Nodejs server returning Http response code 400 to Java

Question

I have a java code which does a http post request to a nodejs server. The nodejs server executes its code for the request correct and sends response back. However the java code is receiving Http response code 400.

Here is what my java code looks like:

protected String httpPostRequest(URL postUrl, byte[] fields, String requestType) {
        try {
            HttpURLConnection conn = (HttpURLConnection) postUrl.openConnection();
            conn.setRequestMethod("POST");
            conn.setRequestProperty("Content-Type", requestType);
            conn.setRequestProperty("Content-Length", String.valueOf(fields.length));
            conn.setDoOutput(true);
            conn.getOutputStream().write(fields);
            Reader in = new BufferedReader(new InputStreamReader(conn.getInputStream(), StandardCharsets.UTF_8));
            StringBuilder sb = new StringBuilder();
            for (int c; (c = in.read()) >= 0;)
                sb.append((char) c);
            return sb.toString();
        } catch (ProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e){
            //e.printStackTrace();
        }
        return "";
    }

And here is how the nodejs code looks like:

app.post("/test", function(req, res){
    res.send("File Created");
    //res.status(200)
    res.end();
});

I have tried res.status(200).send("something"), res.send("something"), res.send("something").end(); But I am still getting response code 400.

EDIT: detailed error:

java.io.IOException: Server returned HTTP response code: 400 for URL: http://localhost:3000/test
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1894)
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1492)
    at controller.utils.http.AbstractHttpClient.httpPostRequest(AbstractHttpClient.java:30)
    at controller.utils.http.HttpClient.callExternalUrl(HttpClient.java:35)
    at model.Project.<init>(Project.java:103)
    at controller.ProjectController.createProject(ProjectController.java:51)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at controller.AbstractApplicantzController.processRequest(AbstractApplicantzController.java:114)
    at view.AbstractWebApi.doRequestAction(AbstractWebApi.java:206)
    at view.AbstractWebApi.processRequest(AbstractWebApi.java:189)
    at view.AbstractWebApi.doPost(AbstractWebApi.java:66)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:936)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1004)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)

Yeah, that was just a mistake while pasting the error, i updated the error. I have handler for "/" and "/test" both and a few others and all of them return 400 — d_void
Have you the same problem with a simple GET request on the same URI ? — Daphoque
Ok, according to this the problem comes from your post data, check again your flow and verify the content type, the encoding and the way you're writing your datas — Daphoque
@Daphoque - Yes i think you are correct let me try a few options and see if it is fixed — d_void

Thomas Dondorf Thomas Dondorf · Accepted Answer · 2019-04-04T16:38:07

You should not be setting the Content-Length header yourself. The error is happening because the value of Content-Length is wrong.

Java will buffer whatever you are sending for you and set this value for you. Don't try to set it yourself. Removing this line should make it work:

javaconn.setRequestProperty("Content-Length", String.valueOf(fields.length));

Nodejs server returning Http response code 400 to Java

4 Answers