feat(reflection): add interactive reflection visualization lab

src/main/java/com/example/scaffold/learning/ReflectionLearningController.java

@@ -0,0 +1,110 @@
+package com.example.scaffold.learning;
+
+import com.example.scaffold.learning.reflection.ReflectionLabTarget;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.RestController;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.Field;
+import java.lang.reflect.Method;
+import java.util.Arrays;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+
+@RestController
+@RequestMapping("/api/learning/reflection")
+public class ReflectionLearningController {
+
+    @GetMapping("/overview")
+    public Map<String, Object> overview() {
+        return Map.of(
+                "whatIsReflection", List.of(
+                        "运行时检查类、字段、方法、构造器",
+                        "运行时动态创建对象",
+                        "运行时调用方法、读写字段",
+                        "Spring / MyBatis / Jackson 等框架大量依赖反射"
+                ),
+                "whyItMatters", List.of(
+                        "理解框架为什么能自动装配、自动绑定、自动序列化",
+                        "理解代理、注解扫描、Bean 创建背后的机制",
+                        "理解反射带来的灵活性与性能成本"
+                )
+        );
+    }
+
+    @GetMapping("/class-info")
+    public Map<String, Object> classInfo() throws Exception {
+        Class<?> clazz = ReflectionLabTarget.class;
+        Map<String, Object> result = new LinkedHashMap<>();
+        result.put("className", clazz.getName());
+        result.put("simpleName", clazz.getSimpleName());
+        result.put("constructors", Arrays.stream(clazz.getDeclaredConstructors()).map(Constructor::toString).toList());
+        result.put("fields", Arrays.stream(clazz.getDeclaredFields()).map(Field::toString).toList());
+        result.put("methods", Arrays.stream(clazz.getDeclaredMethods()).map(Method::toString).toList());
+        return result;
+    }
+
+    @GetMapping("/instantiate")
+    public Map<String, Object> instantiate(@RequestParam(defaultValue = "ref-user") String name,
+                                           @RequestParam(defaultValue = "5") int count) throws Exception {
+        Constructor<ReflectionLabTarget> constructor = ReflectionLabTarget.class.getDeclaredConstructor(String.class, int.class);
+        ReflectionLabTarget obj = constructor.newInstance(name, count);
+        return Map.of(
+                "instance", obj.getClass().getName(),
+                "identityHashCode", System.identityHashCode(obj),
+                "name", obj.getName(),
+                "count", obj.getCount(),
+                "message", "通过反射构造器动态创建对象成功"
+        );
+    }
+
+    @GetMapping("/field-access")
+    public Map<String, Object> fieldAccess(@RequestParam(defaultValue = "changed-by-reflection") String value) throws Exception {
+        ReflectionLabTarget obj = new ReflectionLabTarget();
+        Field field = ReflectionLabTarget.class.getDeclaredField("name");
+        field.setAccessible(true);
+        Object before = field.get(obj);
+        field.set(obj, value);
+        Object after = field.get(obj);
+        return Map.of(
+                "field", field.getName(),
+                "before", before,
+                "after", after,
+                "message", "私有字段已通过反射修改"
+        );
+    }
+
+    @GetMapping("/method-call")
+    public Map<String, Object> methodCall(@RequestParam(defaultValue = "你好") String prefix) throws Exception {
+        ReflectionLabTarget obj = new ReflectionLabTarget("Spring", 2);
+        Method publicMethod = ReflectionLabTarget.class.getDeclaredMethod("greet", String.class);
+        Object publicResult = publicMethod.invoke(obj, prefix);
+
+        Method privateMethod = ReflectionLabTarget.class.getDeclaredMethod("secretFormula", String.class);
+        privateMethod.setAccessible(true);
+        Object privateResult = privateMethod.invoke(obj, "debug");
+
+        Method staticMethod = ReflectionLabTarget.class.getDeclaredMethod("staticInfo");
+        Object staticResult = staticMethod.invoke(null);
+
+        return Map.of(
+                "publicMethodResult", publicResult,
+                "privateMethodResult", privateResult,
+                "staticMethodResult", staticResult,
+                "message", "公开方法、私有方法、静态方法都已通过反射调用"
+        );
+    }
+
+    @GetMapping("/why-frameworks-use-it")
+    public Map<String, Object> whyFrameworksUseIt() {
+        return Map.of(
+                "spring", List.of("扫描注解", "创建 Bean", "依赖注入", "调用生命周期方法"),
+                "jackson", List.of("读取字段", "调用 getter/setter", "对象序列化/反序列化"),
+                "mybatis", List.of("结果集映射到对象", "动态代理 Mapper 接口"),
+                "warning", "反射很强大，但要理解它的性能成本、可读性成本和封装破坏风险"
+        );
+    }
+}

src/main/java/com/example/scaffold/learning/reflection/ReflectionLabTarget.java

@@ -0,0 +1,39 @@
+package com.example.scaffold.learning.reflection;
+
+import java.util.List;
+import java.util.Map;
+
+public class ReflectionLabTarget {
+    private String name = "default-name";
+    private int count = 3;
+    private final List<String> tags = List.of("spring", "reflection", "proxy");
+
+    public ReflectionLabTarget() {
+    }
+
+    public ReflectionLabTarget(String name, int count) {
+        this.name = name;
+        this.count = count;
+    }
+
+    public String greet(String prefix) {
+        return prefix + ", " + name + " x" + count;
+    }
+
+    private String secretFormula(String input) {
+        return "secret:" + input + ":" + (count * 7);
+    }
+
+    public static Map<String, Object> staticInfo() {
+        return Map.of(
+                "topic", "reflection",
+                "message", "静态方法也可以通过反射调用"
+        );
+    }
+
+    public String getName() { return name; }
+    public void setName(String name) { this.name = name; }
+    public int getCount() { return count; }
+    public void setCount(int count) { this.count = count; }
+    public List<String> getTags() { return tags; }
+}

src/main/resources/static/index.html

@@ -98,6 +98,7 @@
             <a href="transaction.html">🔄 事务管理</a>
             <a href="users.html">👥 用户管理</a>
             <a href="advanced.html">🚀 高级功能</a>
+            <a href="reflection.html">🪞 反射实验室</a>
             <a href="auth-lab.html">🔐 鉴权实验室</a>
             <a href="verify-lab.html">🩺 修复验证实验室</a>
             <a href="api.html">🔌 API 测试</a>
@@ -177,6 +178,18 @@
                 <a href="advanced.html" class="btn">进阶学习 →</a>
             </div>
             
+            <div class="card">
+                <h3>🪞 反射实验室</h3>
+                <p>动态查看类结构、通过构造器创建对象、修改私有字段、调用私有方法，理解 Spring 等框架底层为什么依赖反射。</p>
+                <ul class="feature-list">
+                    <li><span class="icon">✅</span>类/字段/方法元信息</li>
+                    <li><span class="icon">✅</span>反射构造对象</li>
+                    <li><span class="icon">✅</span>私有字段修改</li>
+                    <li><span class="icon">✅</span>公开/私有/静态方法调用</li>
+                </ul>
+                <a href="reflection.html" class="btn">开始实验 →</a>
+            </div>
+
             <div class="card">
                 <h3>🔐 鉴权实验室</h3>
                 <p>一步步体验登录、带 Token 请求、鉴权放行/拦截，对比 learn / advanced 模式差异。</p>

