JAVA中的過濾器

 首先先在你需要攔截的地方取到一個值。這裏我寫是登錄，登陸成功後，才把name和pwd的值放入session，然後再寫一個編碼格式的攔截器，這樣的話，以後創建的文件都不需要手動添加編碼格式

@WebServlet("/seee")
public class Deng extends HttpServlet {
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("UTF-8");
        resp.setContentType("text/html;charset=utf-8");
        String name=req.getParameter("name");
        String pwd=req.getParameter("pwd");
        jie j=new Kou();
        People p= j.deng(name,pwd);
        System.out.println(p);
        if(p!=null){
            System.out.println("登录成功");
            req.getSession().setAttribute("p",p);
            resp.sendRedirect("show");
        }else {
            resp.sendRedirect("../index.jsp");
        }
    }
}

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//第一個編碼格式   @WebFilter("/*")其中的*是代表全部項目
@WebFilter("/*")
public class NewFilter implements Filter {
    public void destroy() {
    }
    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
        req.setCharacterEncoding("UTF-8");
        resp.setContentType("text/html;charset=utf-8");
        chain.doFilter(req, resp);
    }
    public void init(FilterConfig config) throws ServletException {

    }

}

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這一部分是攔截aimain下面的jsp代碼，簡稱盜鏈接

@WebFilter("/aimain/*")
public class SecondFilter implements Filter {
    @Override

    public void init(FilterConfig filterConfig) throws ServletException {
    }
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {

        HttpServletRequest req = (HttpServletRequest) servletRequest;
        HttpServletResponse resp = (HttpServletResponse) servletResponse;
        People p = (People) req.getSession().getAttribute("p");

        System.out.println("asda");

        if (p != null) {
            filterChain.doFilter(servletRequest, servletResponse);
        } else {
            resp.sendRedirect("../index.jsp");
        }
    }

    @Override
    public void destroy() {

    }
}