Chapter 61. About the OGSA-DAI data source servlet

61.1. Introduction
61.2. Default data source servlet URL
61.3. How to change the data source servlet name
61.4. Servlet limitations

61.1. Introduction

If OGSA-DAI is deployed onto Tomcat then it supports a data source servlet. This allows the data exposed by an OGSA-DAI data source to be exposed via a servlet and so accessed by any HTTP client. Examples of the utility of the servlet are described in Chapter 103, Writing effective clients - using the data source servlet for delivery. This page outlines information from a server administrator's perspective.

61.2. Default data source servlet URL

The default name of the data source retrieval servlet is DataSourceRetrievalServlet. The URL to access the servlet is defined, by default, to be this appended to the prefix of all services on the OGSA-DAI server.

The prefix of all services is:

http://HOST:PORT/wsrf/services/dai

and the servlet has a default URL of:

http://HOST:PORT/wsrf/services/dai/DataSourceRetrievalServlet

For example:

http://coal.epcc.ed.ac.uk:8080/wsrf/services/dai/DataSourceRetrievalServlet

61.3. How to change the data source servlet name

The servlet name and path, i.e.

/services/DataSourceRetrievalServlet

is defined in a web.xml file in Tomcat.

This file is located in

$CATALINA_HOME/webapps/wsrf/WEB-INF/web.xml

and the servlet entry looks like:

  <servlet>
    <servlet-name>DataSourceRetrievalServlet</servlet-name>
    <display-name>OGSA-DAI Servlet</display-name>
    <servlet-class>uk.org.ogsadai.servlets.DataSourceRetrievalServlet</servlet-class>
  </servlet>
  
  <servlet-mapping>
    <servlet-name>DataSourceRetrievalServlet</servlet-name>
    <url-pattern>/services/dai/DataSourceRetrievalServlet</url-pattern>
  </servlet-mapping>

You can change the name of the servlet by changing the value in the url-pattern field. For example, changing the url-pattern value to be to be servlets/DataSourceRetrievalServlet would mean that the connection URL would be:

http://coal.epcc.ed.ac.uk:8080/wsrf/servlets/DataSourceRetrievalServlet

61.4. Servlet limitations

There is no support for secure access to data exposed via the data source servlet. This could lead to privileged data being accessible to non-privileged users.