Configuring Spring MVC controller to send file to

Question

I think my scenario is pretty common. I have a database and I want my Spring MVC app to accept a request in the controller, invoke the DB service to get data and send that data to the client as a CSV file. I'm using the JavaCSV library found here to assist in the process: http://sourceforge.net/projects/javacsv/

I've found several examples of people doing similar things and cobbled together something that looks correct-ish. When I hit the method, though, nothing is really happening.

I thought writing the data to the HttpServletResponse's outputStream would be sufficient, but apparently, I'm missing something.

Here's my controller code:

@RequestMapping(value="/getFullData.html", method = RequestMethod.GET)
public void getFullData(HttpSession session, HttpServletRequest request, HttpServletResponse response) throws IOException{
    List<CompositeRequirement> allRecords = compReqServ.getFullDataSet((String)session.getAttribute("currentProject"));

    response.setContentType("data:text/csv;charset=utf-8"); 
    response.setHeader("Content-Disposition","attachment; filename=\yourData.csv\"");
    OutputStream resOs= response.getOutputStream();  
    OutputStream buffOs= new BufferedOutputStream(resOs);   
    OutputStreamWriter outputwriter = new OutputStreamWriter(buffOs);  

    CsvWriter writer = new CsvWriter(outputwriter, '\u0009');  
    for(int i=1;i <allRecords.size();i++){              
        CompositeRequirement aReq=allRecords.get(i);  
        writer.write(aReq.toString());  
    }     
    outputwriter.flush();   
    outputwriter.close();

};

What step am I missing here? Basically, the net effect is... nothing. I would have thought setting the header and content type would cause my browser to pick up on the response and trigger a file download action.

Answer 1

It seems to be because your Content-type is set incorrectly, it should be response.setContentType("text/csv;charset=utf-8") instead of response.setContentType("data:text/csv;charset=utf-8").

Additionally, if you are using Spring 3, you should probably use a @ResponseBody HttpMessageConverter for code reuse. For example:

• In the controller:

  @RequestMapping(value = "/getFullData2.html", method = RequestMethod.GET, consumes = "text/csv")
  @ResponseBody // indicate to use a compatible HttpMessageConverter
  public CsvResponse getFullData(HttpSession session) throws IOException {
        List<CompositeRequirement> allRecords = compReqServ.getFullDataSet((String) session.getAttribute("currentProject"));
        return new CsvResponse(allRecords, "yourData.csv");
  }
  

• plus a simple HttpMessageConverter:

  public class CsvMessageConverter extends AbstractHttpMessageConverter<CsvResponse> {
     public static final MediaType MEDIA_TYPE = new MediaType("text", "csv", Charset.forName("utf-8"));
     public CsvMessageConverter() {
         super(MEDIA_TYPE);
     }
  
     protected boolean supports(Class<?> clazz) {
         return CsvResponse.class.equals(clazz);
     }
  
     protected void writeInternal(CsvResponse response, HttpOutputMessage output) throws IOException, HttpMessageNotWritableException {
         output.getHeaders().setContentType(MEDIA_TYPE);
         output.getHeaders().set("Content-Disposition", "attachment; filename=\"" + response.getFilename() + "\"");
         OutputStream out = output.getBody();
         CsvWriter writer = new CsvWriter(new OutputStreamWriter(out), '\u0009');
         List<CompositeRequirement> allRecords = response.getRecords();
         for (int i = 1; i < allRecords.size(); i++) {
              CompositeRequirement aReq = allRecords.get(i);
              writer.write(aReq.toString());
         }
         writer.close();
     }
  }
  

• and a simple object to bind everything together:

  public class CsvResponse {    
     private final String filename;
     private final List<CompositeRequirement> records;
  
     public CsvResponse(List<CompositeRequirement> records, String filename) {
         this.records = records;
         this.filename = filename;
     }
     public String getFilename() {
         return filename;
     }
     public List<CompositeRequirement> getRecords() {
         return records;
     }
  }
  

Answer 2

Based on Pierre answer, i did a converter. Here is the full code, that works with any Object passed:

TsvMessageConverter.java

public class TsvMessageConverter extends AbstractHttpMessageConverter<TsvResponse> {

    public static final MediaType MEDIA_TYPE = new MediaType("text", "tsv", Charset.forName("utf-8"));
    private static final Logger logger = LoggerFactory.getLogger(TsvMessageConverter.class);

    public TsvMessageConverter() {
        super(MEDIA_TYPE);
    }

    protected boolean supports(Class<?> clazz) {
        return TsvResponse.class.equals(clazz);
    }

    @Override
    protected TsvResponse readInternal(Class<? extends TsvResponse> clazz, HttpInputMessage inputMessage) throws IOException, HttpMessageNotReadableException {
        return null;
    }

    protected void writeInternal(TsvResponse tsvResponse, HttpOutputMessage output) throws IOException, HttpMessageNotWritableException {
        output.getHeaders().setContentType(MEDIA_TYPE);
        output.getHeaders().set("Content-Disposition", "attachment; filename=\"" + tsvResponse.getFilename() + "\"");
        final OutputStream out = output.getBody();

        writeColumnTitles(tsvResponse, out);

        if (tsvResponse.getRecords() != null && tsvResponse.getRecords().size() != 0) {
            writeRecords(tsvResponse, out);
        }

        out.close();
    }

    private void writeRecords(TsvResponse response, OutputStream out) throws IOException {
        List<String> getters = getObjectGetters(response);
        for (final Object record : response.getRecords()) {
            for (String getter : getters) {
                try {
                    Method method = ReflectionUtils.findMethod(record.getClass(), getter);
                    out.write(method.invoke(record).toString().getBytes(Charset.forName("utf-8")));
                    out.write('\t');
                } catch (IllegalAccessException | InvocationTargetException e) {
                    logger.error("Erro ao transformar em CSV", e);
                }
            }
            out.write('\n');
        }
    }

    private List<String> getObjectGetters(TsvResponse response) {
        List<String> getters = new ArrayList<>();
        for (Method method : ReflectionUtils.getAllDeclaredMethods(response.getRecords().get(0).getClass())) {
            String methodName = method.getName();
            if (methodName.startsWith("get") && !methodName.equals("getClass")) {
                getters.add(methodName);
            }
        }
        sort(getters);
        return getters;
    }

    private void writeColumnTitles(TsvResponse response, OutputStream out) throws IOException {
        for (String columnTitle : response.getColumnTitles()) {
            out.write(columnTitle.getBytes());
            out.write('\t');
        }
        out.write('\n');
    }
}

TsvResponse.java

public class TsvResponse {
   private final String filename;
   private final List records;
    private final String[] columnTitles;

   public TsvResponse(List records, String filename, String ... columnTitles) {
       this.records = records;
       this.filename = filename;
       this.columnTitles = columnTitles;
   }
   public String getFilename() {
       return filename;
   }
   public List getRecords() {
       return records;
   }

    public String[] getColumnTitles() {
        return columnTitles;
    }
}

And on SpringContext.xml add the following:

<mvc:annotation-driven>
        <mvc:message-converters register-defaults="true">
            <bean class="com.mypackage.TsvMessageConverter"/>
        </mvc:message-converters>
    </mvc:annotation-driven>

So, you can use on your controller like this:

@RequestMapping(value="/tsv", method= RequestMethod.GET, produces = "text/tsv")
    @ResponseBody
    public TsvResponse tsv() {
        return new TsvResponse(myListOfPojos, "fileName.tsv",
                "Name", "Email", "Phone", "Mobile");
    }