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大家好，我是后端架构师。

前言

什么是单点登录？单点登录全称Single Sign On（以下简称SSO），是指在多系统应用群中登录一个系统，便可在其他所有系统中得到授权而无需再次登录，包括单点登录与单点注销两部分，如图(不标准，只是方便理解)。

一、CAS是什么？

CAS 是 Yale 大学发起的一个开源项目，旨在为 Web 应用系统提供一种可靠的单点登录方法，CAS 在 2004 年 12 月正式成为 JA-SIG 的一个项目。CAS 具有以下特点：

• 开源的企业级单点登录解决方案。
• CAS Server 为需要独立部署的 Web 应用。
• CAS Client 支持非常多的客户端(这里指单点登录系统中的各个 Web 应用)，包括 Java, .Net, PHP, Perl, Apache, uPortal, Ruby 等。

二、搭建客户端系统

1.引入CAS

参考：https://www.bilibili.com/video/BV1xy4y1r7BU?t=666&p=8

注意其中将证书导入jdk中，一定要注意精确到cacerts这个文件下，不然一直报拒绝写入，另外最好用管理员下的命令窗口

2.客户端后端搭建

1.添加依赖

<dependency>
    <groupId>org.jasig.cas.client</groupId>
    <artifactId>cas-client-core</artifactId>
    <version>3.3.2</version>
</dependency>
<dependency>
    <groupId>joda-time</groupId>
    <artifactId>joda-time</artifactId>
    <version>2.10.5</version>
</dependency>

<dependency>
    <groupId>org.springframework.security</groupId>
    <artifactId>spring-security-cas</artifactId>
</dependency>

<dependency>
    <groupId>org.springframework.security</groupId>
    <artifactId>spring-security-taglibs</artifactId>
</dependency>

2.配置客户端

server:
  port: 1234

3.添加config(filter)文件

地址全为ip,如果用hosts映射地址，可能会出现问题

package com.casclient1.cas.config;

import org.jasig.cas.client.session.SingleSignOutFilter;
import org.jasig.cas.client.util.HttpServletRequestWrapperFilter;
import org.jasig.cas.client.validation.Cas20ProxyReceivingTicketValidationFilter;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.annotation.Order;
import org.springframework.web.filter.CharacterEncodingFilter;

import javax.servlet.Filter;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;


@Configuration
public class FilterConfig implements Serializable, InitializingBean {

    private static final Logger LOGGER = LoggerFactory.getLogger(FilterConfig.class);

    public static final String CAS_SIGNOUT_FILTER_NAME = "CAS Single Sign Out Filter";
    public static final String CAS_AUTH_FILTER_NAME = "CAS Filter";
    public static final String CAS_IGNOREL_SSL_FILTER_NAME = "CAS Ignore SSL Filter";
    public static final String CAS_FILTER_NAME = "CAS Validation Filter";
    public static final String CAS_WRAPPER_NAME = "CAS HttpServletRequest Wrapper Filter";
    public static final String CAS_ASSERTION_NAME = "CAS Assertion Thread Local Filter";
    public static final String CHARACTER_ENCODING_NAME = "Character encoding Filter";

 //CAS服务器退出地址
    private static String casSigntouServerUrlPrefix = "https://127.0.0.1:8443/cas/logout";
    //CAS服务器登录地址
    private static String casServerLoginUrl = "https://127.0.0.1:8443/cas/login";
    //客户端地址
    private static String clienthosturl="http://127.0.0.1:1234";
    //CAS服务器地址
    private static String casValidationServerUrlPrefix = "https://127.0.0.1:8443/cas";

    public FilterConfig() {

    }

    /**
     * 单点登出功能,放在其他filter之前
     * casSigntouServerUrlPrefix为登出前缀:https://123.207.122.156:8081/cas/logout
     *
     * @return
     */
    @Bean
    @Order(0)
    public FilterRegistrationBean getCasSignoutFilterRegistrationBean() {
        FilterRegistrationBean registration = new FilterRegistrationBean();
        registration.setFilter(getCasSignoutFilter());
        registration.addUrlPatterns("/*", "*.html");
        registration.addInitParameter("casServerUrlPrefix", casSigntouServerUrlPrefix);
        registration.setName(CAS_SIGNOUT_FILTER_NAME);
        registration.setEnabled(true);
        return registration;
    }

