在Spring Boot中集成Shiro进行用户的认证过程主要可以归纳为以下三点：

1. 定义一个ShiroConfig，然后配置SecurityManager Bean，SecurityManager为Shiro的安全管理器，管理着所有Subject；
2. 在ShiroConfig中配置ShiroFilterFactoryBean，其为Shiro过滤器工厂类，依赖于SecurityManager；
3. 自定义Realm实现，Realm包含doGetAuthorizationInfo()和doGetAuthenticationInfo()方法，因为本文只涉及用户认证，所以只实现doGetAuthenticationInfo()方法。
   pom.xml

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>
<dependency>
    <groupId>org.apache.shiro</groupId>
    <artifactId>shiro-spring</artifactId>
    <version>1.4.2</version>
</dependency>
<dependency>
    <groupId>com.github.theborakompanioni</groupId>
    <artifactId>thymeleaf-extras-shiro</artifactId>
    <version>2.0.0</version>
</dependency>
<!-- MyBatis -->
<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>1.3.1</version>
</dependency>
<!--阿里数据库连接池 -->
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid-spring-boot-starter</artifactId>
    <version>${druid.version}</version>
</dependency>

ShiroConfig
创建一个ShiroConfig配置类

@Configuration
public class ShiroConfig {
    @Bean
    public ShiroFilterFactoryBean shiroFilterFactoryBean(SecurityManager securityManager) {
        ShiroFilterFactoryBean shiroFilterFactoryBean = new ShiroFilterFactoryBean();
        // 设置securityManager
        shiroFilterFactoryBean.setSecurityManager(securityManager);
        // 登录的url
        shiroFilterFactoryBean.setLoginUrl("/login");
        // 登录成功后跳转的url
        shiroFilterFactoryBean.setSuccessUrl("/index");
        // 未授权url
        shiroFilterFactoryBean.setUnauthorizedUrl("/403");
        
        LinkedHashMap<String, String> filterChainDefinitionMap = new LinkedHashMap<>();
        
        // 定义filterChain，静态资源不拦截
        filterChainDefinitionMap.put("/css/**", "anon");
        filterChainDefinitionMap.put("/js/**", "anon");
        filterChainDefinitionMap.put("/fonts/**", "anon");
        filterChainDefinitionMap.put("/img/**", "anon");
        // druid数据源监控页面不拦截
        filterChainDefinitionMap.put("/druid/**", "anon");
        // 配置退出过滤器，其中具体的退出代码Shiro已经替我们实现了 
        filterChainDefinitionMap.put("/logout", "logout");
        filterChainDefinitionMap.put("/", "anon");
        // 除上以外所有url都必须认证通过才可以访问，未通过认证自动访问LoginUrl
        filterChainDefinitionMap.put("/**", "authc");
        
        shiroFilterFactoryBean.setFilterChainDefinitionMap(filterChainDefinitionMap);
        return shiroFilterFactoryBean;
    }
    
    @Bean  
    public SecurityManager securityManager(){  
        // 配置SecurityManager，并注入shiroRealm
        DefaultWebSecurityManager securityManager =  new DefaultWebSecurityManager();
        securityManager.setRealm(shiroRealm());
        return securityManager;  
    } 
    
    @Bean  
    public ShiroRealm shiroRealm(){  
        // 配置Realm，需自己实现
        ShiroRealm shiroRealm = new ShiroRealm();  
        return shiroRealm;  
    }  
}

filterChain 过滤器配置,Shiro为我们实现的过滤器，具体如下表所示

配置完ShiroConfig后，接下来对Realm进行实现，然后注入到SecurityManager中。
Realm
自定义Realm实现只需继承AuthorizingRealm类，然后实现doGetAuthorizationInfo()和doGetAuthenticationInfo()方法即可。这两个方法名乍看有点像，authorization发音[ˌɔ:θəraɪˈzeɪʃn]，为授权，批准的意思，即获取用户的角色和权限等信息；authentication发音[ɔ:ˌθentɪ’keɪʃn]，认证，身份验证的意思，即登录时验证用户的合法性，比如验证用户名和密码。

public class ShiroRealm extends AuthorizingRealm {

    @Autowired
    private UserMapper userMapper;
    
    /**
    * 获取用户角色和权限
    */
    @Override
    protected AuthorizationInfo doGetAuthorizationInfo(PrincipalCollection principal) {
        return null;
    }

    /**
     * 登录认证
     */
    @Override
    protected AuthenticationInfo doGetAuthenticationInfo(AuthenticationToken token) throws AuthenticationException {

        // 获取用户输入的用户名和密码
        String userName = (String) token.getPrincipal();
        String password = new String((char[]) token.getCredentials());
        
        System.out.println("用户" + userName + "认证-----ShiroRealm.doGetAuthenticationInfo");

        // 通过用户名到数据库查询用户信息
        User user = userMapper.findByUserName(userName);
        
        if (user == null) {
            throw new UnknownAccountException("用户名或密码错误！");
        }
        if (!password.equals(user.getPassword())) {
            throw new IncorrectCredentialsException("用户名或密码错误！");
        }
        if (user.getStatus().equals("0")) {
            throw new LockedAccountException("账号已被锁定,请联系管理员！");
        }
        SimpleAuthenticationInfo info = new SimpleAuthenticationInfo(user, password, getName());
        return info;
    }
}

