The IDE supports these features:

• Color-coded syntax highlighting

• XML syntax checking

• In-context drop-down lists that help you pick valid XSQL tag names and auto-complete tag and attribute names

• XSQL page deployment and testing

• Debugging tools

• Wizards for creating XSQL actions

To create an XSQL page in an Oracle JDeveloper project:

1. Create or open a project.

2. Select File and then New.

3. In the New Gallery dialog box, select the General category and then XML.

4. In the Item window, select XSQL Page and click OK. Oracle JDeveloper loads a tab for the new XSQL page into the central window.

To add XSQL action elements such as <xsql:query> to your XSQL page, place the cursor where you want the new element to go and click an item in the Component Palette. A wizard opens that takes you through the steps of selecting which XSQL action you want to use and which attributes you must provide.

To check the syntax of an XSQL page, place the cursor in the page and right-click Check XML Syntax. If there are any XML syntax errors, Oracle JDeveloper displays them.

To test an XSQL page, select the page in the navigator and right-click Run. Oracle JDeveloper automatically starts a local web server, properly configured to run XSQL pages, and tests your page by starting your default browser with the appropriate URL to request the page. After you have run the XSQL page, you can continue to make modifications to it in the IDE. And, you can modify any XSLT stylesheets with which it might be associated. After saving the files in the IDE, you can immediately refresh the browser to observe the effect of the changes.

You must add the XSQL runtime library to your project library list so that the CLASSPATH is properly set. The IDE adds this entry automatically when you go through the New Gallery dialog to create a new XSQL page, but you can also add it manually to the project as follows:

Ensure that the appropriate Java Archive (JAR) files are in the CLASSPATH of the Java Virtual Machine (JVM) that processes the XSQL Pages. The complete set of XDK JAR files is described in Table 11-1. The JAR files for the XSQL framework include:

• xml.jar, the XSQL page processor

• xmlparserv2.jar, the Oracle XML parser

• xsu12.jar, the Oracle XML SQL utility (XSU)

• ojdbc6.jar, the Oracle JDBC driver

If you have configured your CLASSPATH as instructed in Setting Up the XDK for Java Environment, you need to add the directory only where the XSQL pages configuration file resides. In the database installation of XDK, the directory for XSQLConfig.xml is $ORACLE_HOME/xdk/admin.

On Windows your %CLASSPATH% variable contains these entries:

%ORACLE_HOME%\lib\ojdbc6.jar;%ORACLE_HOME%\lib\xmlparserv2.jar;
%ORACLE_HOME%\lib\xsu12.jar;C:\xsql\lib\xml.jar;%ORACLE_HOME%\xdk\admin

On UNIX the $CLASSPATH variable contains these entries:

$ORACLE_HOME/lib/ojdbc6.jar:$ORACLE_HOME/lib/xmlparserv2.jar:
$ORACLE_HOME/lib/xsu12.jar:$ORACLE_HOME/lib/xml.jar:$ORACLE_HOME\xdk\admin

The sample XSQL page shown in Example 24-1 contains this connection information:

<xsql:query connection="hr" xmlns:xsql="urn:oracle-xsql">

Connection names are defined in the <connectiondefs> section of the XSQL configuration file. Example 24-2 shows the relevant section of the sample configuration file included with the database, with the hr connection in bold.

For each database connection, you can specify these elements:

• <username>, the database user name

• <password>, the database password

• <dburl>, the JDBC connection string

• <driver>, the fully qualified class name of the JDBC driver to use

• <autocommit>, which optionally forces AUTOCOMMIT to TRUE or FALSE

Specify an <autocommit> child element to control the setting of the JDBC autocommit for any connection. If no <autocommit> child element is set for a <connection>, then the autocommit setting is not set by the XSQL connection manager. In this case, the setting is the default autocommit setting for the JDBC driver.

You can place an arbitrary number of <connection> elements in the XSQL configuration file to define your database connections. An individual XSQL page refers to the connection it wants to use by putting a connection="xxx" attribute on the top-level element in the page (also called the "document element").

If you have set up the XSQL servlet in a web server as described in Configuring the XSQL Servlet Container, then you can access the demos through this URL, substituting appropriate values for yourserver and port:

http://yourserver:port/xsql/index.html

Figure 24-3 shows a section of the XSQL home page in Internet Explorer. (You must use browser version 5 or later.)

Figure 24-3 XSQL Home Page

Description of "Figure 24-3 XSQL Home Page"

The demos are designed to be self-explanatory. Click the demo titles—Hello World Page, Employee Page, and so forth—and follow the online instructions.

