通过反射获取类的完整结构_1属性方法

通过反射获取类的完整结构_1属性方法_2构造器及其他

代码一：

package nineteen;

import java.lang.reflect.Constructor;

import org.junit.Test;

public class TestConstructor {
	@Test
	public void test1() throws Exception{
		String className = "nineteen.Person";
		Class clazz = Class.forName(className);
		//创建对应的运行时类的对象。使用newInstance()，实际上就是调用了运行时类的空参的构造器。
		//要想能够创建成功：①要求对应的运行时类要有空参的构造器。②构造器的权限修饰符的权限要足够。
		Object obj = clazz.newInstance();
		Person p = (Person)obj;
		System.out.println(p);
	}
	
	@Test
	public void test2() throws ClassNotFoundException{
		String className = "nineteen.Person";
		Class clazz = Class.forName(className);
		
		Constructor[] cons = clazz.getDeclaredConstructors();
		for(Constructor c : cons){
			System.out.println(c);
		}
	}
	
	//调用指定的构造器,创建运行时类的对象
	@Test
	public void test3() throws Exception{
		String className = "nineteen.Person";
		Class clazz = Class.forName(className);
		
		Constructor cons = clazz.getDeclaredConstructor(String.class,int.class);
		cons.setAccessible(true);
		Person p = (Person)cons.newInstance("罗伟",20);
		System.out.println(p);
	}
}

代码二：

package nineteen;

public class Creature<T>{
	public double weight;
	
	public void breath(){
		System.out.println("呼吸！");
	}
}

代码三：

package nineteen;

import java.io.Serializable;

public interface MyInterface extends Serializable{

}

代码四：

package nineteen;

import static java.lang.annotation.ElementType.CONSTRUCTOR;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.LOCAL_VARIABLE;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.ElementType.PARAMETER;
import static java.lang.annotation.ElementType.TYPE;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target({TYPE, FIELD, METHOD, PARAMETER, CONSTRUCTOR, LOCAL_VARIABLE})
@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnotation {
	String value();
}

代码五：

package nineteen;

@MyAnnotation(value = "rengui")
public class Person extends Creature<String> implements Comparable,MyInterface{
	public String name;
	private int age;
	int id;
	//创建类时，尽量保留一个空参的构造器。
	public Person() {
		super();
//		System.out.println("今天天气很闷热");
	}
	public Person(String name) {
		super();
		this.name = name;
	}
	private Person(String name, int age) {
		super();
		this.name = name;
		this.age = age;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	@MyAnnotation(value = "abc123")
	public void show(){
		System.out.println("我是一个人！");
	}
	
	private Integer display(String nation,Integer i) throws Exception{
		System.out.println("我的国籍是：" + nation);
		return i;
	}

	@Override
	public String toString() {
		return "Person [name=" + name + ", age=" + age + "]";
	}
	@Override
	public int compareTo(Object o) {
		// TODO Auto-generated method stub
		return 0;
	}
	
	public static void info(){
		System.out.println("中国人！");
	}
	
	class Bird{//内部类
		
	}
}

代码六：

package nineteen;

import java.lang.reflect.Field;
import java.lang.reflect.Modifier;

import org.junit.Test;

public class TestField {
	//获取对应的运行时类的属性
	@Test
	public void test1(){
		Class clazz = Person.class;
		//1.getFields():只能获取到运行时类中及其父类中声明为public的属性
		Field[] fields = clazz.getFields();
		for(int i = 0;i < fields.length;i++){
			System.out.println(fields[i]);//public double nineteen.Creature.weight
											//public java.lang.String nineteen.Person.name
		}
		System.out.println();

		//2.getDeclaredFields():获取运行时类本身声明的所有的属性
		Field[] fields1 = clazz.getDeclaredFields();
		for(Field f : fields1){
			System.out.println(f.getName());//name age id
		}
	}
	//权限修饰符  变量类型 变量名
	//获取属性的各个部分的内容
	@Test
	public void test2(){
		Class clazz = Person.class;
		Field[] fields1 = clazz.getDeclaredFields();
		for(Field f : fields1){
			//1.获取每个属性的权限修饰符
			int i = f.getModifiers();
			String str1 = Modifier.toString(i);
			System.out.print(str1 + " ");//public private

			//2.获取属性的类型
			Class type = f.getType();
			System.out.print(type.getName() + " ");//java.lang.String int int
			//3.获取属性名
			System.out.print(f.getName());//name age id

			System.out.println();
		}
	}
	
	//调用运行时类中指定的属性
	@Test
	public void test3() throws Exception{
		Class clazz = Person.class;
		//1.获取指定的属性
		//getField(String fieldName):获取运行时类中声明为public的指定属性名为fieldName的属性
		Field name = clazz.getField("name");
		//2.创建运行时类的对象 
		Person p = (Person)clazz.newInstance();
		System.out.println(p);
		//3.将运行时类的指定的属性赋值
		name.set(p,"Jerry");
		System.out.println(p);
		System.out.println("%"+name.get(p));
		
