i wrote code check , create cookie.it loops through array returned request object.but throws exception.it's thrown @ beginning of loop.
import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class cookielogin extends httpservlet { printwriter out; boolean flag; public void dopost(httpservletrequest req,httpservletresponse res) throws ioexception,servletexception{ cookie[] cookies = req.getcookies(); out = res.getwriter(); for(int i=0;i<cookies.length;i++){ if(cookies[i].getname().equals("session_started")){ flag=true; out.println("your session started on "+cookies[i].getvalue()); } } if(!flag){ string time = new java.util.date().tostring(); res.addcookie(new cookie("session_started",time)); out.println("just started"); } } } here's stack trace eclipse.
java.lang.nullpointerexception @ cookielogin.dopost(cookielogin.java:11) @ javax.servlet.http.httpservlet.service(httpservlet.java:650) @ javax.servlet.http.httpservlet.service(httpservlet.java:731) @ org.apache.catalina.core.applicationfilterchain.internaldofilter(applicationfilterchain.java:303) @ org.apache.catalina.core.applicationfilterchain.dofilter(applicationfilterchain.java:208) @ org.apache.tomcat.websocket.server.wsfilter.dofilter(wsfilter.java:52) @ org.apache.catalina.core.applicationfilterchain.internaldofilter(applicationfilterchain.java:241) @ org.apache.catalina.core.applicationfilterchain.dofilter(applicationfilterchain.java:208) @ org.apache.catalina.core.standardwrappervalve.invoke(standardwrappervalve.java:220) @ org.apache.catalina.core.standardcontextvalve.invoke(standardcontextvalve.java:122) @ org.apache.catalina.authenticator.authenticatorbase.invoke(authenticatorbase.java:505) @ org.apache.catalina.core.standardhostvalve.invoke(standardhostvalve.java:170) @ org.apache.catalina.valves.errorreportvalve.invoke(errorreportvalve.java:103) @ org.apache.catalina.valves.accesslogvalve.invoke(accesslogvalve.java:956) @ org.apache.catalina.core.standardenginevalve.invoke(standardenginevalve.java:116) @ org.apache.catalina.connector.coyoteadapter.service(coyoteadapter.java:423) @ org.apache.coyote.http11.abstracthttp11processor.process(abstracthttp11processor.java:1079) @ org.apache.coyote.abstractprotocol$abstractconnectionhandler.process(abstractprotocol.java:625) @ org.apache.tomcat.util.net.jioendpoint$socketprocessor.run(jioendpoint.java:318) @ java.util.concurrent.threadpoolexecutor.runworker(threadpoolexecutor.java:1142) @ java.util.concurrent.threadpoolexecutor$worker.run(threadpoolexecutor.java:617) @ org.apache.tomcat.util.threads.taskthread$wrappingrunnable.run(taskthread.java:61) @ java.lang.thread.run(thread.java:745)
req.getcookies() returned null,so cookies.length throws nullpointerexception,
you should check wheather req.getcookies(); null;
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