatalog Optional. The catalog name that you want to get information about.

With most database systems, the catalog name is the name or ﬁlename of

the database. If you don’t specify a catalog name, all information is

returned (for all available catalogs or databases). Can be used for all

actions except

GetCatalogs and GetSchemas.

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MACROMEDIA COLDFUSION 4.5-CFML LANGUAGE Manuel d'utilisateur Page 15

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