    @Bean(name = CAS_SIGNOUT_FILTER_NAME)
    public Filter getCasSignoutFilter() {
        return new SingleSignOutFilter();
    }

    /**
     * 忽略SSL认证
     *
     * @return
     */
    @Bean
    @Order(1)
    public FilterRegistrationBean getCasSkipSSLValidationFilterRegistrationBean() {
        FilterRegistrationBean registration = new FilterRegistrationBean();
        registration.setFilter(getCasSkipSSLValidationFilter());
        registration.addUrlPatterns("/*", "*.html");
        registration.setName(CAS_IGNOREL_SSL_FILTER_NAME);
        registration.setEnabled(true);
        return registration;
    }

    @Bean(name = CAS_IGNOREL_SSL_FILTER_NAME)
    public Filter getCasSkipSSLValidationFilter() {
        return new IgnoreSSLValidateFilter();
    }

    /**
     * 负责用户的认证
     * casServerLoginUrl：https://123.207.122.156:8081/cas/login
     * casServerName：https://123.207.122.156:8080/tdw/alerts/
     *
     * @return
     */
    @Bean
    @Order(2)
    public FilterRegistrationBean getCasAuthFilterRegistrationBean() {
        FilterRegistrationBean registration = new FilterRegistrationBean();
        final Filter casAuthFilter = getCasAuthFilter();
        registration.setFilter(casAuthFilter);
        registration.addUrlPatterns("/*", "*.html");
        registration.addInitParameter("casServerLoginUrl", casServerLoginUrl);
        registration.addInitParameter("serverName", clienthosturl);
        registration.setName(CAS_AUTH_FILTER_NAME);
        registration.setEnabled(true);
        return registration;
    }

    @Bean(name = CAS_AUTH_FILTER_NAME)
    public Filter getCasAuthFilter() {
        return new MyAuthenticationFilter();
    }

    /**
     * 对Ticket进行校验
     * casValidationServerUrlPrefix要用内网ip
     * casValidationServerUrlPrefix：https://123.207.122.156:8081/cas
     * casServerName：https://123.207.122.156:8080/tdw/alerts/
     *
     * @return
     */
    @Bean
    @Order(3)
    public FilterRegistrationBean getCasValidationFilterRegistrationBean() {
        FilterRegistrationBean registration = new FilterRegistrationBean();
        final Filter casValidationFilter = getCasValidationFilter();
        registration.setFilter(casValidationFilter);
        registration.addUrlPatterns("/*", "*.html");
        registration.addInitParameter("casServerUrlPrefix", casValidationServerUrlPrefix);
        registration.addInitParameter("serverName", clienthosturl);
        registration.setName(CAS_FILTER_NAME);
        registration.setEnabled(true);
        return registration;
    }

    @Bean(name = CAS_FILTER_NAME)
    public Filter getCasValidationFilter() {
        return new Cas20ProxyReceivingTicketValidationFilter();
    }

    /**
     * 设置response的默认编码方式：UTF-8。
     *
     * @return
     */
    @Bean
    @Order(4)
    public FilterRegistrationBean getCharacterEncodingFilterRegistrationBean() {
        FilterRegistrationBean registration = new FilterRegistrationBean();
        registration.setFilter(getCharacterEncodingFilter());
        registration.addUrlPatterns("/*", "*.html");
        registration.setName(CHARACTER_ENCODING_NAME);
        registration.setEnabled(true);
        return registration;
    }

    @Bean(name = CHARACTER_ENCODING_NAME)
    public Filter getCharacterEncodingFilter() {
        CharacterEncodingFilter characterEncodingFilter = new CharacterEncodingFilter();
        characterEncodingFilter.setEncoding("UTF-8");
        return characterEncodingFilter;
    }

