session.getAttribute 的个小问题

[boytomato]

public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain arg2) throws IOException, ServletException {
	   
		HttpServletRequest request = (HttpServletRequest)arg0; 
		HttpServletResponse response = (HttpServletResponse)arg1;
		HttpSession session = request.getSession(false);

		arg2.doFilter(arg0, arg1);
	
		if(session.getAttribute("logged-in")!=null)
{}
}

2008-5-16 12:38:58 org.apache.catalina.core.StandardWrapperValve invoke
严重: Servlet.service() for servlet jsp threw exception
java.lang.NullPointerException

已经确认是 if(session.getAttribute("logged-in")!=null)的问题，可如何判断这个 session 为空啊。。。

[xiaoqiangcn]

HttpSession session = request.getSession();不用参数了

[kui1015]

String login=(String)session.getAttribute("login");
if(login!=null && login.equals("login"))

[boytomato]

public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain arg2) throws IOException, ServletException {
	   
		HttpServletRequest request = (HttpServletRequest)arg0; 
		HttpServletResponse response = (HttpServletResponse)arg1;
		HttpSession session = request.getSession();

		arg2.doFilter(arg0, arg1);
		response.sendRedirect("http://localhost:8080/HTJavaPortal/manage/login.jsp");

报的错
Servlet.service() for servlet default threw exception
java.lang.IllegalStateException
at org.apache.catalina.connector.ResponseFacade.sendRedirect(ResponseFacade.java:433)

[huxinyu929]

先判断是否是空
再负值

[awusoft]

response.sendRedirect("/HTJavaPortal/manage/login.jsp");

[boytomato]

public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain arg2) throws IOException, ServletException {

HttpServletRequest request = (HttpServletRequest)arg0;
HttpServletResponse response = (HttpServletResponse)arg1;
////HttpSession session = request.getSession();
arg2.doFilter(arg0, arg1);

if(request.getRequestURI()!="/HTJavaPortal/manage/login.jsp")
{
response.sendRedirect("/HTJavaPortal/manage/login.jsp");
}

出错继续啊。。。
和原来一样。。

[realcbb]

楼主想干什么？是不是希望如果session过期，发送请求时自动跳到登录页面？

public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain arg2) throws IOException, ServletException {
       
        HttpServletRequest request = (HttpServletRequest)arg0; 
        HttpServletResponse response = (HttpServletResponse)arg1;
        HttpSession session = request.getSession();
        if(session.getAttribute("logged-in")==null)
            response.sendRedirect("manage/login.jsp");
        arg2.doFilter(arg0, arg1);

不过这样在登录时又会跳到登录页面的，如果想要实现这个功能，不应该这样做。

[realcbb]

doFilter应该在最后一句

[awusoft]

你应该去判断,如果请求的是登录页面,就不验证.否则就要验证.字符的比较应该用equals()而不是用==

[zhuyl_wind]

[Quote=引用 13 楼 realcbb 的回复:]
楼主想干什么？是不是希望如果session过期，发送请求时自动跳到登录页面？

Java code
public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain arg2) throws IOException, ServletException {

HttpServletRequest request = (HttpServletRequest)arg0;
HttpServletResponse response = (HttpServletResponse)arg1;
HttpSession session = request.getSession()…
[/Quote]

[realcbb]

[Quote=引用 15 楼 AWUSOFT 的回复:]
你应该去判断,如果请求的是登录页面,就不验证.否则就要验证.字符的比较应该用equals()而不是用==
[/Quote]

如果attribute已经不存在，那取出来就不是字符串，而是null了。



如果楼主想要实现如果session过期，发送请求时自动跳到登录页面，可以这样：
在登录页面上用jsp给session写入一个attribute，再写个过滤器每次请求都要取这个attribute，看是不是null来判断。

[Kit_LO]

public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain arg2) throws IOException, ServletException {

HttpServletRequest request = (HttpServletRequest)arg0;
HttpServletResponse response = (HttpServletResponse)arg1;
HttpSession session = request.getSession();

arg2.doFilter(arg0, arg1);
response.sendRedirect("/manage/login.jsp");

[awusoft]

HttpSession session = request.getSession(false);
换成true看看.有可能是session为null了

[awusoft]

还有顺序问题,是不是应该先判断再进入呢?

if(session.getAttribute("logged-in")!=null)
{
arg2.doFilter(arg0, arg1);
}

[南南北北]

if(session==null){

}

不可以吗？

[s_liangchao1s]

HttpSession session = request.getSession(false);

[s_liangchao1s]

HttpSession session = request.getSession(true);

[boytomato]

变成这样好了

	HttpSession session = request.getSession();

这样就好了。。。