java怎么实现cas单点登录

在Java中实现CAS（Central Authentication Service）单点登录，通常需要以下几个步骤：

1. 引入CAS客户端库：首先，你需要在你的项目中引入CAS客户端库。你可以使用Maven或Gradle来添加依赖。例如，使用Maven，你可以在pom.xml中添加以下依赖：

   <dependency>
       <groupId>org.jasig.cas.client</groupId>
       <artifactId>cas-client-core</artifactId>
       <version>3.6.3</version>
   </dependency>
   <dependency>
       <groupId>org.jasig.cas.client</groupId>
       <artifactId>cas-client-servlet</artifactId>
       <version>3.6.3</version>
   </dependency>
   

2. 配置CAS客户端：在你的Web应用的web.xml文件中配置CAS客户端过滤器。以下是一个示例配置：

   <filter>
       <filter-name>casFilter</filter-name>
       <filter-class>org.jasig.cas.client.authentication.AuthenticationFilter</filter-class>
   </filter>
   <filter-mapping>
       <filter-name>casFilter</filter-name>
       <url-pattern>/*</url-pattern>
   </filter-mapping>
   

3. 配置CAS服务端：你需要在你的CAS服务器上配置CAS服务。这通常涉及到设置CAS服务器的URL、证书等信息。具体的配置步骤取决于你使用的CAS服务器实现（如Java CAS Server）。

4. 处理CAS票据：在你的应用中，你需要处理从CAS服务器返回的票据（Ticket）。你可以使用org.jasig.cas.client.ticket.TicketValidator来验证票据的有效性。以下是一个示例代码：

   import org.jasig.cas.client.ticket.TicketValidator;
   import org.jasig.cas.client.validation.Cas20ServiceTicketValidator;
   import org.springframework.security.cas.web.authentication.logout.CasLogoutFilter;
   
   public class CasAuthenticationFilter extends AuthenticationFilter {
   
       private TicketValidator ticketValidator;
   
       @Override
       protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
               throws ServletException, IOException {
           String ticket = request.getParameter("ticket");
           if (ticket != null) {
               ticketValidator = new Cas20ServiceTicketValidator("https://your-cas-server-url");
               ticketValidator.validate(ticket);
           }
           filterChain.doFilter(request, response);
       }
   }
   

5. 集成Spring Security：如果你使用Spring Security，你可以将CAS客户端与Spring Security集成。以下是一个示例配置：

   import org.jasig.cas.client.authentication.AttributePrincipal;
   import org.springframework.security.cas.web.authentication.CasAuthenticationFilter;
   import org.springframework.security.core.Authentication;
   import org.springframework.security.core.context.SecurityContextHolder;
   import org.springframework.security.web.authentication.logout.SecurityContextLogoutHandler;
   
   public class CustomCasAuthenticationFilter extends CasAuthenticationFilter {
   
       @Override
       protected void successfulAuthentication(HttpServletRequest request, HttpServletResponse response, Authentication successfulAuthentication) {
           super.successfulAuthentication(request, response, successfulAuthentication);
           Object principal = successfulAuthentication.getPrincipal();
           if (principal instanceof AttributePrincipal) {
               AttributePrincipal attributePrincipal = (AttributePrincipal) principal;
               SecurityContextHolder.getContext().setAuthentication(createAuthentication(attributePrincipal));
           }
       }
   
       private Authentication createAuthentication(AttributePrincipal attributePrincipal) {
           return new UsernamePasswordAuthenticationToken(
                   attributePrincipal.getName(),
                   null,
                   attributePrincipal.getAttributes().keySet().stream()
                           .map(Object::toString)
                           .collect(Collectors.toList())
           );
       }
   }
   

   然后在你的Spring Security配置中使用这个自定义过滤器：

   import org.springframework.context.annotation.Bean;
   import org.springframework.context.annotation.Configuration;
   import org.springframework.security.config.annotation.web.builders.HttpSecurity;
   import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
   import org.springframework.security.web.authentication.logout.SecurityContextLogoutHandler;
   
   @Configuration
   @EnableWebSecurity
   public class SecurityConfig {
   
       @Bean
       public CustomCasAuthenticationFilter customCasAuthenticationFilter() {
           return new CustomCasAuthenticationFilter();
       }
   
       @Override
       protected void configure(HttpSecurity http) throws Exception {
           http
               .authorizeRequests()
                   .anyRequest().authenticated()
                   .and()
               .formLogin()
                   .loginPage("/login")
                   .permitAll()
                   .and()
               .logout()
                   .logoutUrl("/logout")
                   .logoutSuccessUrl("/login?logout")
                   .logoutHandler(new SecurityContextLogoutHandler());
       }
   }
   

通过以上步骤，你可以在Java应用中实现CAS单点登录。