servlets - Dowload link in Java, Spring MVC -

i trying implement link in webpage download file csv. content of file being appended stringbuffer , flushed response there itself. code below tried achieve :

    public void getdownloadfile(httpservletresponse response) throws ioexception{          response.setcontenttype("application/octet-stream");             response.setheader("content-disposition","attachment;filename=data.csv");             servletoutputstream out = response.getoutputstream();             try{             stringbuffer sb = generatecsvfilebuffer();                       inputstream in =  new bytearrayinputstream(sb.tostring().getbytes("utf-8"));             byte[] outputbyte = new byte[4096];              while(in.read(outputbyte, 0, 4096) != -1)             {                 out.write(outputbyte, 0, 4096);             }             in.close();             out.flush();             out.close();                       }         catch (exception e) {             system.out.println("error in csvfilewriter !!!");             e.printstacktrace();         } {             try {                 out.flush();                 out.close();             } catch (ioexception e) {                 system.out.println("error while flushing/closing filewriter !!!");                 e.printstacktrace();             }         }           return;     } 

and generatecsvfilebuffer() method called details file written. method follows:

public stringbuffer generatecsvfilebuffer(){         stringbuffer writer = new stringbuffer();          writer.append("name");         writer.append(", ");         writer.append("age");         writer.append(", ");         writer.append("address");         writer.append(", ");         writer.append("phone no");         writer.append("\n");          return writer;     } 

the programs runs till last line of code without error no output. when link clicked nothing happens in view. highly appreciated.

i took liberty rewrite code java 7's try-with-resources, better error handling , readability.

package demo.spring.mvc;  import java.io.bytearrayinputstream; import java.io.ioexception; import java.io.inputstream; import javax.servlet.servletoutputstream; import javax.servlet.http.httpservletresponse; import org.springframework.stereotype.controller; import org.springframework.ui.model; import org.springframework.web.bind.annotation.requestmapping;  @controller public class filedownloadcontroller {      @requestmapping("/download")     public void download(model model, httpservletresponse resp) {         resp.setcontenttype("text/csv");         resp.setheader("content-disposition", "attachment;filename=data.csv");         string csv = generatecsv();         try (servletoutputstream out = resp.getoutputstream();) {             byte[] arr = new byte[4096];             try (inputstream in = new bytearrayinputstream(csv.getbytes("utf-8"));) {                 (int c; (c = in.read(arr)) != -1;) {                     out.write(arr, 0, c);                 }             }         } catch (ioexception e) {             system.err.println("error in csvfilewriter!!!");             e.printstacktrace();         }     }      public string generatecsv() {         stringbuilder sb = new stringbuilder();         sb.append("name")                 .append(", ").append("age")                 .append(", ").append("address")                 .append(", ").append("phone no")                 .append("\n");         return sb.tostring();     }  } 

as added bonus, here thoughts original code.

• i changed stringbuffer stringbuilder. since java 5, can better performance switching stringbuffers not synchronized counterpart stringbuilder.
• your while loop had error because didn't test number of characters read (the c int introduced).
• you can chain calls append(...) avoid repeating variable name upon method applied.
• i switched calls system.out calls system.err because it's error handling here. it's far perfect. you'd better off logging system.