Java反射的理解

 1 import java.lang.reflect.Constructor; 2 import java.lang.reflect.Field; 3 import java.lang.reflect.Method; 4 import java.lang.reflect.Modifier; 5  6 //反射基本测试 7 public class ReflectionTest { 8     public static void main(String[] args) { 9         String name = "java.util.Date";10         try {11             Class cl = Class.forName(name);12             Class supercl = cl.getSuperclass();13             String modifiers = Modifier.toString(cl.getModifiers());14             if (modifiers.length() > 0) System.out.print(modifiers + " ");15             System.out.print("class " + name);16             if (supercl != null && supercl != Object.class) System.out.print(" extends "17                     + supercl.getName());18 19             System.out.print("/n{/n");20             printConstructors(cl);21             System.out.println();22             printMethods(cl);23             System.out.println();24             printFields(cl);25             System.out.println("}");26         } catch (ClassNotFoundException e) {27             e.printStackTrace();28         }29         System.exit(0);30     }31 32 33     public static void printConstructors(Class cl) {34         Constructor[] constructors = cl.getDeclaredConstructors();35 36         for (Constructor c : constructors) {37             String name = c.getName();38             System.out.print("   ");39             String modifiers = Modifier.toString(c.getModifiers());40             if (modifiers.length() > 0) System.out.print(modifiers + " ");41             System.out.print(name + "(");42 43             // print parameter types44             Class[] paramTypes = c.getParameterTypes();45             for (int j = 0; j < paramTypes.length; j++) {46                 if (j > 0) System.out.print(", ");47                 System.out.print(paramTypes[j].getName());48             }49             System.out.println(");");50         }51     }52 53 54     public static void printMethods(Class cl) {55         Method[] methods = cl.getDeclaredMethods();56 57         for (Method m : methods) {58 59             Class retType = m.getReturnType();60             String name = m.getName();61 62             System.out.print("   ");63             // print modifiers, return type and method name64             String modifiers = Modifier.toString(m.getModifiers());65             if (modifiers.length() > 0) System.out.print(modifiers + " ");66             System.out.print(retType.getName() + " " + name + "(");67 68             // print parameter types69             Class[] paramTypes = m.getParameterTypes();70             for (int j = 0; j < paramTypes.length; j++) {71                 if (j > 0) System.out.print(", ");72                 System.out.print(paramTypes[j].getName());73             }74             System.out.println(");");75         }76     }77 78 79     public static void printFields(Class cl) {80         Field[] fields = cl.getDeclaredFields();81 82         for (Field f : fields) {83             Class type = f.getType();84             String name = f.getName();85             System.out.print("   ");86             String modifiers = Modifier.toString(f.getModifiers());87             if (modifiers.length() > 0) System.out.print(modifiers + " ");88             System.out.println(type.getName() + " " + name + ";");89         }90     }91 }

 1 import java.lang.reflect.Field; 2 import java.lang.reflect.InvocationTargetException; 3 import java.lang.reflect.Method; 4  5 /** 6  * Created by karlx on 2015/5/29. 7  */ 8 public class ReflectionTest2 { 9     public static void main(String[] args) {10         Person person = new Person();11         person.name = "karl";12         //获取,设置 运行中对象的字段值13         Class clazz = person.getClass();14         try {15             Field field = clazz.getField("name");16             field.setaccessible(true);//避开java的访问检查17             System.out.println(field.get(person));18 19             field.set(person, "xiaoming");20             System.out.println(field.get(person));21 22         } catch (NoSuchFieldException | IllegalAccessException e) {23             e.printStackTrace();24         }25         //运行中调用对象的方法26         try {27             Method method = clazz.getMethod("getName");28             method.setAccessible(true);//避开java的访问检查29             System.out.println(method.invoke(person));30         } catch (NoSuchMethodException | InvocationTargetException | IllegalAccessException e) {31             e.printStackTrace();32         }33     }34 35     static class Person {36         public String name;37 38         public String getName() {39             return name + "hello";40         }41 42         public void setName(String name) {43             this.name = name;44         }45     }46 }