The <xsql:query> element shown in Example 24-3 contains a bind-params attribute that associates the values of parameters in the request to bind variables in the SQL statement included in the <xsql:query> tag. The bind parameters in the SQL statement are represented by question marks.

You can use SQL bind variables to parameterize the results of any of the actions in Table 33-1 that allow SQL statements. Bind variables enable your XSQL page template to produce results based on the values of parameters passed in the request.

To use a bind variable, include a question mark anywhere in a statement where bind variables are allowed by SQL. Whenever a SQL statement is executed in the page, the XSQL engine binds the parameter values to the variable by specifying the bind-params attribute on the action element.

Example 24-5 shows an XSQL page that binds the bind variables to the value of the custid parameter in the page request.

The XML data for a customer with ID of 101 can then be requested by passing the customer id parameter in the request:

http://yourserver.com/fin/CustomerPortfolio.xsql?custid=1001

The value of the bind-params attribute is a space-delimited list of parameter names. The left-to-right order indicates the positional bind variable to which its value is bound in the statement. Thus, if your SQL statement contains five question marks, then the bind-params attribute needs a space-delimited list of five parameter names. If the same parameter value must be bound to several different occurrences of a bind variable, then repeat the name of the parameters in the value of the bind-params attribute at the appropriate position. Failure to include the same number of parameter names in the bind-params attribute as in the query causes an error when the page is executed.

You can use variables in any action that expects a SQL statement or PL/SQL block. The page shown in Example 24-6 shows this technique. The XSQL page contains three action elements:

• <xsql:dml> binds useridCookie to an argument in the log_user_hit procedure.

• <xsql:query> binds parameter custid to a variable in a WHERE clause.

• <xsql:include-owa> binds parameters custid and userCookie to two arguments in the historical_data procedure.

Lexical substitution parameters are referenced with this syntax: {@ParameterName}. Example 24-7 shows how you can use two lexical substitution parameters. One parameter in the <xsql:query> element sets the maximum number of rows to be passed in, whereas the other controls the list of columns to be ordered.

Example 24-7 also contains two bind parameters: dev and prod. For example, you might want to get the open bugs for developer yxsmith against product 817. And, you want to retrieve only 10 rows and order them by bug number. You can fetch the XML for the bug list by specifying parameter values:

http://server.com/bug/DevOpenBugs.xsql?dev=yxsmith&prod=817&max=10&orderby=bugno

You can also use the XSQL command-line utility to make the request:

xsql DevOpenBugs.xsql dev=yxsmith prod=817 max=10 orderby=bugno

Lexical parameters also enable you to specify parameters for the XSQL pages connection and the stylesheet used to process the page. Example 24-8 shows this technique. You can switch between stylesheets test.xsql and prod.xsl by specifying the name/value pairs sheet=test and sheet=prod.

To include a default value for a parameter, add an XML attribute of the same name as the parameter to the action element or to any ancestor element. If a value for a given parameter is not included in the request, then the XSQL page processor searches for an attribute by the same name on the current action element. If it does not find one, it keeps looking for such an attribute on each ancestor element of the current action element until it gets to the document element of the page.

The page in Example 24-9 defaults the value of the max parameter to 10 for both <xsql:query> actions in the page.

This page in Example 24-10 defaults the first query to a max of 5, the second query to a max of 7, and the third query to a max of 10.

All defaults are overridden if a value of max is supplied in the request, as shown in this example:

http://yourserver.com/example.xsql?max=3

Bind variables respect the same defaulting rules. Example 24-11 shows how you can set the val parameter to 10 by default.

If the page in Example 24-11 is requested without any parameters, it returns this XML datagram:

<example>
  <rowset>
    <row>
      <somevalue>10</somevalue>
    </row>
  </row>
</example>

Alternatively, assume that the page is requested with this URL:

http://yourserver.com/example.xsql?val=3

The preceding URL returns this datagram:

<example>
  <rowset>
    <row>
      <somevalue>3</somevalue>
    </row>
  </row>
</example>

You can remove the default value for the val parameter from the page by removing the val attribute. Example 24-12 shows this technique.

A URL request for the page that does not supply a name/value pair returns this datagram:

<example>
  <rowset/>
</example>

A bind variable that is bound to a parameter with neither a default value nor a value supplied in the request is bound to NULL, which causes the WHERE clause in Example 24-12 to return no rows.

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output type="xml" doctype-system="your.dtd"/>
  <xsl:template match="/">
  </xsl:template>
    ...
</xsl:stylesheet>

The preceding stylesheet produces an XML result that includes this code, where "your.dtd" can be any valid absolute or relative URL:

<!DOCTYPE xxxx SYSTEM "your.dtd">

Example 24-17 shows a technique for executing a query based on a test of a parameter value.

