二、反射机制动态操作方法_ 属性_构造器

 

 

 

 

public class User {
    //类的属性
    //public int userId;
    private int userId;
    private String userName;
    private String password;
    //公有的取值，赋值方法
    public int getUserId() {
        return userId;
    }
    public void setUserId(int userId) {
        this.userId = userId;
    }
    public String getUserName() {
        return userName;
    }
    public void setUserName(String userName) {
        this.userName = userName;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    //构造方法
    public User() {
        // TODO Auto-generated constructor stub
    }
    public User(int userId, String userName, String password) {
        super();
        this.userId = userId;
        this.userName = userName;
        this.password = password;
    }
    
    
}

public class Test1 {
    public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException, NoSuchMethodException {
        String path = "fanshe.User";
        //（1）获取类的名称
        Class c = Class.forName(path);
        System.out.println("（1）获取类的名称");
        System.out.println("类的全名称:"+c.getName());  //fanshe.User
        System.out.print("类的名称："+c.getSimpleName());   //User
        System.out.println("
--------------------------");

        //获取父类的Class对象
        Class csuper = c.getSuperclass();
        System.out.println("获取父类的Class对象");
        System.out.println("类的全名称:"+csuper.getName());   //java.lang.Object
        System.out.print("类的名称："+csuper.getSimpleName());    //Object
        System.out.println("
--------------------------");

        //(2)获取类的属性信息
        //Field f=c.getField("userId"); //只能获取公共的属性
        //System.out.println(f);
        System.out.println("获取类的属性信息");
        Field [] fields=c.getFields(); //只能获取公共的属性
        System.out.println(fields.length);    //0

        Field [] fields2 = c.getDeclaredFields();
        System.out.println(fields2.length);  //3
        for (Field field : fields2){
            //System.out.println(field);//调用了toString()方法
            System.out.println(field.getModifiers()+"	"+field.getType()+"	"+field.getName());  //field.getModifiers():访问权限，2代表private
        }


        //(3)获取类的方法信息
        System.out.println("(3)获取类的方法信息");
        Method[] methods = c.getDeclaredMethods();//本类中的公共的方法对象
        //System.out.println(methods.length);  //6
        for(Method method:methods){
            //System.out.println(method);
            System.out.println("访问权限"+method.getModifiers());
            System.out.println("返回值类型:"+method.getReturnType());
            System.out.println("方法的名称:"+method.getName());
            //获取方法的参数
            System.out.println("//获取方法的参数");
            Class [] cPara=method.getParameterTypes();
            for (Class c1 : cPara) {
                System.out.println(c1.getTypeName()+"	");
            }
            System.out.println("
--------------------------");
        }
        System.out.println("
=============================
");


        //(4)获取类的构造器
        System.out.println("(4)获取类的构造器");
        Constructor [] cons=c.getConstructors();
        for (Constructor constructor : cons) {
            System.out.println(constructor);
        }
        System.out.println("
=====================");
        //获取指定的构造方法
        System.out.println("获取指定的构造方法");
        Constructor con=c.getConstructor(null);
        System.out.println(con);
        System.out.println("
=====================");
        Constructor con2=c.getConstructor(int.class,String.class,String.class);
        System.out.println(con2);
    }
}

2.5 动态的操作属性、方法、构造方法

public class Test2 {
    public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException, NoSuchFieldException {
        //获到Class类的对象
        Class c=Class.forName("com.bjsxt.entity.User");
        
        //(1)得到无参构造方法的对象
        Constructor cons=c.getConstructor(null);
        //通过无参构造方法的对象，创建User类的对象
        User user=(User) cons.newInstance();
        
        //(2)动态操作属性
        Field field=c.getDeclaredField("userId");
        field.setAccessible(true);//这个属性不需要做安全检查了，可以直接访问
        field.set(user, 1001);  //通过反射直接赋值
        System.out.println("取出userId这个属性的值:"+field.get(user));//通过反射直接取值
        
        //(3)动态操作方法
        Method m=c.getDeclaredMethod("setUserName", String.class);
        //执行setUserName这个方法
        m.invoke(user, "张三");
        Method m2=c.getDeclaredMethod("getUserName", null);
        System.out.println(m2.invoke(user));
    }
}