Servlet03

11.练习

快捷键-可以快速地在访问的文件件切换

ctrl+alt+向左箭头：回到上次访问的位置

ctrl+alt+向右箭头：回到下一步访问的位置

11.1CatServlet

首先创建项目servlet，配置好Tomcat，添加web应用支持。在web目录下面的WEB-INF目录下创建lib目录，在Tomcat安装包的lib目录中找到servlet-api，并添加到idea的web目录下面的WEB-INF/lib目录，选择引用为库文件

在src目录下创建目录，编写CatServlet类：

	`package servlet;`

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

	`public class CatServlet implements Servlet {`
	`public int count = 0;`

	`@Override`
	`public void init(ServletConfig servletConfig) throws ServletException {`

	`}`

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

	`@Override`
	`public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {`
	`count++;//每次访问service方法，count累加`
	`System.out.println("该servlet访问次数=" + count);`
	`//获取请求的方式`
	`HttpServletRequest httpServletRequest = (HttpServletRequest) servletRequest;`
	`String method = httpServletRequest.getMethod();`
	`if (method.equals("GET")) {`
	`doGet();`
	`} else if (method.equals("POST")) {`
	`doPost();`
	`}`
	`}`

	`public void doGet() {`
	`System.out.println("CatServlet doGet()...");`
	`}`

	`public void doPost() {`
	`System.out.println("CatServlet doPost()...");`
	`}`

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

	`@Override`
	`public void destroy() {`

	`}`
	`}`

在web.xml文件中进行Servlet配置：

	`<?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>`
	`<servlet-name>CatServlet</servlet-name>`
	`<servlet-class>servlet.CatServlet</servlet-class>`
	`</servlet>`
	`<servlet-mapping>`
	`<servlet-name>CatServlet</servlet-name>`
	`<url-pattern>/cat</url-pattern>`
	`</servlet-mapping>`
	`</web-app>`

在WEB-INF目录下编写一个html，用于测试

	`<!DOCTYPE html>`
	`<html lang="en">`
	`<head>`
	`<meta charset="UTF-8">`
	`<title>login</title>`
	`</head>`
	`<body>`
	`<form action="http://localhost:8080/servlet/cat" method="get">`
	`name: <input type="text"/><br/><br/>`
	`<input type="submit" value="login"/>`
	`</form>`
	`</body>`
	`</html>`

点击启动Tomcat，在浏览器中输入地址：http://localhost:8080/servlet/login.html

点击login按钮，成功跳转到CatServlet中：

后台输出：（如果表单方式改变了，仍然调用的是旧的访问方法，点击保存html，并刷新浏览器页面即可解决）

11.2DogServlet

在11.1的项目框架上进行编程

首先在src目录下创建DogServlet类

	`package servlet;`

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

	`public class DogServlet extends HttpServlet {`
	`private int getCount = 0;`
	`private int postCount = 0;`

	`@Override`
	`protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {`
	`getCount++;`
	`System.out.println("getCount=" + getCount);`
	`System.out.println("DogServlet-访问doGet()");`
	`}`

	`@Override`
	`protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {`
	`postCount++;`
	`System.out.println("postCount=" + postCount);`
	`System.out.println("DogServlet-访问doPost()");`
	`}`
	`}`

注意：这里没有重写service方法，因此当浏览器请求DogServlet时，会去父类HttpServlet类中去找调用的service方法，在HttpServlet类中的service方法会根据请求类型如get、post去调用当前运行类型（即DogServlet）的doPost、doGet方法，因此在自己创建的Servlet中不用判断请求方式

在web.xml文件中配置该Servlet:

	`<servlet>`
	`<servlet-name>DogServlet</servlet-name>`
	`<servlet-class>servlet.DogServlet</servlet-class>`
	`</servlet>`
	`<servlet-mapping>`
	`<servlet-name>DogServlet</servlet-name>`
	`<url-pattern>/dog</url-pattern>`
	`</servlet-mapping>`

修改之前的login.html文件

	`<!DOCTYPE html>`
	`<html lang="en">`
	`<head>`
	`<meta charset="UTF-8">`
	`<title>login</title>`
	`</head>`
	`<body>`
	`<form action="http://localhost:8080/servlet/dog" method="post">`
	`name: <input type="text"/><br/><br/>`
	`<input type="submit" value="login"/>`
	`</form>`
	`</body>`
	`</html>`

点击redeploy Tomcat，在浏览器输入地址http://localhost:8080/servlet/login.html，点击login按钮，成功跳转到DogServlet

将login.html文件中表单提交方式反复该为post或者get，多次访问，后台输出如下：

（如果表单方式改变了，仍然调用的是旧的访问方法，点击保存html，并刷新浏览器页面即可解决）

11.3PigServlet

在11.1的项目框架上进行编程

在src目录下编写PigServlet

	`package servlet;`

	`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(urlPatterns = {"/pig1", "/pig2"},loadOnStartup = 1)`
	`public class PigServlet extends HttpServlet {`
	`private int getCount = 0;`
	`private int postCount = 0;`

	`@Override`
	`protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {`
	`getCount++;`
	`System.out.println("PigServlet-访问doGet()-get访问次数=" + getCount);`
	`System.out.println("客户端地址="+req.getRemoteAddr());`
	`}`

	`@Override`
	`protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {`
	`postCount++;`
	`System.out.println("PigServlet-访问doPost()-post访问次数=" + postCount);`
	`System.out.println("客户端地址="+req.getRemoteAddr());`
	`}`
	`}`

修改login.html文件

	`<!DOCTYPE html>`
	`<html lang="en">`
	`<head>`
	`<meta charset="UTF-8">`
	`<title>login</title>`
	`</head>`
	`<body>`
	`<form action="http://localhost:8080/servlet/pig1" method="get">`
	`name: <input type="text"/><br/><br/>`
	`<input type="submit" value="login"/>`
	`</form>`
	`</body>`
	`</html>`