Develop Reference

Tomcat Java Servlet path

I'm messing around with Maven/Tomcat/Java in Eclipse. I have made this java servlet, but when I go to localhost:xxxx/myapp/rest I don't get a response on my GET request, I get a 404. I thought if I put the #path to /rest I can send a GET request to the url, but it's not working.
Does anyone know what the issue is? Thank you!
#Path("/rest")
public class WorldResource {
#GET
#Produces("application/json")
public String getOrders() {
WorldService service = ServiceProvider.getWorldService();
JsonArrayBuilder jab = Json.createArrayBuilder();
for (Country o : service.getAllCountries()) {
JsonObjectBuilder job = Json.createObjectBuilder();
job.add("iso2Code", o.getCode());
job.add("iso3Code", o.getIso3Code());
job.add("capital", o.getCapital());
job.add("continent", o.getContinent());
job.add("region", o.getRegion());
job.add("surface", o.getSurface());
job.add("population", o.getPopulation());
job.add("government", o.getGovernment());
job.add("latitude", o.getLatitude());
job.add("longitude", o.getLongitude());
jab.add(job);
}
JsonArray array = jab.build();
System.out.println(array);
return array.toString();
}
}

This is not a servlet, it's a JAX-RS Resource. This will not work "out of the box" within Tomcat, you'll need to deploy a JAX-RS implementation along with it (like Jersey).
A Servlet would look something like this:
#WebServlet(name = "WorldServlet", urlPatterns = {"/rest"})
public class WorldServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("application/json");
try (PrintWriter out = response.getWriter()) {
... // your code
out.println(array.toString());
}
}
}
So, you really just need to look in to installing a JAX-RS provider. Also, when you do that, odds are high it STILL won't be at /rest, because the JAX-RS implementation is normally rooted at some path, so you might end up with something like /resources/rest.
That's all configurable of course.

This can happen because your servlet is incapable of converting your POJO to appropriate HTTP response.
Instead of return array.toString();
try return Response.status(200).entity(array.toString()).build();

Restlet & MULTIPART_FORM_DATA or another way to put files on Google App Engine via Restlet

I tried to receive files via restlet but only gets the complete MULTIPART_FORM_DATA.
How can I extract my specific file?
I found some code-blocks but the types of them are not available...
RESTlet: How to process multipart/form-data requests?
DiskFileItemFactory factory = new DiskFileItemFactory();
factory.setSizeThreshold(1000240);
// 2/ Create a new file upload handler
RestletFileUpload upload = new RestletFileUpload(factory);
My current code:
#Put
public void handleUpload(Representation entity) {
if (entity !=null) {
if (MediaType.MULTIPART_FORM_DATA.equals(entity.getMediaType(), true)) {
Request restletRequest = getRequest();
Response restletResponse = getResponse();
HttpServletRequest servletRequest = ServletUtils.getRequest(restletRequest);
HttpServletResponse servletResponse = ServletUtils.getResponse(restletResponse);
try {
Upload2(restletRequest, entity);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
public void Upload2(Request req, Representation entity) throws IOException
{
...
GcsOutputChannel outputChannel = gcsService.createOrReplace(fileName, GcsFileOptions.getDefaultInstance());
ObjectOutputStream oout = new ObjectOutputStream(Channels.newOutputStream(outputChannel));
copy(entity.getStream(), oout);
oout.close();
After storing with this method I have something like that and I only want to store the content with the name "picture":
��z------WebKitFormBoundarysOvzWKPqyqW7DiTu
Content-Disposition: form-data; name="picture"; filename="_MG_4369.jpg"
Content-Type: image/jpeg
����*ExifII*
As far as I read parsing of multipart form data isn’t supported yet? But there must be a solution to send files via restlet
I tried the rest-calls via postman for chrome. The is only on multiparts the support for files. Is a possible solution to send the image as a raw-text?

You will need to add Exception handling and deal with the InputStream and potentially clean up of temp files (see DiskFileItemFactory docs) but the basics are as follows, when using the org.restlet.ext.fileupload library.
#Put
public void handleUpload(Representation entity) {
List<FileItem> items = new RestletFileUpload(new DiskFileItemFactory())
.parseRepresentation(representation);
for (FileItem item : items) {
if (!item.isFormField()) {
MediaType type = MediaType.valueOf(item.getContentType());
InputStream inputStream = item.getInputStream();
}
}
}
for a gae Solution try replacing the DiskFileItemFactory with a gwtupload.server.MemoryFileItemFactory.

