(转)Java的反射机制
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原地址:http://blog.csdn.net/zml_2015/article/details/52424019
Java中的反射首先是能够获取到Java中要反射类的字节码,获取字节码有三种方法,1.Class.forName(className) 2.类名.class 3.this.getClass()。然后将字节码中的方法,变量,构造函数等映射成相应的Method、Filed、Constructor等类,这些类提供了丰富的方法可以被我们所使用。
下面就通过一个简单的例子来说明一下怎样使用java的反射机制
PS
: java的反射机制相当有用,当在我们使用第三方的类库时,有些成员方法是私有的,我们没有办法直接使用,而通过java的反射机制,我管你是不是私有的,我照用不误
class User { String username; int age; @Override public String toString() { return "User [username=" + username + ", age=" + age + "]"; } public User() { super(); } public User(String username, int age) { super(); this.username = username; this.age = age; } /** * @return the username */ public String getUsername() { return username; } /** * @param username * the username to set */ private void setUsername(String username) { this.username = username; } /** * @return the age */ public int getAge() { return age; } /** * @param age * the age to set */ public void setAge(int age) { this.age = age; }}
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/** * @author 郑明亮 * @Time:2016年9月3日 上午16:30:40 * @version 1.0 */ @org.junit.Test public void testFanShe() throws ClassNotFoundException, InstantiationException, IllegalAccessException, NoSuchMethodException, SecurityException, IllegalArgumentException, InvocationTargetException{ Class clas =User.class; Constructor[] constructors = clas.getConstructors(); String classname = clas.getSimpleName(); Field[] fields = clas.getDeclaredFields(); Method[] methods = clas.getDeclaredMethods(); String CanonicalName = clas.getCanonicalName(); System.out.println("类名:"+classname); System.out.println("完整类名:"+CanonicalName); System.out.println("构造方法:"); for (int i = 0; i < constructors.length; i++) { System.out.print(constructors[i]+" "); } System.out.println("成员变量:"); for (int i = 0; i < fields.length; i++) { System.out.println(fields[i].getType().getSimpleName()+" "+fields[i].getName()); } System.out.println("成员方法:"); for (int i = 0; i < methods.length; i++) { System.out.println(methods[i]+" "); } System.out.println("-----------------------华丽的分割线---------------------------------------"); User user = (User) clas.newInstance(); Method setName = clas.getDeclaredMethod("setUsername",new Class[]{String.class}); setName.setAccessible(true); setName.invoke(user,new Object[]{"张三"}); Method toString = clas.getDeclaredMethod("toString"); System.out.println(toString.invoke(user).toString()); }
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