Reading properties file in Java web application

Question

I am currently using a ServletContextListener to set the paths of JSPs in a web application. The paths are stored as context parameters in web.xml and retrieved by the listener:

    @Override
    public void contextInitialized(ServletContextEvent sce) {        
        ServletContext sc = sce.getServletContext();                           
        sc.setAttribute("urlOfThisPage", sc.getInitParameter("urlOfThisPage"));   
        sc.setAttribute("urlOfThatPage", sc.getInitParameter("urlOfThatPage"));    

In the application servlets, the path of a particular JSP can easily be retrieved from ServletContext .

My question relates to handling a properties file in the same way. I read a lot about this on other StackOverflow pages like 2161045 .

Am I correct in assuming that the properties file should be read by a listener and stored in ServletContext using a Property object? but then if this is the case, how would I retrieve a particular property from the properties file?

At the moment I am using this sort of code in my servlets to get the value of an attribute from ServletContext .

String url = (String) sc.getAttribute("urlOfThisPage");  // Use ServletContext to get JSP's URL.    

But I am not sure how to extend this to accessing a properties file.

I have tried the following in the ServletContextListener :

    Properties properties = new Properties();
    properties.setProperty("name", "Akechi Jinsai");
    sc.setAttribute("properties", properties);

And in a servlet, using code:

   ServletContext sc = request.getSession().getServletContext();        
   Properties properties = (Properties) sc.getAttribute("properties");
   System.out.println("Here: " + properties.getProperty("name"));

"Here: Akechi Jinsai" is displayed but is there a better way of getting a single property in a servlet without looking up things in this way?

Answer 1

Simply load the properties file in Servlet and move the values into HashMap and store it as application attribute. Now access it in JSP using JavaServer Pages Standard Tag Library .

Read more about Load properties file in Servlet/JSP .

---

Sample code:

JSP: (Different ways to access the map)

<c:forEach items="${map}" var="entry">
    Key="${entry.key}" Value=${entry.value}
</c:forEach>

URL Of This Page = ${map.urlOfThisPage }
URL Of That Page = ${map.urlOfThatPage }


URL Of This Page = ${map['urlOfThisPage'] }
URL Of That Page = ${map['urlOfThatPage'] }

ServletContextListener

public class MyServletContextListener implements ServletContextListener {

    @Override
    public void contextDestroyed(ServletContextEvent sc) {

    }

    @Override
    public void contextInitialized(ServletContextEvent sce) {
        ServletContext sc = sce.getServletContext();
        // load the properties file if needed
        // read the path from web.xml as init parameter 

        Map<String, String> map = new HashMap<String, String>();
        map.put("urlOfThisPage", sc.getInitParameter("urlOfThisPage"));
        map.put("urlOfThatPage", sc.getInitParameter("urlOfThatPage"));

        sc.setAttribute("map", map);
    }

}

web.xml:

<context-param>
    <param-name>urlOfThisPage</param-name>
    <param-value>url</param-value>
</context-param>
<context-param>
    <param-name>urlOfThatPage</param-name>
    <param-value>url</param-value>
</context-param>

<listener>
    <listener-class>com.x.y.z.MyServletContextListener</listener-class>
</listener>