AOP的作用:把通用处理逻辑提炼到一个单独的地方,其它地方需要调用,添加这个"特性"即可,不需要再次进行编写,比如AOP的过滤、异常处理、权限控制等
一、自定义Attribute
1、项目结构
2、UserModelFiledAttribute代码实例,此类是定义特性
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Property, Inherited = true)]
public class UserModelLengthAttribute : Attribute
{
private int maxLength;
public UserModelLengthAttribute(int maxLength)
{
this.maxLength = maxLength;
}
public int MaxLength { get => maxLength; set => maxLength = value; }
}
3、AopHandler类用于实现特性需要处理的逻辑,如本实例验证了字段最大长度,需要引入:using System.Reflection;
public void ValidateLength(object obj)
{
Type tType = obj.GetType();
var properties = tType.GetProperties();
foreach (var item in properties)
{
if (!item.IsDefined(typeof(UserModelLengthAttribute), false)) continue;
var attributes = item.GetCustomAttributes();
foreach (var attributeItem in attributes)
{
//获取特性的属性值(MaxLength为UserModelFiledAttribute定义的参数)
var maxLen = (int)attributeItem.GetType().GetProperty("MaxLength").GetValue(attributeItem);
//获取字段属性值
var value = item.GetValue(obj) as string;
if (string.IsNullOrEmpty(value))
{
Console.WriteLine(item.Name + "的值为null");
}
else
{
if (value.Length > maxLen)
{
Console.WriteLine(item.Name + "的值的长度为" + value.Length + ",超出了范围");
}
}
}
}
}
4、UserModel
public class UserModel
{
public string UserName { get; set; }
[UserModelLength(10)]//引用特性
public string UserPassword { get; set; }
[UserModelFiled(true)]//引用特性
public string UserSex { get; set; }
public int Age { get; set; }
}
5、使用方式:
var userModel = new UserModel() { UserName = "test", UserPassword = "yxj2222345234234234" };
new AopHandler().ValidateLength(userModel);//调用此函数进行特性效验后执行功能代码
二、使用扩展Attribute
第一种方式有些繁琐,因此可以通过vs自带的特性进行扩展,此实例是通过MVC验证一个登陆功能,通过Login登陆后跳转至Index页面,Index页面调用特性去效验是否登录
1、Login控制器代码
1、Validate特性类
贴代码:
public class LoginAttribute : ActionFilterAttribute, IResultFilter
{
public override void OnActionExecuting(ActionExecutingContext actionExecutingContext)
{
if (HttpContext.Current.Request.Cookies["token"]["userid"] == null)
{
actionExecutingContext.HttpContext.Response.Write("<script>window.parent.location.href='http://localhost:59087/User/Login'</script>");
}
base.OnActionExecuting(actionExecutingContext);
}
}
3、Index调用特性
[Login]
public ActionResult Index()
{
return View();
}
参考博客:https://www.cnblogs.com/ldyblogs/p/attribute.html