Why is Internal 500 Server Error happening in my code?

Question

JavaScript

@WebServlet(name = "registration servlet", urlPatterns = "/register")
public class Register extends HttpServlet{

PrintWriter output;
private final static int EMPTY = 0;
private static int byteContainer = 0;
private static int lines = 0;
private static String charContainer = "";

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

    output = resp.getWriter();
    output.print("The Do Get METHOD");

}

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

    output = resp.getWriter();

    ServletInputStream servletInputStream = req.getInputStream();

    if(servletInputStream.isReady()){

        byte [] bytes = new byte[4096];

        while((byteContainer = servletInputStream.read()) != -1){

            bytes [lines] = (byte)byteContainer;
            lines++;

            if((servletInputStream.read()) == -1){

                char [] chars = new char[4096];

                for(int  i = 0, k = 0 ; i < lines; i++, k++){

                    chars[i] = (char) bytes [k];
                    charContainer += chars[i];
                }
            }
        }
    }

    lines = EMPTY;
    output.print(charContainer);
    servletInputStream.close();

Запрос Ajax: 

$("#register-button").click(function () {

var user = {

    firstName:$("#first-name").val(),
    lastName:$("#last-name").val(),
    nickName:$("#nick_name").val(),
    email:$("#email_").val(),
    password:$("#password_").val(),
    customerType:$("#cust-type").val()
}

console.log(user);

var JSONString = JSON.stringify(user);

var JSONObject = JSON.parse(JSONString);

console.log(JSONObject);

var url = "http://localhost:8080/CouponProject/register";

$.ajax({

    url:url,
    method:"post",
    data:JSONObject,
    contentType:"application/json",
    error:function (message) {
        console.log(message+" In the error function!")
    },
    success:function (data) {

        console.log(data);

    },
    headers:
    {
        "Accept":"application/json",
        "Accept-Language":"en",
        "Cache-Control":"max-age=3600"
     }
  });

});

at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:528) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1100) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:687) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1520) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1476) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:745)

24-Sep-2016 11:45:27.632 SEVERE [http-nio-8080-exec-6] org.apache.catalina.core.StandardWrapperValve.invoke Servlet.service() for servlet [registration servlet] in context with path [/CouponProject] threw exception java.lang.IllegalStateException: Not available in non blocking mode at org.apache.catalina.connector.InputBuffer.isReady(InputBuffer.java:297) at org.apache.catalina.connector.CoyoteInputStream.isReady(CoyoteInputStream.java:242) at coupon.registration.Register.doPost(Register.java:37) at javax.servlet.http.HttpServlet.service(HttpServlet.java:648) at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:528) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1100) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:687) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1520) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1476) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:745)

When requesting this servlet code.. I get this error.
I know that this is a server-related error, but I can’t understand what kind of error it is and why does it happen in my case?

Answer 1

I can be wrong, but it seems to me that the problem is in
servletInputStream.isReady ()
try to comment out this condition

Answer 2

Well, you have an answer and it is written in the log:
"Not available in non blocking mode at org.apache.catalina.connector.InputBuffer.isReady(InputBuffer.java:297)"
Replace
with
if(servletInputStream.isFinished()){}