web后端 文件上传

需要Commons-fileupload和commons-io两个jar包.可搜索apache commons下载

jar复制在项目下的web->WEB-INF->lib下    复制在apache-tomcat本地文件的lib下

jsp中 ：注意 form的 method="post" enctype="multipart/form-data"   注意input 的name要加上  要加上，不然找不到

servlet中：

package action;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

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 java.io.File;
import java.io.IOException;
import java.util.List;

/**
 * Created by Au on 2015/11/25.
 */
@WebServlet(name = "action")
public class action extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        try {
            upLoadFile(request,response);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private void upLoadFile(HttpServletRequest request, HttpServletResponse response) throws Exception {
        DiskFileItemFactory diskFileItemFactory=new DiskFileItemFactory();
//        构建文件上传类
        ServletFileUpload servletFileUpload=new ServletFileUpload(diskFileItemFactory);
        List<FileItem> list=servletFileUpload.parseRequest(request);
        for(FileItem fileItem:list) {
//          判断是文字还是文件
            if(fileItem.isFormField()){

            }else {
                String image = fileItem.getName();
                String upload_path = request.getSession().getServletContext().getRealPath("/upload3");
//                创建那个文件夹
                if(!new File(upload_path).exists()){
                    new File(upload_path).mkdirs();
                }
                File real_path = new File(upload_path + "/" + image);
                fileItem.write(real_path);
            }
        }
    }

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