    @Bean
    public FilterRegistrationBean casHttpServletRequestWrapperFilter(){
        FilterRegistrationBean authenticationFilter = new FilterRegistrationBean();
        authenticationFilter.setFilter(new HttpServletRequestWrapperFilter());
        authenticationFilter.setOrder(6);
        List<String> urlPatterns = new ArrayList<>();
        urlPatterns.add("/*");
        authenticationFilter.setUrlPatterns(urlPatterns);
        return authenticationFilter;
    }

    @Override
    public void afterPropertiesSet() throws Exception {

    }
}

4.filter类中的MyAuthenticationFilter是重写cas jar包中的AuthenticationFilter，原因是CAS源码无法认证直接重定向，而ajax请求又不能直接重定向，导致前端302，而302vue response拦截器是拦截不到的。所以就想到不让cas给我重定向，给我返回状态码，告诉前端认证失败，让前端直接跳转cas服务器登录地址。另外，搜索公众号Linux就该这样学后台回复“猴子”，获取一份惊喜礼包。

修改cas源码过滤器，复制源码AuthenticationFilter这个过滤器，重写他，其实这里只改了重定向的代码其他都一样。上MyAuthenticationFilter代码

package com.casclient1.cas.config;

import org.jasig.cas.client.authentication.*;
import org.jasig.cas.client.util.AbstractCasFilter;
import org.jasig.cas.client.util.CommonUtils;
import org.jasig.cas.client.util.ReflectUtils;
import org.jasig.cas.client.validation.Assertion;

import javax.servlet.FilterConfig;
import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

public class MyAuthenticationFilter extends AbstractCasFilter {
    private String casServerLoginUrl;
    private boolean renew = false;
    private boolean gateway = false;
    private GatewayResolver gatewayStorage = new DefaultGatewayResolverImpl();
    private AuthenticationRedirectStrategy authenticationRedirectStrategy = new DefaultAuthenticationRedirectStrategy();
    private UrlPatternMatcherStrategy ignoreUrlPatternMatcherStrategyClass = null;
    private static final Map<String, Class<? extends UrlPatternMatcherStrategy>> PATTERN_MATCHER_TYPES = new HashMap();

    public MyAuthenticationFilter() {
    }

    @Override
    protected void initInternal(FilterConfig filterConfig) throws ServletException {
        if (!this.isIgnoreInitConfiguration()) {
            super.initInternal(filterConfig);
            this.setCasServerLoginUrl(this.getPropertyFromInitParams(filterConfig, "casServerLoginUrl", (String)null));
            this.logger.trace("Loaded CasServerLoginUrl parameter: {}", this.casServerLoginUrl);
            this.setRenew(this.parseBoolean(this.getPropertyFromInitParams(filterConfig, "renew", "false")));
            this.logger.trace("Loaded renew parameter: {}", this.renew);
            this.setGateway(this.parseBoolean(this.getPropertyFromInitParams(filterConfig, "gateway", "false")));
            this.logger.trace("Loaded gateway parameter: {}", this.gateway);
            String ignorePattern = this.getPropertyFromInitParams(filterConfig, "ignorePattern", (String)null);
            this.logger.trace("Loaded ignorePattern parameter: {}", ignorePattern);
            String ignoreUrlPatternType = this.getPropertyFromInitParams(filterConfig, "ignoreUrlPatternType", "REGEX");
            this.logger.trace("Loaded ignoreUrlPatternType parameter: {}", ignoreUrlPatternType);
            if (ignorePattern != null) {
                Class<? extends UrlPatternMatcherStrategy> ignoreUrlMatcherClass = (Class)PATTERN_MATCHER_TYPES.get(ignoreUrlPatternType);
                if (ignoreUrlMatcherClass != null) {
                    this.ignoreUrlPatternMatcherStrategyClass = (UrlPatternMatcherStrategy) ReflectUtils.newInstance(ignoreUrlMatcherClass.getName(), new Object[0]);
                } else {
                    try {
                        this.logger.trace("Assuming {} is a qualified class name...", ignoreUrlPatternType);
                        this.ignoreUrlPatternMatcherStrategyClass = (UrlPatternMatcherStrategy)ReflectUtils.newInstance(ignoreUrlPatternType, new Object[0]);
                    } catch (IllegalArgumentException var6) {
                        this.logger.error("Could not instantiate class [{}]", ignoreUrlPatternType, var6);
                    }
                }

