Servlet initializing database parameters from web.xml

Question

I have problem with my context-params in my web application. My methodes

 getServletContext().getInitParameter("pass");

Are returning null. Here is my web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>Log4jWebDemo1</display-name>
<context-param>
    <param-name>log4j-config-location</param-name>
    <param-value>WEB-INF/log4j.properties</param-value>
</context-param>
    <context-param>
        <param-name>url</param-name>
        <param-value>dbc:postgresql://localhost/OlapTest</param-value>
    </context-param>
    <context-param>
        <param-name>name</param-name>
        <param-value>org.postgresql.Driver</param-value>
    </context-param>
    <context-param>
        <param-name>usr</param-name>
        <param-value>postgres</param-value>
    </context-param>
    <context-param>
        <param-name>pass</param-name>
        <param-value>admin</param-value>
    </context-param>
  <servlet>
    <servlet-name>Hello World</servlet-name>
    <servlet-class>pl.javastart.servlets.HelloWorldServlet</servlet-class>

  </servlet>
  <servlet-mapping>
    <servlet-name>Hello World</servlet-name>
    <url-pattern>/test</url-pattern>
  </servlet-mapping>
</web-app>

And my servlet:

public class HelloWorldServlet extends HttpServlet {
       private static final long serialVersionUID = 1L;
       private String url2 = ""; 
       private String driver = ""; 
       private String username = ""; 
       private String password = ""; 

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {


        PrintWriter out = response.getWriter();
        url2 = getServletContext().getInitParameter("url");
        driver = getServletContext().getInitParameter("name");
        username = getServletContext().getInitParameter("usr");
        password = getServletContext().getInitParameter("pass");

        DatabaseHandling d1 = new DatabaseHandling(driver,url2,username,password);

        d1.createConnection(out);

        }
}

After executing my application it throws

java.lang.NullPointerException

Its redundant I think, when I manualy put string values where I am executing getServletContext().getInitParameter(); The app works fine — LucasPG
– LucasPG, Commented Sep 30, 2016 at 10:39
before calling DatabaseHandling d1 = new DatabaseHandling(driver,url2,username,password); this line just print all string values. — santosh gore
– santosh gore, Commented Sep 30, 2016 at 10:40

Rohit Gaikwad · Accepted Answer · 2016-09-30 11:48:55Z

1

There can be few possibilities that leads to the NullPointerException exception

PostgresSQl driver(jar file) library is not added in your classpath.
You need to share your DatabaseHandling class so as to check the code written for connecting with DB.
change the web.xml as below:

<context-param> <param-name>url</param-name> <param-value>jdbc:postgresql://localhost/OlapTest</param-value> </context-param>

J is missing. Check the error it says dbc.

edited Sep 30, 2016 at 11:48

answered Sep 30, 2016 at 11:37

Rohit Gaikwad

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