Quick Start: DataDirect XQuery®

This quick start provides basic information for getting started with DataDirect XQuery immediately after installation. It covers the following topics:

Getting Started with DataDirect XQuery

This section shows you how to get up and running with DataDirect XQuery. It covers the following topics:

1. Setting the CLASSPATH
2. Configuring Connections
3. Developing a Java Application that Executes a Query

1. Setting the CLASSPATH

Only one DataDirect XQuery jar file, ddxq.jar, must be defined in your CLASSPATH. The CLASSPATH is the search string your Java Virtual Machine (JVM) uses to locate DataDirect XQuery on your computer. If ddxq.jar is not defined on your CLASSPATH, you receive a ClassNotFoundException exception when trying to use DataDirect XQuery.

NOTE: If you are connecting to PostgreSQL, you must add the PostgreSQL JDBC driver jar file to the CLASSPATH in addition to ddxq.jar. Refer to your PostgreSQL JDBC driver documentation for the name of the jar file.

2. Configuring Connections

DataDirect XQuery provides multiple ways to configure connections to XML data sources and relational data sources. This section shows how to use XQJ to create a DDXQDataSource instance in your Java application explicitly.

XML Data Source Connections

If your Java application contains queries that access an XML file, you can directly access the file as shown in the following XQJ code, where the location and name of the XML file is specified as a parameter of fn:doc(), an XQuery function.

Relational Data Source Connections

How you configure connection information for relational databases using XQJ depends on whether you are accessing a single database or multiple databases. This section shows how to configure connection information to access a single database.

To configure a single relational data source connection, use the DDXQDataSource class as shown in the following XQJ code example. This example specifies a connection URL (represented by URL) for the relational data source that you want to access and the user ID and password required to access the relational data source.

Sample Connection URLs

The following URLs are examples of the minimum information that must be specified in a connection URL.

DB2 for Linux/UNIX/Windows

DB2 for z/OS and iSeries

Informix

Microsoft SQL Server

MySQL Enterprise

Oracle

PostgreSQL

Sybase

3. Developing a Java Application that Executes a Query

Using DataDirect XQuery, a Java application uses XQJ to execute a query. The Java package name of the XQJ classes is:

The Java class name of the DataDirect XQuery implementation of the XQJ standard interface, XQDataSource, is:

The following sample Java code illustrates the basic steps that an application would perform to execute an XQuery expression using DataDirect XQuery. This example accesses a Microsoft SQL Server data source. To simplify the example, this code does not include error handling.

// import the XQJ classes 
import javax.xml.xquery.*; 
import com.ddtek.xquery.xqj.DDXQDataSource; 
 
// establish a connection to a relational data source 
// specify the URL and the user ID and password 
DDXQDataSource ds = new DDXQDataSource(); 
ds.setJdbcUrl("jdbc:xquery:sqlserver://server1:1433;databaseName=stocks"); 
XQConnection conn = ds.getConnection("myuserid", "mypswd"); 
// create an expression object that is used to execute a query 
XQExpression xqExpression = conn.createExpression(); 
 
// the query 
String es = "for $h in collection('holdings')/holdings " + 
                        "where $h/stockticker='AMZN' " + 
                        "return $h"; 
 
// execute the query 
XQResultSequence result = xqExpression.executeQuery(es); 
result.writeSequence(System.out, null); 
 
// free all resources 
result.close(); 
xqExpression.close(); 
conn.close();

NOTE: XQJ examples are shipped with the product and are located in the /examples subdirectory in the DataDirect XQuery installation directory.

Using the Command Line Utility

The DataDirect XQuery command line utility allows you to quickly run and test XQueries through a console window.

To invoke this utility, enter the following command at a prompt from the /lib subdirectory of your DataDirect XQuery installation directory (for example, ddxq/lib):

Alternatively, you can specify the path to the lib directory in the command line, for example:

NOTE: If your XQuery needs to locate classes other than the DataDirect XQuery classes, for example, if you are specifying a custom URI resolver, you must perform one of the following actions:

Set your CLASSPATH to include the path to the jar files or directories for these classes and invoke the utility using the following command:

java com.ddtek.xquery.Query

Add the class path to the command line:

java -cp c:\myClasses com.ddtek.xquery.Query

See Example 8.

Table 1. Command Line Utility Options
Option	Description
-cr classname	Specifies the CollectionURIResolver class to use. See the NOTE about setting your CLASSPATH for custom URI resolvers.
-e [xhtml\|xml]	Generates an XQuery execution plan and, optionally, specifies the format of the plan. If a format is not specified, XHTML is generated.
-jdbc jdbcurl	Specifies a connection URI. See Relational Data Source Connections in the DataDirect XQuery User's Guide and Reference for more information. NOTE: On UNIX and Linux, the value for this option must be enclosed with double quotes, for example: java -jar ddxq.jar -jdbc "jdbc:xquery:sqlserver://localhost:1433 ;databaseName=pubs;user=sa"
-mr classname	Specifies the ModuleURIResolver class to use. See the NOTE about setting your CLASSPATH for custom URI resolvers.
-noext	Disallows calls to Java methods.
-o filename	Sends results (output) to specified file.
-option property=value	Specifies XQuery or JDBC global options. See Using Option Declarations and Extension Expressions in the DataDirect XQuery User's Guide and Reference for more information.
-prop property=value	Specifies data source and connection options. See DDXQDataSource and DDXQJDBCConnection Properties in the DataDirect XQuery User's Guide and Reference for more information.
-p	Displays a stack trace in case of an exception.
-r classname	Specifies the URIResolver class to use. See the NOTE about setting your CLASSPATH for custom URI resolvers.
-s file\|URI	Specifies an initial context item in the form of a file name or a URI.
-t	Displays version and timing information.
-u	Enables automatic updating of sources.
-version	Display version information.
-?	Displays the help for the command-line utility.
param=value	Specifies a query string parameter and its value.
#param=value	Specifies a query number parameter and its value. On UNIX and Linux, the value for this option must be enclosed with double quotes, for example: java -jar ddxq.jar q.xq "#i=2"
+param=value	Specifies a query document parameter and its value.
!option=value	Specifies a serialization option and its value.

Example 1: Executes a Simple XQuery

Example 2: Retrieves Values from an Initial Context Item

This example retrieves all values for UserId from the initial context item users.xml.

Example 3: Retrieves Values and Writes Them to a File

This example retrieves all values for UserId and writes the results to a file named out.xml.

Example 4: Executes an XQuery in a File

This example executes the XQuery contained in the file myXQuery.xq using the initial context item input.xml.

Example 5: Binds a Query Document Parameter

This example executes the XQuery contained in the file myXQuery.xq binding the query document parameter inputDoc to the input.xml document.

Example 6: Binds a Query String Parameter and Sets an Option

This example executes the XQuery contained in the file myXQuery.xq binding the query string parameter param1 to the character string Jonathan and setting the serialization option indent to yes so that results are indented.

Example 7: Accesses a Relational Data Source

This example executes the XQuery contained in the file myXQuery2.xq that accesses a relational data source. See the NOTE about specifying connection URLs.

Example 8: Specifies a Document URI

This example retrieves all values for UserId, specifies a document URI, and writes the results to a file named out.xml.