java 反射机制获取类名、属性、方法、构造器和反射动态使用

被反射的类:

@Table("tb_student")
public class Student {

	@Fields(columnName="id",type="int",length=10)
	private int id;

	@Fields(columnName="studentName",type="varchar",length=10)
	private String studentName;

	@Fields(columnName="age",type="int",length=3)
	private int age;

	public int getId() {
			return id;
	}
	public void setId(int id) {
			this.id = id;
	}
	public String getStudentName() {
			return studentName;
	}
	public void setStudentName(String studentName) {
			this.studentName = studentName;
	}
	public int getAge() {
			return age;
	}
	public void setAge(int age) {
			this.age = age;
	}
	public Student(int id, String studentName, int age) {
		super();
		this.id = id;
		this.studentName = studentName;
		this.age = age;
	}

	public Student() {

	}

反射获取类的信息:

@SuppressWarnings("all") //压制警告
public class Deam {

public static void main(String[] args) throws NoSuchFieldException, SecurityException, NoSuchMethodException {

	Class c;
	try {
		c = Class.forName("cn.sxt.in.Student");
		//获取类名
		System.out.println(c.getName());  //获取包名+类名
		System.out.println(c.getSimpleName()); //只获取类名
		
		//获取属性
		Field[] fields=c.getFields();   //返回属性数组,只能获取公开属性
		System.out.println(fields.length);
		
		Field[] fields2=c.getDeclaredFields(); //获得所有类型的属性
		
		for(Field e:fields2)
		{
			System.out.println("aa");
			System.out.println(e);
		}
		
		System.out.println(fields2.length);
		

		Field f=c.getDeclaredField("studentName");
		System.out.println(f);


		//获取方法
		
		Method[] method =c.getMethods();  //获取公开方法
		Method[] method2=c.getDeclaredMethods();  //获取所有方法
		for(Method mm:method2)
		{
			System.out.println(mm);
		}
		
		Method m=c.getDeclaredMethod("getStudentName", null); //第二个为参数类型，没有为null
		Method m2=c.getDeclaredMethod("setStudentName", String.class); //方法的参数类型是String
		//获取构造器
		Constructor[] co=c.getDeclaredConstructors();
		for(Constructor cc:co)
		{
			System.out.println(cc);
		}
		
		Constructor coo=c.getDeclaredConstructor(null);  //获取无参构造器
		System.out.println(coo);  
		Constructor coo2=c.getDeclaredConstructor(int.class,String.class,int.class);//获取指定有参构造器
		System.out.println(coo2);  
	} catch (ClassNotFoundException e) {
		e.printStackTrace();
	}

	
}

}
}

通过反射动态操作方法属性:

public class play {

public static void main(String[] args) throws NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException, NoSuchFieldException
{
	try {
		Class c=Class.forName("cn.sxt.in.Student");
		//Class<Student> c=(Class<Student>)Class.forName("cn.sxt.in.Student");后面操作不用强转
		
		//通过反射调用构造方法，构造对象
		Student s=(Student)c.newInstance();  //实际上调用了User的无参构造方法
		System.out.println(s);
		
		//指定构造对象
		Constructor<Student> cc=c.getDeclaredConstructor(int.class,String.class,int.class); //获得构造器方法
		Student s2=cc.newInstance(001,"me",19);    //传入实际参数生成对象
		System.out.println(s2.getStudentName());
		
		//反射调用普通方法
		Student s3=(Student) c.newInstance();
		Method method=c.getDeclaredMethod("setStudentName", String.class);
		method.invoke(s3, "mee");  //激活方法,第一个参数为对象，第二个参数为传入信息,相当于s3.setStudentName(String s);
		System.out.println(s3.getStudentName());
		
		//通过反射操作属性
		Student s4=(Student)c.newInstance();
		Field f=c.getDeclaredField("studentName"); //获得属性
	//	f.set(s4,"yyy"); //设置属性信息，第一个参数为设定的对象，第二个为实际信息，相当于s4.set(String s);
	//	System.out.println(s4.getStudentName()); //因为是私有属性，不能直接调用
		
		//访问私有属性
		Student s5=(Student) c.newInstance();
		
		Field ff=c.getDeclaredField("studentName");
		ff.setAccessible(true); //不需安全检查，可直接访问私有属性，其他类型也有该方法(类等)
		ff.set(s5, "ada");
		System.out.println(s5.getStudentName());
		System.out.println(ff.get(s5)); //直接通过属性对象调用
		
		
	} catch (ClassNotFoundException e) {
		
		e.printStackTrace();
	}
}
}