Servlet使用

文章目录

简介
一、快速入门
二、Servlet 执行流程
三、Servlet 生命周期
四、Servlet 方法介绍
五、Servlet 体系结构
六、Servlet urlPattern配置
七、XML 配置方式编写 Servlet

简介

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一、快速入门

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 <dependencies><dependency><groupId>javax.servlet</groupId><artifactId>javax.servlet-api</artifactId><version>3.1.0</version><scope>provided</scope></dependency></dependencies>

package com.itheima.web;import javax.jws.WebService;
import javax.servlet.*;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;@WebServlet("/demo1")
public class MyHttpServlet implements Servlet {@Overridepublic void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {System.out.println("Hello World");}@Overridepublic void init(ServletConfig config) throws ServletException {}@Overridepublic ServletConfig getServletConfig() {return null;}protected void doPost(ServletRequest req, ServletResponse res) {}protected void doGet(ServletRequest req, ServletResponse res) {}@Overridepublic String getServletInfo() {return null;}@Overridepublic void destroy() {}
}

二、Servlet 执行流程

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三、Servlet 生命周期

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package com.itheima.web;import javax.servlet.*;
import javax.servlet.annotation.WebServlet;
import java.io.IOException;/*** Servlet 生命周期方法*/
@WebServlet(urlPatterns="/demo2",loadOnStartup = 1)
public class ServletDemo2 implements Servlet {/*** 初始化方法* 1. 调用时机：默认情况下，Servlet被第一次访问时，调用*      * loadOnStartup:* 2. 调用次数：1次* @param config* @throws ServletException*/@Overridepublic void init(ServletConfig config) throws ServletException {System.out.println("init...");}/*** 提供服务* 1. 调用时机：每一次Servlet被访问时，调用* 2. 调用次数：多次*** @param req* @param res* @throws ServletException* @throws IOException*/@Overridepublic void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {System.out.println("servlet hello world~");}/*** 销毁方法* 1. 调用时机：内存释放或者服务器关闭的时候，Servlet对象会被销毁，调用* 2. 调用次数：1次*/@Overridepublic void destroy() {System.out.println("destroy...");}@Overridepublic String getServletInfo() {return null;}@Overridepublic ServletConfig getServletConfig() {return null;}
}

四、Servlet 方法介绍

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package com.itheima.web;import javax.servlet.*;
import javax.servlet.annotation.WebServlet;
import java.io.IOException;/*** Servlet 方法介绍*/
@WebServlet(urlPatterns="/demo3",loadOnStartup = 1)
public class ServletDemo3 implements Servlet {private ServletConfig config;/*** 初始化方法* 1. 调用时机：默认情况下，Servlet被第一次访问时，调用*      * loadOnStartup:* 2. 调用次数：1次* @param config* @throws ServletException*/@Overridepublic void init(ServletConfig config) throws ServletException {this.config = config;System.out.println("init...");}@Overridepublic ServletConfig getServletConfig() {return config;}/*** 提供服务* 1. 调用时机：每一次Servlet被访问时，调用* 2. 调用次数：多次*** @param req* @param res* @throws ServletException* @throws IOException*/@Overridepublic void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {System.out.println("servlet hello world~");}/*** 销毁方法* 1. 调用时机：内存释放或者服务器关闭的时候，Servlet对象会被销毁，调用* 2. 调用次数：1次*/@Overridepublic void destroy() {System.out.println("destroy...");}@Overridepublic String getServletInfo() {return "";}}

五、Servlet 体系结构

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package com.itheima.web;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;@WebServlet("/demo4")
public class ServletDemo4 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {System.out.println("get...");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {System.out.println("post...");}
}

要调用dopost方法时，要在webapp中写一个html，方便查看

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>Title</title>
</head>
<body><form action="/web-demo/demo5" method="post"><input name="username"><input type="submit">
</form>
</body>
</html>

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package com.itheima.web;import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;public class MyHttpServlet implements Servlet {@Overridepublic void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {// 根据请求方式的不同，进行分别的处理HttpServletRequest request = (HttpServletRequest) req;//1. 获取请求方式String method = request.getMethod();//2. 判断if("GET".equals(method)){// get方式的处理逻辑doGet(req,res);}else if("POST".equals(method)){// post方式的处理逻辑doPost(req,res);}}@Overridepublic void init(ServletConfig config) throws ServletException {}@Overridepublic ServletConfig getServletConfig() {return null;}protected void doPost(ServletRequest req, ServletResponse res) {}protected void doGet(ServletRequest req, ServletResponse res) {}@Overridepublic String getServletInfo() {return null;}@Overridepublic void destroy() {}
}

继承HttpServlet

package com.itheima.web;import javax.servlet.*;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;@WebServlet("/demo5")
public class ServletDemo5 extends MyHttpServlet {@Overrideprotected void doGet(ServletRequest req, ServletResponse res) {System.out.println("get。。。。");}@Overrideprotected void doPost(ServletRequest req, ServletResponse res) {System.out.println("post。。。。");}
}

六、Servlet urlPattern配置

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七、XML 配置方式编写 Servlet

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<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"version="4.0"><!--Servlet 全类名--><servlet><servlet-name>demo13</servlet-name><servlet-class>com.itheima.web.ServletDemo13</servlet-class></servlet><!--Servlet 访问路径--><servlet-mapping><servlet-name>demo13</servlet-name><url-pattern>/demo13</url-pattern></servlet-mapping>
</web-app>