		System.out.println();
		//getDeclaredField(String fieldName):获取运行时类中指定的名为fieldName的属性
		Field age = clazz.getDeclaredField("age");
		//由于属性权限修饰符的限制，为了保证可以给属性赋值，需要在操作前使得此属性可被操作。
		age.setAccessible(true);
		age.set(p,10);
		System.out.println(p);
		
//		Field id = clazz.getField("id");
		
	}
	
}

代码七：

package nineteen;

import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;

import org.junit.Test;

public class TestMethod {
	//1.获取运行时类的方法
	
	@Test
	public void test1(){
		Class clazz = Person.class;
		//1.getMethods():获取运行时类及其父类中所有的声明为public的方法
		Method[] m1 = clazz.getMethods();
		for(Method m : m1){//强制for循环
			System.out.println(m);
		}
		System.out.println();
		
		//2.getDeclaredMethods():获取运行时类本身声明的所有的方法
		Method[] m2 = clazz.getDeclaredMethods();
		for(Method m : m2){
			System.out.println(m);
		}
	}
	//注解 权限修饰符 返回值类型 方法名 形参列表 异常
	@Test
	public void test2(){
		Class clazz = Person.class;
		
		Method[] m2 = clazz.getDeclaredMethods();
		for(Method m : m2){
			//1.注解
			Annotation[] ann = m.getAnnotations();
			for(Annotation a : ann){
				System.out.println(a);
			}
			
			//2.权限修饰符
			String str = Modifier.toString(m.getModifiers());
			System.out.print(str + " ");
			//3.返回值类型
			Class returnType = m.getReturnType();
			System.out.print(returnType.getName() + " ");
			//4.方法名
			System.out.print(m.getName() + " ");
			
			//5.形参列表
			System.out.print("(");
			Class[] params = m.getParameterTypes();
			for(int i = 0;i < params.length;i++){
				System.out.print(params[i].getName() + " args-" + i + " ");
			}
			System.out.print(")");
			
			//6.异常类型
			Class[] exps = m.getExceptionTypes();
			if(exps.length != 0){
				System.out.print("throws ");
			}
			for(int i = 0;i < exps.length;i++){
				System.out.print(exps[i].getName() + " ");
			}
			System.out.println();
		}
	}
	//调用运行时类中指定的方法
	@Test
	public void test3() throws Exception{
		Class clazz = Person.class;
		//getMethod(String methodName,Class ... params):获取运行时类中声明为public的指定的方法
		Method m1 = clazz.getMethod("show");
		Person p = (Person)clazz.newInstance();
		//调用指定的方法：Object invoke(Object obj,Object ... obj)
		Object returnVal = m1.invoke(p);//我是一个人
		System.out.println(returnVal);//null
		
		Method m2 = clazz.getMethod("toString");
		Object returnVal1 = m2.invoke(p);
		System.out.println(returnVal1);//Person [name=null, age=0]
		//对于运行时类中静态方法的调用
		Method m3 = clazz.getMethod("info");
		m3.invoke(Person.class);
		
		//getDeclaredMethod(String methodName,Class ... params):获取运行时类中声明了的指定的方法
		Method m4 = clazz.getDeclaredMethod("display",String.class,Integer.class);
		m4.setAccessible(true);
		Object value = m4.invoke(p,"CHN",10);//我的国籍是：CHN
		System.out.println(value);//10
	}
}

获取构造器及其他代码八：

package nineteen;

import java.lang.annotation.Annotation;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;

import org.junit.Test;

public class TestOthers {
	//6.获取注解
	@Test
	public void test6(){
		Class clazz = Person.class;
		Annotation[] anns = clazz.getAnnotations();
		for(Annotation a : anns){
			System.out.println(a);
		}
	}
	
	//5.获取所在的包
	@Test
	public void test5(){
		Class clazz = Person.class;
		Package pack = clazz.getPackage();
		System.out.println(pack);
	}
	
	//4.获取实现的接口
	@Test
	public void test4(){
		Class clazz = Person.class;
		Class[] interfaces = clazz.getInterfaces();
		for(Class i : interfaces){
			System.out.println(i);
		}
	}
	
	//3*.获取父类的泛型
	@Test
	public void test3(){
		Class clazz = Person.class;
		Type type1 = clazz.getGenericSuperclass();//获取带泛型的父类
		
		ParameterizedType param = (ParameterizedType)type1;//强转为它的子接口
		Type[] ars = param.getActualTypeArguments();//调取getActualTypeArguments方法获取参数类型
		
		System.out.println(((Class)ars[0]).getName());//这里只有一个数据，故用0.然后强转为class
	}
	
	//2.获取带泛型的父类
	@Test
	public void test2(){
		Class clazz = Person.class;
		Type type1 = clazz.getGenericSuperclass();
		System.out.println(type1);
	}
	
	//1.获取运行时类的父类
	@Test
	public void test1(){
		Class clazz = Person.class;
		Class superClass = clazz.getSuperclass();
		System.out.println(superClass);
	}
}