Servlet实现简单文件上传功能-创新互联

本文实例为大家分享了Servlet文件上传的具体代码，供大家参考，具体内容如下

两点要素：

1.表单提交方式必须是post
2.enctype一定要是multipart/form-data。
enctype的默认值是application/x-www-form-urlencoded，
这种编码格式只支持键值对的数据，?键=值&键=值，只能是字符串，无法传输文件。
multipart/form-data这种编码可以上传文件

需要的jar包：

实现：

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;

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

public class UploadServlet extends HttpServlet {

  //文件夹路径常量
  private static String TEMP_PATH = "E:/Learning/temp/170926";

  private static final long serialVersionUID = 3364746345428715093L;

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

  public void doPost(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {

    response.setContentType("text/html;charset=UTF-8");
    PrintWriter out = response.getWriter();

    // 接收文件
    boolean isMultipart = ServletFileUpload.isMultipartContent(request);

    // 判断是否是文件上传请求
    if (!isMultipart) {
      out.println("Error : 表单必须包含 enctype=multipart/form-data");
      return;
    }

    // 用于创建解析文件上传的工厂类
    DiskFileItemFactory factory = new DiskFileItemFactory();

    // 用于从请求中解析出文件
    ServletFileUpload upload = new ServletFileUpload(factory);

    try {

      // 获取所有提交过来的文件(包含表单内容) 这个FileItem叫做一个项，这个项有可能是文件也有可能是表单参数 
      List items = upload.parseRequest(request);

      // 定义一个输出流
      FileOutputStream fos = null;

      //缓冲区
      byte [] buf = new byte[8192];

      if (items != null && items.size() > 0) { // 不为空且长度大于0则遍历之
        for (FileItem item : items) {
          if (item.isFormField()) { // isFormField = true 文本框的值
            out.println("用户名: " + item.getString() + "
");
          } else {
            //获取输入流
            BufferedInputStream bis = new BufferedInputStream(item.getInputStream());

            //初始化本地输出流
            fos = new FileOutputStream(new File(TEMP_PATH + "/" + item.getName()));

            int len = -1;
            while ((len = bis.read(buf)) != -1) {
              fos.write(buf , 0 , len);
              fos.flush();
            }
            out.println("文件: " + item.getName() + "已上传 
");
          }
        }
      }
    } catch (FileUploadException e) {
      out.println("Error: 文件解析异常");
    }

  }

}