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    3. 创建servlet的三种方式 1.实现 servlet接口 2.继承GenericServlet类 3.继承HttpServlet类

    创建servlet的三种方式 1.实现 servlet接口 2.继承GenericServlet类 3.继承HttpServlet类

    科技2024-12-23  12

    创建servlet的三种方式

    1.实现 servlet接口

     

    package servlet_mvn_jd2007; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.Servlet; import javax.servlet.ServletConfig; import javax.servlet.ServletException; import javax.servlet.ServletRequest; import javax.servlet.ServletResponse; public class FirstServlet implements Servlet{ public FirstServlet() { System.out.println("FirstServlet 构造器。。。。"); } @Override public void destroy() { System.out.println("destory.....删除方法"); } @Override public ServletConfig getServletConfig() { // TODO Auto-generated method stub return null; } @Override public String getServletInfo() { // TODO Auto-generated method stub return null; } @Override public void init(ServletConfig arg0) throws ServletException { System.out.println("FirstServlet init......初始化方法init"); } @Override public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException { System.out.println("service----------------"); res.setContentType("text/html;charset=UTF-8"); double r = Math.random(); PrintWriter pw = res.getWriter(); pw.println("<html>"); pw.println("<head>"); pw.println("<meta charset='UTF-8'>"); pw.println("<title>First Servlet</title>"); pw.println("</head>"); pw.println("<body>"); pw.println( "<font color='green' size='7'>随机数为:"+r+"</font>"); pw.println("</body>"); pw.println("</html>"); } }

    注意:三种方法都要在web.xml中配置<servlet>信息才可以运行,servlet3.0以后也可以通过写注解的方式来实现,第三种方法见

    <servlet>中的顺序必须下面的一样

    <?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1"> <display-name>servlet_jd2007</display-name> <welcome-file-list> <welcome-file>index.html</welcome-file> <welcome-file>index.htm</welcome-file> <welcome-file>index.jsp</welcome-file> <welcome-file>default.html</welcome-file> <welcome-file>default.htm</welcome-file> <welcome-file>default.jsp</welcome-file> </welcome-file-list> <servlet> <!-- 两个name必须相同,class里面时该类的权限类名,URL除通配符*外都必须以/开头 --> <servlet-name>first</servlet-name> <servlet-class>servlet_mvn_jd2007.FirstServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>first</servlet-name> <url-pattern>/first.do</url-pattern> </servlet-mapping> <!--第二种方法的配置信息--> <servlet> <servlet-name>Second</servlet-name> <servlet-class>servlet_mvn_jd2007.SecondServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>Second</servlet-name> <url-pattern>/second.do</url-pattern> </servlet-mapping> </web-app>

    2.继承GenericServlet类

    package servlet_mvn_jd2007; import java.io.IOException; import java.io.PrintWriter; import javax.security.auth.Refreshable; import javax.servlet.GenericServlet; import javax.servlet.ServletException; import javax.servlet.ServletRequest; import javax.servlet.ServletResponse; public class SecondServlet extends GenericServlet{ private static final long serialVersionUID = 1L; public SecondServlet() { System.out.println("SecondServlet Construtor...."); } @Override public void init() throws ServletException { System.out.println("SecondServlet init ...."); } @Override public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException { res.setContentType("application/xml;charset+UTF-8"); PrintWriter pw = res.getWriter(); pw.println("<students>"); pw.println("<student sno='s1'>"); pw.println("<name>briup1</name>"); pw.println("<age>18</age>"); pw.println("</student>"); pw.println("<student sno='s2'>"); pw.println("<name>briup2</name>"); pw.println("<age>19</age>"); pw.println("</student>"); pw.println("</students>"); pw.flush(); } }

    3.继承HttpServlet类

    package servlet_mvn_jd2007; import java.io.BufferedInputStream; import java.io.BufferedOutputStream; import java.io.FileInputStream; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; //通过注解的方式,就不需要在web.xml中配置信息了,name可以省略.推荐使用该方法 //@WebServlet(name = "three",urlPatterns = {"/three.do"}) @WebServlet("/three.do") public class ThreeServlet extends HttpServlet{ private static final long serialVersionUID = 1L; public ThreeServlet() { System.out.println("Threeservlet constructor.."); } @Override public void init() throws ServletException { System.out.println("ThreeServlet init..."); } @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { System.out.println("doGet.....threServlet.."); resp.setContentType("image/jpeg"); try(BufferedInputStream bis = new BufferedInputStream(new FileInputStream("F:\\A图片\\1.jpg")); BufferedOutputStream bos = new BufferedOutputStream(resp.getOutputStream()); ) { byte[] b = new byte[1024]; int len = 0; while((len=bis.read(b))!=-1) { bos.write(b, 0, len); } bos.flush(); } catch (Exception e) { e.printStackTrace(); } } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doGet(req, resp); } @Override public void destroy() { System.out.println("ThreeServlet destory..."); System.out.println(""); } }

    注意:在maven项目中要在pom.xml中配置一些信息才可以写servlet

    <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.briup.jd2007</groupId> <artifactId>servlet_mvn_jd2007</artifactId> <version>0.0.1-SNAPSHOT</version> <packaging>war</packaging> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <maven.compiler.source>1.8</maven.compiler.source> <maven.compiler.target>1.8</maven.compiler.target> </properties> <dependencies> <!-- 引入servlet3.1的依赖 --> <dependency> <groupId>javax.servlet</groupId> <artifactId>javax.servlet-api</artifactId> <version>3.1.0</version> <scope>provided</scope> </dependency> <!-- 引入jstl的依赖，jsp页面中会使用到 --> <dependency> <groupId>javax.servlet</groupId> <artifactId>jstl</artifactId> <version>1.2</version></dependency> </dependencies> </project>

     

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