form表单文件上传 servlet文件接收

需要导入jar包

Upload.Jsp代码

<%@ 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>$title$/title>
</head>
<body>
<form method="post" action="/test/UploadServlet" enctype="multipart/form-data">
    选择一个文件:
    <input type="file" name="uploadFile" />
    <br/><br/>
    <input type="submit" value="上传" />
</form>
</body>
</html>

servlet接收文件代码

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;
 
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.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
 


@WebServlet("/UploadServlet")
public class UploadServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
     
    // 上传文件存储目录
    private static final String UPLOAD_DIRECTORY = "upload";
 
    // 上传配置
    private static final int MEMORY_THRESHOLD   = 1024 * 1024 * 3;  // 3MB
    private static final int MAX_FILE_SIZE      = 1024 * 1024 * 40; // 40MB
    private static final int MAX_REQUEST_SIZE   = 1024 * 1024 * 50; // 50MB
 
    /**
     * 上传数据及保存文件
     */
    protected void doPost(HttpServletRequest request,
		HttpServletResponse response) throws ServletException, IOException {
		// 检测是否为多媒体上传
		if (!ServletFileUpload.isMultipartContent(request)) {
		    // 如果不是则停止
		    PrintWriter writer = response.getWriter();
		    writer.println("Error: 表单必须包含 enctype=multipart/form-data");
		    writer.flush();
		    return;
		}
 
        // 配置上传参数
        DiskFileItemFactory factory = new DiskFileItemFactory();
        // 设置内存临界值 - 超过后将产生临时文件并存储于临时目录中
        factory.setSizeThreshold(MEMORY_THRESHOLD);
        // 设置临时存储目录
        factory.setRepository(new File(System.getProperty("java.io.tmpdir")));
 
        ServletFileUpload upload = new ServletFileUpload(factory);
         
        // 设置最大文件上传值
        upload.setFileSizeMax(MAX_FILE_SIZE);
         
        // 设置最大请求值 (包含文件和表单数据)
        upload.setSizeMax(MAX_REQUEST_SIZE);
 
        // 构造临时路径来存储上传的文件
        // 这个路径相对当前应用的目录
        String uploadPath = getServletContext().getRealPath("./") + File.separator + UPLOAD_DIRECTORY;
       
         
        // 如果目录不存在则创建
        File uploadDir = new File(uploadPath);
        if (!uploadDir.exists()) {
            uploadDir.mkdir();
        }
 
        try {
            // 解析请求的内容提取文件数据
            @SuppressWarnings("unchecked")
            List<FileItem> formItems = upload.parseRequest(request);
 
            if (formItems != null && formItems.size() > 0) {
                // 迭代表单数据
                for (FileItem item : formItems) {
                    // 处理不在表单中的字段
                    if (!item.isFormField()) {
                        String fileName = new File(item.getName()).getName();
                        String filePath = uploadPath + File.separator + fileName;
                        File storeFile = new File(filePath);
                        // 在控制台输出文件的上传路径
                        System.out.println(filePath);
                        // 保存文件到硬盘
                        item.write(storeFile);
                        request.setAttribute("message",
                            "文件上传成功!");
                    }
                }
            }
        } catch (Exception ex) {
            request.setAttribute("message",
                    "错误信息: " + ex.getMessage());
        }
        // 跳转到 message.jsp
        getServletContext().getRequestDispatcher("/message.jsp").forward(
                request, response);
    }
}

Servlet3.0新特性：

import org.apache.catalina.core.ApplicationPart;

import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;
import java.io.IOException;
import java.io.PrintWriter;

/**
 * Created by IMP on 2016/9/9.
 */
@WebServlet("UploadServlet")
@MultipartConfig(location = "D://")
public class UploadServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          response.setContentType("text/html;charset=UTF-8");
        PrintWriter out=response.getWriter();
        String path=this.getServletContext().getRealPath("/");
        Part p=request.getPart("file1");
        if(p.getContentType().contains("image")){
            ApplicationPart ap= (ApplicationPart) p;
            String fname1=ap.getSubmittedFileName();
            int path_idx=fname1.lastIndexOf("\\")+1;
            String fname2=fname1.substring(path_idx,fname1.length());
            p.write(path+"/upload/"+fname2);
            out.write("文件上传成功");
        }else{
            out.write("请选择图片文件");   
        }
            
    }
}