                if (this.ignoreUrlPatternMatcherStrategyClass != null) {
                    this.ignoreUrlPatternMatcherStrategyClass.setPattern(ignorePattern);
                }
            }

            String gatewayStorageClass = this.getPropertyFromInitParams(filterConfig, "gatewayStorageClass", (String)null);
            if (gatewayStorageClass != null) {
                this.gatewayStorage = (GatewayResolver)ReflectUtils.newInstance(gatewayStorageClass, new Object[0]);
            }

            String authenticationRedirectStrategyClass = this.getPropertyFromInitParams(filterConfig, "authenticationRedirectStrategyClass", (String)null);
            if (authenticationRedirectStrategyClass != null) {
                this.authenticationRedirectStrategy = (AuthenticationRedirectStrategy)ReflectUtils.newInstance(authenticationRedirectStrategyClass, new Object[0]);
            }
        }

    }

    @Override
    public void init() {
        super.init();
        CommonUtils.assertNotNull(this.casServerLoginUrl, "casServerLoginUrl cannot be null.");
    }

    @Override
    public final void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest)servletRequest;
        HttpServletResponse response = (HttpServletResponse)servletResponse;
        if (this.isRequestUrlExcluded(request)) {
            this.logger.debug("Request is ignored.");
            filterChain.doFilter(request, response);
        } else {
            HttpSession session = request.getSession(false);
            Assertion assertion = session != null ? (Assertion)session.getAttribute("_const_cas_assertion_") : null;
            if (assertion != null) {
                filterChain.doFilter(request, response);
            } else {
                String serviceUrl = this.constructServiceUrl(request, response);
                String ticket = this.retrieveTicketFromRequest(request);
                boolean wasGatewayed = this.gateway && this.gatewayStorage.hasGatewayedAlready(request, serviceUrl);
                if (!CommonUtils.isNotBlank(ticket) && !wasGatewayed) {
                    this.logger.debug("no ticket and no assertion found");
                    String modifiedServiceUrl;
                    if (this.gateway) {
                        this.logger.debug("setting gateway attribute in session");
                        modifiedServiceUrl = this.gatewayStorage.storeGatewayInformation(request, serviceUrl);
                    } else {
                        modifiedServiceUrl = serviceUrl;
                    }

                    this.logger.debug("Constructed service url: {}", modifiedServiceUrl);

                    String xRequested =request.getHeader("x-requested-with");
                    if("XMLHttpRequest".equals(xRequested)){
                        response.getWriter().write("{\"code\":202, \"msg\":\"no ticket and no assertion found\"}");
                    }else{
                        String urlToRedirectTo = CommonUtils.constructRedirectUrl(this.casServerLoginUrl, this.getServiceParameterName(), modifiedServiceUrl, this.renew, this.gateway);
                        this.logger.debug("redirecting to \"{}\"", urlToRedirectTo);
                        this.authenticationRedirectStrategy.redirect(request, response, urlToRedirectTo);
                    }
                } else {
                    filterChain.doFilter(request, response);
                }
            }
        }
    }

    public final void setRenew(boolean renew) {
        this.renew = renew;
    }

    public final void setGateway(boolean gateway) {
        this.gateway = gateway;
    }

    public final void setCasServerLoginUrl(String casServerLoginUrl) {
        this.casServerLoginUrl = casServerLoginUrl;
    }

    public final void setGatewayStorage(GatewayResolver gatewayStorage) {
        this.gatewayStorage = gatewayStorage;
    }

    private boolean isRequestUrlExcluded(HttpServletRequest request) {
        if (this.ignoreUrlPatternMatcherStrategyClass == null) {
            return false;
        } else {
            StringBuffer urlBuffer = request.getRequestURL();
            if (request.getQueryString() != null) {
                urlBuffer.append("?").append(request.getQueryString());
            }

