servlet传值给JSP是空值需要重新加载下才有值

[星抹微云]

servlet 代码
package com.servlet;
import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.text.SimpleDateFormat;
import java.util.Arrays;
import java.util.Date;
import java.util.Iterator;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import javax.servlet.RequestDispatcher;
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.SizeLimitExceededException;
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 {
@SuppressWarnings("rawtypes")
public void service(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String u_name;
PrintWriter out=response.getWriter();//getWriter()返回一个PrintWriter object
try{
final long MAX_SIZE = 3* 1024 * 1024;// 设置上传文件最大为 3M
// 允许上传的文件格式的列表
final String[] allowedExt = new String[] {"jpg","jpeg","gif"};
response.setContentType("text/html");
// 实例化一个硬盘文件工厂,用来配置上传组件ServletFileUpload
DiskFileItemFactory dfif = new DiskFileItemFactory();
dfif.setSizeThreshold(4096);// 设置上传文件时用于临时存放文件的内存大小,这里是4K.多于的部分将临时存在硬盘
dfif.setRepository(new File(request.getRealPath("/")+ "upload"));// 设置存放临时文件的目录,web根目录下的upload目录
System.out.println("临时目录:"+new File(request.getRealPath("/")+ "upload"));
// 用以上工厂实例化上传组件
ServletFileUpload sfu = new ServletFileUpload(dfif);
// 设置最大上传尺寸
sfu.setSizeMax(MAX_SIZE);
// 从request得到 所有 上传域的列表
List fileList = null;
try {
fileList = sfu.parseRequest(request);
} catch (FileUploadException e) {// 处理文件尺寸过大异常
if (e instanceof SizeLimitExceededException) {
out.println("文件尺寸超过规定大小:" + MAX_SIZE + "字节!");
return;
}
e.printStackTrace();
}
// 没有文件上传
if (fileList == null || fileList.size() == 0) {
out.println("请选择上传文件!");
return;
}
// 得到所有上传的文件
Iterator fileItr = fileList.iterator();
// 循环处理所有文件
while (fileItr.hasNext()) {
FileItem fileItem = null;
String path = null;
long size = 0;
// 得到当前文件
fileItem = (FileItem) fileItr.next();

// 忽略简单form字段而不是上传域的文件域(<input type="text" />等)
if (fileItem == null || fileItem.isFormField()) {
continue;
}
// 得到文件的完整路径
path = fileItem.getName();

// 得到文件的大小
size = fileItem.getSize();
if ("".equals(path) || size == 0) {
out.println("请选择上传文件!");
return;
}
// 得到去除路径的文件名
String t_name = path.substring(path.lastIndexOf("//") + 1);//kaola.jpeg
//System.out.println("t_name:"+t_name);
// 得到文件的扩展名(无扩展名时将得到全名)
String t_ext = t_name.substring(t_name.lastIndexOf(".") + 1);//jpeg
String t_ext_1 = t_name.substring(0, t_name.lastIndexOf("."));
//System.out.println("t_ext_1====="+t_ext_1);

// 拒绝接受规定文件格式之外的文件类型
String tmp=Arrays.toString(allowedExt);
Pattern p = Pattern.compile(t_ext);
Matcher m = p.matcher(tmp);

if (m.find()==true) {
//如果符合上传的格式
String now=new SimpleDateFormat("yyyyMMddhhmmss").format(new Date());
System.out.println(now);

// 根据系统时间生成上传后保存的文件名
String prefix = now;
//截取图片名字
//System.out.println(number.split("\\.")[0]);

// 保存的最终文件完整路径,保存在web根目录下的upload目录下
u_name = request.getRealPath("/") + "upload/"
+ prefix + t_ext_1 + "." + t_ext;
//request.setAttribute("u_name", u_name);
//request.getRequestDispatcher("/files1/xinzengchandizhengmingguanli.jsp").forward(request, response);
request.getSession().setAttribute("u_name", u_name);
//request.getRequestDispatcher("/files1/xinzengchandizhengmingguanli.jsp");
//getServletContext().setAttribute("u_name",u_name);

System.out.println("最终保存目录:"+u_name);
try {
File file = new File(u_name);
// 保存文件
fileItem.write(file);
out.println("文件上传成功. 已保存为: " + prefix + "." + t_ext
+ "   文件大小: " + size + "字节<p />");
} catch (Exception e) {
e.printStackTrace();
}
}else {
System.out.println("不符合规定");
out.print("上传文件不符合规定!");
}
}
}catch(Exception e){
out.print("系统异常,请稍后再试!");
e.printStackTrace();
}

}

}

[江湖南哥]

你把值放进了Session里，那么在JSP页面加载的时候，要先在JS中获取Session里对应的值，然后赋值给对应控件

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web.xml代码 <?xml version="1.0" encoding="UTF-8"?> <web-app id="WebApp_9" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"> <filter> <filter-name>struts2</filter-name> <filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class> </filter> <filter-mapping> <filter-name>struts2</filter-name> <url-pattern>*.action</url-pattern> </filter-mapping> <welcome-file-list> <welcome-file>index.html</welcome-file> <welcome-file>index.jsp</welcome-file> </welcome-file-list> <servlet> <servlet-name>uploadServlet</servlet-name> <servlet-class>com.servlet.UploadServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>uploadServlet</servlet-name> <url-pattern>/uploadServlet</url-pattern> </servlet-mapping> <filter> <filter-name>CharacterEncodingfilter</filter-name> <filter-class>com.filter.CharacterEncodingfilter</filter-class> <!--初始化参数值--> <init-param> <param-name>encoding</param-name> <param-value>UTF-8</param-value> </init-param> </filter> <filter-mapping> <filter-name>CharacterEncodingfilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> </web-app>

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JSP 代码 <input type="text" class="input-text" value='${u_name }' placeholder="" id="" name="">