Assume that you have a multivalued parameter named guy. You can use the array parameter notation in an XSQL page as shown in Example 24-19.

Assume that you request this page is requested with this URL, which contains multiple parameters of the same name to produce a multivalued attribute:

http://yourserver.com/page.xsql?guy=Curly&guy=Larry&guy=Moe

The page returned looks like this:

<page>
  <guy-list>Curly,Larry,Moe</guy-list>
  <quoted-guys>'Curly','Larry','Moe'</quoted-guys>
  <guy>
    <value>Curly</value>
    <value>Larry</value>
    <value>Moe</value>
  </guy>
</page>

You can also use the value of a multivalued page parameter in a SQL statement WHERE clause by using the code shown in Example 24-20.

You cannot set parameter values by binding them in the position of OUT variables with <xsql:dml>. Only IN parameters are supported for binding. You can create a wrapper procedure, however, that constructs XML elements with the HTTP package. Your XSQL page can then invoke the wrapper procedure with <xsql:include-owa>.

Example 24-21 shows a PL/SQL procedure that accepts two IN parameters, multiplies them and puts the value in one OUT parameter, then adds them and puts the result in a second OUT parameter.

You can write the PL/SQL procedure in Example 24-22 to wrap the procedure in Example 24-21. The addmultwrapper procedure accepts the IN arguments that the addmult procedure preceding expects, and then encodes the OUT values as an XML datagram that you print to the Open Web Analytics (OWA) page buffer.

The XSQL page shown in Example 24-23 constructs an XML document by including a call to the PL/SQL wrapper procedure.

You can invoke addmult.xsql by entering a URL in a browser:

http://yourserver.com/addmult.xsql?arg1=30&arg2=45

The XML datagram returned by the servlet reflects the OUT values:

<page>
  <addmult><sum>75</sum><product>1350</product></addmult>
</page>

For example, an XSQL page can access the contents of an inbound SOAP message by using the xpath="XpathExpression" attribute in the <xsql:set-page-param> action. Alternatively, custom action handlers can gain direct access to the SOAP message body by invoking getPageRequest().getPostedDocument(). To create the SOAP response body to return to the client, use an XSLT stylesheet or a custom serializer implementation to write the XML response in an appropriate SOAP-encoded format.

Define an attribute of the same name to serve as the default value for the connection name.

Assume that in your XSQL configuration file you define connections for database testdb and proddb. You then write an XSQL page with this <xsql:query> element:

<xsql:query conn="testdb" connection="{@conn}" xmlns:xsql="urn:oracle-xsql">
  ...
</xsql:query> 

If you request this page without any parameters, then the value of the conn parameter is testdb, so the page uses the connection named testdb defined in the XSQL configuration file. If you request the page with conn=proddb, then the page uses the connection named proddb instead.

You can use a helper method like the one shown in Example 24-24 to retrieve the name of the page inside a custom action handler.

XML information posted to an XSQL page for processing must be sent by HTTP POST. This transfer can be effected by an HTML form or an XML document sent by HTTP POST.

The only required permissions for the configuration file are read permission granted to the UNIX account that owns the servlet engine. Failure to follow this recommendation could mean that a user of your site could browse the contents of your configuration file, thereby getting the passwords to database accounts.

You can also globally change the default setting in the XSQLConfig.xml file to disallow client stylesheet overrides. If you take either approach, then the only pages that allow client stylesheet overrides are those that include the allow-client-style="yes" attribute on their document element.

Any product that supports the use of lexical substitution variables in a SQL query can cause a developer problems. Any time you deploy an XSQL page that allows part of all of a SQL statement to be substituted by a lexical parameter, you must ensure that you have taken appropriate precautions against misuse.

For example, one of the demonstrations that comes with XSQL Pages is the Adhoc Query Demo. It shows how you can supply the entire SQL statement of an <xsql:query> action handler as a parameter. This technique is a powerful and beneficial tool when in the right hands, but if you deploy a similar page to your production system, then the user can execute any query that the database security privileges for the connection associated with the page allows. For example, the Adhoc Query Demo is set up to use a connection that maps to the scott account, so a user can query any data that scott would be allowed to query from SQL*Plus.

You can use these techniques to ensure that your pages are not abused:

• Ensure the database user account associated with the page has only the privileges for reading the tables and views you want your users to see.

• Use true bind variables instead of lexical bind variables when substituting single values in a SELECT statement. If you must parameterize syntactic parts of your SQL statement, then lexical parameters are the only way to proceed. Otherwise, use true bind variables so that any attempt to pass an invalid value generates an error instead of producing an unexpected result.