javaee-----servlet生命周期（五）

servlet调用流程

1. 加载和实例化
2. 初始化
3. 处理请求
4. 终止服务

package servlet;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 1. @author lihuaqing
 2. @create 2019-01-29 22:43
 **/
@WebServlet("/lifecycle")
public class LifeServlet extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
        System.out.println("doPost....");
    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doGet(req, resp);
        System.out.println("doGet....");
    }

    public LifeServlet() {
        super();
        System.out.println("LifeServlet....");
    }

    @Override
    public void init() throws ServletException {
        super.init();
        System.out.println("init....");
    }

    @Override
    public void destroy() {
        super.destroy();
        System.out.println("destroy....");
    }

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.service(req, resp);
        System.out.println("service....");
    }
}

连续调用两次结果

loadOnStartup控制启动顺序

@WebServlet(urlPatterns = "/lifecycletwo",loadOnStartup = 2)

@WebServlet(urlPatterns = "/lifecycle",loadOnStartup = 1)

加载顺序结果

总结

1. servlet 是单例模式
2. loadOnStartup 当为负数时，不随容器启动而加载
3. loadOnStartup 当为0或者正数时，随容器启动而加载
4. loadOnStartup 值越小，优先级越高
5. loadOnStartup 默认值为-1