Question

当我读到有关servlet生命周期的书时，它说它首先调用服务方法，然后服务方法调用另一个方法来处理特定的HTTP请求（GET或POST）。但是当我尝试这个时，我发现在调用服务方法之前首先调用doGet或doPost方法。我的代码和结果如下，很多！

public class Main extends HttpServlet {

    @Override
    public void init() throws ServletException {
        // TODO Auto-generated method stub
        super.init();
        System.out.println("init has been called");
    }

    @Override
    protected void service(HttpServletRequest arg0, HttpServletResponse arg1)
            throws ServletException, IOException {
        // TODO Auto-generated method stub
        super.service(arg0, arg1);
        System.out.println("service has been called");
    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        // TODO Auto-generated method stub
        System.out.println("get has been called");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        // TODO Auto-generated method stub
        System.out.println("post has been called");
    }
}

结果：

init has been called

get has been called

service has been called

post has been called

service has been called

Answer 1

你的书是对的。在您覆盖的service()方法中，您在super.service()电话之前呼叫System.out.println();正在从超类doPost()的{{1}}方法调用doGet()和service()。尝试在调用HttpServlet之前输出输出行，你会看到。

如果您从方法中移除super.service()，则根本不会调用super.service()或doPost();这就是为什么覆盖doGet()通常不是一个好主意，除非你知道你在做什么，并且有充分的理由这样做。

servlet的生命周期：对service（）和doGet（）的调用是相反的

1 个答案: