"Head first Servlets and JSP" Note 5

"HttpServletResponse resp"

1, generally can be used through the RESP to obtain an output stream (writer), and then through the output stream to write the HTML response. For example:

      Resp.setcontenttype ("text/html");         = Resp.getwriter ();        Out.println ("Beer Selection advice<br>");

2, a number of common methods.

3. Sometimes it will be used.

4. Of course, it is more common to use JSP to return HTML.

5. Suppose you want to send a jar to the client ...

//a bunch of import Public classCodereturnextendsHttpServlet { Public voidDoget (httpservletrequest req, HttpServletResponse resp)throwsIOException, servletexception { resp.setcontexttype ( "Application/jar"); // things you want your browser to know ServletContext CTX=Getservetcontext (); InputStream is= Ctx.getresourceasstream ("/bookcode.jar"); intRead = 0; byte[] bytes =New byte[1024]; OutputStream OS=Resp.getoutputstream ();  while(read = Is.read (bytes))! =-1) {os.write (bytes,0, read); } //The jar packet is read into memory before being transcribed into the output stream. Os.flush ();    Os.close (); }}

PS: You cannot write a type first, and then change to another type to continue writing.

6. Why should I return a file through a servlet instead of returning it directly? The reason is that you want to perform some logic before and after returning a specific type of file, such as determining whether the user has permission to download the file.

7, some things to remember, about the output, there are only two choices: characters or bytes.

Output streams that can be returned via resp ...

        /* Omit parameter */ // can write any content        // similar to SYSTEM.OUT.PRINTLN () for processing character data. is actually the advanced flow printwriter that wraps the OutputStream

"Head first Servlets and JSP" Note 5