Java对各种文件的操作详解

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/html;charset=gb2312"%>
<%
//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/html;charset=gb2312"%>
<%@ 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/html;charset=gb2312"%>
<%
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/html; charset=gb2312" %>
<%@ page import="java.io.*" %>
<%
int bytesum=0;
int byteread=0;
//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[1444];
int length;
while ((byteread=inStream.read(buffer))!=-1)
{
   out.println("<DT><B>"+byteread+"</B></DT>");
   bytesum+=byteread;
   out.println(bytesum);
   fs.write(buffer,0,byteread);
}
inStream.close();
%>

整个文件夹拷贝
<%@ page contentType="text/html;charset=gb2312"%>
<%@ page import="java.io.*" %>
<%String url1="C:/aaa";
  String url2="d:/java/";
  (new File(url2)).mkdirs();
File[] file=(new File(url1)).listFiles();
for(int i=0;i<file.length;i++){
  if(file[i].isFile()){
   file[i].toString();
   FileInputStream input=new FileInputStream(file[i]);
   FileOutputStream output=new FileOutputStream(url2+"/"+(file[i].getName()).toString());
   byte[] b=new byte[1024*5];
    int len;
    while((len=input.read(b))!=-1){
    output.write(b,0,len);
    }
    output.flush();
    output.close();
    input.close();
  }
}
%>

文件下载
<%@ page contentType="text/html; charset=gb2312"%>
<%@ 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[100];
  int len;
  ServletOutputStream outStream = response.getOutputStream();

  while((len=inStream.read(b)) >0)
  outStream.write(b,0,len);
  outStream.flush();
  outStream.close();
  inStream.close();
%>

数据库字段中的文件下载
<%@ page contentType="text/html;charset=gb2312"%>
<%@ 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
       {
com.gzrealmap.lib.jdbc.JDBCUtil  SqlBean= com.gzrealmap.lib.jdbc.JDBCUtil.getInstance();
               SqlBean.connect();
               String sql = "select * from innernews where id = '"+79+"'";
               ResultSet rs = SqlBean.queryforUpdate(sql);
               rs.next();
               //String fileNamedb = rs.getString("imageName");
               String file= rs.getString("acc");
               //String fileName = new String(fileNamedb.getBytes(),"iso-8859-1");
               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=GB2312");
               }
               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/html;charset=gb2312"%>
<%@ page import="java.text.*,java.util.*,java.net.*,java.io.*"%>
<%
URL stdURL = null;
BufferedReader stdIn = null;
PrintWriter stdOut = null;
try {
  stdURL = new URL("http://www.163.com");
}
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//163.html";
    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);
   }
}
%>

直接下载网上的文件
<%@ page contentType="text/html;charset=gb2312"%>
<%@ page import="java.io.*"%>
<%@ page import="java.net.*"%>
<%
  int bytesum=0;
  int byteread=0;
  URL url = new URL("http://pimg.163.com/sms/micheal/logo.gif");
  URLConnection conn = url.openConnection();
  InputStream inStream = conn.getInputStream();

  /**
  String theFileName = "c:/测试/logo.gif";
  theFileName = theFileName.toString();
  File myFilePath=new File(theFileName);
  if(!myFilePath.exists())
  myFilePath.createNewFile();
  **/

  FileOutputStream fs=new FileOutputStream("c:/测试/logo2.gif");
  byte[]  buffer =new  byte[1444];
    while ((byteread=inStream.read(buffer))!=-1)
    {
       out.println("<DT><B>"+byteread+"</B></DT>");
       bytesum+=byteread;
       //System.out.println(bytesum);
       fs.write(buffer,0,byteread);
     }
%>

按行读文件 <%@ page contentType="text/html; charset=gb2312" %>
<%@ page import="java.io.*" %>
<%
FileReader myFileReader=new FileReader("c:/哈哈.txt");
BufferedReader myBufferedReader=new BufferedReader(myFileReader);
String myString=null;
String resultString=new String();
while((myString=myBufferedReader.readLine())!=null) {
resultString=resultString+myString+"<br>";
}
out.println(resultString);
myFileReader.close();
%>

对word文档的处理（上传与下载）<%@ page contentType="application/msword" %>
<!-- 以上这行设定本网页为excel格式的网页 -->
<%
   response.setHeader("Content-disposition","inline; filename=test1.doc"); //线上浏览方式
  // response.setHeader("Content-disposition","attachment; filename=test1.doc");//下载方式
   //以上这行设定传送到前端浏览器时的档名为test1.doc
   //就是靠这一行，让前端浏览器以为接收到一个word档
%>
//然后输出动态内容就可以得到一个word文档了

1,打开：
1）文件头上加：<%@ page  contentType="application/msword"%>
xml文件里：
<mime-mapping>
        <extension>doc</extension>
        <mime-type>application/msword</mime-type>
</mime-mapping>
2）可以用js,以下代码来自引用：
<%@ page contentType="text/html;charset=gb2312" import= "java.io.*"%>
<HTML>
<script>
var wrd=new ActiveXObject("Word.Application")
wrd.visible=true
alert ("您的"+wrd.Application.Caption+"安装路径为：\n"+wrd.Application.Path+"\n版本号是："+ wrd.Application.version+"\n注册使用者是："+wrd.Application.UserName)
wrd.Documents.Add()
//wrd.Documents.Open("c:\\exam.doc")
wrd.Selection.TypeText("This is some text.")
wrd.Application.Activate()
wrd.ActiveDocument.SaveAs("c:\\exam111.doc")
wrd=null
</script>
</HTML>

2，下载：
<%@ page contentType="text/html;charset=gb2312" import= "java.io.*"%>
<%// 得到文件名字和路径
  String filename = "jsp.doc";
  String filepath = "C:\\";

  // 设置响应头和下载保存的文件名
  response.setContentType("APPLICATION/OCTET-STREAM");
  response.setHeader("Content-Disposition","attachment; filename=\"" + filename + "\"");

  // 打开指定文件的流信息
  java.io.FileInputStream fileInputStream = new java.io.FileInputStream(filepath + filename);
  //FileOutputStream out  = new FileOutputStream(filepath+"测试\\" + filename);
  // 写出流信息
  int i;
  while ((i=fileInputStream.read()) != -1) {
   out.write(i);
  }
  fileInputStream.close();
  out.close();
%>