Spring之关于PropertyDescriptor的扩展剖析

 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());
       }
    }
}

org.springframework.beans.ExtendedBeanInfo#isCandidateWriteMethod

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]);

**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]);
    }