Tomcat: Null Pointer Exception when trying to access web service

Question

I have a dynamic web project that contains a web service. I have exported it as a WAR file and placed it in the webapps directory of tomcat. Tomcat shows that the web app is running. When I attempt to invoke one of the operations of my service, I get the following exception:

java.lang.NullPointerException
    sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
    java.lang.ClassLoader.loadClass(ClassLoader.java:247)
    org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1629)
    org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1559)
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:461)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
    org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:931)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
    org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1004)
    org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
    org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
    java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
    java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
    java.lang.Thread.run(Thread.java:680)

Any idea what this means?

Here's my class the defines the web service:

package webservice;

import java.sql.*;

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.QueryParam;
import javax.ws.rs.HeaderParam;
import javax.ws.rs.core.MediaType;

@Path("/operations")
public class NotifyWebService {

    @Path("/insertNewPatron")
    @GET

    public String insertNewPatron(@QueryParam("cardNumber")String cardNumber,
                                    @QueryParam("pin") String pin,
                                    @QueryParam("nickname") String nickname,
                                    @QueryParam("deviceID")String deviceID) throws Exception {


        String connectionUrl = "jdbc:sqlserver://mssql.acpl.lib.in.us:1433;" +
                   "databaseName=MobileNotify;user=Mobile_Notification_User;password=xxxxxxx;";




            Connection c = DriverManager.getConnection(connectionUrl);

            String insertPatronStatement = "INSERT INTO dbo.Patron VALUES ('"+cardNumber+"','"+pin+"','"+nickname+"')";
            String insertDeviceOwner = "INSERT INTO dbo.DeviceOwner VALUES ('"+deviceID+"','"+cardNumber+"')";
            Statement state = null;

            state = c.createStatement();
            state.executeUpdate(insertPatronStatement);
            state.executeUpdate(insertDeviceOwner);


            c.close();


            return "true";
    }


    @Path("/initializeDevice")
    @GET

    public String initializeDevice( @QueryParam("deviceID")String deviceID) throws Exception{

        String connectionUrl = "jdbc:sqlserver://mssql.acpl.lib.in.us:1433;" +
                   "databaseName=MobileNotify;user=Mobile_Notification_User;password=xxxxxx;";


        Connection c = DriverManager.getConnection(connectionUrl);

        String insertDeviceStatement = "INSERT INTO dbo.Devices VALUES ('"+deviceID+"',1,3,1,3)";
        Statement state = c.createStatement();
        state.executeUpdate(insertDeviceStatement);


        return "true";
    }


    @Path("/updateDevicePreferences")
    @GET

    public String updateDevicePreferences(@QueryParam("deviceID") String deviceID, 
                                            @QueryParam("dueDateNotice")String dueDateNotice,
                                            @QueryParam("dueDateNoticeAdvance") String dueDateNoticeAdvance,
                                            @QueryParam("holdsNotice") String holdsNotice, 
                                            @QueryParam("eventNoticeAdvance")String eventNoticeAdvance) throws Exception{
        String connectionUrl = "jdbc:sqlserver://mssql.acpl.lib.in.us:1433;" +
                   "databaseName=MobileNotify;user=Mobile_Notification_User;password=xxxxxx;";


        Connection c = DriverManager.getConnection(connectionUrl);

        String updateDeviceStatement = "UPDATE dbo.Devices SET dueDateNotice="+dueDateNotice+", dueDateNoticeAdvance="+dueDateNoticeAdvance
                                    +", holdsNotice="+holdsNotice+", eventNoticeAdvance="+eventNoticeAdvance+" WHERE deviceID='"+deviceID+"'";
        Statement state = c.createStatement();
        state.executeUpdate(updateDeviceStatement);

        return "true";
    }


    @Path("/removeUser")
    @GET

    public String removeUser(@QueryParam("cardNumber")String cardNumber) throws Exception{
        String connectionUrl = "jdbc:sqlserver://mssql.acpl.lib.in.us:1433;" +
                   "databaseName=MobileNotify;user=Mobile_Notification_User;password=xxxxxx;";


