java中下拉框select和单选按钮的回显操作

前提:

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>

1.下拉框select

<select name="departmentId" id="departmentId">
  <option value="http://www.cppcns.com/ruanjian/java/0">请选择部门</option>
    <c:forEach items="${departmentList }" var="department">
      <!-- 下拉框回显 -->
      <option value="http://www.cppcns.com/ruanjian/java/${department.id }"
        <c:if test="${department.id== departmentId}">
          selected="selected"
        </c:if>>${department.department}
      </option>
    </c:forEach>
</select>

2.单选按钮radio的回显

<!-- 单选按钮的回显 -->
<input type="radio" name="sex" value="http://www.cppcns.com/ruanjian/java/男" title="男" class="sex" 
  <c:if test="${employee.sex==109 }">
    checked="checked"
  </c:if>
> 
 
<input type="radio" name="sex" value="http://www.cppcns.com/ruanjian/java/女" title="女" class="sex" 
  <c:if test="${employee.sex==119 }">
    checked="checked"
  </c:if>
>

补充知识:java使用apache commons-fileupload组件实现文件上传(控制文件上传的类型、文件上传的大小)

1.导入jar包

common-fileupload.jar

common-io.jar

2.jsp页面(样式省略)

<body>
  <form action="UploadServlet" enctype="multipart/form-data" method="post">
  用户名:<input type="text" name="username" /><br> 
  上传文件:<input type="file" name="fileName" /><br> 
      <input type="submit" value="http://www.cppcns.com/ruanjian/java/文件上传" /><br> 
  </form>
  </body>

3.创建名为UploadServlet的Servlet,并在doPost()方法中编写实现代码,如下所示:

package com.upload.servlet;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;
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.FileUploadBase;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.commons.io.IOUtils;

/**
 * Servlet implementation class UploadServlet
 */
public class UploadServlet extends HttpServlet {
  private static final long serialVersionUID = 1L;

  /**
   * @see HttpServlet#HttpServlet()
   */
  public UploadServlet() {
    super();
    // TODO Auto-generated constructor stub
  }

  /**
   * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
   *   response)
   */
  protected void doGet(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
    // TODO Auto-generated method stub
    doPost(request, response);
  }

  /**
   * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
   *   response)
   */
  protected void doPost(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
    // TODO Auto-generated method stub
    request.setCharacterEncoding("utf-8");// 设置响应编码
    // 得到上传文件的保存目录,将上传的文件存放于WEB-INF目录下,不允许外界直接访问,保证上传文件的安全
    String savePath = request.getServletContext().getRealPath("/WEB-INF/upload");
    // 上传时生成的临时文件保存目录
    String tempPath = request.getServletContext().getRealPath("/WEB-INF/temp");
    File tmpFile = new File(tempPath);
    if (!tmpFile.exists()) {
      // 创建临时目录
      tmpFile.mkdir();
    }
    // System.out.println("文件临时保存路径1:"+tempPath);
    // 1.创建磁盘工厂
    DiskFileItemFactory factory = new DiskFileItemFactory();
    factory.setSizeThreshold(1024 * 100);// 设置缓冲区的大小为100KB,如果不指定,那么缓冲区的大小默认是10KB
    factory.setRepository(new File(tempPath));// 设置上传时文件的保存目录

    // 2.创建文件上传解析器
    ServletFileUpload upload = new ServletFileUpload(factory);
    // 设置允许上传文件的内存,这里设置为100KB,根据实际情况设置
    upload.setSizeMax(1024 * 100);

    // 3.判断提交上来的数据是否是上传表单的数据
    if (ServletFileUpload.isMultipartContent(request)) {
      try {
        // 4、使用ServletFileUpload解析器解析上传数据,解析结果返回的是一个List<FileItem>集合,每一个FileItem对应一个Form表单的输入项
        List<FileItem> list = upload.parseRequest(request);
        // 设置解析到的文件编码格式
        upload.setHeaderEncoding("utf-8");
        for (FileItem fileItem : list) {
          // 判断是否文件,结果为“true”就是普通表单,如果为“false”则是文件
          if (fileItem.isFormField()) {
            String fileName = fileItem.getFieldName();// 获得表单name属性名
            System.out.println(fileItem.getString("utf-8"));// 获取表单value值,并设定编码方式
          } else {
            String name = fileItem.getName();// 获取上传文件的名字
            // 限制上传文件的类型
            List<String> fileType = Arrays.asList("gif", "bmp", "jpg", "png");//允许上传文件的类型
            String fileExtName = name.substring(name.lastIndexOf(".") + 1);//获得文件的后缀名
            //System.out.println("上传文件的后缀名为:"+fileExtName);
            if (!fileType.contains(fileExtName)) {
              System.out.println("上传失败!文件类型只能是gif、bmp、jpg、png!");
            } else {
              InputStream input = fileItem.getInputStream();// 获得上传文件字节流

              // 创建输出文件
              String outPath = request.getServletContext().getRealPath(name);
              FileOutputStream output = new FileOutputStream(new File(outPath));
              // 使用IOUtils工具输出,也就是copy文件
              IOUtils.copy(input, output);
              System.out.println("上传成功!");
              System.out.println("保存的路径为:" + outPath);
              // 关闭输入流
              input.close();
              // 关闭输出流
              output.close();
              // 删除处理文件上传时生成的临时文件
              fileItem.delete();
            }
          }
        }
      } catch (FileUploadBase.SizeLimitExceededException e) {
        System.out.println("上传失败!上传的文件大小超出限制,最大只能上传"+upload.getSizeMax()+"bytes的文件");
      } catch (Exception e) {
        System.out.println("上传失败!");
        e.printStackTrace();
      }
    } else {
      // 如果不是文件上传类型,则采用普通表单获取方式
      request.setCharacterEncoding("UTF-8");
      String parameter = request.getParameter("username");
      System.out.println(parameter);
    }
  }
}

java中下拉框select和单选按钮的回显操作

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