asj177 asj177 - 1 year ago 2207
Java Question

Download Large file from server using REST template Java Spring MVC

I have a REST service which sends me a large ISO file ,there are no issues in the REST service .
Now I have written a Web application which calls the rest service to get the file ,on the client(web app) side I receive a Out Of memory Exception.Below is my code

HttpHeaders headers = new HttpHeaders();//1 Line

headers.setAccept(Arrays.asList(MediaType.APPLICATION_OCTET_STREAM));//2 Line
headers.set("Content-Type","application/json");//3 Line
headers.set("Cookie", "session=abc");//4 Line
HttpEntity statusEntity=new HttpEntity(headers);//5 Line
String uri_status=new String("http://"+ip+":8080/pcap/file?fileName={name}");//6 Line

ResponseEntity<byte[]>resp_status=rt.exchange(uri_status, HttpMethod.GET, statusEntity, byte[].class,"File5.iso");//7 Line


I receive out of memory exception at 7 line ,I guess i will have to buffer and get in parts ,but dont know how can i get this file from the server ,the size of the file is around 500 to 700 MB .
Can anyone please assist .

Exception Stack:

org.springframework.web.util.NestedServletException: Handler processing failed; nested exception is java.lang.OutOfMemoryError: Java heap space
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:972)
org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:852)
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)
org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:778)
javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
root cause

java.lang.OutOfMemoryError: Java heap space
java.util.Arrays.copyOf(Arrays.java:3236)
java.io.ByteArrayOutputStream.grow(ByteArrayOutputStream.java:118)
java.io.ByteArrayOutputStream.ensureCapacity(ByteArrayOutputStream.java:93)
java.io.ByteArrayOutputStream.write(ByteArrayOutputStream.java:153)
org.springframework.util.FileCopyUtils.copy(FileCopyUtils.java:113)
org.springframework.util.FileCopyUtils.copyToByteArray(FileCopyUtils.java:164)
org.springframework.http.converter.ByteArrayHttpMessageConverter.readInternal(ByteArrayHttpMessageConverter.java:58)
org.springframework.http.converter.ByteArrayHttpMessageConverter.readInternal(ByteArrayHttpMessageConverter.java:1)
org.springframework.http.converter.AbstractHttpMessageConverter.read(AbstractHttpMessageConverter.java:153)
org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:81)
org.springframework.web.client.RestTemplate$ResponseEntityResponseExtractor.extractData(RestTemplate.java:627)
org.springframework.web.client.RestTemplate$ResponseEntityResponseExtractor.extractData(RestTemplate.java:1)
org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:454)
org.springframework.web.client.RestTemplate.execute(RestTemplate.java:409)
org.springframework.web.client.RestTemplate.exchange(RestTemplate.java:385)
com.pcap.webapp.HomeController.getPcapFile(HomeController.java:186)


My Server Side REST Service Code which is working fine is

@RequestMapping(value = URIConstansts.GET_FILE, produces = { MediaType.APPLICATION_OCTET_STREAM_VALUE}, method = RequestMethod.GET)
public void getFile(@RequestParam(value="fileName", required=false) String fileName,HttpServletRequest request,HttpServletResponse response) throws IOException{



byte[] reportBytes = null;
File result=new File("/home/arpit/Documents/PCAP/dummyPath/"+fileName);

if(result.exists()){
InputStream inputStream = new FileInputStream("/home/arpit/Documents/PCAP/dummyPath/"+fileName);
String type=result.toURL().openConnection().guessContentTypeFromName(fileName);
response.setHeader("Content-Disposition", "attachment; filename=" + fileName);
response.setHeader("Content-Type",type);

reportBytes=new byte[100];//New change
OutputStream os=response.getOutputStream();//New change
int read=0;
while((read=inputStream.read(reportBytes))!=-1){
os.write(reportBytes,0,read);
}
os.flush();
os.close();






}

Answer Source

Here is how I do it. Based on hints from this Spring Jira issue.

RestTemplate restTemplate // = ...;

// Optional Accept header
RequestCallback requestCallback = request -> request.getHeaders()
        .setAccept(Arrays.asList(MediaType.APPLICATION_OCTET_STREAM, MediaType.ALL));

// Streams the response instead of loading it all in memory
ResponseExtractor<Void> responseExtractor = response -> {
    // Here I write the response to a file but do what you like
    Path path = Paths.get("some/path");
    Files.copy(response.getBody(), path);
    return null;
};
restTemplate.execute(URI.create("www.something.com"), HttpMethod.GET, requestCallback, responseExtractor);

From the aforementioned Jira issue:

Note that you cannot simply return the InputStream from the extractor, because by the time the execute method returns, the underlying connection and stream are already closed.

Recommended from our users: Dynamic Network Monitoring from WhatsUp Gold from IPSwitch. Free Download