这个技术就是用在这么一种情况下。比如我一个接口,有N个实现,但是我有个需求,我需要遍历所有的实现类。怎么办?
这就需要介绍下自己讲过的Instance接口了。这个可以泛型的接口本身是继承了Iterable接口的。所以说可以for each循环啊。\
比如这个接口
package com.srchy.cdilookup; public interface HelloInterface { public String say(); }小写字母的实现
package com.srchy.cdilookup;
import java.io.Serializable;
import javax.enterprise.context.RequestScoped;
@RequestScoped
public class LowerHelloBean implements Serializable,HelloInterface{
private static final long serialVersionUID = 1L;
public String say(){
return "hello world!";
}
}
大写字母的实现
package com.srchy.cdilookup; import java.io.Serializable; import javax.enterprise.context.RequestScoped; @RequestScoped public class UpperHelloBean implements Serializable,HelloInterface{ private static final long serialVersionUID = 1L; public String say(){ return "HELLO WORLD!"; } }
然后在servlet中用代码遍历实现:
package com.srchy.cdilookup; import java.io.IOException; import javax.enterprise.inject.Instance; import javax.inject.Inject; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; @WebServlet("/hello.html") public class HelloServlet extends HttpServlet { private static final long serialVersionUID = 1L; @Inject private Instance<HelloInterface> bean; @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { for(HelloInterface hi:bean){ resp.getWriter().append(hi.say()); } } }运行结果: