正确代码：

@Configuration
public class ShiroConfig {

    @Bean
    public MyRealm createMyRealm(){
        
        MyRealm myRealm = new MyRealm();

        return myRealm;

    }

    @Bean
    public SecurityManager createSecurityManager(MyRealm myRealm){

        SecurityManager securityManager = new SecurityManager();
        securityManager.setRealm(myRealm);


        return securityManager;

    }



    @Bean
    public ShiroFilterFactoryBean createShiroFilterFactoryBean(DefaultWebSecurityManager defaultWebSecurityManager){
        ShiroFilterFactoryBean shiroFilterFactoryBean = new ShiroFilterFactoryBean();
        shiroFilterFactoryBean.setSecurityManager(defaultWebSecurityManager);

        // 设置拦截的规则
        HashMap<String, String> rule = new HashMap<>();

        // 设置登录页面
        shiroFilterFactoryBean.setLoginUrl("/login.html");

        // 设置未授权的页面
        shiroFilterFactoryBean.setUnauthorizedUrl("/unauthorized.html");

        // 拦截全部资源
        rule.put("/**","authc");
        // 放行登录页面
        rule.put("/login.html","anon");
        rule.put("/unauthorized.html","anon");

        // 设置拦截规则
        shiroFilterFactoryBean.setFilterChainDefinitionMap(rule);
        return shiroFilterFactoryBean;

    }

    







}

常见错误：

一、@Configuration注解未写导致容器无法注入

二、使用@Autowired的方式注入myRealm导致多线程使用时数据混乱，因为@Autowired注入的方式为单例模式

三、SecurityManager 类导入错误，到成java.lang包下面的SecurityManager，正确的应该是Shiro包下的SecurityManager