反射使用指南反射使用指南

反射反射的作用：
在运行状态中，

对于任意一个类，都能够知道这个类的所有属性和方法
对于任意一个类，都能够调用它的任意一个属性和方法

当然，还可以获知类的父类、接口和包等信息。
反射还是比较重要的知识点，这里主要介绍反射的各个方法的使用，可以做工具参考。
实体类

import java.io.Serializable; import java.util.List; public class ReflectionEntity implements Cloneable, Serializable { private String str; private double d; public boolean b; public static short s; public ReflectionEntity() {}public ReflectionEntity(String str) { this.str = str; }public ReflectionEntity(String str, double d, boolean b) { this.str = str; this.b = b; this.d = d; }private void privateMethod() {}public String publicMethod(int i) { return null; }public String publicMethod(int i, double d, List l) { return "Reflection.publicMethod(int i, double d, List l), result: " + "i = " + i + ", d = " + d; }public static int returnOne() { return 1; }public String toString() { return "Str = " + str + ", d = " + d + ", b = " + b; } }

测试类

import javafx.scene.effect.Reflection; import java.awt.*; import java.lang.reflect.Constructor; import java.lang.reflect.Field; import java.lang.reflect.Method; import java.util.ArrayList; import java.util.List; public class ReflectionTest { public static void main(String[] args) throws Exception { Class c = Class.forName("ReflectionEntity"); ReflectionEntity re = (ReflectionEntity) c.newInstance(); ReflectionEntity[] res = new ReflectionEntity[2]; // -------------- Class and ClassLoader -------------- System.out.println("Class.getClass(): " + c.getClass()); System.out.println("Class.getClassLoader(): " + c.getClassLoader()); System.out.println("Class.getSuperclass(): " + c.getSuperclass()); // 获取类的接口列表，返回的是一个数组 System.out.println("Class.getInterfaces(): " + c.getInterfaces()[0] + ", " + c.getInterfaces()[1]); // 获取该数组的 Class 对象 System.out.println("Class.getComponentType(): " + res.getClass().getComponentType()); // 默认调用无参构造方法实例化 System.out.println("Class.newInstance(): " + re); // -------------- Method -------------- Method method1 = c.getMethod("publicMethod", int.class, double.class, List.class); System.out.println("Method.getMethod(): " + method1); Method method2 = c.getDeclaredMethod("privateMethod"); System.out.println("Method.getDeclareMethod(): " +method2); // 获取此类包括其父类中所有的 public 方法 Method[] md1 = c.getMethods(); System.out.println("Method.getMethods(): "); for (Method m : md1) System.out.println(m + "\n"); // 返回此类中所有的方法(无访问权限限制),但不包括继承的方法 Method[] md2 = c.getDeclaredMethods(); System.out.println("Method.getDeclaredMethods(): "); for (Method m : md2) System.out.println(m + "\n"); System.out.println("getName: " + method1.getName()); System.out.println("isAccessible(): " + method1.isAccessible()); System.out.println("isVarArgs(): " + method1.isVarArgs()); System.out.println("getReturnType(): " + method1.getReturnType()); // 获取方法的参数类型，数组形式 System.out.println("getParameterTypes(): " + method1.getParameterTypes()[0] + ", " + method1.getParameterTypes()[1] + ", " + method1.getParameterTypes()[2]); // 获取方法的参数化（带泛型）类型，数组形式 System.out.println("getGenericParameterTypes(): " + method1.getGenericParameterTypes()[0] + ", " + method1.getGenericParameterTypes()[1] + ", " + method1.getGenericParameterTypes()[2]); System.out.println(method1.invoke(re, 233, 666, new ArrayList())); // -------------- Field -------------- Field f1 = c.getField("b"); Field f2 = c.getDeclaredField("d"); System.out.println("getField(): " + f1); System.out.println("getDeclareField(): " + f2); Field[] fs1 = c.getFields(); Field[] fs2 = c.getDeclaredFields(); System.out.println("getFields(): "); for (Field f : fs1) System.out.println(f); System.out.println("getDeclareFields(): "); for (Field f : fs2) System.out.println(f); System.out.println("getName and getType: " + f1.getName() + ", " + f1.getType()); System.out.println("getBoolean(): " + f1.getBoolean(re)); // 由于 isAccessible 为 false 故会报异常 //System.out.println("getDouble(): " + f2.getDouble(re)); // 以整数形式返回此Field对象的Java语言修饰符，如public、static、final等 System.out.println("getModifiers(): " + f1.getModifiers()); // 返回Field的访问权限 System.out.println("isAccessible(): " + f1.isAccessible()); f2.setAccessible(true); System.out.println("getDouble(): " + f2.getDouble(re)); System.out.println(re); f2.setDouble(re, 233.666); System.out.println(re); f2.setAccessible(false); // -------------- Constructor -------------- Constructor constructor = c.getConstructor(String.class); Constructor[] constructors = c.getConstructors(); System.out.println("constructor: " + constructor); System.out.println("constructors: "); for (Constructor cc : constructors) System.out.println(cc); System.out.println("getName: " + constructor.getName()); System.out.println("isAccessible(): " + constructor.isAccessible()); System.out.println("isVarArgs(): " + constructor.isVarArgs()); System.out.println("getModifiers(): " + constructor.getModifiers()); // 获取方法的参数类型，数组形式 System.out.println("getParameterTypes(): " + constructor.getParameterTypes()[0]); ReflectionEntity r = (ReflectionEntity) constructor.newInstance("AE86"); System.out.println("newInstance(): " + r); Field f3 = c.getField("s"); System.out.println("f3.getModified :" + f3.getModifiers()); } }