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();
%>