You should send your file uploads as an InputStream. Then you can use this:
#Put
public void handleUpload(InputStream entity) {
}
The file is now its stream and will no longer have form data inside of it. To send a file as a stream, you can set up a client in java (using jersey, for example).
import com.sun.jersey.api.client.Client;
import com.sun.jersey.api.client.ClientResponse;
import com.sun.jersey.api.client.WebResource;
File f = new File("C:/file/to/upload.zip");
InputStream data = new FileInputStream(f);
Client client = Client.create();
client.setChunkedEncodingSize(1024);
WebResource resource = client.resource("http://localhost:80/your/uri");
ClientResponse response = resource.accept("application/x-octet-stream").type("application/x-octet-stream").post(ClientResponse.class, data);
Now that you have data, you can set up a client to post data to your server. I was trying this using multipart form data and postman before. I went mad trying to get multipart data to work. But this is the solution I have been using instead. And it works perfectly.

Servlet mixes header and content and writing twice same in output?

I have implemented servlet which behaves not stable, sometimes it mixes header in content and writing same twice.
and sometimes it is returning file which contains response header mixed by content like this:
Server: Apache-Coyote/1.1
: W/"43-1353687036000"
DatCCoonntenntt--DDiissppoosittiioonn: : atatatacehnmte;n tf;i lfenlaemnea=m20=12201112211127325421_4W1_Wirnkgi_nSgc_Seern.xnlsx
sx
Content-Typ-eT: ype: applaipcatciaoti/on/toctestt-rstare
am
ConCtoententy-pTeype: appalicatcion/oon/octet-setarm
m
CCoonntent-Lnegtht h: 4199
Date: te: FriF,r i2,3 2No vNo2v0 120162: 215:25 :G4M2T
....
File content bytes ...
And again same header and content
UPDATE
*This situation happens on Tomcat7*
I have tested also on Tomcat6 and Jetty, in both cases there is no injection of HTTP-Header to response content but HTTP-Header is wrong and returns wrong file name, the file content is correct file. I have noticed that wrong return from servlet happens when
returns transfer-encoding is chunked.
When I am removing header stuff, and second part of bytes, it is valid file.
Is it possible that is synchronization issue ?
UPDATE
Here is full source of servlet :
public class ExcelDownloadServlet extends HttpServlet
{
private static final long serialVersionUID = 1L;
private static final Logger LOG = Logger
.getLogger (ExcelDownloadServlet.class);
#Override
protected void doGet (HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException
{
try
{
TransactionId transactionId = getTransactionId (request);
String fileName =
request.getParameter (GlobalConstants.EXCEL_FILE);
ExcelDownloadType downloadType =
ExcelDownloadType
.valueOf (request
.getParameter (GlobalConstants.EXCEL_DOWNLOAD_TYPE));
ActionContextFactory actionContextFactory =
ApplicationContext.getContext ()
.getActionContextFactory ();
//suppress warning. HttpServletRequest.getLocales does not support generics
#SuppressWarnings("unchecked")
ActionContext actionContext =
actionContextFactory.create (request.getSession ()
.getId (), Collections.<Locale> list (request
.getLocales ()));
GetExcelDataResponse dataResponse =
new GetExcelData (transactionId, fileName, downloadType)
.execute (actionContext);
writeToResponse (response, dataResponse.getFileName (),
dataResponse.getData ());
}
catch (InvalidSessionException e)
{
LOG.error ("Invalid session in Excel download", e);
throw new ServletException (e);
}
catch (ActionException e)
{
LOG.error ("Could not download into excel.", e);
throw new ServletException (e);
}
}
protected TransactionId getTransactionId (HttpServletRequest request)
{
return RequestParameterDeserializer.<TransactionId> deserialize (
request, GlobalConstants.TRANSACTION_ID);
}
protected void writeToResponse (HttpServletResponse response,
String rawFileName, byte[] data) throws IOException
{
ServletOutputStream sout = null;
try
{
response.setContentType ("application/octet-stream");
response.setContentLength (data.length);
// removing blanks from the file name, since FF cuts file names
// otherwise.
String fileNameWithTime = rawFileName.replaceAll (" ", "_");
response.setHeader ("Content-Disposition", "attachment; filename="
+ fileNameWithTime);
sout = response.getOutputStream ();
sout.write (data, 0, data.length);
}
finally
{
if (sout != null)
{
sout.close ();
}
}
}
UPDATE
*The call comes from GWT application when is generating the URL of servlet with required parameters and sets in IFrame, then servlet calls and file is downloading. Are there any suggestions ?*

I had a similar issue a long time ago.
It turned out that closing the ServletOutputStream triggered an unexpected behaviour on the request flow.
Servlets are not supposed to close the container provided OutputStream.
Another issue could be manually setting the content length, it is responsibility of the container producing the correct value.
To summarize, try removing out.close() and response.setContentLength()

