怎么把我所要的值放到session里去了,并且在jsp中能直接从session中取出来,没有写过这方面的,我只要把session.setAttribute("num",img);写进去,程序就会报错,请大家帮忙看看。package com.pxc;
/**
* 验证码
*/
import java.util.*;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpServletRequest;public class RandomImage
{
HttpServletRequest request=null;;
HttpSession session=request.getSession();
/*
* 随机产生的6位数,有字母有数字
*/
public String getNumber(){
String character="ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
Random rand =new Random();
StringBuffer temp=new StringBuffer();
char[] chars=character.toCharArray();
int i=0,j=0;
while(i<6){
j=rand.nextInt(chars.length);
temp=temp.append(String.valueOf(chars[j]));
i++;
}
return temp.toString();
}
public String getImage(){
String img=getNumber();
char[] chars=img.toCharArray();
String var="";
int i=0;
while(i<chars.length){
var+="<img src=img\\"+String.valueOf(chars[i])+".jpg>";
i++;
}
//session.setAttribute("num",img);
System.out.println(img);
return var;
}
public static void main(String[] args)
{
RandomImage ri=new RandomImage();
System.out.println(ri.getImage());
}
}
怎么把我所要的值放到session里去了,并且在jsp中能直接从session中取出来,没有写过这方面的,我只要把session.setAttribute("num",img);写进去,程序就会报错,
请大家帮帮我,谢谢了!
/**
* 验证码
*/
import java.util.*;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpServletRequest;public class RandomImage
{
HttpServletRequest request=null;;
HttpSession session=request.getSession();
/*
* 随机产生的6位数,有字母有数字
*/
public String getNumber(){
String character="ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
Random rand =new Random();
StringBuffer temp=new StringBuffer();
char[] chars=character.toCharArray();
int i=0,j=0;
while(i<6){
j=rand.nextInt(chars.length);
temp=temp.append(String.valueOf(chars[j]));
i++;
}
return temp.toString();
}
public String getImage(){
String img=getNumber();
char[] chars=img.toCharArray();
String var="";
int i=0;
while(i<chars.length){
var+="<img src=img\\"+String.valueOf(chars[i])+".jpg>";
i++;
}
//session.setAttribute("num",img);
System.out.println(img);
return var;
}
public static void main(String[] args)
{
RandomImage ri=new RandomImage();
System.out.println(ri.getImage());
}
}
怎么把我所要的值放到session里去了,并且在jsp中能直接从session中取出来,没有写过这方面的,我只要把session.setAttribute("num",img);写进去,程序就会报错,
请大家帮帮我,谢谢了!
HttpSession session=request.getSession();
这样也行,没搞错吧,会出NullPointException的.
session.setAttribute("num",img);这个写法没错,不知道你所谓的报错,是编译还是运行的时候.
1.session.setAttribute("num",img);
2.session.getAttribute("num");
打印异常看看吧?
HttpSession session=request.getSession();
你这样写当然报NullPointException错了,你都没有初始化request对象就拿来用
2:你这个程序需要容器,自己写个mock object测试