文件上傳的基本操作
1、 表單屬性enctype的設置
multipart/form-data和application/x-www-form-urlencoded的區別
FORM元素的enctype屬性指定了表單數據向服務器提交時所採用的編碼類型,默認的缺省值是“application/x-www-form-urlencoded”。
然而,在向服務器發送大量的文本、包含非ASCII字符的文本或二進制數據時這種編碼方式效率很低。
在文件上載時,所使用的編碼類型應當是“multipart/form-data”,它既可以發送文本數據,也支持二進制數據上載。
Browser端<form>表單的ENCTYPE屬性值爲multipart/form-data,它告訴我們傳輸的數據要用到多媒體傳輸協議,由於多媒體傳輸的都是大量的數據,所以規定上傳文件必須是post方法,<input>的type屬性必須是file。
2、 實現代碼
///////////////////////////servlet層////////////////////////////////////////
package cn.class3g.servlet;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.List;
import java.util.UUID;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadBase.FileSizeLimitExceededException;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
public class UserServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
try {
//1 建立工廠對象
DiskFileItemFactory factory = new DiskFileItemFactory();
factory.setRepository(new File("d:\\temp"));//上傳文件到緩存文件夾
//2 得到上傳文件解析器
ServletFileUpload upload = new ServletFileUpload(factory);
upload.setHeaderEncoding("utf-8"); //處理上傳文件的亂碼
//設定上傳文件尺寸
upload.setFileSizeMax(1024*1024);
//3 進行解析 得到存放FileItem的List對象
List<FileItem> list = upload.parseRequest(request);
//4 對List進行迭代處理
for(FileItem item : list){
if(item.isFormField()){//表單普通輸入項
String paramName = item.getFieldName();
//String paramValue = item.getString();
String paramValue = item.getString("utf-8");
System.out.println("普通輸入項" +paramName +"=" +paramValue);
}else{//上傳文件處理
//獲取上傳文件名
String fileName = item.getName();
//如果文件名中有目錄 則去掉目錄部分 只保留文件名
fileName = fileName.substring(fileName.lastIndexOf("\\")+1);
System.out.println(fileName);
if(!fileName.equals("")){
fileName =refactorFileName(fileName) ;
System.out.println("filename = " + fileName);
InputStream in = item.getInputStream();
File file = new File("d:\\" +fileName);
FileOutputStream fos = new FileOutputStream(file);
byte[] buffer = new byte[1024];
int len = 0;
while((len = in.read(buffer))>0){
fos.write(buffer,0,len);
}
fos.flush();
fos.close();
in.close();
request.setAttribute("message", "文件上傳成功");
}
}
}
} catch(FileSizeLimitExceededException e1){
e1.printStackTrace();
request.setAttribute("message", "上傳文件尺寸太大!!!");
}catch (FileUploadException e) {
// TODO Auto-generated catch block
e.printStackTrace();
request.setAttribute("message", "文件上傳失敗");
}
request.getRequestDispatcher("/message.jsp").forward(request, response);
}
public String refactorFileName(String fileName){
return UUID.randomUUID().toString() + "_" + fileName;
}
}
/////////////////jsp層/////////////////////
<form action="${pageContext.request.contextPath }/servlet/UploadServlet2" method="post" enctype="multipart/form-data">
用戶名:<input type="text" name="username"/><br>
文件1:<input type="file" name="file1"/><br>
文件2:<input type="file" name="file2"/><br>
<input type="submit" value="上傳"/><br>
</form>