feat(reflection): add interactive reflection visualization lab
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likingcode
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package com.example.scaffold.learning;
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import com.example.scaffold.learning.reflection.ReflectionLabTarget;
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import org.springframework.web.bind.annotation.GetMapping;
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import org.springframework.web.bind.annotation.RequestMapping;
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import org.springframework.web.bind.annotation.RequestParam;
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import org.springframework.web.bind.annotation.RestController;
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import java.lang.reflect.Constructor;
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import java.lang.reflect.Field;
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import java.lang.reflect.Method;
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import java.util.Arrays;
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import java.util.LinkedHashMap;
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import java.util.List;
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import java.util.Map;
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@RestController
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@RequestMapping("/api/learning/reflection")
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public class ReflectionLearningController {
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@GetMapping("/overview")
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public Map<String, Object> overview() {
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return Map.of(
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"whatIsReflection", List.of(
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"运行时检查类、字段、方法、构造器",
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"运行时动态创建对象",
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"运行时调用方法、读写字段",
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"Spring / MyBatis / Jackson 等框架大量依赖反射"
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),
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"whyItMatters", List.of(
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"理解框架为什么能自动装配、自动绑定、自动序列化",
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"理解代理、注解扫描、Bean 创建背后的机制",
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"理解反射带来的灵活性与性能成本"
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)
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);
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}
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@GetMapping("/class-info")
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public Map<String, Object> classInfo() throws Exception {
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Class<?> clazz = ReflectionLabTarget.class;
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Map<String, Object> result = new LinkedHashMap<>();
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result.put("className", clazz.getName());
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result.put("simpleName", clazz.getSimpleName());
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result.put("constructors", Arrays.stream(clazz.getDeclaredConstructors()).map(Constructor::toString).toList());
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result.put("fields", Arrays.stream(clazz.getDeclaredFields()).map(Field::toString).toList());
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result.put("methods", Arrays.stream(clazz.getDeclaredMethods()).map(Method::toString).toList());
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return result;
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}
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@GetMapping("/instantiate")
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public Map<String, Object> instantiate(@RequestParam(defaultValue = "ref-user") String name,
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@RequestParam(defaultValue = "5") int count) throws Exception {
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Constructor<ReflectionLabTarget> constructor = ReflectionLabTarget.class.getDeclaredConstructor(String.class, int.class);
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ReflectionLabTarget obj = constructor.newInstance(name, count);
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return Map.of(
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"instance", obj.getClass().getName(),
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"identityHashCode", System.identityHashCode(obj),
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"name", obj.getName(),
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"count", obj.getCount(),
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"message", "通过反射构造器动态创建对象成功"
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);
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}
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@GetMapping("/field-access")
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public Map<String, Object> fieldAccess(@RequestParam(defaultValue = "changed-by-reflection") String value) throws Exception {
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ReflectionLabTarget obj = new ReflectionLabTarget();
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Field field = ReflectionLabTarget.class.getDeclaredField("name");
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field.setAccessible(true);
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Object before = field.get(obj);
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field.set(obj, value);
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Object after = field.get(obj);
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return Map.of(
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"field", field.getName(),
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"before", before,
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"after", after,
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"message", "私有字段已通过反射修改"
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);
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}
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@GetMapping("/method-call")
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public Map<String, Object> methodCall(@RequestParam(defaultValue = "你好") String prefix) throws Exception {
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ReflectionLabTarget obj = new ReflectionLabTarget("Spring", 2);
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Method publicMethod = ReflectionLabTarget.class.getDeclaredMethod("greet", String.class);
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Object publicResult = publicMethod.invoke(obj, prefix);
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Method privateMethod = ReflectionLabTarget.class.getDeclaredMethod("secretFormula", String.class);
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privateMethod.setAccessible(true);
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Object privateResult = privateMethod.invoke(obj, "debug");
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Method staticMethod = ReflectionLabTarget.class.getDeclaredMethod("staticInfo");
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Object staticResult = staticMethod.invoke(null);
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return Map.of(
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"publicMethodResult", publicResult,
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"privateMethodResult", privateResult,
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"staticMethodResult", staticResult,
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"message", "公开方法、私有方法、静态方法都已通过反射调用"
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);
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}
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@GetMapping("/why-frameworks-use-it")
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public Map<String, Object> whyFrameworksUseIt() {
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return Map.of(
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"spring", List.of("扫描注解", "创建 Bean", "依赖注入", "调用生命周期方法"),
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"jackson", List.of("读取字段", "调用 getter/setter", "对象序列化/反序列化"),
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"mybatis", List.of("结果集映射到对象", "动态代理 Mapper 接口"),
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"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"
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);
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}
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}
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@@ -0,0 +1,39 @@
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package com.example.scaffold.learning.reflection;
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import java.util.List;
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import java.util.Map;
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public class ReflectionLabTarget {
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private String name = "default-name";
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private int count = 3;
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private final List<String> tags = List.of("spring", "reflection", "proxy");
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public ReflectionLabTarget() {
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}
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public ReflectionLabTarget(String name, int count) {
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this.name = name;
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this.count = count;
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}
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public String greet(String prefix) {
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return prefix + ", " + name + " x" + count;
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}
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private String secretFormula(String input) {
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return "secret:" + input + ":" + (count * 7);
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}
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public static Map<String, Object> staticInfo() {
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return Map.of(
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"topic", "reflection",
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"message", "静态方法也可以通过反射调用"
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);
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}
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public String getName() { return name; }
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public void setName(String name) { this.name = name; }
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public int getCount() { return count; }
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public void setCount(int count) { this.count = count; }
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public List<String> getTags() { return tags; }
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}
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