知识大全 Java对各种文件的操作详解

Posted 2022-07-18 文件

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　　java中提供了io类库可以轻松的用java实现对文件的各种操作下面就来说一下如何用java来实现这些操作 新建目录<%@ page contentType= text/;charset=gb %><%//String URL = request getRequestURI();String filePath= C:\\\\测试\\\\ ;filePath=filePath toString();//中文转换java io File myFilePath=new java io File(filePath);if(!myFilePath exists())myFilePath mkdir();%> 新建文件<%@ page contentType= text/;charset=gb %><%@ page import= java io * %><%String filePath= c:/测试/newFile txt ;filePath=filePath toString();File myFilePath=new File(filePath);if(!myFilePath exists())myFilePath createNewFile();FileWriter resultFile=new FileWriter(myFilePath);PrintWriter myFile=new PrintWriter(resultFile);String content = 这是测试数据 ;String strContent = content toString();myFile println(strContent);resultFile close();%> 删除文件<%@ page contentType= text/;charset=gb %><%String filePath= c://测试//newFile txt ;filePath=filePath toString();java io File myDelFile=new java io File(filePath);if(myDelFile exists()) myDelFile delete(); out println(filePath+ 删除成功！！！ );else out println(filePath+ 该文件不存在 );%>文件拷贝<%@ page contentType= text/; charset=gb %><%@ page import= java io * %><%int bytesum= ;int byteread= ;//file:读到流中InputStream inStream=new FileInputStream( c://测试//newFile txt );FileOutputStream fs=new FileOutputStream( c://测试//copyFile txt );byte[] buffer =new byte[ ];int length;while ((byteread=inStream read(buffer))!= ) out println( <DT><B> +byteread+ </B></DT> ); bytesum+=byteread; out println(bytesum); fs write(buffer byteread); inStream close();%> 整个文件夹拷贝<%@ page contentType= text/;charset=gb %><%@ page import= java io * %><%String url = C:/aaa ; String url = d:/java/ ; (new File(url )) mkdirs(); File[] file=(new File(url )) listFiles(); for(int i= ;i<file length;i++) if(file[i] isFile()) file[i] toString(); FileInputStream input=new FileInputStream(file[i]); FileOutputStream output=new FileOutputStream(url + / +(file[i] getName()) toString()); byte[] b=new byte[ * ]; int len; while((len=input read(b))!= ) output write(b len); output flush(); output close(); input close(); %>

　　文件下载<%@ page contentType= text/; charset=gb %><%@ page import= java io * %><% String fileName = newFile txt toString(); //读到流中 InputStream inStream=new FileInputStream( c://测试//newFile txt ); //设置输出的格式 response reset(); response setContentType( text/plain ); response addHeader( Content Disposition attachment; filename=\\ + fileName + \\ ); //循环取出流中的数据 byte[] b = new byte[ ]; int len; ServletOutputStream outStream = response getOutputStream(); while((len=inStream read(b)) > ) outStream write(b len); outStream flush(); outStream close(); inStream close();%> 数据库字段中的文件下载<%@ page contentType= text/;charset=gb %><%@ page import= java util * java sql * java io * %><% String id = request getParameter( id ); if(id==null) throw new Exception ( 没有找到图片 ); else try gzrealmap lib jdbc JDBCUtil SqlBean= gzrealmap lib jdbc JDBCUtil getInstance(); nnect(); String sql = select * from innernews where id = + + ; ResultSet rs = SqlBean queryforUpdate(sql); rs next(); //String fileNamedb = rs getString( imageName ); String file= rs getString( acc ); //String fileName = new String(fileNamedb getBytes() iso ); String fileName = a jpg ; response setHeader( Content Disposition inline; filename=\\ + fileName + \\ ); String filter = fileName substring(fileName lastIndexOf( )); if(filter equals( txt )) response setContentType( text/plain ); else if(filter equals( doc )||filter equals( dot )) response setContentType( application/msword ); else response setContentType( image/jpeg;charset=GB ); ServletOutputStream o = response getOutputStream(); //o write(file); out println(file); //o flush(); //o close(); SqlBean disconnect(); catch(Exception ex) out println(ex getMessage()); %> 把网页保存成文件<%@ page contentType= text/;charset=gb %><%@ page import= java text * java util * * java io * %><% URL stdURL = null; BufferedReader stdIn = null; PrintWriter stdOut = null; try stdURL = new URL( ); catch (MalformedURLException e) throw e; try //将字节流转变成为字符流 stdIn = new BufferedReader(new InputStreamReader(stdURL openStream())); String theFileName = c://测试//l ; stdOut = new PrintWriter(new BufferedWriter(new FileWriter(theFileName toString()))); catch (IOException e) /***把URL指定的页面以流的形式读出写成指定的文件***/ try String strHtml = ; while((strHtml = stdIn readLine())!=null) stdOut println(strHtml); catch (IOException e) throw e; finally try if(stdIn != null) stdIn close(); if(stdOut != null) stdOut close(); catch (Exception e) System out println(e); %>

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