            String requestUri = urlBuffer.toString();
            return this.ignoreUrlPatternMatcherStrategyClass.matches(requestUri);
        }
    }

    static {
        PATTERN_MATCHER_TYPES.put("CONTAINS", ContainsPatternUrlPatternMatcherStrategy.class);
        PATTERN_MATCHER_TYPES.put("REGEX", RegexUrlPatternMatcherStrategy.class);
        PATTERN_MATCHER_TYPES.put("EXACT", ExactUrlPatternMatcherStrategy.class);
    }
}

测试Controller

package com.casclient1.cas.controller;

import com.casclient1.cas.domain.UserDomain;
import com.casclient1.cas.tools.Result;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.Console;
import java.io.IOException;

@Controller
public class TestController {
    /**
     * 测试
     * @return
     */
    @GetMapping("/test")
    @ResponseBody
    public Result<UserDomain>  login(HttpServletRequest httpServletRequest){
        System.out.println("sss");
        return new Result<>(new UserDomain(httpServletRequest.getRemoteUser()));
    }

    @GetMapping("/checkTicket")
    public void index(HttpServletResponse response) throws IOException {
        // 前端页面地址
        response.sendRedirect("http://127.0.0.1:8088/Home");
    }
        /**
     * 注销
     * @return
     */
    @RequestMapping("/logout")
    public String logout(){
        return "redirect:https://127.0.0.1:8443/cas/logout";
    }
    }

3.前端

<template xmlns="http://www.w3.org/1999/html">
  <div >

    <header style="height: 60px">
      <span>客户端2验证:{{name}}</span>
        <button @click="logout">安全退出</button>
    </header>
    <router-view></router-view>
    <!--

  <my-vue v-bind:lineID="lineID"></my-vue>-->
  </div>
</template>
<style lang="scss">
</style>
<script type="text/ecmascript-6">

  export default {

    data() {

      return {
            name:'ss'
      }

    },
mounted(){
    var _this = this;
    this.$http.get('/test', {headers: {'x-requested-with': 'XMLHttpRequest'}})
            .then(function (response) {
                console.log("sss");
                if (response.data.code === 202) {
                    debugger
                    console.log("sss");
                    window.location.href = "http://127.0.0.1:1235/checkTicket"
                } else if (response.data.code === 200) {
                    console.log("sss");
                    _this.name = response.data.data.name
                }
                console.log(response);
            })
            .catch(function (error) {
                console.log(error);
            });
        },
      methods: {
          logout() {
              window.location.href = "http://127.0.0.1:1234/logout"

          },
      }
  }
</script>

5.效果

未登录:

点击客户端1超链接

登录成功

点击客户端2超链接，直接进入，无需登录

退出

总结

网上有很多CAS单点登录的demo，但是对于前后端分离讲的比较详细的很少，前后端分离，必定会出现跨域，导致CAS登录无法重定向等等原因，结合和网上一些想法和部门代码后，大致做了一个比较完善，但很基础的单点登录系统，当然单点登录不光有CAS，还有JWT(1.所有服务靠约定来生成token，2.要么集中生成集中判断,所有服务都能生成都认这个，要么一个服务管控全局)，OAuth2等等。

欢迎有需要的同学试试，如果本文对您有帮助，也请帮忙点个 赞 + 在看 啦！❤️

在 GitHub猿 还有更多优质项目系统学习资源，欢迎分享给其他同学吧！

PS：如果觉得我的分享不错，欢迎大家随手点赞、转发、在看。

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