Posting object to REST web service in Java

I am writing a java application where I want to add events through a RESTful web service. When I try adding an event from my client application I get the following exception:

INFO: Error parsing HTTP request header
 Note: further occurrences of HTTP request parsing errors will be logged at DEBUG level.
java.lang.IllegalArgumentException: Invalid character found in the HTTP protocol
at org.apache.coyote.http11.Http11InputBuffer.parseRequestLine(Http11InputBuffer.java:517)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:291)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:754)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1376)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.base/java.lang.Thread.run(Unknown Source)

But when I call that same URL from the browser it works if I add annotation @GET, but if I put annotation @PUT, or @POST instead of @GET I get 405 status code.I changed these annotations in the web service method. I was wondering what might be causing the issue, since it works fine from the browser but throws the exception when called from the client app.

Here is the method on the REST service:

@POST
@Path("/add/{name}/{start}/{end}/{location}/{category}/{description}") 
@Produces(MediaType.APPLICATION_JSON)
public Response addEvent(@PathParam("name") String name,@PathParam("start") String startStr,@PathParam("end") String endStr,
    @PathParam("location") String location,@PathParam("category") String category,@PathParam("description") String description) {
    System.out.println(name);
    LocalDateTime start=service.parseLocalDateTime(startStr);
    LocalDateTime end=service.parseLocalDateTime(endStr);
    Event event=new Event(name,start,end,location,category,description,false);
    if(service.addEvent(event)) {
        return Response.status(200).build();
    }
    return Response.status(500).entity("Error in event adding.").build();
}

Here is my client method:

public void addEvent(Event event) {
    String baseUrl="http://localhost:8080/InfoEvent/api/events/";
    StringBuilder sb=new StringBuilder();
    sb.append(event.getName());
    sb.append("/");
    sb.append(event.getStart());
    sb.append("/");
    sb.append(event.getEnd());
    sb.append("/");
    sb.append(event.getLocation());
    sb.append("/");
    sb.append(event.getCategory());
    sb.append("/");
    sb.append(event.getDescription());
    String parameter=sb.toString();
    String stringURL=baseUrl+"add/"+parameter;
    System.out.println(stringURL);
    try {
        URL url = new URL(stringURL);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setDoOutput(true);
        conn.setRequestMethod("POST");
        OutputStream os = conn.getOutputStream();
        // os.write("");
        os.flush();
        if (conn.getResponseCode() != HttpURLConnection.HTTP_OK) {
            throw new RuntimeException("Failed-greskaa : HTTP error code : " + conn.getResponseCode());
        }
        os.close();
        conn.disconnect();
    } catch (Exception e) {
        e.printStackTrace();
    }
}   

I also tried changing the annotations in the client method, while also changing it in the web service method, but it didn't help.