动态加载及Servlet容器加载

动态加载

package app14a.servlet;

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

public class FirstServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    private String name;
    
    public void setName(String name) {
        this.name = name;
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html");
        PrintWriter writer = response.getWriter();
        writer.println("<html>");
        writer.println("<head>");
        writer.println("<title>First Servlet</title>");
        writer.println("</head>");
        writer.println("<body>");
        writer.println(name);
        writer.println("</body>");
        writer.println("</html>");
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

package app14a.listener;

import javax.servlet.Servlet;
import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.ServletRegistration;
import javax.servlet.annotation.WebListener;

import app14a.servlet.FirstServlet;

@WebListener
public class DynRegListener implements ServletContextListener {

    @Override
    public void contextInitialized(ServletContextEvent sce) {
        ServletContext servletContext = sce.getServletContext();
        Servlet firstServlet = null;
        try {
            firstServlet = servletContext.createServlet(FirstServlet.class);
        } catch (Exception e) {
            e.printStackTrace();
        }
        if (firstServlet != null && firstServlet instanceof FirstServlet) {
            ((FirstServlet) firstServlet).setName("Dynamically registered servlet");
        }
        ServletRegistration.Dynamic dynamic = servletContext.addServlet("firstServlet", firstServlet);
        dynamic.addMapping("/dynamic");
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
    }

}

Servlet容器加载

package app14a.initializer;

import java.util.Set;
import javax.servlet.ServletContainerInitializer;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRegistration;
import javax.servlet.annotation.HandlesTypes;

@HandlesTypes({UsefulServlet.class})
public class MyServletContainerInitializer implements ServletContainerInitializer {

    @Override
    public void onStartup(Set<Class<?>> classes, ServletContext servletContext) throws ServletException {
        System.out.println("onStartup");
        ServletRegistration registration = servletContext.addServlet("usefulServlet", "servlet.usefulServlet");
        registration.addMapping("/usefull");
        System.out.println("leaving onStartup");
    }
}

package app14a.initializer;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class UsefulServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html");
        PrintWriter writer = response.getWriter();
        writer.println("<html>");
        writer.println("<head>");
        writer.println("<title>First Servlet</title>");
        writer.println("</head>");
        writer.println("<body>");
        writer.println("This is from UsefulServlet");
        writer.println("</body>");
        writer.println("</html>");
    }

}

app14a.initializer.MyServletContainerInitializer

动态加载及Servlet容器加载

动态加载

Servlet容器加载

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