java 文件操作

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。
1。新建目录
<%@ page contentType="text/html;charset=gb2312"%>
<%
String filePath="c:/aaa/";
filePath=filePath.toString();//中文转换
java.io.File myFilePath=new java.io.File(filePath);
if(!myFilePath.exists())
myFilePath.mkdir();
%>
2。新建文件
<%@ page contentType="text/html;charset=gb2312"%>
<%@ page import="java.io.*" %>
<%
String filePath="c:/哈哈.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 strContent = "中文测试".toString();
myFile.println(strContent);
resultFile.close();
%>
3。删除文件
<%@ page contentType="text/html;charset=gb2312"%>
<%
String filePath="c:/支出证明单.xls";
filePath=filePath.toString();
java.io.File myDelFile=new java.io.File(filePath);
myDelFile.delete();
%>
4。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:/aaa.doc");
FileOutputStream fs=new FileOutputStream( "d:/aaa.doc");byte[] buffer =new byte[1444];
int length;
while ((byteread=inStream.read(buffer))!=-1)
{
out.println("<DT><B>"+byteread+"</B></DT>");
bytesum+=byteread;
System.out.println(bytesum);
fs.write(buffer,0,byteread);
}
inStream.close();
%>
5。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();
}
}
%>
6。文件下载
<%@ page contentType="text/html; charset=gb2312" %>
<%@ page import="java.io.*" %>
<%
String fileName = "zsc104.swf".toString();
//读到流中
InputStream inStream=new FileInputStream("c:/zsc104.swf");
//设置输出的格式
response.reset();
response.setContentType("bin");
response.addHeader("Content-Disposition","attachment; filename="" + fileName + """);
//循环取出流中的数据
byte[] b = new byte[100];
int len;
while((len=inStream.read(b)) >0)
response.getOutputStream().write(b,0,len);
inStream.close();
%>
7。数据库字段中的文件下载
<%@ page contentType="text/html; charset=gb2312" %>
<%@ page import="java.sql.*"%>
<%@ page import="java.lang.*" %>
<%@ page import="java.io.*" %>
<%@ page import="com.jspsmart.upload.*" %>
<%@ page import="DBstep.iDBManager2000.*"%>
<%
int bytesum=0;
int byteread=0;
//打开数据库
ResultSet result=null;
String Sql=null;
PreparedStatement prestmt=null;
DBstep.iDBManager2000 DbaObj=new DBstep.iDBManager2000();
DbaObj.OpenConnection();
//取得数据库中的数据
Sql="select * from t_local_zhongzhuan ";
result=DbaObj.ExecuteQuery(Sql);
result.next();
file:// 将数据库中的数据读到流中
InputStream inStream=result.getBinaryStream("content");
FileOutputStream fs=new FileOutputStream( "c:/dffdsafd.doc");
byte[] buffer =new byte[1444];
int length;
while ((byteread=inStream.read(buffer))!=-1)
{
out.println("<DT><B>"+byteread+"</B></DT>");
bytesum+=byteread;
System.out.println(bytesum);
fs.write(buffer,0,byteread);
}
%>
8。把网页保存成文件
<%@ page import="java.text.*"%>
<%@ page import="java.util.*"%>
<%@ page import="java.io.*"%>
<%@ page import="java.net.*"%>
<%
URL stdURL = null;
BufferedReader stdIn = null;
PrintWriter stdOut = null;
try {
stdURL = new URL("http://www.163.com");
}
catch (MalformedURLException e) {
throw e;
}
try {
stdIn = new BufferedReader(new InputStreamReader(stdURL.openStream()));
stdOut = new PrintWriter(new BufferedWriter(new FileWriter("c:/163.html")));
}
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);
}
}
%>
9。直接下载网上的文件
<%@ 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();
FileOutputStream fs=new FileOutputStream( "c:/abc.gif");
byte[] buffer =new byte[1444];
int length;
while ((byteread=inStream.read(buffer))!=-1)
{
out.println("<DT><B>"+byteread+"</B></DT>");
bytesum+=byteread;
System.out.println(bytesum);
fs.write(buffer,0,byteread);
}
%>
10。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();
%>
11。 数据库里字段文件直接下载到客户端
<%@ page import="java.sql.*"%>
<%@ page import="java.lang.*" %>
<%@ page import="java.io.*" %>
<%@ page import="com.jspsmart.upload.*" %>
<%@ page import="DBstep.iDBManager2000.*"%>
<%
String fileName = "bb.doc".toString();
//打开数据库
ResultSet result=null;
String Sql=null;
PreparedStatement prestmt=null;
DBstep.iDBManager2000 DbaObj=new DBstep.iDBManager2000();
DbaObj.OpenConnection();
//取得数据库中的数据
Sql="select * from marklist order by markdate desc";
result=DbaObj.ExecuteQuery(Sql);
result.next();
// 将数据库中的数据读到流中
InputStream in =result.getBinaryStream("markbody");
// 设置输出的格式
response.reset();
response.setContentType("application/Msword");
response.addHeader("Content-Disposition","attachment; filename="" + fileName + """);
//循环取出流中的数据
byte[] b = new byte[1024];
int len;
while((len=in.read(b)) >0)
response.getOutputStream().write(b,0,len);
in.close();
%>

12。文件夹遍历
<%@ page contentType="text/html; charset=gb2312" %>
<%@ page import="java.io.*" %>
<%
String url1="C:/aaa";
File f=(new File(url1));
if(f.isDirectory()){
File [] fe = f.listFiles();
go_on:
for (int i = 0;i<fe.length;i++){
if (fe[i].isDirectory()){
File [] fe1 = fe[i].listFiles();
for (int j = 0;j<fe1.length;j++){
if (fe1[j].isDirectory())
continue go_on;
out.println(fe1[j].toString());
}
}
else out.println(fe[i].toString());
}
}

%>
13。通过字符编码移动文件
<%@ page contentType="text/html; charset=gb2312" %>
<%@ page import="java.io.*" %>
<%
String ret=new String();
try
{
byte[] bytes=new byte[102400];
InputStream in=new FileInputStream("c:/aaa.doc");
in.read(bytes);
ret=new sun.misc.BASE64Encoder().encode(bytes); //具体的编码方法
in.close();
}
catch(FileNotFoundException e)
{
e.printStackTrace();
}
catch(java.io.IOException ex)
{
ex.printStackTrace();
}
out.println(ret);
byte[] bytes = new sun.misc.BASE64Decoder().decodeBuffer(ret);
java.io.ByteArrayInputStream inStream=new java.io.ByteArrayInputStream(bytes);
byte[] buffer =new byte[1444];
FileOutputStream fs=new FileOutputStream( "d:/aaa.doc");
int bytesum=0;
int byteread=0;
while ((byteread=inStream.read(buffer))!=-1)
{
bytesum+=byteread;
fs.write(buffer,0,byteread);
}
%>
14。把文件编码成base64字符串
<%
String ret=new String();
byte[] bytes=new byte[1024];
String aa="aaaa";
bytes=aa.getBytes();
ret=new sun.misc.BASE64Encoder().encode(bytes); //具体的编码方法
bytes = new sun.misc.BASE64Decoder().decodeBuffer(ret);
aa=new String(bytes);
out.println(aa);
%>