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In this article Barry Mavin, CEO and Chief Software Architect for Recital, details how to use the Client Drivers provided with the Recital Database Server to work with local or remote server-side OLE DB data sources.

Overview

The Recital Universal .NET Data Provider provides connectivity to the Recital Database Server running on any supported platform (Windows, Linux, Unix, OpenVMS) using the RecitalConnection object.

The Recital Universal JDBC Driver provides the same functionality for java applications.

The Recital Universal ODBC Driver provides the same functionality for applications that use ODBC.

Each of the above Client Drivers use a connection string to describe connections parameters.

The basic format of a connection string consists of a series of keyword/value pairs separated by semicolons. The equal sign (=) connects each keyword and its value.

The following table lists the valid names for keyword/values.


Name Default Description

Data Source
-or-
Server
-or-
Nodename

 

  The name or network address of the instance of the Recital Database Server which to connect to.
Directory   The target directory on the remote server where data to be accessed resides. This is ignored when a Database is specified.

Encrypt
-or-
Encryption

false When true, DES3 encryption is used for all data sent between the client and server.
Initial Catalog
-or-
Database
  The name of the database on the remote server.
Password
-or-
Pwd
  The password used to authenticate access to the remote server.
User ID   The user name used to authenticate access to the remote server.

Connection Pooling
-or-
Pool

false Enable connection pooling to the server. This provides for one connection to be shared.
Logging false Provides for the ability to log all server requests for debugging purposes
Rowid true When Rowid is true (the default) a column will be post-fixed to each SELECT query that is a unique row identifier. This is used to provide optimised UPDATE and DELETE operations. If you use the RecitalSqlGrid, RecitalSqlForm, or RecitalSqlGridForm components then this column is not visible but is used to handle updates to the underlying data source.
Logfile   The name of the logfile for logging
Gateway  

Opens an SQL gateway(Connection) to a foreign SQL data source on the remote server.

Using Gateways, you can transparently access the following local or remote data sources:

  • Recital
  • Oracle
  • ODBC (Server-side ODBC data sources)
  • JDBC (Server-side JDBC data sources)
  • ADO (Use this to connect to SQL Server and other Native Windows OLEDB data sources)
  • MySQL
  • PostgreSQL

The gateway can be specified in several formats:

servertype@nodename:username/password-database

e.g.

oracle@nodename:username/password-database

mysql@nodename:username/password-database

postgresql@nodename:username/password-database

-or-

odbc:odbc_data_source_name_on_server

oledb:oledb_connection_string_on_server

jdbc:jdbc_driver_path_on_server;jdbc:Recital:args


To connect to a server-side OLE DB data source, you use the gateway=value key/value pair in the following way.

gateway=oledb:oledb_connection_string_on_server

Important
When specifying the connection string be sure to quote the gateway= with "...".

You can find examples of connection strings for most ODBC and OLE DB data sources by clicking here.

Example in C# using the Recital Universal .NET Data Provider:
////////////////////////////////////////////////////////////////////////
// include the references below
using System.Data;
using Recital.Data;
 
////////////////////////////////////////////////////////////////////////
// The following code example creates an instance of a DataAdapter that 
// uses a Connection to the Recital Database Server, and a gateway to
// the SQL server Northwind database. It then populates a DataTable 
// in a DataSet with the list of customers. The SQL statement and 
// Connection arguments passed to the DataAdapter constructor are used 
// to create the SelectCommand property of the DataAdapter.
public DataSet SelectCustomers()
{
	string gateway = "oledb:Provider=sqloledb;Initial Catalog=Northwind;
		Data Source=localhost;Integrated Security=SSPI";
	RecitalConnection swindConn = new 
		RecitalConnection("Data Source=localhost;gateway=\""+gateway+"\");
	RecitalCommand selectCMD = new 
		RecitalCommand("SELECT CustomerID, CompanyName FROM Customers", swindConn);
	selectCMD.CommandTimeout = 30;
	RecitalDataAdapter custDA = new RecitalDataAdapter();
	custDA.SelectCommand = selectCMD;
	swindConn.Open();
	DataSet custDS = new DataSet();
	custDA.Fill(custDS, "Customers");
	swindConn.Close();
	return custDS;
}
Example in Java using the Recital Universal JDBC Driver:
////////////////////////////////////////////////////////////////////////
// standard imports required by the JDBC driver
import java.sql.*;
import java.io.*;
import java.net.URL;
import java.math.BigDecimal;
import Recital.sql.*;
 
