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+"
"; }

out.println(resultString); myFileReader.close();

%>