获取反射的类
//获取反射的类
public static void printReflectionClass() throws Exception {
Fruit fruit = new Fruit();
Class<?> class1 = fruit.getClass();
System.out.println(class1);
Class<?> class2 = Fruit.class;
System.out.println(class2);
Class<?> class3 = Class.forName("com.golearning.learning.bean.Fruit");
System.out.println(class3);
}
运行结果：
class com.golearning.learning.bean.Fruit
class com.golearning.learning.bean.Fruit
class com.golearning.learning.bean.Fruit
获取一下传入的类的属性和类型
/**
* 获取一下传入的类的属性和类型
* @param cla
*/
public static void getRefClassField(Class<?> cla){
Field[] fields = cla.getDeclaredFields();
for (Field field : fields) {
System.out.println(field.getName()+" = "+field.getType());
}
}
Class<?> cla = Class.forName("com.golearning.learning.bean.Fruit");
getRefClassField(cla);
运行结果为：
size = int
color = class java.lang.String
shape = class java.lang.String
获取一下传入的类里面的方法
/**
* 获取一下传入的类里面的方法
* @param cla
*/
public static void getRefClassMethod(Class<?> cla) throws NoSuchMethodException, InstantiationException, IllegalAccessException, InvocationTargetException {
Method[] methods = cla.getDeclaredMethods();
for (Method method : methods) {
//获取方法的名字和有参参数个数数
System.out.println(method.getName() + " == 参数个数 == "+method.getParameterCount());
//获取方法的参数类型
Class[] classes = method.getParameterTypes();
for (Class aClass : classes) {
System.out.println(aClass);
}
}
//执行反射获取到的方法
Method method1 = cla.getDeclaredMethod("setColor",String.class);
Object object = cla.newInstance();
method1.invoke(object,"红色");
System.out.println(object);
}
给一个泛型List 插入一条非泛型的数据
/**
* 给一个泛型List 插入一条非泛型的数据
* @param list
* @throws NoSuchMethodException
* @throws InvocationTargetException
* @throws IllegalAccessException
*/
public static void addDataInGenericList(List<String> list) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException {
//获取它的类
Class<?> cla = list.getClass();
//获取它的add方法 参数为任意对象
Method method = cla.getDeclaredMethod("add",Object.class);
method.invoke(list,514);
for (Object o : list) {
System.out.println(o);
}
}
List<String> list = new ArrayList<>();
list.add("爷爷今年有");
list.add("99了");
//给一个泛型List 插入一条非泛型的数据
addDataInGenericList(list);
运行结果：
爷爷今年有
99了
514
获取传入类的构造器创建对象
public class Fruit {
//大小
private Integer size;
//颜色
private String color;
//形状
private String shape;
public Fruit(Integer size, String color, String shape) {
System.out.println("=====================获取有参构造器===================");
this.size = size;
this.color = color;
this.shape = shape;
}
public Fruit() {
System.out.println("=====================获取无参构造器===================");
}
public int getSize() {
return size;
}
public void setSize(Integer size) {
this.size = size;
}
public String getColor() {
return color;
}
public void setColor(String color) {
this.color = color;
}
public String getShape() {
return shape;
}
public void setShape(String shape) {
this.shape = shape;
}
@Override
public String toString() {
return "Fruit{" +
"size=" + size +
", color='" + color + '\'' +
", shape='" + shape + '\'' +
'}';
}
}
/**
* 获取传入类的构造器创建对象
* @param cla
*/
public static void getRefClassConstractor(Class<?> cla) throws NoSuchMethodException, InvocationTargetException, InstantiationException, IllegalAccessException {
//获取无参构造器
Constructor<?> constructor = cla.getConstructor(null);
Object object = constructor.newInstance(null);
System.out.println(object);
//获取有参构造器
Constructor<?> constructor2 = cla.getConstructor(Integer.class,String.class,String.class);
Object object2 = constructor2.newInstance(40,"红色","圆形");
System.out.println(object2);
}
Class<?> cla = Class.forName("com.golearning.learning.bean.Fruit");
getRefClassConstractor(cla);
运行结果为：
=====================获取无参构造器===================
Fruit{size=null, color='null', shape='null'}
=====================获取有参构造器===================
Fruit{size=40, color='红色', shape='圆形'}
注解的反射
在一个类中使用注解
//多个属性之间要用逗号隔开，赋值方式在括号内以value = ""的方式。
@AnnotationClass(height = 11,shape = "ddd",deep = 45)
public class Plants {
private int height;
private String shape;
private int deep;
private int width;
public Plants(int height, String shape, int deep, int width) {
this.height = height;
this.shape = shape;
this.deep = deep;
this.width = width;
}
public Plants() {
}
public int getHeight() {
return height;
}
public void setHeight(int height) {
this.height = height;
}
public String getShape() {
return shape;
}
public void setShape(String shape) {
this.shape = shape;
}
public int getDeep() {
return deep;
}
public void setDeep(int deep) {
this.deep = deep;
}
public int getWidth() {
return width;
}
public void setWidth(int width) {
this.width = width;
}
@Override
public String toString() {
return "Plants{" +
"height=" + height +
", shape='" + shape + '\'' +
", deep=" + deep +
", width=" + width +
'}';
}
}
定义一个注解
@Target(ElementType.TYPE) //表示AnnotationClass注解可以用于什么地方，可用于给一个类型进行注解，比如类、接口、枚举
@Retention(RetentionPolicy.RUNTIME)//表示AnnotationClass注解传递存活时间，注解可保留到程序运行时被加载到JVM中
public @interface AnnotationClass
{
//Integer heightx();//不能使用封装类型
int height();//参数的类型只能是基本类型
String shape();
int deep();
int width() default 10;
}
获取传入类的注解属性
/**
* 获取传入类的注解属性
* @param cla
*/
public static void getAnnotationInfo(Class cla){
AnnotationClass annotationClass = (AnnotationClass) cla.getAnnotation(AnnotationClass.class);
if(annotationClass!=null){
System.out.println("deep=="+annotationClass.deep());
System.out.println("height=="+annotationClass.height());
System.out.println("shape=="+annotationClass.shape());
System.out.println("width=="+annotationClass.width());
}
}
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