拦截器在Servlet的方法级别上不起作用 [英] Interceptor not working at method level in a Servlet
问题描述
我有一个具有以下结构的简单Web应用程序Maven项目:
I have a simple web-app maven project with the following structure:
SimpleServlet.java 是具有以下代码的servlet:
SimpleServlet.java is a servlet with the following code:
@Logger
public class SimpleServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
@Override
public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
resp.getWriter().write("hello");
}
}
Logger 类是具有以下代码的拦截器接口:
And the Logger class is an interceptor interface with the following code:
@InterceptorBinding
@Retention(RUNTIME)
@Target({ METHOD, TYPE })
public @interface Logger {}
MyLogger 类是具有以下代码的拦截器实现:
And the MyLogger class is an interceptor implementation with the following code:
@Interceptor
@Logger
public class MyLogger {
@AroundInvoke
public Object veQuePedo(InvocationContext ctx) throws Exception {
System.out.println("Logged");
return ctx.proceed();
}
}
我的 web.xml :
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
version="3.0">
<display-name>Archetype Created Web Application</display-name>
<servlet>
<servlet-name>ThaServlet</servlet-name>
<servlet-class>com.SimpleServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>ThaServlet</servlet-name>
<url-pattern>/hola</url-pattern>
</servlet-mapping>
</web-app>
还有我的 beans.xml :
<?xml version="1.0" encoding="UTF-8"?>
<beans
xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
http://xmlns.jcp.org/xml/ns/javaee/beans_1_1.xsd"
version="1.1"
bean-discovery-mode="all">
<interceptors>
<class>com.MyLogger</class>
</interceptors>
</beans>
这种情况是，我读取了一个拦截器，该拦截器仅适用于 CDI bean ，我测试并发现它是正确的.
The case is that I read an interceptor only works on CDI beans, which I tested and noticed is correct.
在此示例中，我们谈论的是servlet，因此我向您提出以下问题:
For this example we are talking about a servlet, so I come to you with the following questions:
1)如果我的servlet(示例中的servlet)不被视为CDI bean，为什么在我设置 @Logger 拦截器时起作用?
1) If the my servlet (the one in my example) is not considered a CDI bean, why when I set the @Logger interceptor works?
2)为什么我的servlet中的拦截器 @Logger 在方法级别不起作用，而在类级别却可以正常工作?
2) Why the interceptor @Logger in my servlet does not work at method level and does work fine at class level?
在方法级别使用注释进行调试，我看到servlet被包装了，但是由于某种原因，@ AroundInvoke方法被忽略了.
Debugging with the annotation at method level I see the servlet is wrapped, but for some reason the @AroundInvoke method is ignored.
推荐答案
CDI提供的服务(例如侦听)通常仅在业务方法调用上发生.
Services provided by CDI, like interception, generally only happen on business method invocations.
从本质上讲，这些是通过上下文引用(注入的Bean或在像Servlets一样被视为Bean的组件上对方法的容器调用)对方法的调用.
Essentially, these are invocations of a method through a contextual reference (an injected bean, or the containers invocation of methods on components that are treated as beans like Servlets).
在您的情况下，从bean外部调用到bean内部的方法不是doGet()－这是其他继承的方法.对doGet()的调用来自Bean本身，无法被拦截.
In your case, the method called from "outside" the bean to "inside" the bean is not doGet() -- it's some other inherited method. The call to doGet() comes from within the bean itself and cannot be intercepted.
这就是为什么您在类级别的拦截似乎被拦截了一次的原因，尽管它不在doGet()上，您稍后尝试直接对其进行注释.
That's why your interception at the class level seems to be intercepted once, although it's not on the doGet() that you later try to annotate directly.
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