jsp实现登录验证的过滤器（jsp验证用户名和密码怎么输入）学到了

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package filter;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

@WebFilter(filterName=”loginFilter”, urlPatterns={ “/*” })
public class LoginFilter implements Filter {

public void destroy() {
}

public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest req=(HttpServletRequest) request;
HttpServletResponse resp=(HttpServletResponse) response;
HttpSession session=req.getSession(true);
resp.setContentType(“text/html;”);
resp.setCharacterEncoding(“utf-8”);
PrintWriter out=resp.getWriter();
String request_uri=req.getRequestURI();
String ctxPath=req.getContextPath();
String uri=request_uri.substring(ctxPath.length());
if (uri.contains(“login.jsp”) || uri.contains(“loginServlet”)) {
chain.doFilter(request, response);
} else {
if (session.getAttribute(“user”) !=null) {
chain.doFilter(request, response);
} else {
out.println(“您没有登录，请先登录！3秒后回到登录页面。”);
resp.setHeader(“refresh”, “3;url=” + ctxPath + “/login.jsp”);
return;
}
}
}