2018-07-16-Java反射

** Java反射总结**

1，反射获取类的class对象的方式

Class<Student> c1 = (Class<Student>) stu1.getClass();
            
Class<Student> c2 = Student.class;

Class<Student> c = (Class<Student>) Class.forName("com.reflex.Student");

2，证明在运行期间，一个类，只有一个Class对象产生

System.out.println("是否c1=c2" + (c1 == c2));
System.out.println("是否c=c1" + (c == c1));

3，通过class对象获取类的实例

Student stu = c.newInstance();  

4，获取类的私有变量

Field f = c.getDeclaredField("name");

5，允许通过反射访问字段

f.setAccessible(true);

6，给字段赋值

f.set(stu, "刘德华");

7，获取类的构造函数并初始化该类

Constructor<Student> constructor = c.getDeclaredConstructor(String.class);
Student student = constructor.newInstance("aaaa");

String.class是构造参数

8，获取类方法并执行方法

Method method = c.getDeclaredMethod("setName", String.class);
method.invoke(stu, "zzz");  

Method getName = c.getDeclaredMethod("getName");
String name = (String) getName.invoke(stu);

9，通过反射越过泛型检查

List<?> list = stu.getList();
Class<?> listClass = list.getClass();
Method listAdd = listClass.getDeclaredMethod("add", Object.class);
listAdd.invoke(list, 100);
System.out.println("list设置=" + list.get(0));

10，通过使用配置文件，反射给对象赋值

10.1，新建文件setting.txt

className=com.reflex.Student
methodName=setCourseName

10.2 获取配置文件中的数据

private static String getProperty(String key) throws IOException {
    Properties properties = new Properties();
    FileReader reader = new FileReader("setting.txt");
    properties.load(reader);
    reader.close();
    return properties.getProperty(key);
}

10.3 赋值

String className = getProperty("className");
String methodName = getProperty("methodName");

Method propertyMethod = stu.getDeclaredMethod(methodName, String.class);
Student propertyStudent = stu.newInstance();
propertyMethod.invoke(propertyStudent, "cccc");

Field teaName = stu.getDeclaredField("name");
teaName.setAccessible(true);