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java中对文件的操作
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();
%>