src/main/resources/static/reflection.html

@@ -0,0 +1,119 @@
+<!DOCTYPE html>
+<html lang="zh-CN">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>反射可视化实验室 - Spring Boot</title>
+    <style>
+        * { margin:0; padding:0; box-sizing:border-box; }
+        body { font-family:-apple-system,BlinkMacSystemFont,'Segoe UI',Roboto,sans-serif; background:#f5f5f5; }
+        .container { max-width:1200px; margin:0 auto; padding:20px; }
+        .header { background:linear-gradient(135deg,#0f766e,#14b8a6); color:#fff; padding:28px 20px; border-radius:12px; text-align:center; margin-bottom:20px; }
+        .nav { display:flex; gap:10px; flex-wrap:wrap; justify-content:center; margin-bottom:20px; }
+        .nav a { padding:10px 18px; background:#fff; border-radius:20px; text-decoration:none; color:#333; }
+        .nav a.active { background:#0f766e; color:#fff; }
+        .lab { background:#fff7e6; border-left:4px solid #fa8c16; padding:15px; border-radius:8px; margin-bottom:20px; }
+        .grid { display:grid; grid-template-columns:repeat(auto-fit,minmax(320px,1fr)); gap:16px; }
+        .card { background:#fff; border-radius:12px; padding:18px; box-shadow:0 2px 10px rgba(0,0,0,.08); }
+        .card h3 { color:#0f766e; margin-bottom:10px; }
+        .result { background:#111827; color:#d1d5db; padding:12px; border-radius:8px; min-height:180px; white-space:pre-wrap; font-family:monospace; margin-top:10px; overflow:auto; }
+        button { padding:10px 14px; background:#0f766e; color:#fff; border:none; border-radius:6px; cursor:pointer; margin-right:8px; margin-bottom:8px; }
+        input { padding:10px; border:1px solid #ddd; border-radius:6px; margin-right:8px; margin-bottom:8px; }
+    </style>
+</head>
+<body>
+<div class="container">
+    <div class="header">
+        <h1>🪞 反射可视化实验室</h1>
+        <p>不只说“反射很重要”，而是让你自己查看类信息、动态构造对象、读写字段、调用私有方法。</p>
+    </div>
+
+    <div class="nav">
+        <a href="index.html">🏠 首页</a>
+        <a href="ioc.html">📦 IoC</a>
+        <a href="reflection.html" class="active">🪞 反射</a>
+        <a href="verify-lab.html">🩺 修复验证</a>
+    </div>
+
+    <div class="lab">
+        <strong>实验任务卡</strong>
+        <ul style="padding-left:20px; line-height:1.8; margin-top:8px;">
+            <li>先看类信息，理解反射能拿到哪些元数据</li>
+            <li>再用构造器动态创建对象，观察实例内容</li>
+            <li>再读写私有字段，理解为什么框架可以“跳过表面上的访问限制”</li>
+            <li>最后调用私有方法和静态方法，感受反射为什么是框架底层利器</li>
+        </ul>
+    </div>
+
+    <div class="grid">
+        <div class="card">
+            <h3>概念总览</h3>
+            <button onclick="callApi('/api/learning/reflection/overview','overview')">加载总览</button>
+            <div id="overview" class="result"></div>
+        </div>
+        <div class="card">
+            <h3>类元信息</h3>
+            <button onclick="callApi('/api/learning/reflection/class-info','classInfo')">查看类信息</button>
+            <div id="classInfo" class="result"></div>
+        </div>
+    </div>
+
+    <div class="grid">
+        <div class="card">
+            <h3>动态构造对象</h3>
+            <input id="ctorName" value="ref-user" placeholder="name">
+            <input id="ctorCount" value="5" placeholder="count">
+            <button onclick="instantiate()">反射创建对象</button>
+            <div id="ctorResult" class="result"></div>
+        </div>
+        <div class="card">
+            <h3>私有字段读写</h3>
+            <input id="fieldValue" value="changed-by-reflection" placeholder="new field value">
+            <button onclick="fieldAccess()">修改私有字段</button>
+            <div id="fieldResult" class="result"></div>
+        </div>
+    </div>
+
+    <div class="grid">
+        <div class="card">
+            <h3>方法调用实验</h3>
+            <input id="prefix" value="你好" placeholder="prefix">
+            <button onclick="methodCall()">调用公开/私有/静态方法</button>
+            <div id="methodResult" class="result"></div>
+        </div>
+        <div class="card">
+            <h3>框架为什么依赖反射</h3>
+            <button onclick="callApi('/api/learning/reflection/why-frameworks-use-it','frameworkResult')">查看框架视角</button>
+            <div id="frameworkResult" class="result"></div>
+        </div>
+    </div>
+</div>
+<script>
+async function callApi(url, id) {
+    const el = document.getElementById(id);
+    el.textContent = '加载中...';
+    try {
+        const res = await fetch(url);
+        const data = await res.json();
+        el.textContent = JSON.stringify(data, null, 2);
+    } catch (e) {
+        el.textContent = '失败: ' + e.message;
+    }
+}
+async function instantiate() {
+    const name = encodeURIComponent(document.getElementById('ctorName').value);
+    const count = encodeURIComponent(document.getElementById('ctorCount').value);
+    callApi(`/api/learning/reflection/instantiate?name=${name}&count=${count}`, 'ctorResult');
+}
+async function fieldAccess() {
+    const value = encodeURIComponent(document.getElementById('fieldValue').value);
+    callApi(`/api/learning/reflection/field-access?value=${value}`, 'fieldResult');
+}
+async function methodCall() {
+    const prefix = encodeURIComponent(document.getElementById('prefix').value);
+    callApi(`/api/learning/reflection/method-call?prefix=${prefix}`, 'methodResult');
+}
+callApi('/api/learning/reflection/overview','overview');
+</script>
+</body>
+</html>