Java反射的用法
Class类
在Java中,每个class都有一个相应的Class对象。也就是说,当我们编写一个类,编译完成后,在生成的.class文件中,就会产生一个Class对象,用于表示这个类的类型信息。
反射
Java的反射主要就是使用class对象生成对应类的实例、调用类的方法等对操作。示例代码:
Car.java
public class Car {
private String brand;
private String color;
private Integer maxSpeed;
public Car() {
}
public Car(String brand, String color, Integer maxSpeed) {
super();
this.brand = brand;
this.color = color;
this.maxSpeed = maxSpeed;
}
public String getBrand() {
return brand;
}
public void setBrand(String brand) {
this.brand = brand;
}
public String getColor() {
return color;
}
public void setColor(String color) {
this.color = color;
}
public Integer getMaxSpeed() {
return maxSpeed;
}
public void setMaxSpeed(Integer maxSpeed) {
this.maxSpeed = maxSpeed;
}
@Override
public String toString() {
return "Car [brand=" + brand + ", color=" + color + ", maxSpeed="
+ maxSpeed + "]";
}
public void testPrivate() {
System.out.println("call testPrivate()");
}
}
ReflectTest.java
public class RelectTest {
public static void main(String[] args) throws ClassNotFoundException,
InstantiationException, IllegalAccessException, SecurityException,
NoSuchFieldException, NoSuchMethodException,
IllegalArgumentException, InvocationTargetException {
// 创建class,方法1
Class<?> clazz = Class.forName("com.Car");
// 创建class,方法2,相对来说,方法1更适合从配置中读取包的限定名字符串,避免了方法2中需要导包的操作
clazz = Car.class;
// 创建对象
Car car = (Car) clazz.newInstance();
// 获取所有的属性
Field[] fields = clazz.getDeclaredFields();
System.out.print("All fields:");
for (Field field : fields) {
System.out.print(field.getName() + ",");
}
System.out.println();
// 获取所有的public属性
Field[] publicFilds = clazz.getFields();
System.out.print("All public fields:");
for (Field field : publicFilds) {
System.out.print(field.getName() + ",");
}
System.out.println();
// 获取继承或接口中的所有方法
Method[] methods = clazz.getMethods();
System.out.println("All methods:");
for (Method method : methods) {
System.out.println(method.getReturnType() + " " + method.getName()
+ "(" + displayClass(method.getParameterTypes()) + ")");
}
System.out.println();
// 获取本类中的public, protected, private方法,不包括继承的方法
Method[] selfMethods = clazz.getDeclaredMethods();
System.out.println("All self methods:");
for (Method method : selfMethods) {
System.out.println(method.getReturnType() + " " + method.getName()
+ "(" + displayClass(method.getParameterTypes()) + ")");
}
System.out.println();
// 获取构造函数
Constructor[] constructors = clazz.getDeclaredConstructors();
System.out.println("All Constructor:");
for (Constructor constructor : constructors) {
System.out.println(constructor.getName() + "("
+ displayClass(constructor.getParameterTypes()) + ")");
}
System.out.println();
// 获取指定的属性
Field brandField = clazz.getDeclaredField("brand");
// 通过属性为字段赋值
brandField.setAccessible(true);// 由于brand属性为private,必须设置覆盖java对该字段的访问控制检查
brandField.set(car, "奔驰");
System.out.println(car);
// 获取指定的方法
Method colorSetMethod = clazz.getDeclaredMethod("setColor",
String.class);
colorSetMethod.invoke(car, "黑色");
System.out.println(car);
Method testPrivateMethod = clazz.getDeclaredMethod("testPrivate");
testPrivateMethod.invoke(car, null);
}
public static String displayClass(Class[] s) {
StringBuilder sb = new StringBuilder();
for (Class c : s) {
if (sb.length() > 0)
sb.append(", ");
sb.append(c.getName());
}
return sb.toString();
}
}
作者: Acode
出处: http://www.cnblogs.com/acode/
本文版权归作者和博客园共有,欢迎转载,但未经作者同意必须保留此段声明,且在文章页面明显位置给出, 原文链接 如有问题, 可留言咨询.