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

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

where install_dir is the path to your DataDirect XQuery installation directory.

NOTE: If you are connecting to PostgreSQL, you must also add the PostgreSQL JDBC driver jar file to the CLASSPATH. 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 example, where the location and name of the XML file is specified as a parameter of fn:doc(), an XQuery function.

DDXQDataSource ds = new DDXQDataSource(); 
XQConnection conn = ds.getConnection(); 
conn.createExpression().executeQuery("doc('path_and_filename')");

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 URI (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.

DDXQDataSource ds = new DDXQDataSource(); 
ds.setJdbcUrl("URL"); 
XQConnection conn = ds.getConnection("myuserid","mypswd");

Sample Connection URIs

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

jdbc:xquery:db2://server_name:50000;databaseName=your_database

jdbc:xquery:db2://server_name:446;locationName=db2_location

jdbc:xquery:informix://server_name;1526;InformixServer=dbserver_name

jdbc:xquery:sqlserver://server_name:1433

jdbc:xquery:mysql://server_name

jdbc:xquery:oracle://server_name:1521

jdbc:postgresql:your_database

jdbc:xquery:sybase://server_name:5000

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.