Parse HttpServletRequest contains jsonp string

When I try to send cross-domain jsonp request with:
$.getJSON(url + "?callback=?",
value : 'John',
record : {
value : 'a',
list : [ 1, 2 ]
});
Then i try to get it with java servlet like this:
public class TestServlet extends HttpServlet {
protected void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
String output = request.getParameter("callback")
+ "({\"response\":\"test\"});";
response.setContentType("application/javascript;charset=utf-8");
PrintWriter out = response.getWriter();
out.println(output);
}
}
Inside servlet request string has parameter names:
_=1353482336546
value=John
record[value]=a
How can i parse request string to original JSON?
Im using embedded jetty server and I want to use "JSON to Object" jetty parser on JSON string

You can apply flexjson to parse json string to an object. Please take a look at:
live example
flexjson library

Use GZIP, JSON responses and JQuery

However, I want to compress my responses with GZIP wheren possible. I tried using the Compression filter code available for free download in the headfirst site. It works great for html, images, css and javascript.
I post the filter next. It checks if GZIP is an accepted encoding and it adds gzip as Content-Encoding. See: wrappedResp.setHeader("Content-Encoding", "gzip");
public class CompressionFilter implements Filter {
private ServletContext ctx;
private FilterConfig cfg;
/**
* The init method saves the config object and a quick reference to the
* servlet context object (for logging purposes).
*/
public void init(FilterConfig cfg)
throws ServletException {
this.cfg = cfg;
ctx = cfg.getServletContext();
//ctx.log(cfg.getFilterName() + " initialized.");
}
/**
* The heart of this filter wraps the response object with a Decorator
* that wraps the output stream with a compression I/O stream.
* Compression of the output stream is only performed if and only if
* the client includes an Accept-Encoding header (specifically, for gzip).
*/
public void doFilter(ServletRequest req,
ServletResponse resp,
FilterChain fc)
throws IOException, ServletException {
HttpServletRequest request = (HttpServletRequest) req;
HttpServletResponse response = (HttpServletResponse) resp;
// Dose the client accept GZIP compression?
String valid_encodings = request.getHeader("Accept-Encoding");
if ( (valid_encodings != null) && (valid_encodings.indexOf("gzip") > -1) ) {
// Then wrap the response object with a compression wrapper
// We'll look at this class in a minute.
CompressionResponseWrapper wrappedResp = new CompressionResponseWrapper(response);
// Declare that the response content is being GZIP encoded.
wrappedResp.setHeader("Content-Encoding", "gzip");
// Chain to the next component (thus processing the request)
fc.doFilter(request, wrappedResp);
// A GZIP compression stream must be "finished" which also
// flushes the GZIP stream buffer which sends all of its
// data to the original response stream.
GZIPOutputStream gzos = wrappedResp.getGZIPOutputStream();
gzos.finish();
// The container handles the rest of the work.
//ctx.log(cfg.getFilterName() + ": finished the request.");
} else {
fc.doFilter(request, response);
//ctx.log(cfg.getFilterName() + ": no encoding performed.");
}
}
public void destroy() {
// nulling out my instance variables
cfg = null;
ctx = null;
}
}
I was using the next code to send JSON responses in Struts web application.
public ActionForward get(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response) {
JSONObject json = // Do some logic here
RequestUtils.populateWithJSON(response, json);
return null;
}
public static void populateWithJSON(HttpServletResponse response,JSONObject json) {
if(json!=null) {
response.setContentType("text/x-json;charset=UTF-8");
response.setHeader("Cache-Control", "no-cache");
try {
response.getWriter().write(json.toString());
} catch (IOException e) {
throw new ApplicationException("IOException in populateWithJSON", e);
}
}
}
It works fine without compression but if I compress JSON responses, I can not see my JSON objects anymore. I handle JSON Ajax calls with JQuery with code snippets as follows:
$.post(url,parameters, function(json) {
// Do some DOM manipulation with the data contained in the JSON Object
}, "json");
If I see the response with Firebug it is empty.
Should I refractor my compression filter to skip compression in JSON responses? or there is a workaround to this?
For me, it looks like JQuery does not recognize the response as JSON because I am adding the Gzip compression.

If I see the response with Firebug it
is empty.
There's your clue - it's not a JQuery problem, it's server-side. (I'm afraid I can't help you with that, other than to suggest you stop looking at the client-side)
There's no problem gzipping ajax responses - if you can't see the response in Firebug, then JQuery can't see it either.

you have to add one more header "content-encoding: gzip" if you are compressing it.

Have you tried with an explicit java-based client to ensure it's a problem with jQuery or browser? If java client fails, something is wrong with server response.
But I am guessing that whereas browser can deal with uncompression with direct requests, this is perhaps not applied to Ajax calls.
It's an interesting question, I hope we'll get a more definitive answer. :)