////////////////////////////////////////////////////////////////////////
// The following code example creates a Connection to the Recital 
// Database Server, and a gateway to the SQL server Northwind database. 
// It then retrieves all the customers.
public void SelectCustomers()
{
    // setup the Connection URL for JDBC
	String gateway = "oledb:Provider=sqloledb;Initial Catalog=Northwind;
		Data Source=localhost;Integrated Security=SSPI";
	String url = "jdbc:Recital:Data Source=localhost;gateway=\""+gateway+"\";
	// load the Recital Universal JDBC Driver
	new RecitalDriver();
 
	// create the connection
	Connection con = DriverManager.getConnection(url);
	// create the statement
	Statement stmt = con.createStatement();
	// perform the SQL query
	ResultSet rs = stmt.executeQuery("SELECT CustomerID, CompanyName FROM Customers");
	// fetch the data
	while (rs.next()) 
	{
		String CompanyID = rs.getString("CustomerID");
		String CompanyName = rs.getString("CompanyName");
		// do something with the data...
	}
    
	// Release the statement
	stmt.close();
	
	// Disconnect from the server
	con.close();
}
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STRERROR()

Syntax

STRERROR( [ <expN> ] )

Description

The STRERROR() function returns a string describing the last operating system error message. If the optional error number is specified then the related operating system error message will be returned.

Example

mqdes=mqcreate("/myqueue", 2)
 if (mqdes < 0)
     messagebox(strerror()+",errno="+alltrim(str(error())))
    return
 endif
 rc = mqsend(mqdes, "Test message")
 if (rc < 0)
     messagebox(strerror()+",errno="+alltrim(str(error())))
    return
 endif
 mqclose(mqdes)

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When using Recital Web you can maintain the exact state of each work area between pages like this.

On exit of an .rsp page.

SAVE DATASESSION TO m_state 
_SESSION["state"] = m_state

On entry to an .rsp page.

IF type( _session["state"] ) != "U" 
    m_state = _session["state"]
    RESTORE DATASESSION FROM m_state
ENDIF
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By default Recital uses PAM to authenticate users.  It is also possible to tell PAM to use Kerberos.  Simply replace the existing entries in the /etc/pam.d/recital file with the ones below:

auth       sufficient   pam_krb5.so try_first_pass
auth       sufficient   pam_unix.so shadow nullok try_first_pass
account    required     pam_unix.so broken_shadow
account    [default=bad success=ok user_unknown=ignore] pam_krb5.so
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This link provides a decent covering of this topic.
http://www.the-art-of-web.com/css/border-radius/
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One of the attractive features of Linux is the impressive 3D desktop that even works on most older hardware.

You can enabled the 3D Desktop on CentOS5 by installing the compiz package:

yum install compiz 

After you have done this, go to the top panel and click System, then select Preferences > and click 'Desktop Effects.

You will get a new dialog. To test and see if your hardware supports the 3D Desktop, press the button Enable Desktop Effects. If everything works fine, you can select Keep Settings.

Then test your 3D Desktop by pressing Ctrl-Alt-Left and Ctrl-Alt-Right, or drag a window around or even out of the screen to the left or right. If you maximize a window, you will see another cool effect. If you move the mouse to the upper-right corner of the screen you see all your opened applications.

Way cool!
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In this article Chris Mavin, explains and details how to use the Recital Database Server with the Open Source Servlet Container Apache Tomcat.

Overview

PHP has exploded on the Internet, but its not the only way to create web applications and dynamic websites. Using Java Servlets, JavaServer Pages and Apache Tomcat you can develop web applications in a more powerful full featured Object Oriented Language, that is easier to debug, maintain, and improve.

Tomcat Installation

There are a number of popular Java application servers such as IBM Web Sphere and BEA WebLogic but today we will be talking about the use of Apache Tomcat 5, the Open Source implementation of the Java Servlet and JavaServer Pages technologies developed at the Apache Software Foundation. The Tomcat Servlet engine is the official reference implementation for both the Servlet and JSP specifications, which are developed by Sun under the Java Community Process. What this means is that the Tomcat Server implements the Servlet and JSP specifications as well or better than most commercial application servers.

Apache Tomcat is available for free but offers many of the same features that commercially available Web application containers boast.

