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);
}
}