java propertydescriptor_Spring Integration

  jdk中Introspector类为工具提供了一种标准的方法来了解目标Java Bean支持的属性、事件和方法。
java.beans.Introspector#getTargetPropertyInfo
private PropertyDescriptor[] getTargetPropertyInfo() {
// Apply some reflection to the current class.
// First get an array of all the public methods at this level
Method methodList[] = getPublicDeclaredMethods(beanClass);
// Now analyze each method.
//遍历所有方法看是否是符合PropertyDescriptor
for (int i = 0; i < methodList.length; i++) {
Method method = methodList[i];
if (method == null) {
continue;
}
// skip static methods.
int mods = method.getModifiers();
if (Modifier.isStatic(mods)) {
continue;
}
String name = method.getName();
Class<?>[] argTypes = method.getParameterTypes();
Class<?> resultType = method.getReturnType();
int argCount = argTypes.length;
PropertyDescriptor pd = null;
if (name.length() <= 3 && !name.startsWith(IS_PREFIX)) {
// Optimization. Don't bother with invalid propertyNames.
continue;
}
try {
if (argCount == 0) {
/**
* 方法没有参数：方法有readMethod没有writeMehtod
*    1、普通get开头方法
*    2、返回值boolean 以is开头的
*/
if (name.startsWith(GET_PREFIX)) {
// Simple getter
pd = new PropertyDescriptor(this.beanClass, name.substring(3), method, null);
} else if (resultType == boolean.class && name.startsWith(IS_PREFIX)) {
// Boolean getter
pd = new PropertyDescriptor(this.beanClass, name.substring(2), method, null);
}
} else if (argCount == 1) {
/**
* 有一个参数
* 1、有一个参数且int类型，方法get开头的，没有readMethod  writeMehtod等属性
* 2、没有返回值、set方法开头的,具有writeMethod
*/
if (int.class.equals(argTypes[0]) && name.startsWith(GET_PREFIX)) {
pd = new IndexedPropertyDescriptor(this.beanClass, name.substring(3), null, null, method, null);
} else if (void.class.equals(resultType) && name.startsWith(SET_PREFIX)) {
// Simple setter
pd = new PropertyDescriptor(this.beanClass, name.substring(3), null, method);
if (throwsException(method, PropertyVetoException.class)) {
pd.setConstrained(true);
}
}
} else if (argCount == 2) {
/**
* 两个参数
* 1、返回值void ,第一个参数int类型，set开头的会生成PropertyDescriptor（注意此时没有writeMethod）
*/
if (void.class.equals(resultType) && int.class.equals(argTypes[0]) && name.startsWith(SET_PREFIX)) {
pd = new IndexedPropertyDescriptor(this.beanClass, name.substring(3), null, null, null, method);
if (throwsException(method, PropertyVetoException.class)) {
pd.setConstrained(true);
}
}
}
} catch (IntrospectionException ex) {
pd = null;
}
if (pd != null) {
if (propertyChangeSource) {
pd.setBound(true);
}
addPropertyDescriptor(pd);
}
}
processPropertyDescriptors();
}

//@Component
public class UserService { 

private  OrderService  orderService;
//返回值不为void
public  OrderService  setOrderService(OrderService orderService){ 

//this.orderService=orderService;
return orderService;
}
//返回值不为void
public  OrderService  setOrderService(int  test,OrderService orderService){ 

this.orderService=orderService;
return orderService;
}
//返回值void 一个参数满足要求
public  void  setService12123(OrderService orderService1){ 

System.out.println("1231"+orderService);
}
//返回值void 参数个数大于2不满足
public  void  setOrderService(int  test,OrderService orderService,StockService stockService){ 

this.orderService=orderService;
}
}
public class Test { 

public static void main(String[] args) throws IntrospectionException { 

BeanInfo beanInfo= Introspector.getBeanInfo(UserService.class);
PropertyDescriptor[] propertyDescriptors = beanInfo.getPropertyDescriptors();
for(PropertyDescriptor propertyDescriptor:propertyDescriptors){ 

System.out.println(propertyDescriptor.getWriteMethod());
}
}
}

此时满足条件方法有getClass（继承父类的Object） 、setService12123会生成PropertyDescriptor且具有写方法

 **满足以下条件才会生成PropertyDescriptor
1、set开头方法
2、public方法
3、返回值不是void或者是静态
4、参数一个或者2个（2个实话第一个参数必须为int类型）**

     //1、set开头方法
2、public方法
3、返回值不是void或者是静态
4、参数一个或者2个（2个实话第一个参数必须为int类型）
public static boolean isCandidateWriteMethod(Method method) { 

String methodName = method.getName();
int nParams = method.getParameterCount();
return methodName.length() > 3 && methodName.startsWith("set") && Modifier.isPublic(method.getModifiers()) && (!Void.TYPE.isAssignableFrom(method.getReturnType()) || Modifier.isStatic(method.getModifiers())) && (nParams == 1 || nParams == 2 && Integer.TYPE == method.getParameterTypes()[0]);
}