jsp程序设计（三）－初试jsp程序设计（2）－Servlet简介

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一、什么是Servlet

Servlet 是一个用 Java 编写的程序，此程序在服务器上运行以处理客户端请求。

二、接口和类

1、javax.servlet 包中的接口

2、javax.servlet 包中的类

ServletInputStream 类用于从客户端读取二进制数据；

ServletOutputStream 类用于将二进制数据发送到客户端；

HttpServletResponse 接口提供 HTTP 响应；

三、Servlet 的生命周期

Servlet 的生命周期就是指创建 Servlet 实例之后其存在的时间以及何时消失；

1、生命周期的 3个方法为：

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<stroke endarrow="block"></stroke><stroke endarrow="block"></stroke>

2、生命周期的各个阶段为：

实例化 Servlet 容器创建 Servlet 的实例

初始化该容器调用 init() 方法

服务如果请求 Servlet，则容器调用 service() 方法

销毁销毁实例之前调用 destroy() 方法

不可用销毁实例并标记为垃圾收集

四、HTTP Servlet 基础知识：

public void doGet(HttpServletRequest req,HttpServletResponse res) public void doPost(HttpServletRequest req,HttpServletResponse res)

doGet() 方法处理客户端作出的 GET 请求。doPost() 方法处理客户端作出的 POST 请求。

五、Servlet 的部署

web.xml文件中配置Servlet：

<fill type="gradient" focus="100%"></fill><lock grouping="t" v:ext="edit"></lock><textbox><table cellspacing="0" cellpadding="0" width="100%"><tbody><tr> <td style="BORDER-RIGHT: #ece9d8; BORDER-TOP: #ece9d8; BORDER-LEFT: #ece9d8; BORDER-BOTTOM: #ece9d8; BACKGROUND-COLOR: transparent"> <div> <p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt 27pt; TEXT-INDENT: -27pt; mso-layout-grid-align: none"><span lang="EN-US" style="FONT-SIZE: 12pt; COLOR: black; FONT-FAMILY: Arial; mso-bidi-font-size: 19.0pt; mso-fareast-font-family: 'Times New Roman'; mso-bidi-font-family: 'Times New Roman'"><span style="mso-spacerun: yes"> </span><servlet><p></p></span></p> <p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt 27pt; TEXT-INDENT: -27pt; mso-layout-grid-align: none"><span lang="EN-US" style="FONT-SIZE: 12pt; COLOR: black; FONT-FAMILY: Arial; mso-bidi-font-size: 19.0pt; mso-fareast-font-family: 'Times New Roman'; mso-bidi-font-family: 'Times New Roman'"><span style="mso-spacerun: yes"> </span><servlet-name>clientservlet</servlet-name><p></p></span></p> <p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt 27pt; TEXT-INDENT: -27pt; mso-layout-grid-align: none"><span lang="EN-US" style="FONT-SIZE: 12pt; COLOR: black; FONT-FAMILY: Arial; mso-bidi-font-size: 19.0pt; mso-fareast-font-family: 'Times New Roman'; mso-bidi-font-family: 'Times New Roman'"><span style="mso-spacerun: yes"> </span><servlet-class>chapter2.ClientServlet</servlet-class><p></p></span></p> <p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt 27pt; TEXT-INDENT: -27pt; mso-layout-grid-align: none"><span lang="EN-US" style="FONT-SIZE: 12pt; COLOR: black; FONT-FAMILY: Arial; mso-bidi-font-size: 19.0pt; mso-fareast-font-family: 'Times New Roman'; mso-bidi-font-family: 'Times New Roman'"><span style="mso-spacerun: yes"> </span></servlet><p></p></span></p> <p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt 27pt; TEXT-INDENT: -27pt; mso-layout-grid-align: none"><span lang="EN-US" style="FONT-SIZE: 12pt; COLOR: black; FONT-FAMILY: Arial; mso-bidi-font-size: 19.0pt; mso-fareast-font-family: 'Times New Roman'; mso-bidi-font-family: 'Times New Roman'"><span style="mso-spacerun: yes"> </span><servlet-mapping><p></p></span></p> <p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt 27pt; TEXT-INDENT: -27pt; mso-layout-grid-align: none"><span lang="EN-US" style="FONT-SIZE: 12pt; COLOR: black; FONT-FAMILY: Arial; mso-bidi-font-size: 19.0pt; mso-fareast-font-family: 'Times New Roman'; mso-bidi-font-family: 'Times New Roman'"><span style="mso-spacerun: yes"> </span><servlet-name>clientservlet</servlet-name><p></p></span></p> <p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt 27pt; TEXT-INDENT: -27pt; mso-layout-grid-align: none"><span lang="EN-US" style="FONT-SIZE: 12pt; COLOR: black; FONT-FAMILY: Arial; mso-bidi-font-size: 19.0pt; mso-fareast-font-family: 'Times New Roman'; mso-bidi-font-family: 'Times New Roman'"><span style="mso-spacerun: yes"> </span><url-pattern>/clientservlet</url-pattern></span><span lang="EN-US" style="FONT-SIZE: 19pt; COLOR: black; FONT-FAMILY: Arial; mso-fareast-font-family: 'Times New Roman'; mso-bidi-font-family: 'Times New Roman'"><p></p></span></p> <p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt 27pt; TEXT-INDENT: -27pt; mso-layout-grid-align: none"><span lang="EN-US" style="FONT-SIZE: 12pt; COLOR: black; FONT-FAMILY: Arial; mso-bidi-font-size: 19.0pt; mso-fareast-font-family: 'Times New Roman'; mso-bidi-font-family: 'Times New Roman'"><span style="mso-spacerun: yes"> </span></servlet-mapping><p></p></span></p> </div> </td> </tr></tbody></table></textbox><shapetype id="_x0000_t202" path="m0,0l0,21600,21600,21600,21600,0xe" o:spt="202" coordsize="21600,21600"><stroke joinstyle="miter"></stroke><path o:connecttype="rect" gradientshapeok="t"></path></shapetype><shape id="_x0000_s1034" style="MARGIN-TOP: 60pt; Z-INDEX: 9; MARGIN-LEFT: 162pt; WIDTH: 96.35pt; POSITION: absolute; HEIGHT: 23.4pt; mso-wrap-style: none; mso-position-horizontal: absolute; mso-position-vertical: absolute; v-text-anchor: top-baseline" strokeweight="1.25pt" fillcolor="#fc0" type="#_x0000_t202"><fill type="gradient" focus="100%"></fill><shadow opacity=".5" offset2="2pt,2pt" offset="3pt,3pt" on="t"></shadow><textbox style="mso-fit-shape-to-text: t"><table style="WIDTH: 128px; HEIGHT: 21px" cellspacing="0" cellpadding="0" width="128"><tbody><tr> <td style="BORDER-RIGHT: #ece9d8; BORDER-TOP: #ece9d8; BORDER-LEFT: #ece9d8; BORDER-BOTTOM: #ece9d8; BACKGROUND-COLOR: transparent"> <div> <p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt; mso-layout-grid-align: none"><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: 宋体; mso-bidi-font-size: 18.0pt; mso-ansi-language: ZH-CN; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial">两个名称必须相同</span><span style="FONT-SIZE: 9pt; COLOR: black; FONT-FAMILY: Arial; mso-bidi-font-size: 18.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ansi-language: ZH-CN"><p></p></span></p> </div> </td> </tr></tbody></table></textbox></shape><stroke endarrow="block"></stroke>

HttpServlet 类提供一个抽象类以创建 HTTP Servlet，实现其两个方法：

3、javax.servlet.http 包的接口

HttpServletRequest 接口提供 HTTP 请求信息；

ServletConfig 接口在初始化的过程中由 Servlet 容器使用；

ServletContext 接口定义 Servlet 用于获取来自其容器的信息的方法；

ServletRequest 接口向服务器请求信息；

ServletResponse 接口响应客户端请求；

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