Tomcat 5 supports the latest Servlet and JSP specifications, Servlet 2.4, and JSP 2.0, along with features such as:

  • Tomcat can run as a standalone webserver or a Servlet/JSP engine for other Web Servers.

  • Multiple connectors - for enabling multiple protocol handlers to access the same Servlet engine.

  • JNDI - The Java Naming and Domain Interface is supported.

  • Realms - Databases of usernames and passwords that identify valid users of a web application.

  • Virtual hosts - a single server can host applications for multiple domain names. You need to edit server.xml to configure virtual hosts.

  • Valve chains.

  • JDBC - Tomcat can be configured to use any JDBC driver.

  • DBCP - Tomcat can use the Apache commons DBCP for connection pooling.

  • Servlet reloading (Tomcat monitors any changes to the classes deployed within that web server.)

  • HTTP functionality - Tomcat functions as a fully featured Web Server.

  • JMX, JSP and Struts-based administration.

Tomcat Installation

In this next two sections we will walk through the install and setup of Tomcat for use with the Recital database server.

To download Tomcat visit the Apache Tomcat web site is at http://jakarta.apache.org/tomcat.
Follow the download links to the binary for the hardware and operating system you require.

For Tomcat to function fully you need a full Java Development Kit (JDK). If you intend to simply run pre compiled JavaServer pages you can do so using just the Java Runtime Environment(JRE).

The JDK 1.5 is the preferred Java install to work with Tomcat 5, although it is possible to run Tomcat 5 with JDK 1.4 but you will have to download and install the compat archive available from the Tomcat website.

For the purpose of this article we will be downloading and using Tomcat 5 for Linux and JDK 5.0, 
you can download the JDK at http://java.sun.com/javase/downloads/index.jsp.

Now we have the JDK, if the JAVA_HOME environment variable isn't set we need to set it to refer to the base JDK install directory.

Linux/Unix:
$ JAVA_HOME= /usr/lib/j2se/1.4/
$ EXPORT $JAVA_HOME
Windows NT/2000/XP:

Follow the following steps:

1. Open Control Panel.
2. Click the System icon.
3. Go to the Advanced tab.
4. Click the Environment Variables button.
5. Add the JAVA_HOME variable into the system environment variables.


The directory structure of a Tomcat installation comprises of the following:

/bin 			- Contains startup, shutdown and other scripts. 
	/common  	- Common classes that the container and web applications can use.
	/conf 		- Contains Tomcat XML configuration files XML files.
	/logs 		- Serlvet container and application logs.
	/server 		- Classes used only by the Container.
	/shared 		- Classes shared by all web application.
	/webapps 	- Directory containing the web applications.
	/work 		- Temporary directory for files and directories.

The important files that you should know about are the following:

  • server.xml

The Tomcat Server main configuration file is the [tomcat install path]\conf\server.xml file. This file is mostly setup correctly for general use. It is within this file where you specify the port you wish to be running the server on. Later in this article I show you how to change the default port used from 8080 to port 80.

  • web.xml

The web.xml file provides the configuration for your web applications. There are two locations where the web.xml file is used, 
web-inf\web.xml provides individual web application configurations and [tomcat install path]conf\web.xml contains the server wide configuration.

Setting up Tomcat for use

We'll start by changing the port that Tomcat will be listening on to 80.

To do this we need to edit [tomcat install path]/conf/server.xml and change the port attribute of the connector element from 8080 to 80.

After you have made the alteration the entry should read as:

<!-- Define a non-SSL HTTP/1.1 Connector on port 8080 -->
<Connector port="80" maxHttpHeaderSize="8192"

Next we want to turn on Servlet reloading, this will cause the web application to be recompiled each time it is accessed, allowing us to make changes to the files without having to worry about if the page is being recompiled or not.

To enable this you need to edit [tomcat install path]/conf/context.xml and change <Context> element to <Context reloadable="true">.

After you have made the alteration the entry should read as:

<Context reloadable="true">
<WatchedResource>WEB-INF/web.xml</WatchedResource>
</Context>

Next we want to enable the invoker Servlet.

The "invoker" Servlet executes anonymous Servlet classes that have not been defined in a web.xml file.  Traditionally, this Servlet is mapped to the URL pattern "/servlet/*", but you can map it to other patterns as well.  The extra path info portion of such a request must be the fully qualified class name of a Java class that implements Servlet, or the Servlet name of an existing Servlet definition.

