Servlet Fehler beim Start der Serveranwendung

[MARJAVA]

Leider startet meine Anwendung nicht und folgende Fehlermeldung wird ausgelöst:

Aug 26, 2018 4:42:17 PM org.apache.coyote.AbstractProtocol start
INFORMATION: Starting ProtocolHandler ["http-nio-8080"]
Aug 26, 2018 4:42:17 PM org.apache.coyote.AbstractProtocol start
INFORMATION: Starting ProtocolHandler ["ajp-nio-8009"]
Aug 26, 2018 4:42:17 PM org.apache.catalina.startup.Catalina start
INFORMATION: Server startup in 28600 ms
Aug 26, 2018 4:43:22 PM org.apache.catalina.core.StandardWrapperValve invoke
SCHWERWIEGEND: Servlet.service() for servlet [FrontController] in context with path [/Buecherverwaltung] threw exception
java.lang.NullPointerException
    at controller.command.Read.executeGET(Read.java:21)
    at controller.FrontControllerServlet.doGet(FrontControllerServlet.java:48)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:493)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:650)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:800)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:800)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1471)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:748)

Die Stelle ist folgende :

package controller.command;

import java.io.IOException;
import java.sql.SQLException;
import java.util.ArrayList;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import model.Buch;
import persistence.BuchDAO;

public class Read implements Command {

    @Override
    public void executeGET(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
   
        try {
[COLOR=#ff0000]            ArrayList<Buch> buecher = ((BuchDAO) request.getServletContext().getAttribute("buchDAO")).findAll();[/COLOR]
           
            request.setAttribute("buecher", buecher);

            RequestDispatcher dispatcher = request.getServletContext().getRequestDispatcher(JSPPATH+"read.jsp");
            dispatcher.include(request, response);

        } catch (SQLException e) {
            throw new ServletException(e);
        }
       

    }

    @Override
    public void executePOST(HttpServletRequest request, HttpServletResponse response) {
        // TODO Auto-generated method stub

    }

    @Override
    public String getTitel() {
        return "Buecherliste";
    }

}

 

[mihe7]

request == null || request.getServletContext() == null || request.getServletContext().getAttribute("buchDAO") == null

 

[MARJAVA]

das Attribut "buchDao" ist nicht vorhanden

 

[mihe7]

Dann reagiere entsprechend darauf.