Question

我在jsp页面中为会话对象设置了一个属性，如下所示：

String remoteAddr = request.getRemoteAddr();
session.setAttribute("remoteAddr",remoteAddr);

然后，我试图在servlet过滤器中检索该会话属性：

public void doFilter(ServletRequest request, ServletResponse response,
                        FilterChain chain) throws IOException, ServletException {

HttpServletRequest httpServletRequest = (HttpServletRequest) request;
String remoteIP = httpServletRequest.getSession(false).getAttribute("remoteAddr");
}

但是我在这里获得了会话对象的空值。在这里获取相同会话对象的正确方法是什么？

Answer 1

方法HttpServletRequest.html#getSession(boolean)可能会返回null

如果create为false且请求没有有效的HttpSession，则此方法返回null。

在请求资源之前或请求资源之后，可以调用Filter，具体取决于您执行chain.doFilter(request, response);

的时间

在您的情况下，似乎您在执行jsp之前查询会话，即执行以下操作：

HttpServletRequest httpServletRequest = (HttpServletRequest) request;
String remoteIP = (String) httpServletRequest.getSession(false).getAttribute("remoteAddr");

// pass the request along the filter chain
chain.doFilter(request, response);

将其更改为

// pass the request along the filter chain
chain.doFilter(request, response);

HttpServletRequest httpServletRequest = (HttpServletRequest) request;
String remoteIP = (String) httpServletRequest.getSession(false).getAttribute("remoteAddr");

会让它工作，但我怀疑这是你打算做的，因为你可能想要检查远程IP并决定是允许访问还是拒绝它到所请求的资源，在这种情况下你可能想要做这样的事情：

String remoteIP= request.getRemoteAddr();

if(remoteIP.matches("some pattern")) {
    ((HttpServletResponse)response).setStatus(HttpServletResponse.SC_FORBIDDEN);
} else {
    // pass the request along the filter chain
    chain.doFilter(request, response);  
}

在jsp和Servlet过滤器中获取相同的会话对象？

1 个答案: