过滤器Filter

标准版

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import java.io.IOException;

@WebFilter("/*")
public class Filter implements javax.servlet.Filter {
    public void destroy() {
    }

    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {

        chain.doFilter(req, resp);
    }

    public void init(FilterConfig config) throws ServletException {

    }

}

---

字符过滤

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import java.io.IOException;

@WebFilter("/*")
public class EncodingFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        servletRequest.setCharacterEncoding("UTF-8");
        servletResponse.setContentType("text/html;charset=UTF-8");
        filterChain.doFilter(servletRequest, servletResponse);
    }

    @Override
    public void destroy() {

    }
}

---

登录过滤

每次运行Tomcat，如果没有登录，自动跳转到登录页面

Constants接口，常量为访问Servlet的路径

import util.Constants;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebFilter("/*")
public class LoginFilter implements Filter {
    //不需要登陆就能访问的地址
    private static final String[] IGNORE_LOGIN_URL = {"/login", "/index.jsp", "/vcode"};

    public void destroy() {
    }

    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) resp;
        String path = request.getServletPath();
        if (check(path)) {
            chain.doFilter(request, response);
            return;
        }
        if (request.getSession().getAttribute(Constants.MANAGER) == null) {
            response.sendRedirect("index.jsp");
        } else {
            chain.doFilter(request, response);
        }
        chain.doFilter(req, resp);
    }

    private boolean check(String path) {
        for (String s : IGNORE_LOGIN_URL) {
            if (s.equals(path)) {
                return true;
            }
        }
        return false;
    }

    public void init(FilterConfig config) throws ServletException {

    }

}