Java中文网 - Java利用io类库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
//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
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
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
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("
"+byteread+"");bytesum+=byteread;
out.println(bytesum);
fs.write(buffer,0,byteread);
}
inStream.close();
%>
整个文件夹拷贝
String url2="d:/java/";
(new File(url2)).mkdirs();
File[] file=(new File(url1)).listFiles();
for(int i=0;i
if(file.isFile()){
file.toString();
FileInputStream input=new FileInputStream(file);
FileOutputStream output=new FileOutputStream(url2+"/"+(file.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
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
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=gbk");
}
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
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
int bytesum=0;
int byteread=0;
byte[] buffer =new byte[1444];
while ((byteread=inStream.read(buffer))!=-1)
{
out.println("
"+byteread+"");bytesum+=byteread;
//System.out.println(bytesum);
fs.write(buffer,0,byteread);
}
%>
按行读文件
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+"
";
}
out.println(resultString);
myFileReader.close();
%>
对word文档的处理(上传与下载)
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：
xml文件里：
doc
application/msword
2)可以用js,以下代码来自引用：
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
2，下载：
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();
%>
本文出自java 中文网(http://www.javaweb.cc/) -Java利用io类库对各种文件的操作详解
 演讲ppt)
