JAVA-EE解析Tomcat服务器解析servlet上注解的原理------计算机网络经典

素颜马尾好姑娘i 2024-02-22 07:09 42阅读 0赞

> package com.powernode.javaweb.Reflect;
> 
> import jakarta.servlet.annotation.WebServlet;
> 
> public class ReflectAnnotation
> {
> public static void main(String[] args) throws Exception
> {
> //使用反射机制对类上面的注解进行解析
> Class<?> helloServletClass = Class.forName("com.powernode.javaweb.servlet.HelloServlet");
> boolean flag = helloServletClass.isAnnotationPresent(WebServlet.class);
> WebServlet annotation = helloServletClass.getAnnotation(WebServlet.class);
> String[] value = annotation.value();
> for (int i = 0; i < value.length; i++) {
> System.out.println(value[i]);
> }
> }
> }
> 
> package com.powernode.javaweb.Reflect;
> 
> import jakarta.servlet.annotation.WebServlet;
> 
> public class ReflectAnnotation
> {
> public static void main(String[] args) throws Exception
> {
> //使用反射机制对类上面的注解进行解析
> Class<?> helloServletClass = Class.forName("com.powernode.javaweb.servlet.HelloServlet");
> boolean flag = helloServletClass.isAnnotationPresent(WebServlet.class);
> WebServlet annotation = helloServletClass.getAnnotation(WebServlet.class);
> String[] value = annotation.value();
> for (int i = 0; i < value.length; i++) {
> System.out.println(value[i]);
> }
> }
> }

> package com.powernode.javaweb.servlet;
> 
> import jakarta.servlet.Servlet;
> import jakarta.servlet.ServletException;
> import jakarta.servlet.annotation.WebInitParam;
> import jakarta.servlet.annotation.WebServlet;
> import jakarta.servlet.http.HttpServlet;
> import jakarta.servlet.http.HttpServletRequest;
> import jakarta.servlet.http.HttpServletResponse;
> 
> import java.io.IOException;
> import java.io.PrintWriter;
> import java.util.Enumeration;
> 
> //loadOnStartup启动时创建对象<loadOnStartup = 1>
> @WebServlet(name = "Hello",value = {"/Hello1","/Hello2"},urlPatterns = {"/Hello1","/Hello2"},loadOnStartup = 1,
> initParams = {@WebInitParam(name = "user",value = "root"),@WebInitParam(name = "password",value = "abc123"),
> @WebInitParam(name = "driver",value = "com.mysql.jdbc.Driver")})
> public class HelloServlet extends HttpServlet
> {
> public HelloServlet() {
> System.out.println("Hello启动!");
> }
> 
> @Override
> protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
> {
> //获取Servlet名字
> String servletName = getServletName();
> response.setContentType("text/html;charset=UTF-8");
> PrintWriter out = response.getWriter();
> out.println(servletName);
> out.println(" ");
> out.println(request.getServletPath());
> Enumeration<String> names = getInitParameterNames();
> out.println(" ");
> while(names.hasMoreElements())
> {
> String name = names.nextElement();
> String value = getInitParameter(name);
> out.println(name + ":" + value);
> out.println(" ");
> }
> }
> }
> 
> package com.powernode.javaweb.servlet;
> 
> import jakarta.servlet.Servlet;
> import jakarta.servlet.ServletException;
> import jakarta.servlet.annotation.WebInitParam;
> import jakarta.servlet.annotation.WebServlet;
> import jakarta.servlet.http.HttpServlet;
> import jakarta.servlet.http.HttpServletRequest;
> import jakarta.servlet.http.HttpServletResponse;
> 
> import java.io.IOException;
> import java.io.PrintWriter;
> import java.util.Enumeration;
> 
> //loadOnStartup启动时创建对象<loadOnStartup = 1>
> @WebServlet(name = "Hello",value = {"/Hello1","/Hello2"},urlPatterns = {"/Hello1","/Hello2"},loadOnStartup = 1,
> initParams = {@WebInitParam(name = "user",value = "root"),@WebInitParam(name = "password",value = "abc123"),
> @WebInitParam(name = "driver",value = "com.mysql.jdbc.Driver")})
> public class HelloServlet extends HttpServlet
> {
> public HelloServlet() {
> System.out.println("Hello启动!");
> }
> 
> @Override
> protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
> {
> //获取Servlet名字
> String servletName = getServletName();
> response.setContentType("text/html;charset=UTF-8");
> PrintWriter out = response.getWriter();
> out.println(servletName);
> out.println(" ");
> out.println(request.getServletPath());
> Enumeration<String> names = getInitParameterNames();
> out.println(" ");
> while(names.hasMoreElements())
> {
> String name = names.nextElement();
> String value = getInitParameter(name);
> out.println(name + ":" + value);
> out.println(" ");
> }
> }
> }