服务器端 文件上传模版代码

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("当前已解析：" + pBytesRead);
                }
            });

            upload.setFileSizeMax(1024*1024*5);
            if(!upload.isMultipartContent(request)){
                //按照传统方式获取表单数据
                request.getParameter("username");
                return;
            }
            upload.setHeaderEncoding("UTF-8");
            List<FileItem> list = upload.parseRequest(request);

            for(FileItem item : list){
                if(item.isFormField()){
                    //为普通输入项
                    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", "本系统不支持" + ext + "这种类型");
                        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();  //删除临时文件
                }
            }
        }catch (FileUploadBase.FileSizeLimitExceededException e) {
            request.setAttribute("message", "文件大小不能超过5m");
            request.getRequestDispatcher("/message.jsp").forward(request, response);
            return;
        }catch (Exception e) {
            throw new RuntimeException(e);
        }
        request.setAttribute("message", "上传成功！！");
        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 应用的事务管理

ThreadLocal:可以在线程范围内实现数据共享.

jdbc多表操作

尽量不用一对多关系

文件上传注意事项

1.上传文件中文乱码问题:
1.1解决文件的乱码
ServletFileUpload upload=new ServletFileUpload( factory );
upload.setHeaderEncoding( ” UTF-8 ” );
1.2解决普通输入项的乱码
注意:表单类型为multipart/form-data的时候,设置request的编码是无效的

String inputValue=new String( inputValue.getBytes(" iso8859-1 ")," UTF-8 ");  

String inputValue=item.getString( " UTF-8 " );

2.在处理表单之前，要记得调用：
ServletFileUpload.isMultipartContent方法判断提交表单的类型，如果该方法返回true，则按上传方式处理，否则按照传统方式处理表单即可

3.设置解析器缓冲区的大小，以及临时文件的删除
设置解析器缓冲区的大小 DiskFileItemFactory.setSizeThreshold(1024*1024);
临时文件的删除：在程序中处理完上传文件后，一定要记得调用item.delete()方法，以删除临时文

4.在做上传系统时，千万要注意上传文件的保存目录，这个上传文件的保存目录绝对不能让外界直接访问到。

5.限制上传文件的类型
在处理上传文件时，判断上传文件的后缀名是不是允许的

6.限制上传文件的大小
调用解析器的ServletFileUpload.setFileSizeMax(1024*1024*5);就可以限制上传文件的大小，如果上传文件超出限制，则解析器会抛FileUploadBase.FileSizeLimitExceededException异常，程序员通过是否抓到这个异常，进而就可以给用户友好提示。

7.如何判断空的上传输入项
String filename = item.getName().substring(item.getName().lastIndexOf(“\”)+1); //””
if(filename==null || filename.trim().equals(“”)){
continue;
}

8、为避免上传文件的覆盖，程序在保存上传文件时，要为每一个文件生成一个唯一的文件名
public String generateFileName(String filename){
//83434-83u483-934934
return UUID.randomUUID().toString() + “_” + filename;
}

9、为避免在一个文件夹下面保存超过1000个文件，影响文件访问性能，程序应该把上传文件打散后存储。
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、监听上传进度
ServletFileUpload upload = new ServletFileUpload(factory);
upload.setProgressListener(new ProgressListener(){
public void update(long pBytesRead, long pContentLength, int pItems) {
System.out.println(“当前已解析：” + pBytesRead);
}
});

11、在web页面中添加动态上传输入项