To enable the invoker Servlet you need to edit the to [tomcat install path]/conf/web.xml and uncomment the Servlet and Servlet-mapping elements that map the invoker /servlet/*.

After you have made the alteration the entry should read as:

<servlet>
<servlet-name>invoker</servlet-name>
<servlet-class>org.apache.catalina.servlets.InvokerServlet</servlet-class>
<init-param>
<param-name>debug</param-name>
<param-value>0</param-value>
</init-param>
<load-on-startup>2</load-on-startup>
</servlet>

<servlet-mapping>
<servlet-name>invoker</servlet-name>
<url-pattern>/servlet/*</url-pattern>
</servlet-mapping>

If you are you not interested in setting up your own install of Tomcat there are prebuilt versions Tomcat that has all of the above changes already made, and has the test HTML, JSP, and Servlet files already bundled. Just unzip the file, set your JAVA_HOME

Next we will give Tomcat and your web applications access to the Recital JDBC driver.

For the purposes of this article we are going to install the Recital JDBC driver in the /[tomcat install path]/common/lib/ this gives Tomcat and your web applications access to the Recital JDBC driver. The driver can be installed in a number of places in the Tomcat tree, giving access to the driver to specific application or just to the web application and not the container. For more information refer to the Tomcat documentation.

Copy the recitalJDBC.jar which is located at /[recital install path]/drivers/recitalJDBC.jar to the /[tomcat install path]/common/lib/ directory.

Linux:
$cp /[recital install path]/drivers/recitalJDBC.jar /[tomcat install path]/common/lib/
Once you have completed all the steps detailed above, fire up the server using the script used by your platform's Tomcat installation.

Linux/Unix:
[tomcat install path]/bin/startup.sh
Windows:
[tomcat install path]/bin/startup

If you are having problems configuring your Tomcat Installation or would like more detail visit the online documentation a the Apache Tomcat site.

Example and Links

Now we have setup our Tomcat installation, lets get down to it with a JSP example which uses the Recital JDBC driver to access the demonstration database (southwind) shipped with the Recital Database Server.

The example provided below is a basic JDBC web application, where the user simply selects a supplier from the listbox and requests the products supplied by that supplier.

To run the example download and extract the tar archive or simple save each of the two jsp pages individually into /[tomcat install path]/webapps/ROOT/ on your server.

By enabling the invoker Servlet earlier we have removed the need to set the example up as a web application in the Tomcat configuration files.

You can now access the example web application at http://[Server Name]/supplier.jsp if the page doesn't display, check you have followed all the Tomcat installation steps detailed earlier in this article and then make sure both Tomcat and a licensed Recital UAS are running.

Downloads:
Archive: jspExample.tar

Right click and save as individual files and rename as .jsp files:
supplier.txt details.txt

Further Reading on JSP and JDBC can be found at http://www-128.ibm.com/developerworks/java/library/j-webdata/

Final Thoughts

Recital and Apache tomcat are a powerful combination, using Java Servlet technology you can separate application logic and the presentation extremely well. Tomcat, JSP, Java Servlets and the Recital database server form a robust platform independent, easily maintained and administered solution with which to unlock the power of your Recital, Foxpro, Foxbase, Clipper, RMS and C-SAM data.

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Key features of the Recital database include:

  • SQL-92 and a broad subset of ANSI SQL 99, as well as extensions
  • Cross-platform support
  • Stored procedures
  • Triggers
  • Cursors
  • Updatable Views
  • System Tables
  • Query caching
  • High-performance
  • Single-User and Multi-User
  • Multi-Process
  • ACID Transactions
  • Referential Integrity
  • Cascading Updates and Deletes
  • Multi-table Joins
  • Row-level Locking
  • BLOBs (Binary Large Objects)
  • UDFs (User Defined Functions)
  • OLTP (On-Line Transaction Processing)
  • Drivers for ODBC, JDBC, and .NET
  • Sub-SELECTs (i.e. nested SELECTs)
  • Embedded database library
  • Database timelines providing data undo functionality
  • Fault tolerant clustering support
  • Hot backup
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TIP
The Recital Oracle Gateway requires the Oracle libclntsh.so shared library.  If this file is unknown to ld.so.conf, add it using the ldconfig command. 
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In this article Barry Mavin, CEO and Chief Software Architect for Recital, details how to use the Recital Database Server with Visual FoxPro. 

 

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