内省，英文中称作introspector。主要对javaBean进行操作，JavaBean是一个特殊的Java类，该类中方法名符合特定的规则（其实就是getXXX,setXXX）,我们一般是利用get，set方法来推断属性的名称，而不是直接根据属性来获得名称，因为属性都是私有的，而get，set方法都是共有的。推断规则：如果第二个字母为小写，则首字母小写，例如：
- getAge—>age
- setage—>age
由于自己根据方法名来推断属性名称非常麻烦，因此我们可以通过内省的方式来调用set，get方法，看看下面的例子：
@Test
public void test4() {
Person p1 = new Person();
Object value = "zhangsan";
String propertyName = "username";
try {
// 给属性设置值
setProperty(p1, value, propertyName);
// 获得属性值
System.out.println(getProperty(p1, propertyName));
} catch (IllegalAccessException | IllegalArgumentException
| InvocationTargetException | IntrospectionException e) {
e.printStackTrace();
}
}
private Object getProperty(Object p1, String propertyName)
throws IntrospectionException, IllegalAccessException,
IllegalArgumentException, InvocationTargetException {
PropertyDescriptor pd1 = new PropertyDescriptor(propertyName,
p1.getClass());
Method methodGetProperty = pd1.getReadMethod();
return methodGetProperty.invoke(p1);
}
private void setProperty(Object p1, Object value, String propertyName)
throws IntrospectionException, IllegalAccessException,
IllegalArgumentException, InvocationTargetException {
PropertyDescriptor pd1 = new PropertyDescriptor(propertyName,
p1.getClass());
Method methodSetProperty = pd1.getWriteMethod();
methodSetProperty.invoke(p1, value);
}
Person.java
public class Person {
private String username;
private String password;
private int money;
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public int getMoney() {
return money;
}
public void setMoney(int money) {
this.money = money;
}
}使用JavaBean中提供的BeanInfo类来操作，这样略微麻烦，但也是一种实现方式：
private Object getProperty(Object p1, String propertyName)
throws IntrospectionException, IllegalAccessException,
IllegalArgumentException, InvocationTargetException {
/*PropertyDescriptor pd1 = new PropertyDescriptor(propertyName,
p1.getClass());
Method methodGetProperty = pd1.getReadMethod();
return methodGetProperty.invoke(p1);*/
BeanInfo beanInfo = Introspector.getBeanInfo(p1.getClass());
PropertyDescriptor[] pds = beanInfo.getPropertyDescriptors();
for(PropertyDescriptor pd : pds){
if(pd.getName().equals(propertyName)){
Method methodGetProperty = pd.getReadMethod();
return methodGetProperty.invoke(p1);
}
}
return null;
}