/*
因为本节只讲述用户认证，所以doGetAuthorizationInfo()方法先不进行实现。
其中UnknownAccountException等异常为Shiro自带异常，
Shiro具有丰富的运行时AuthenticationException层次结构，
可以准确指出尝试失败的原因。
你可以包装在一个try/catch块，并捕捉任何你希望的异常，并作出相应的反应。例如：
*/
try {
    currentUser.login(token);
} catch ( UnknownAccountException uae ) {
   ...
} catch ( IncorrectCredentialsException ice ) { 
  ...
} catch ( LockedAccountException lae ) { 
  ...
} catch ( ExcessiveAttemptsException eae ) { 
  ...
} catch ( AuthenticationException ae ) {
    //unexpected error?
}

※虽然我们可以准确的获取异常信息，并根据这些信息给用户提示具体错误，但最安全的做法是在登录失败时仅向用户显示通用错误提示信息，例如“用户名或密码错误”。这样可以防止数据库被恶意扫描。
在Realm中UserMapper为Dao层，标准的做法应该还有Service层，但这里为了方便就不再定义Service层了。接下来编写和数据库打交道的Dao层。
DAO层
创建一个User表
创建一个User的Entity

public class User implements Serializable{

    private static final long serialVersionUID = -4352868070794165001L;
    
    private Integer id;
    private String userName;
    private String password;
    private Date createTime;
    private String status;
    
    // getter,setter...
}

创建UserMapper接口

@Mapper
public interface UserMapper {
    User findByUserName(String userName);
}

创建UserMapper.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.springboot.dao.UserMapper">
    <resultMap type="com.springboot.entity.User" id="User">
        <id column="id" property="id" javaType="java.lang.Integer" jdbcType="NUMERIC"/>
        <id column="username" property="userName" javaType="java.lang.String" jdbcType="VARCHAR"/>
        <id column="passwd" property="password" javaType="java.lang.String" jdbcType="VARCHAR"/>
        <id column="create_time" property="createTime" javaType="java.util.Date" jdbcType="DATE"/>
        <id column="status" property="status" javaType="java.lang.String" jdbcType="VARCHAR"/>
    </resultMap>
    <select id="findByUserName" resultMap="User">
        select * from user where username = #{userName}
    </select>
</mapper>

数据层准备完了，接下来编写login.html和index.html页面
登录页面login.html

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>登录</title>
    <link rel="stylesheet" th:href="@{/css/login.css}" type="text/css">
    <script th:src="@{/js/jquery-1.11.1.min.js}"></script>
</head>
<body>
    <div class="login-page">
        <div class="form">
            <input type="text" placeholder="用户名" name="username" required="required"/>
            <input type="password" placeholder="密码" name="password" required="required"/>
            <button onclick="login()">登录</button>
        </div>
    </div>
</body>
<script th:inline="javascript"> 
    var ctx = [[@{/}]];
    function login() {
        var username = $("input[name='username']").val();
        var password = $("input[name='password']").val();
        $.ajax({
            type: "post",
            url: ctx + "login",
            data: {"username": username,"password": password},
            dataType: "json",
            success: function (r) {
                if (r.code == 0) {
                    location.href = ctx + 'index';
                } else {
                    alert(r.msg);
                }
            }
        });
    }
</script>
</html>

主页index.html

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>首页</title>
</head>
<body>
    <p>你好！[[${user.userName}]]</p>
    <a th:href="@{/logout}">注销</a>
</body>
</html>

Controller层
LoginController

@Controller
public class LoginController {

    @GetMapping("/login")
    public String login() {
        return "login";
    }

    @PostMapping("/login")
    @ResponseBody
    public ResponseBo login(String username, String password) {
        // 密码MD5加密
        password = MD5Utils.encrypt(username, password);
        UsernamePasswordToken token = new UsernamePasswordToken(username, password);
        // 获取Subject对象
        Subject subject = SecurityUtils.getSubject();
        try {
            subject.login(token);
            return ResponseBo.ok();
        } catch (UnknownAccountException e) {
            return ResponseBo.error(e.getMessage());
        } catch (IncorrectCredentialsException e) {
            return ResponseBo.error(e.getMessage());
        } catch (LockedAccountException e) {
            return ResponseBo.error(e.getMessage());
        } catch (AuthenticationException e) {
            return ResponseBo.error("认证失败！");
        }
    }

    @RequestMapping("/")
    public String redirectIndex() {
        return "redirect:/index";
    }

    @RequestMapping("/index")
    public String index(Model model) {
        // 登录成后，即可通过Subject获取登录的用户信息
        User user = (User) SecurityUtils.getSubject().getPrincipal();
        model.addAttribute("user", user);
        return "index";
    }
}

登录成功后，根据之前在ShiroConfig中的配置shiroFilterFactoryBean.setSuccessUrl("/index")，页面会自动访问/index路径。