Redirect to another servlets path through Java Method

Question

I have a method inside my doGet that starts a thread if the date is not equal to today. The scheduler will find the execute() method. Inside this method() I try to use the redirect.

Method 1: I used the ScriptEngine to call my js method through Java but it always gives me the following error:

Js method:

function httpGet(theUrl){
window.open(theUrl)
}

Java Method:

ScriptEngine engine = manager.getEngineByName("js");
              // read script file

              engine.eval(Files.newBufferedReader(Paths.get(url), StandardCharsets.UTF_8));
              Invocable inv = (Invocable) engine;
              // call function from script file
              inv.invokeFunction("httpGet", "http://localhost:8080/myProject/StartScript?duration="+minutes);

Error:

javax.script.ScriptException: ReferenceError: "window" is not defined in <eval> at line number 3
at jdk.nashorn.api.scripting.NashornScriptEngine.throwAsScriptException(NashornScriptEngine.java:470)
at jdk.nashorn.api.scripting.NashornScriptEngine.invokeImpl(NashornScriptEngine.java:392)
at jdk.nashorn.api.scripting.NashornScriptEngine.invokeFunction(NashornScriptEngine.java:190)
at watering.WateringScheduler.execute(WateringScheduler.java:99)
at org.quartz.core.JobRunShell.run(JobRunShell.java:213)
at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:557)Caused by: <eval>:3 ReferenceError: "window" is not defined

Method 2:

I tried to use HttpUrlConnection but the problem is that it never redirects me to the page even though it connects.

 URL url;
              log.info("hi "+ minutes);
              url = new URL("http://localhost:8080/myProject/StartScript?duration="+minutes);
              HttpURLConnection urlConnection = (HttpURLConnection)url.openConnection();
              urlConnection.setDoOutput(true);
              urlConnection.setRequestMethod("GET");
              urlConnection.connect();
              BufferedReader reader = new BufferedReader(new InputStreamReader(urlConnection.getInputStream()));
              int responseCode = urlConnection.getResponseCode();
              System.out.println(responseCode);
              if(responseCode==200) {
                  urlConnection = (HttpURLConnection) url.openConnection();
                  System.out.println("Redirect to URL : " + url);
              }
              BufferedReader in = new BufferedReader(
                      new InputStreamReader(urlConnection.getInputStream()));
                String inputLine;
                StringBuffer html = new StringBuffer();

                while ((inputLine = in.readLine()) != null) {
                    html.append(inputLine);
                }
                in.close();

The problem is that everything I read online points to redirect through the doGet or doPost. I want to redirect through my execute() method.

Thanks!

score 0 · Answer 1 · answered Mar 08 '18 at 16:36

0

The script engine in Java provides the ability to execute Javascript code, but does not provide an emulation of a browser. Use HTTP clients like okhttp to download the raw HTML of the page.

For more information please visit “document” is not defined in java ScriptEngine

answered Mar 08 '18 at 16:36

Mujahid Masood

111
2
8

Hi and thank you for your response. If I have a getMethod to the url that I want to call will it execute it or it will just print its content? – Mike S. Mar 08 '18 at 16:40
You can use JSP scheduler and Servlets to achieve this functionality. – Mujahid Masood Mar 08 '18 at 16:45
That's exactly what I am using. The servlet that I try to redirect to holds a doGet method. If I understand correctly okttp prints the http section of the page, it does not redirect you to the actual page. – Mike S. Mar 08 '18 at 16:50
In the doGet you can first check if the date is today, and start scheduler and when timeout will occur just call response.sendRedirect("/toyoururl"); – Mujahid Masood Mar 08 '18 at 16:53
This is the first part that I implement. The second part stores the date in a database and executes the thread when the stored date is equal to Calendars day. This thread must then call my doGet to do everything... – Mike S. Mar 08 '18 at 17:09
Introduce a new Servlet and implement database logic in that and call that servlet using `RequestDispatcher rd = request.getRequestDispatcher("servlet2"); rd.forward(request,response);` – Mujahid Masood Mar 08 '18 at 19:04
Didn't know about that. The problem again with that is that the method that must be implemented is either a doPost or a doGet. I am trying to do that through an execute method that does not hold an HttpServletRequest request. – Mike S. Mar 08 '18 at 19:18
What does your execute method looks like? If its helper method you can invoke it from doGet as well. – Mujahid Masood Mar 08 '18 at 19:25
My execute method is the execute() method of Quartz scheduler. – Mike S. Mar 08 '18 at 19:28
You can easily call execute method from doGet or doPost. You can also use QuartzInitializerServlet or please have a look at this. https://www.splinter.com.au/using-quartz-scheduler-in-a-java-web-app-serv/ – Mujahid Masood Mar 08 '18 at 19:32
Ok. I'll have a look and update you with the results! Thank you for your time! – Mike S. Mar 08 '18 at 19:38

Redirect to another servlets path through Java Method

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