Spring-AOP之工作实践（二）

案例二、前端页面权限控制

　　对controllor控制器中的某写方法进行增强，如实现页面的按钮权限控制。

/**
 * 保存session的容器
 */
public class SessionContext {
    private static Map<String, HttpSession> sessionMap;

    // 单例
    private SessionContext() { sessionMap = new ConcurrentHashMap<>(); }

    private enum SessionContextSingle {
        INSTANCE;
        private SessionContext sessionContext;
        SessionContextSingle() {
            sessionContext = new SessionContext();
        }
        public SessionContext getInstance() { return sessionContext; }
    }

    public static SessionContext getInstance() {
        return SessionContextSingle.INSTANCE.getInstance();
    }

    // 添加session
    public synchronized void addSession(HttpSession httpSession) {
        if (httpSession != null) {
            sessionMap.put(httpSession.getId(), httpSession);
        }
    }

    // 删除session
    public synchronized void deleteSession(HttpSession httpSession) {
        if (httpSession != null) {
            sessionMap.remove(httpSession.getId());
        }
    }

    // 根据sessionId获取session
    public HttpSession getSession(String sessionId) {
        if (StringUtils.isBlank(sessionId)) {
            return null;
        }
        return sessionMap.get(sessionId);
    }
}

/**
 * session监听器
 */
public class SessionListener implements HttpSessionListener {
    private SessionContext sessionContext = SessionContext.getInstance();

    // 在会话中第一次登录时，就调用该方法创建session
    @Override
    public void sessionCreated(HttpSessionEvent httpSessionEvent) {
        HttpSession httpSession = httpSessionEvent.getSession();
        httpSession.setMaxInactiveInterval(10);
        sessionContext.addSession(httpSession);
    }

    @Override
    public void sessionDestroyed(HttpSessionEvent httpSessionEvent) {
        HttpSession httpSession = httpSessionEvent.getSession();
        sessionContext.deleteSession(httpSession);
    }
}

/**
 * main方法处理切面
 */
@Component
@Aspect
@Order(-1)
public class MainAspect {
    @Autowired
    private UserService userService;

    // 切入点
    @Pointcut("execution(* com.demo.*.controller.*Controller.*main(String, ..))")
    private void pointCut() {}

    // 前置通知，在执行目标方法之前执行
    @Before("pointCut()")
    public void main(Joinpoint joinpoint) {
        // 获取sessionid
        String sessionId = (String) joinpoint.getArgs()[0];
        // 获取当前上下文的session对象
        HttpSession httpSession = ((ServletRequestAttributes) RequestContextHolder.getRequestAttributes()).getRequest().getSession();
        // 根据sessionId获取session对象
        User user = SessionContext.getInstance().getSession(sessionId).getAttribute("user");
        // 对当前上下文的session赋值
        httpSession.setAttribute("user", user);
        // 权限传到前端
        ModelAndView modelAndView = (ModelAndView) joinpoint.getArgs()[1];
        Map<String, Object> model = Maps.newHashMap();
        model.put("hasAdminRole", userService.hasRole(NeedRole.ADMIN));
        modelAndView.addAllObjects(model);
    }
}

/**
 * 前端处理器
 */
@Controller
public class DemoController {
    @PostMapping("/main")
    public String main(String sessionId, ModelAndView modelAndView) {
        Map<String, Object> model = Maps.newHashMap();
        modelAndView.setViewName("demo/main");;
        return modelAndView;
    }
}

<!--页面：可以使用切面中保存到request域中的权限值来判断，进而实现页面按钮角色权限控制-->
<a th:if="${hasAdminRole}" href="javascript:void(0)" onclick="submit()">提交</a>