Servlet+jsp文件上传及要注意的问题

た入场券 2022-07-12 07:14 145阅读 0赞

文件上传要注意的问题：

1、非上传文件的乱码问题，此时通过request设置字符编码无效

2、上传文件的名字含有中文字符，会乱码

3、文件重名会覆盖

4、所有上传的文件要保存在不同的目录下面

5、可以设置文件上传的类型限制

6、可以设置文件上传大小

7、可以设置文件上传总量的大小

后面三个在代码中没有写，5，可以获取文件的后缀名，判断一下就行了，67 api更是有对应的方法，两行代码搞定了

package cn.web.upload;
    
    import java.io.File;
    import java.io.FileOutputStream;
    import java.io.IOException;
    import java.io.InputStream;
    import java.util.List;
    import java.util.Map;
    import java.util.UUID;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import org.apache.tomcat.util.http.fileupload.FileItem;
    import org.apache.tomcat.util.http.fileupload.disk.DiskFileItemFactory;
    import org.apache.tomcat.util.http.fileupload.servlet.ServletFileUpload;
    
    /**
     * Servlet implementation class UploadServlet
     */
    @WebServlet("/UploadServlet")
    public class UploadServlet extends HttpServlet {
           
    	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		try{
    			DiskFileItemFactory factory = new DiskFileItemFactory();
    			ServletFileUpload upload = new ServletFileUpload(factory);
    			
    			upload.setHeaderEncoding("UTF-8");//解决上传中文文件名字乱码问题
    			
    			if(!upload.isMultipartContent(request)){
    				//不是上传文件表单，按照传统方式获取内容即可
    				return;
    			}
    			Map<String,List<FileItem>> map = upload.parseParameterMap(request);
    			
    			String savepath = this.getServletContext().getRealPath("/WEB-INF/upload");
    			int i = 0;
    			for(Map.Entry<String,List<FileItem>> me : map.entrySet()){
    				FileItem item = me.getValue().get(i);
    				if(item.isFormField()){
    					String name = item.getFieldName();
    					String value = item.getString("UTF-8");//解决表单数据乱码的问题
    //					value = new String(value.getBytes("iso8859-1"),"UTF-8");
    					System.out.println(name + " = " + value);
    				}else{
    					InputStream in = item.getInputStream();
    					String name = item.getName();	//得到文件的名字或者路径名+名字
    					name = name.substring(name.lastIndexOf("\\") + 1);
    					
    					String fileName = this.makeFileName(name);//解决问价重名，覆盖的问题
    					String realPath = this.makePath(fileName, savepath);//解决文件都在同一个目录下的问题
    					
    					File file = new File(realPath + "\\" + fileName);
    					FileOutputStream out = new FileOutputStream(file);
    					
    					int len=0;
    					byte buffer[] = new byte[1024];
    					while((len=in.read(buffer))!=-1){
    						out.write(buffer, 0, len);
    					}
    					out.close();
    					in.close();
    				}
    			}
    			
    		}catch (Exception e){
    			throw new RuntimeException(e);
    		}
    	}
    	
    	//为文件生成一个唯一的名字
    	public String makeFileName(String name){
    		return UUID.randomUUID().toString() + "_" + name;
    	}
    	//生成目录
    	public String makePath(String fileName,String path){
    		int hashCode = fileName.hashCode();
    		int dir1 = hashCode&0xf;
    		int dir2 = (hashCode&0xf0)>>4;
    		String dir = path +"\\"+ dir1 +"\\" + dir2;
    		File file = new File(dir);
    		if(!file.exists()){
    			file.mkdirs();
    		}
    		return dir;
    	}
    	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		doGet(request, response);
    	}
    
    }

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>上传页面</title> </head> <body> <form action="${pageContext.request.contextPath }/UploadServlet" method="post" enctype="multipart/form-data"> 姓名：<input type="text" name="name"/><br> 上传文件1：<input type="file" name="file1"/><br> 上传文件2：<input type="file" name="file2"/><br> <input type="submit" value="提交"/> </form> </body> </html>

注意：上传的文件一定要有enctype="multipart/form-data";这句话