java反射详解编程语言

public class Student { 
 
    private String name = "小黑黑"; 
    public Integer age; 
    protected Date birthday; 
    int num; 
 
    static { 
        System.out.println("student的静态代码块"); 
    } 
 
    public static void testStudent() { 
        System.out.println("这是静态方法...."); 
    } 
 
    // 私有的方法 
    private int getNum(int num) { 
 
        return num + 10; 
    } 
 
    /* 
     * 在获取 私有属性值的时候 需要注释掉 private Student() { 
     * System.out.println("这是Student无参构造"); } 
     */ 
    public Student() { 
        System.out.println("这是Student无参构造"); 
    } 
 
    public Student(String name, int age, Date birthday) { 
        System.out.println("这是Student带参构造"); 
        this.name = name; 
        this.age = age; 
        this.birthday = birthday; 
    } 
 
    public String getName() { 
        return name; 
    } 
 
    public void setName(String name) { 
        this.name = name; 
    } 
 
    public Integer getAge() { 
        return age; 
    } 
 
    public void setAge(Integer age) { 
        this.age = age; 
    } 
 
    public Date getBirthday() { 
        return birthday; 
    } 
 
    public void setBirthday(Date birthday) { 
        this.birthday = birthday; 
    } 
 
}

public class ReflectTest { // 反射 
 
    /** 
     * 所有类的对象 都是Class的实例 
     * 所有类的父类都是Object 
     */ 
    @Test 
    public void getClassName() { 
        Student stu = new Student(); 
        System.out.println(stu.getClass().getSuperclass()); 
        System.out.println(Student.class.getSuperclass()); 
        System.out.println(String.class.getSuperclass()); 
        System.out.println(Integer.class.getSuperclass().getSuperclass()); 
    } 
 
    // 三种方式 获取 指定类的 完整限定名 
    @Test 
    public void getClazz() throws Exception { 
        System.out.println(Class.forName("cn.bdqn.test.Student").getName()); 
        System.out.println(new Student().getClass().getName()); 
        System.out.println(Student.class.getName()); 
    } 
 
    // 通过反射获取指定类的信息 
    @Test 
    public void getMsg() throws Exception { 
        Class c = Class.forName("cn.bdqn.test.Student"); 
        System.out.println("全类名：" + c.getName()); 
        System.out.println("包名：" + c.getPackage().getName()); 
        System.out.println("类名：" + c.getSimpleName()); 
 
        int num = c.getModifiers(); 
        System.out.println(num); 
        System.out.println(Modifier.toString(num)); 
    } 
 
    // 通过反射获取属性的信息 
    @Test 
    public void getFileds() throws Exception { 
        Class c = Class.forName("cn.bdqn.test.Student"); 
        // 获取所有public修饰的字段 
        Field[] fields = c.getFields(); 
        for (int i = 0; i < fields.length; i++) { 
            System.out.println(fields[i]); 
        } 
        System.out.println("获取所有的属性名称****************"); 
        fields = c.getDeclaredFields(); 
        for (int i = 0; i < fields.length; i++) { 
            System.out.println(fields[i].getName()); 
        } 
        System.out.println("获取所有属性的修饰符*****************"); 
        // default的int值 是 0 
        for (int i = 0; i < fields.length; i++) { 
            System.out.println(Modifier.toString(fields[i].getModifiers())); 
        } 
    } 
 
    // 通过反射观察执行顺序 
    @Test 
    public void getC() throws Exception { 
        Class c = Class.forName("cn.bdqn.test.Student"); // 加载静态代码块 
        // Student.testStudent(); 
        // Student student = new Student(); // 耦合 无参构造 
        Student student = (Student) c.newInstance(); // 解耦合 无参构造 
    } 
 
    // 通过反射获取类中的构造方法 
    @Test 
    public void getConstructors() throws Exception { 
        Class c = Class.forName("cn.bdqn.test.Student"); // 加载静态代码块 
        Constructor[] constructors = c.getDeclaredConstructors(); 
        for (int i = 0; i < constructors.length; i++) { 
            System.out.println("构造的修饰符：" 
                    + Modifier.toString(constructors[i].getModifiers())); 
            System.out.println("构造的名称：" + constructors[i].getName()); 
            // 1.8才有getParameterCount 
            System.out 
                    .println("构造的参数个数：" + constructors[i].getParameterCount()); 
 
            Class[] types = constructors[i].getParameterTypes(); // 参数的类型 
            for (Class class1 : types) { 
                System.out.println("参数的类型：" + class1.getName()); 
                System.out.println("参数的类型简写：" + class1.getSimpleName()); 
            } 
            System.out.println("******************************"); 
        } 
    } 
 
    // 通过反射获取类中的属性 
    @Test 
    public void setFiledName() throws Exception { 
        Student student = Student.class.newInstance(); 
        Class c = student.getClass(); 
 
        // 获取指定的属性 
        Field field = c.getDeclaredField("name"); 
        // 设置属性的访问权限 
        field.setAccessible(true); 
        System.out.println(field.get(student)); 
    } 
 
    // 通过反射获取类中的构造方法赋值 
    @SuppressWarnings("unchecked") 
    @Test 
    public void getMethod() throws Exception { 
        Student student = Student.class.newInstance(); 
        Class c = student.getClass(); 
        System.out.println(student.age); 
        Method method = c.getDeclaredMethod("setAge", Integer.class); 
        // 执行方法 
        method.invoke(student, 50); 
        System.out.println(student.age); 
        // 执行私有的带有参数的 并且有返回值的方法 
        method = c.getDeclaredMethod("getNum", int.class); 
        // 开启方法的权限 
        method.setAccessible(true); 
        int num = (Integer) method.invoke(student, 50); 
        System.out.println(num); 
 
    } 
 
}