单文件上传

<!--记得要使用post方法，和指定格式-->
<form action="/LayUI/up" method="post" enctype="multipart/form-data">
    <input type="file" name="file"><br>
    <input type="submit" value="上传">
</form>

在servlet中通过name获取文件路径，MultipartConfig注释在使用Part类时要存在，不然会报错

@WebServlet(name = "UpServlet",urlPatterns = "/up")
@MultipartConfig(location = "F:/work/img",fileSizeThreshold = 1024*102,maxFileSize = 1024*1024*5,maxRequestSize = 1024*1024*5*5)
public class UpServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Part part = request.getPart("file");
        //获取文件名
        System.out.println(part.getSubmittedFileName());
        //随机生成文件名，可以防止上传文件重复
        String filename = UUID.randomUUID().toString()+".jpg";
        //文件复制，放在location目录下
        part.write(filename);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request,response);
    }
}

多文件上传

<form action="/LayUI/ups" method="post" enctype="multipart/form-data">
    <input name="file" type="file"><br>
    <input name="file" type="file"><br>
    <input name="file" type="file"><br>
    <input name="file" type="file"><br>
    <input type="submit" value="上传">
</form>

这里只是简单的模拟，一般是通过foreach循环判断你选择了多少个文件

@WebServlet(name = "UPsServlet",urlPatterns = "/ups")
@MultipartConfig(location = "F:/work/img",fileSizeThreshold = 1024*102,maxFileSize = 1024*1024*5,maxRequestSize = 1024*1024*5*5)
public class UPsServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Collection<Part> parts = request.getParts();
        List<String> up_list=new ArrayList<>();
        String path="F:/work/img";
        for (Part part : parts) {
            String filename = UUID.randomUUID().toString()+".jpg";
            if(!part.getSubmittedFileName().equals("")){//如果没有选择图片不保存与展示
                part.write(path+ File.separator +filename);
                //用于文件展示，upload是虚拟路径，因为你转发的是jsp页面，直接使用真实路径是无法显示图片的
                up_list.add("/upload/"+filename);
            }
        }
        request.setAttribute("up_list",up_list);
        request.getRequestDispatcher("show.jsp").forward(request,response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request,response);
    }
}

设置虚拟路径

1、找到tomcat目录下conf--》 server.xml文件中，找到Host标签，在里面写上

<Context path="/upload" docBase="f:/work/img"/>
<!--path是虚拟路径名称，docBase是真实路径名-->

2、如果是使用idea，需要在配置tomcat里面勾选上如下所示复选框，否则使用虚拟路径无法生效

上传文件