写入文件，

String spna=(String)session.getAttribute("spname");String spfor=(String)session.getAttribute("spformat");spna=spna+spfor;String msg = "";String local = request.getRequestURL().toString();//out.println(local);//out.flush();//local="http://localhost:8090/myjsp/spbf.jsp"String url0;        url0 ="/myjsp/spwj/"+spna;        url0 = url0.replaceAll(" ","%20");        msg += "mkList(\"";        msg += local.substring(0,local.substring(0,local.lastIndexOf("/")).lastIndexOf("/"))+url0;        //out.println(msg);        //out.flush();        msg += "\",\"";        msg += spna;                msg += "\");\n";        //out.println(msg);        //out.flush();        //下面开始生成播放列表的操作String msghead="<asx version=\"3\">\n<title>JSPBOOK</title>\n<repeat>\n";String msgtail="</repeat>\n</asx>";msg=new StringBuffer(msghead).append(msg).append(msgtail).toString();//out.print(msg);//out.flush();    String s=(String)session.getAttribute("loginuser");    if (s==null);{     s="";    } String filename = request.getRealPath("mylist/ulist"+s+".asx" );   //out.print(filename); //out.flush(); java.io.File f = new java.io.File(filename);if(!f.exists())//如果文件不存，则建立{  f.createNewFile();}try{  PrintWriter pw = new PrintWriter(new FileOutputStream(filename));  pw.println(msg);//写内容  pw.close();}catch(IOException e){  out.println(e.getMessage());}%>

if(!f.exists())//如果文件不存，则建立{  f.mkdirs();}try{  PrintWriter pw = new PrintWriter(new FileOutputStream(filename));  pw.println(msg);//写内容  pw.flush();  pw.close();}
------解决方案--------------------
FileWriter writer = new FileWriter(file , true);
writer.write("----------------------------");
writer.flush();
writer.close();
------解决方案--------------------
有注释的，可以参考下。。。
http://hi.baidu.com/snowgod/blog/item/919d797e0aa81e0028388ab8.html