Servlet使用 - 技术栈

文章目录

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

简介

一、快速入门

xml 复制代码

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

java 复制代码

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 {
    @Override
    public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
        System.out.println("Hello World");
    }

    @Override
    public void init(ServletConfig config) throws ServletException {

    }

    @Override
    public ServletConfig getServletConfig() {
        return null;
    }

    protected void doPost(ServletRequest req, ServletResponse res) {
    }

    protected void doGet(ServletRequest req, ServletResponse res) {
    }

    @Override
    public String getServletInfo() {
        return null;
    }

    @Override
    public void destroy() {

    }
}

二、Servlet 执行流程

三、Servlet 生命周期

java 复制代码

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

    @Override
    public String getServletInfo() {
        return null;
    }

    @Override
    public ServletConfig getServletConfig() {
        return null;
    }
}

四、Servlet 方法介绍

java 复制代码

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
     */
    @Override
    public void init(ServletConfig config) throws ServletException {
        this.config = config;
        System.out.println("init...");
    }
    @Override
    public 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
     */
    @Override
    public 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
     */
    @Override
    public void destroy() {
        System.out.println("destroy...");
    }

    @Override
    public String getServletInfo() {
        return "";
    }


}

五、Servlet 体系结构

java 复制代码

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 {

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

    @Override
    protected 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

html 复制代码

<!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>

java 复制代码

package com.itheima.web;

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;

public class MyHttpServlet implements Servlet {
    @Override
    public 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);
        }
    }

    @Override
    public void init(ServletConfig config) throws ServletException {

    }

    @Override
    public ServletConfig getServletConfig() {
        return null;
    }

    protected void doPost(ServletRequest req, ServletResponse res) {
    }

    protected void doGet(ServletRequest req, ServletResponse res) {
    }

    @Override
    public String getServletInfo() {
        return null;
    }

    @Override
    public void destroy() {

    }
}

继承HttpServlet

java 复制代码

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 {

    @Override
    protected void doGet(ServletRequest req, ServletResponse res) {
        System.out.println("get。。。。");
    }

    @Override
    protected void doPost(ServletRequest req, ServletResponse res) {
        System.out.println("post。。。。");
    }
}

六、Servlet urlPattern配置

七、XML 配置方式编写 Servlet

xml 复制代码

<?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>