jsp ajax read,java - JSP AJAX file uploading - Stack Overflow

I tried to upload a file and display content of the file back to the browser with ajax and jsp. However, it doesn't seem to work very well for me.

Apparently, in JSP page Upload.jsp, when I try to getContentType() from request, request.getcontentType() == null .

Does anyone have experience with this? Thank you much.

Form

This is the Javascript function upload(ifile)

function upload(ifile){

if (window.XMLHttpRequest){

//IE7 + and other browsers

xmlhttp = new XMLHttpRequest();

}else{

//IE 6, 5

xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");

}

if(xmlhttp == null){

alert("File Uploading is not available because your browser does not support AJAX");

return;

}

//Function to process response form upload.jsp

xmlhttp.onreadystatechange = function(){

if(xmlhttp.readyState == 4 && xmlhttp.status == 200){

var response = xmlhttp.responseText;

alert(response);

}

}

xmlhttp.open("POST", "Upload.jsp?file="+ifile, true);

xmlhttp.send(null);

}

And this is the JSP page Upload.jsp

response.setContentType("text/html");

response.setHeader("Cache-control", "no-cache");

String contentType = request.getContentType();

if ((contentType != null) && (contentType.indexOf("multipart/form-data") >= 0)) {

DataInputStream in = new DataInputStream(request.getInputStream());

//get length of Content type data

int formDataLength = request.getContentLength();

byte dataBytes[] = new byte[formDataLength];

int byteRead = 0;

int totalBytesRead = 0;

//convert the uploaded file into byte code

while (totalBytesRead < formDataLength) {

byteRead = in.read(dataBytes, totalBytesRead,formDataLength);

totalBytesRead += byteRead;

}

//decode byte array using default charset

String file = new String(dataBytes);

//Using StringTokenizer to extract genes list

StringTokenizer st = new StringTokenizer(file, " ");

int numtoken = st.countTokens();

for(int i = 0; i < numtoken-1; i++){

st.nextToken();

}

String a = st.nextToken();

st = new StringTokenizer(a, " \n");

numtoken = st.countTokens();

String postlink = "";

st.nextToken();

st.nextToken();

for(int i = 1; i < numtoken-3; i++){

String temp = st.nextToken();

char[] c = temp.toCharArray();

temp = new String(c, 0, c.length-1);

if(!" ".equalsIgnoreCase(temp)){

postlink = postlink + temp + ",";

}

}

String temp = st.nextToken();

postlink = postlink + temp;

out.println(postlink);

out.flush();

out.close();

}else if (contentType == null){

out.println("Not a valid file");

out.flush();

}

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