【Autofac打标签模式】Aspect拦截器

【 Autofac打标签模式】开源DI框架扩展地址：

https://github.com/yuzd/Autofac.Annotation/wiki

前提条件

自己new一个对象不能实现拦截器功能，必须得从DI容器拿到的对象才能具备拦截器功能 可以参考 我写的文章介绍

拦截器原理简单介绍

用了Castle.Core组件 把你想要实现拦截器的目标类生成一个代理类。 然后织入拦截器，有2种方式

1. class + 方法为virtual的方式
   • 这种方式需要 从容器中是根据一个classType来获取到目标实例
2. interface + 方法重写的方式
   • 这种方式需要 从容器中是根据一个interfaceType来获取到目标实例

拦截器开关

在你想要实现拦截的目标类上打上 【Aspect】标签，如上面的解释，Aspect标签可以根据InterceptorType属性值设定你是哪种方式的拦截器

目的是打个标签就能够拦截目标方法

使得我们自定义的方法能够

• 在指定的目标方法执行之前先执行(比如参数校验)
• 或者在指定的目标方法执行之后执行(比如说检验返回值，或其他收尾工作)
• 或者环绕目标的方法，比如事务：TransactionScope或者记录方法执行的时间

拦截器的方法参数 AspectContext 属性说明

Exception说明

前置拦截器若抛了没有被catch住的异常

• 如果有后置拦截器，可以在AspectContext的Exception字段获取。
• 如果没有后置拦截器则抛出

前置拦截器

1. 首先要自己写一个类继承 前置拦截器AspectBeforeAttribute(抽象标签类)
2. 实现该抽象类的Before方法

1. 然后在被拦截方法的所在类上打上 【Aspect】标签;

2. 被拦截方法上打上 【TestHelloBefor】标签

3. 被拦截方法需要有 virtual 关键字

前置拦截器方法的执行顺序为：先执行 TestHelloBefor的Before方法再执行你的Say方法

后置拦截器

1. 首先要自己写一个类继承后置拦截器AspectAfterAttribute(抽象标签类)
2. 实现该抽象类的After方法

1. 然后在被拦截方法的所在类上打上 【Aspect】标签;

2. 被拦截方法上打上 【TestHelloAfter】标签

3. 被拦截方法需要有 virtual 关键字

后置拦截器方法的执行顺序为：先执行你的SayAfter方法再执行 TestHelloAfter的After方法

前置+后置拦截器

1. 首先要自己写一个类继承拦截器AspectAroundAttribute(抽象标签类)
2. 实现该抽象类的Before 和 After方法

1. 然后在被拦截方法的所在类上打上 【Aspect】标签;

2. 被拦截方法上打上 【TestHelloArround】标签

3. 被拦截方法需要有 virtual 关键字

方法的执行顺序为：

1. 先执行TestHelloArround的Before方法
2. 然后执行你的SayArround方法
3. 再执行 先执行TestHelloArround的After方法

环绕拦截器的前置+后置的另外一种方式(更灵活)

注意：OnInvocation方法除了AspectContext参数以外 还有一个 AspectDelegate _next 参数， 如果只有一个环绕拦截器的话，那么这个参数就是被拦截方法的本体， 如果有多个环绕拦截器的话，那么最后一个就是被拦截方法的本体。

1. 首先要自己写一个类继承拦截器PointcutAttribute(抽象标签类)
2. 实现该抽象类的OnInvocation方法

1. 然后在被拦截方法的所在类上打上 【Aspect】标签;

2. 被拦截方法上打上 【TransactionInterceptor】标签

3. 被拦截方法需要有 virtual 关键字

方法的执行顺序为：

1. 先执行TransactionInterceptor的OnInvocation方法
2. 然后TransactionInterceptor的OnInvocation方法里面执行的 await _next(aspectContext); 就会执行被拦截方法TestInterceptor；

如果有多个环绕拦截器的话，如下图：

如上图 代码的执行顺序为：

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@media print {
body {
overflow: visible !important;
}
.markdown-body table {
overflow: visible !important;
}
.ui-layout-north,
.ui-layout-center,
.ui-layout-toggler {
display: none !important;
}
.ui-layout-east {
left: 0 !important;
top: 0 !important;
right: 0 !important;
width: auto !important;
background: white !important;
overflow: visible !important;
}
.ui-layout-east .ui-layout-toggler {
display: none !important;
}
.ui-layout-east .markdown-body {
display: block !important;
padding: 20px !important;
}
.ui-layout-east .markdown-body [data-source-line] {
break-inside: avoid;
}
.markdown-body pre > code {
word-break: normal;
word-wrap: break-word;
white-space: pre-wrap;
}
}
body {
margin: 0;
padding: 0;
}
.ui-layout-east {
position: relative;
}
.markdown-body {
min-width: 256px;
max-width: 978px;
margin: 0 auto;
padding: 20px;
font-size: 14px;
tab-size: 4;
font-family: "-apple-system", BlinkMacSystemFont, "\5FAE\8F6F\96C5\9ED1", "PingFang SC", Helvetica, Arial, "Hiragino Sans GB", "Microsoft YaHei", SimSun, "\5B8B\4F53", Heiti, "\9ED1\4F53", sans-serif;
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}
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font-family: ‘Microsoft YaHei‘, ‘\5FAE\8F6F\96C5\9ED1‘, SimSun, sans-serif;
}
.markdown-body img:not([src]),
.markdown-body img[src=""] {
display: none;
}
div[data-role=mermaid] {
text-align: center;
}
hr.footnotes-sep {
margin: 64px 0 32px 0;
height: 1px;
}
.footnotes {
font-size: 90%;
padding-left: 16px;
}
li.footnote-item > p {
margin: 8px 0;
}
.success,
.info,
.warning,
.danger {
padding: 15px;
margin-bottom: 20px;
border: 1px solid transparent;
border-radius: 4px;
}
.success > p:last-child,
.info > p:last-child,
.warning > p:last-child,
.danger > p:last-child {
margin-bottom: 0;
}
.success {
color: #3c763d;
background-color: #dff0d8;
border-color: #d6e9c6;
}
.info {
color: #31708f;
background-color: #d9edf7;
border-color: #bce8f1;
}
.warning {
color: #8a6d3b;
background-color: #fcf8e3;
border-color: #faebcc;
}
.danger {
color: #a94442;
background-color: #f2dede;
border-color: #ebccd1;
}
abbr[title] {
cursor: help;
border-bottom: 1px dotted #777;
}
ul.table-of-contents {
list-style-type: none;
}
ul.table-of-contents li {
margin: 4px 0;
}
.markdown-body table {
width: auto;
display: table;
}
.markdown-body table td {
word-break: break-all;
}
.markdown-body.ace_search .highlight pre,
.markdown-body.ace_search pre {
overflow: visible !important;
width: -webkit-fit-content !important;
width: fit-content !important;
}
-->

原文地址：https://www.cnblogs.com/yudongdong/p/11747235.html