        Connection c = DriverManager.getConnection(connectionUrl);

        String removeStatement = "DELETE FROM dbo.Patron WHERE cardNumber='"+cardNumber+"'";

        Statement state = c.createStatement();
        state.executeUpdate(removeStatement);




        return "true";
    }

    @Path("/addEvent")
    @GET

    public String addEvent(@QueryParam("deviceID")String deviceID, @QueryParam("eventID")String eventID) throws Exception{

        String connectionUrl = "jdbc:sqlserver://mssql.acpl.lib.in.us:1433;" +
                   "databaseName=MobileNotify;user=Mobile_Notification_User;password=xxxxx;";


        Connection c = DriverManager.getConnection(connectionUrl);

        String eventStatement = "INSERT INTO dbo.Events VALUES ('"+deviceID+"','"+eventID+"')";
        Statement state = c.createStatement();
        state.executeUpdate(eventStatement);


        return "true";
    }

    @Path("/removeEvent")
    @GET

    public String removeEvent(@QueryParam("deviceID")String deviceID, @QueryParam("eventID")String eventID) throws Exception{

        String connectionUrl = "jdbc:sqlserver://mssql.acpl.lib.in.us:1433;" +
                   "databaseName=MobileNotify;user=Mobile_Notification_User;password=xxxxx;";


        Connection c = DriverManager.getConnection(connectionUrl);

        String eventStatement = "DELETE FROM dbo.Events WHERE deviceID='"+deviceID+"' AND eventID='"+eventID+"'";
        Statement state = c.createStatement();
        state.executeUpdate(eventStatement);


        return "true";
    }

    @Path("/removeAllEvents")
    @GET

    public String removeAllEvents(@QueryParam("deviceID")String deviceID) throws Exception{

        String connectionUrl = "jdbc:sqlserver://mssql.acpl.lib.in.us:1433;" +
                   "databaseName=MobileNotify;user=Mobile_Notification_User;password=xxxx;";


        Connection c = DriverManager.getConnection(connectionUrl);

        String eventStatement = "DELETE FROM dbo.Events WHERE deviceID='"+deviceID+"'";
        Statement state = c.createStatement();
        state.executeUpdate(eventStatement);


        return "true";
    }
}

Here's my web.xml file:

<?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>APNS_WebService</display-name>
   <servlet>
        <servlet-name>javax.ws.rs.core.Application</servlet-name>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>javax.ws.rs.core.Application</servlet-name>
        <url-pattern>/rest/*</url-pattern>
    </servlet-mapping>
</web-app>

Let me know if more information is required!

Community · Accepted Answer · 2017-05-23 11:48:57Z

2

I believe that the cause of your NPE is the lack of a <servlet-class> element in your <servlet> block. However, deciding what the servlet-class should be raises a bigger problem...

It looks like you have not chosen a JAX-RS framework. See JAX-RS Frameworks for insight on various alternatives.

I am currently using Jersey. A typical web.xml for Jersey might contain:

  <servlet>
    <servlet-name>WebService</servlet-name>
    <servlet-class>com.sun.jersey.spi.container.servlet.ServletContainer</servlet-class>
    <init-param>
       <param-name>com.sun.jersey.config.property.packages</param-name>
       <param-value>webservice</param-value>
    </init-param>
    <init-param>
      <param-name>com.sun.jersey.api.json.POJOMappingFeature</param-name>
      <param-value>true</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
  </servlet>

  <servlet-mapping>
    <servlet-name>WebService</servlet-name>
    <url-pattern>/api/rest/*</url-pattern>
  </servlet-mapping>

For many JAX-RS frameworks, the choice of framework will determine what you should enter as the <servlet-class>

Also note that since your root resource is in package webservice, I set the com.sun.jersey.config.property.packages parameter to webservice so Jersey will scan your package for any JAX-RS annotated classes.

edited May 23, 2017 at 11:48

CommunityBot

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answered Dec 7, 2012 at 21:43

Guido Simone

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1 Comment

James Harpe Over a year ago

Thanks, that did it! I thought I had a web.xml similar to that previously but I guess I was wrong!

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