伺服器端 檔案上傳模版程式碼
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;
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;
import org.apache.commons.fileupload.ProgressListener;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
public class UploadServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
List types = Arrays.asList("jpg","gif","avi","txt");
try{
DiskFileItemFactory factory = new DiskFileItemFactory(); //10k
factory.setSizeThreshold(1024*1024);
factory.setRepository(new File(this.getServletContext().getRealPath("/temp")));
ServletFileUpload upload = new ServletFileUpload(factory);
upload.setProgressListener(new ProgressListener(){
public void update(long pBytesRead, long pContentLength, int pItems) {
System.out.println("當前已解析:" + pBytesRead);
}
});
upload.setFileSizeMax(1024*1024*5);
if(!upload.isMultipartContent(request)){
//按照傳統方式獲取表單資料
request.getParameter("username");
return;
}
upload.setHeaderEncoding("UTF-8");
List<FileItem> list = upload.parseRequest(request);
for(FileItem item : list){
if(item.isFormField()){
//為普通輸入項
String inputName = item.getFieldName();
String inputValue = item.getString("UTF-8");
//inputValue = new String(inputValue.getBytes("iso8859-1"),"UTF-8");
System.out.println(inputName + "=" + inputValue);
}else{
String filename = item.getName().substring(item.getName().lastIndexOf("\\")+1); //""
if(filename==null || filename.trim().equals("")){
continue;
}
/*String ext = filename.substring(filename.lastIndexOf(".")+1);
if(!types.contains(ext)){
request.setAttribute("message", "本系統不支援" + ext + "這種型別");
request.getRequestDispatcher("/message.jsp").forward(request, response);
return;
}*/
InputStream in = item.getInputStream();
int len = 0;
byte buffer[] = new byte[1024];
String saveFileName = generateFileName(filename);
String savepath = generateSavePath(this.getServletContext().getRealPath("/WEB-INF/upload"),saveFileName);
FileOutputStream out = new FileOutputStream(savepath + File.separator + saveFileName);
while((len=in.read(buffer))>0){
out.write(buffer, 0, len);
}
in.close();
out.close();
item.delete(); //刪除臨時檔案
}
}
}catch (FileUploadBase.FileSizeLimitExceededException e) {
request.setAttribute("message", "檔案大小不能超過5m");
request.getRequestDispatcher("/message.jsp").forward(request, response);
return;
}catch (Exception e) {
throw new RuntimeException(e);
}
request.setAttribute("message", "上傳成功!!");
request.getRequestDispatcher("/message.jsp").forward(request, response);
}
//
public String generateSavePath(String path,String filename){
int hashcode = filename.hashCode(); //121221
int dir1 = hashcode&15;
int dir2 = (hashcode>>4)&0xf;
String savepath = path + File.separator + dir1 + File.separator + dir2;
File file = new File(savepath);
if(!file.exists()){
file.mkdirs();
}
return savepath;
}
public String generateFileName(String filename){
//83434-83u483-934934
return UUID.randomUUID().toString() + "_" + filename;
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
jdbc 應用的事務管理
ThreadLocal:可以線上程範圍內實現資料共享.
jdbc多表操作
儘量不用一對多關係
檔案上傳注意事項
1.上傳檔案中文亂碼問題:
1.1解決檔案的亂碼
ServletFileUpload upload=new ServletFileUpload( factory );
upload.setHeaderEncoding( ” UTF-8 ” );
1.2解決普通輸入項的亂碼
注意:表單型別為multipart/form-data的時候,設定request的編碼是無效的
String inputValue=new String( inputValue.getBytes(" iso8859-1 ")," UTF-8 ");
String inputValue=item.getString( " UTF-8 " );
2.在處理表單之前,要記得呼叫:
ServletFileUpload.isMultipartContent方法判斷提交表單的型別,如果該方法返回true,則按上傳方式處理,否則按照傳統方式處理表單即可
3.設定解析器緩衝區的大小,以及臨時檔案的刪除
設定解析器緩衝區的大小 DiskFileItemFactory.setSizeThreshold(1024*1024);
臨時檔案的刪除:在程式中處理完上傳檔案後,一定要記得呼叫item.delete()方法,以刪除臨時文
4.在做上傳系統時,千萬要注意上傳檔案的儲存目錄,這個上傳檔案的儲存目錄絕對不能讓外界直接訪問到。
5.限制上傳檔案的型別
在處理上傳檔案時,判斷上傳檔案的字尾名是不是允許的
6.限制上傳檔案的大小
呼叫解析器的ServletFileUpload.setFileSizeMax(1024*1024*5);就可以限制上傳檔案的大小,如果上傳檔案超出限制,則解析器會拋FileUploadBase.FileSizeLimitExceededException異常,程式設計師通過是否抓到這個異常,進而就可以給使用者友好提示。
7.如何判斷空的上傳輸入項
String filename = item.getName().substring(item.getName().lastIndexOf(“\”)+1); //””
if(filename==null || filename.trim().equals(“”)){
continue;
}
8、為避免上傳檔案的覆蓋,程式在儲存上傳檔案時,要為每一個檔案生成一個唯一的檔名
public String generateFileName(String filename){
//83434-83u483-934934
return UUID.randomUUID().toString() + “_” + filename;
}
9、為避免在一個資料夾下面儲存超過1000個檔案,影響檔案訪問效能,程式應該把上傳檔案打散後儲存。
public String generateSavePath(String path,String filename){
int hashcode = filename.hashCode(); //121221
int dir1 = hashcode&15;
int dir2 = (hashcode>>4)&0xf;
String savepath = path + File.separator + dir1 + File.separator + dir2;
File file = new File(savepath);
if(!file.exists()){
file.mkdirs();
}
return savepath;
}
10、監聽上傳進度
ServletFileUpload upload = new ServletFileUpload(factory);
upload.setProgressListener(new ProgressListener(){
public void update(long pBytesRead, long pContentLength, int pItems) {
System.out.println(“當前已解析:” + pBytesRead);
}
});
11、在web頁面中新增動態上傳輸入項