File Upload core point 1 (59), file upload core point 59

File Upload core point 1 (59), file upload core point 59

1: Use <input type = "file"/> to declare a file field. File: _____ <browse>.

2: You must use a post form.

3: You must set the form type to multipart/form-data. This is not the key = value passed by the form. The byte code is passed.

Example: how to obtain the content of an uploaded file (obtain a txt file)

PackageCn. hx. servlet;

ImportJava. io. BufferedReader;

ImportJava. io. IOException;

ImportJava. io. InputStream;

ImportJava. io. InputStreamReader;

ImportJava. io. PrintWriter;

ImportJavax. servlet. ServletException;

ImportJavax. servlet. http. HttpServlet;

ImportJavax. servlet. http. HttpServletRequest;

ImportJavax. servlet. http. HttpServletResponse;

/**

* If the type of a form is post and the enctype is multipart/form-date

* All data is transmitted to the server in binary mode.

* Therefore, req. getParameter ("xxx") is always null.

* You can only use req. getInputStream () to obtain data and body data.

*/

Public ClassUpServletExtendsHttpServlet {

Public VoidDoPost (HttpServletRequest req, HttpServletResponse resp)

ThrowsServletException, IOException {

Req. setCharacterEncoding ("UTF-8 ");

String txt = req. getParameter ("txt"); // The returned value is null.

System.Err. Println ("txt is:" + txt );

System.Err. Println ("========================================== ==== ");

InputStream in = req. getInputStream ();

// Byte [] B = new byte [1, 1024];

// Int len = 0;

// While (len = in. read (B ))! =-1 ){

// String s = new String (B, 0, len );

// System. err. print (s );

//}

BufferedReader br =NewBufferedReader (NewInputStreamReader (in ));

String firstLine = br. readLine (); // read the first line, and the first line is the separator number

String fileName = br. readLine ();

FileName = fileName. substring (fileName. lastIndexOf ("\") + 1); // bafasd.txt"

FileName = fileName. substring (0, fileName. length ()-1 );

Br. readLine ();

Br. readLine ();

String data =Null;

// Obtain the running path of the current project

String projectPath = getServletContext (). getRealPath ("/up ");

PrintWriter out =NewPrintWriter (projectPath + "/" + fileName );

While(Data = br. readLine ())! =Null){

If(Data. equals (firstLine + "--")){

Break;

}

Out. println (data );

}

Out. close ();

}

}