target/classes/static/aop.html

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    <title>AOP 切面编程 - Spring Boot</title>
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    <div class="nav">
        <a href="/">← 返回首页</a>
        <a href="/users.html">用户管理</a>
        <a href="/events.html">事件机制</a>
    </div>
    
    <h1>🔪 AOP 切面编程</h1>

    <div class="lab">
        <h4>🧪 实验任务卡（AOP）</h4>
        <label style="display:block;margin-bottom:8px;"><input id="aopTaskDone" type="checkbox" onchange="toggleAopTaskDone(this)"> 本任务我已经完成</label>
        <ul style="padding-left:20px;line-height:1.8;">
            <li>目标：观察同一请求如何触发 Before/After/Around 通知</li>
            <li>步骤1：调用用户接口 <code>/api/users</code></li>
            <li>步骤2：回到本页点击“刷新统计数据”</li>
            <li>预期：统计里能看到 Controller/Service 方法耗时累积</li>
            <li>常见坑：只看页面不看控制台，容易错过切面日志</li>
        </ul>
    </div>
    
    <div class="card">
        <h3>📊 实时性能统计</h3>
        <p>AOP 自动统计所有 Controller 和 Service 方法的执行时间</p>
        <button class="btn btn-primary" onclick="loadStats()">刷新统计数据</button>
        <button class="btn btn-info" onclick="demoValidationError()">演示校验失败</button>
        <div class="result-box" id="statsResult">点击按钮查看...</div>
    </div>
    
    <h2>📚 AOP 核心概念</h2>
    
    <div class="card">
        <h3>1. 什么是 AOP？</h3>
        <p>AOP (Aspect-Oriented Programming) 面向切面编程，是将<strong>横切关注点</strong>与<strong>业务逻辑</strong>分离的编程范式。</p>
        <div class="tip">
            <strong>横切关注点：</strong>日志、事务、安全、性能监控等，散布在多个模块中的公共功能。
        </div>
    </div>
    
    <div class="card">
        <h3>2. 核心术语</h3>
        <table>
            <tr><th>术语</th><th>说明</th></tr>
            <tr><td><strong>Aspect (切面)</strong></td><td>横切关注点的模块化封装</td></tr>
            <tr><td><strong>JoinPoint (连接点)</strong></td><td>程序执行的某个点（方法调用、异常抛出等）</td></tr>
            <tr><td><strong>Pointcut (切入点)</strong></td><td>匹配连接点的表达式</td></tr>
            <tr><td><strong>Advice (通知)</strong></td><td>在连接点执行的动作</td></tr>
            <tr><td><strong>Weaving (织入)</strong></td><td>将切面应用到目标对象的过程</td></tr>
        </table>
    </div>
    
    <div class="card">
        <h3>3. 五种通知类型</h3>
        <table>
            <tr><th>注解</th><th>执行时机</th><th>用途</th></tr>
            <tr><td><code>@Before</code></td><td>方法执行前</td><td>参数校验、权限检查</td></tr>
            <tr><td><code>@After</code></td><td>方法执行后（无论成功或异常）</td><td>资源清理</td></tr>
            <tr><td><code>@AfterReturning</code></td><td>方法成功返回后</td><td>结果处理、日志记录</td></tr>
            <tr><td><code>@AfterThrowing</code></td><td>方法抛出异常后</td><td>异常处理、错误日志</td></tr>
            <tr><td><code>@Around</code></td><td>环绕方法执行（最强大）</td><td>性能统计、事务管理</td></tr>
        </table>
    </div>
    
    <h2>💻 代码示例</h2>
    
    <div class="card">
        <h3>日志切面示例</h3>
        <pre><code>@Aspect
@Component
public class LoggingAspect {
    
    // 切入点：匹配所有 Controller 方法
    @Pointcut("execution(* com.example.demo.controller.*.*(..))")
    public void controllerMethods() {}
    
    // 前置通知
    @Before("controllerMethods()")
    public void logBefore(JoinPoint jp) {
        System.out.println("[AOP-Before] 方法开始: " + jp.getSignature().getName());
    }
    
    // 返回通知
    @AfterReturning(pointcut = "controllerMethods()", returning = "result")
    public void logAfterReturning(JoinPoint jp, Object result) {
        System.out.println("[AOP-AfterReturning] 返回值: " + result);
    }
}</code></pre>
    </div>
    
    <div class="card">
        <h3>性能监控切面 (@Around)</h3>
        <pre><code>@Aspect
@Component
public class PerformanceAspect {
    
    @Around("execution(* com.example.demo..*.*(..))")
    public Object measureTime(ProceedingJoinPoint pjp) throws Throwable {
        long start = System.currentTimeMillis();
        
        try {
            Object result = pjp.proceed(); // 执行目标方法
            long duration = System.currentTimeMillis() - start;
            System.out.println("[AOP] " + pjp.getSignature() + " 耗时: " + duration + "ms");
            return result;
        } catch (Throwable e) {
            System.out.println("[AOP] 方法异常: " + e.getMessage());
            throw e;
        }
    }
}</code></pre>
    </div>
    
    <div class="card">
        <h3>切入点表达式语法</h3>
        <pre><code>// 匹配任意公共方法
execution(public * *(..))

// 匹配 com.example 包下所有方法
execution(* com.example.*.*(..))

// 匹配 Controller 层所有方法
execution(* com.example.demo.controller.*.*(..))

// 匹配所有 Service 层的 save 开头的方法
execution(* com.example.demo.service.*.save*(..))

// 匹配带有 @Service 注解的类
@within(org.springframework.stereotype.Service)

// 匹配带有自定义注解的方法
@annotation(com.example.demo.aop.RateLimited)</code></pre>
    </div>
    
    <h2>🎯 实际应用场景</h2>
    
    <div class="card">
        <table>
            <tr><th>场景</th><th>实现方式</th></tr>
            <tr><td>日志记录</td><td>@Before + @AfterReturning</td></tr>
            <tr><td>性能监控</td><td>@Around</td></tr>
            <tr><td>事务管理</td><td>@Around (Spring 已内置)</td></tr>
            <tr><td>权限检查</td><td>@Before</td></tr>
            <tr><td>限流控制</td><td>@Around + 自定义注解</td></tr>
            <tr><td>缓存</td><td>@Around (Spring Cache)</td></tr>
        </table>
    </div>
    
    <p style="margin-top: 30px;"><a href="/">← 返回学习中心</a></p>
    
    <script>
        const AOP_TASK_KEY = 'task.aop.done';

        function toggleAopTaskDone(el) {
            localStorage.setItem(AOP_TASK_KEY, el.checked ? '1' : '0');
        }

        function initAopTaskState() {
            const done = localStorage.getItem(AOP_TASK_KEY) === '1';
            const checkbox = document.getElementById('aopTaskDone');
            if (checkbox) checkbox.checked = done;
        }

        async function demoValidationError() {
            const box = document.getElementById('statsResult');
            box.textContent = '发送错误示例请求中...';
            try {
                const res = await fetch('/api/users', {
                    method: 'POST',
                    headers: { 'Content-Type': 'application/json' },
                    body: JSON.stringify({ name: '', email: 'bad', age: 999 })
                });
                const data = await res.json();
                box.textContent = JSON.stringify(data, null, 2);
            } catch (e) {
                box.textContent = '错误: ' + e.message;
            }
        }

        async function loadStats() {
            const res = await fetch('/aop/stats');
            const data = await res.json();
            document.getElementById('statsResult').textContent = JSON.stringify(data, null, 2);
        }

        initAopTaskState();
    </script>
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