Java反射的详细解析一

//1.Class这个类里面的静态方法forName
//Class.forName("类的全类名")： 全类名 = 包名 + 类名
Class clazz1 = Class.forName("com.itheima.reflectdemo.Student");
//源代码阶段获取 --- 先把Student加载到内存中，再获取字节码文件的对象
//clazz 就表示Student这个类的字节码文件对象。
//就是当Student.class这个文件加载到内存之后，产生的字节码文件对象
​
​
//2.通过class属性获取
//类名.class
Class clazz2 = Student.class;
​
//因为class文件在硬盘中是唯一的，所以，当这个文件加载到内存之后产生的对象也是唯一的
System.out.println(clazz1 == clazz2);//true
​
​
//3.通过Student对象获取字节码文件对象
Student s = new Student();
Class clazz3 = s.getClass();
System.out.println(clazz1 == clazz2);//true
System.out.println(clazz2 == clazz3);//true

public class ReflectDemo2 {
    public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException {
        //1.获得整体（class字节码文件对象）
        Class clazz = Class.forName("com.itheima.reflectdemo.Student");
​
​
        //2.获取构造方法对象
        //获取所有构造方法（public）
        Constructor[] constructors1 = clazz.getConstructors();
        for (Constructor constructor : constructors1) {
            System.out.println(constructor);
        }
​
        System.out.println("=======================");
​
        //获取所有构造（带私有的）
        Constructor[] constructors2 = clazz.getDeclaredConstructors();
​
        for (Constructor constructor : constructors2) {
            System.out.println(constructor);
        }
        System.out.println("=======================");
​
        //获取指定的空参构造
        Constructor con1 = clazz.getConstructor();
        System.out.println(con1);
​
        Constructor con2 = clazz.getConstructor(String.class,int.class);
        System.out.println(con2);
​
        System.out.println("=======================");
        //获取指定的构造(所有构造都可以获取到，包括public包括private)
        Constructor con3 = clazz.getDeclaredConstructor();
        System.out.println(con3);
        //了解 System.out.println(con3 == con1);
        //每一次获取构造方法对象的时候，都会新new一个。
​
        Constructor con4 = clazz.getDeclaredConstructor(String.class);
        System.out.println(con4);
    }
}

//首先要有一个javabean类
public class Student {
    private String name;
​
    private int age;
​
​
    public Student() {
​
    }
​
    public Student(String name) {
        this.name = name;
    }
​
    private Student(String name, int age) {
        this.name = name;
        this.age = age;
    }
​
​
    /**
     * 获取
     * @return name
     */
    public String getName() {
        return name;
    }
​
    /**
     * 设置
     * @param name
     */
    public void setName(String name) {
        this.name = name;
    }
​
    /**
     * 获取
     * @return age
     */
    public int getAge() {
        return age;
    }
​
    /**
     * 设置
     * @param age
     */
    public void setAge(int age) {
        this.age = age;
    }
​
    public String toString() {
        return "Student{name = " + name + ", age = " + age + "}";
    }
}

public class ReflectDemo4 {
    public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException {
        //获取成员变量对象
​
        //1.获取class对象
        Class clazz = Class.forName("com.itheima.reflectdemo.Student");
​
        //2.获取成员变量的对象（Field对象)只能获取public修饰的
        Field[] fields1 = clazz.getFields();
        for (Field field : fields1) {
            System.out.println(field);
        }
​
        System.out.println("===============================");
​
        //获取成员变量的对象（public + private）
        Field[] fields2 = clazz.getDeclaredFields();
        for (Field field : fields2) {
            System.out.println(field);
        }
​
        System.out.println("===============================");
        //获得单个成员变量对象
        //如果获取的属性是不存在的，那么会报异常
        //Field field3 = clazz.getField("aaa");
        //System.out.println(field3);//NoSuchFieldException
​
        Field field4 = clazz.getField("gender");
        System.out.println(field4);
​
        System.out.println("===============================");
        //获取单个成员变量（私有）
        Field field5 = clazz.getDeclaredField("name");
        System.out.println(field5);
​
    }
}
​
​
​
public class Student {
    private String name;
​
    private int age;
​
    public String gender;
​
    public String address;
​
​
    public Student() {
    }
​
    public Student(String name, int age, String address) {
        this.name = name;
        this.age = age;
        this.address = address;
    }
​
​
    public Student(String name, int age, String gender, String address) {
        this.name = name;
        this.age = age;
        this.gender = gender;
        this.address = address;
    }
​
    /**
     * 获取
     * @return name
     */
    public String getName() {
        return name;
    }
​
    /**
     * 设置
     * @param name
     */
    public void setName(String name) {
        this.name = name;
    }
​
    /**
     * 获取
     * @return age
     */
    public int getAge() {
        return age;
    }
​
    /**
     * 设置
     * @param age
     */
    public void setAge(int age) {
        this.age = age;
    }
​
    /**
     * 获取
     * @return gender
     */
    public String getGender() {
        return gender;
    }
​
    /**
     * 设置
     * @param gender
     */
    public void setGender(String gender) {
        this.gender = gender;
    }
​
    /**
     * 获取
     * @return address
     */
    public String getAddress() {
        return address;
    }
​
    /**
     * 设置
     * @param address
     */
    public void setAddress(String address) {
        this.address = address;
    }
​
    public String toString() {
        return "Student{name = " + name + ", age = " + age + ", gender = " + gender + ", address = " + address + "}";
    }
}
​