我正在学习Java EE 6教程,试图理解无状态(stateless)和有状态(stateful)会话Bean之间的区别。如果无状态会话Bean在方法调用之间不保留它们的状态,为什么我的程序会表现出这样的行为?
package mybeans;
import javax.ejb.LocalBean;
import javax.ejb.Stateless;
@LocalBean
@Stateless
public class MyBean {
private int number = 0;
public int getNumber() {
return number;
}
public void increment() {
this.number++;
}
}
客户端
import java.io.IOException;
import javax.ejb.EJB;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.WebServlet;
import mybeans.MyBean;
import java.io.PrintWriter;
@WebServlet(name = "ServletClient", urlPatterns = { "/ServletClient" })
public class ServletClient extends HttpServlet {
private static final long serialVersionUID = 1L;
@EJB
MyBean mybean;
protected void doGet(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
PrintWriter out = response.getWriter();
mybean.increment();
out.println(mybean.getNumber());
}
}
我本以为每次调用getNumber方法都会返回0,但实际上它返回1,并且在浏览器中重新加载servlet会使其增加更多。问题出在我的理解无状态会话bean的工作方式上,而不是库或应用服务器上,当然了。有人能给我一个简单的“hello world”类型的无状态会话bean示例,在将其更改为有状态时行为不同吗?