反射_通过反射获取成员变量、构造方法、成员方法的使用

末蓝、 2022-06-17 02:42 217阅读 0赞

package cn.itcast_01;
    
    public class Person {
    	private String name;
    	int age;
    	public String address;
    
    	public Person() {
    
    	}
    
    	private Person(String name) {
    		this.name = name;
    	}
    
    	Person(String name, int age) {
    		this.name = name;
    		this.age = age;
    	}
    
    	public Person(String name, int age, String address) {
    		this.name = name;
    		this.age = age;
    		this.address = address;
    	}
    
    	public void show() {
    		System.out.println("show");
    	}
    
    	public void method(String s) {
    		System.out.println("method:" + s);
    	}
    
    	public String getString(String name, int age) {
    		return name + "----" + age;
    	}
    
    	private void function() {
    		System.out.println("function");
    	}
    
    	@Override
    	public String toString() {
    		return "Person [" + "name=" + name + ", " + "age=" + age + ", "
    				+ "address=" + address + "]";
    	}
    }

package cn.itcast_04;
    
    import java.lang.reflect.Constructor;
    import java.lang.reflect.Field;
    import java.lang.reflect.Method;
    
    /*
     * 需求:通过反射对Person进行操作使用
     * 
     * private String name;
     * int age;
     * public String address;
     * 	
     * public Person()
     * private Person(String name)
     * Person(String name, int age) 
     * public Person(String name, int age, String address) 
     * 
     * public void show()
     * public void method(String s) 
     * public String getString(String name, int age)
     * private void function() 
     */
    public class ReflectDemo2 {
    	public static void main(String[] args) throws Exception {
    		// 获取字节码文件对象
    		Class c = Class.forName("cn.itcast_01.Person");
    
    		// 获取无参构造方法对象
    		Constructor con = c.getConstructor();
    		// 通过无参构造方法对象创建对象
    		Object obj = con.newInstance();
    		System.out.println(obj);
    
    		// 通过反射给所有成员变量赋值
    		System.out.println("****通过反射给所有成员变量赋值****");
    		// private String name;
    		Field nameField = c.getDeclaredField("name");
    		nameField.setAccessible(true);
    		nameField.set(obj, "风清杨");
    		System.out.println(obj);
    		// int age;
    		Field ageField = c.getDeclaredField("age");
    		ageField.setAccessible(true);
    		ageField.set(obj, 27);
    		System.out.println(obj);
    		// public String address;
    		Field addressField = c.getField("address");
    		addressField.set(obj, "上海");
    		System.out.println(obj);
    
    		// 通过反射给所有构造方法赋值
    		System.out.println("****通过反射给所有构造方法赋值****");
    		// public Person()
    		// private Person(String name)
    		Constructor con2 = c.getDeclaredConstructor(String.class);
    		con2.setAccessible(true);
    		Object obj2 = con2.newInstance("王小明");
    		System.out.println(obj2);
    		// Person(String name, int age)
    		Constructor con3 = c.getDeclaredConstructor(String.class, int.class);
    		con3.setAccessible(true);
    		Object obj3 = con3.newInstance("林子聪", 35);
    		System.out.println(obj3);
    		// public Person(String name, int age, String address)
    		Constructor con4 = c.getConstructor(String.class, int.class,
    				String.class);
    		Object obj4 = con4.newInstance("江小斐", 56, "山东");
    		System.out.println(obj4);
    
    		// 通过反射调用所有成员方法
    		System.out.println("****通过反射调用所有成员方法****");
    		// public void show()
    		Method m1 = c.getMethod("show");
    		m1.invoke(obj);
    		// public void method(String s)
    		Method m2 = c.getMethod("method", String.class);
    		m2.invoke(obj, "hello");
    		// public String getString(String name, int age)
    		Method m3 = c.getMethod("getString", String.class, int.class);
    		Object objString = m3.invoke(obj, "world", 100);
    		System.out.println(objString);
    		// private void function()
    		Method m4 = c.getDeclaredMethod("function");
    		m4.setAccessible(true);
    		m4.invoke(obj);
    	}
    }