Servlet基础编程

编写第一个ServletDemo

继承HttpServlet

@WebServlet("/WelcomeServlet")public class WelcomeServlet extends HttpServlet {    @Override    protected void doGet(HttpServletRequest request,            HttpServletResponse response) throws IOException {        // TODO Auto-generated method stub        response.setContentType("text/html;charset=GB18030");        PrintWriter out = response.getWriter();        out.println("欢迎进入Servlet");    }}

配置web.xml

 <display-name>ServletDemo</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>     <servlet-name>WelcomeServlet</servlet-name>     <!--包和类名-->     <servlet-class>servlets.WelcomeServlet</servlet-class>  </servlet>  <servlet-mapping>     <servlet-name>WelcomeServlet</servlet-name>     <!--访问的url-->     <url-pattern>/servlets/WelcomeServlet</url-pattern>  </servlet-mapping>

运行结果

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Serlvet运行机制

在WelcomeServlet.Java添加一个构造方法

public class WelcomeServlet extends HttpServlet {    public  WelcomeServlet()    {        System.out.println("创建WelcomeServlet对象");    }    @Override    protected void doGet(HttpServletRequest request,            HttpServletResponse response) throws IOException {        // TODO Auto-generated method stub        System.out.println("调用doGet()函数!");        response.setContentType("text/html;charset=GB18030");        PrintWriter out = response.getWriter();        out.println("欢迎进入Servlet");    }}

测试

Servlet对象只创建了一次

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在Servlet中读取参数

设置参数

 <display-name>ServletDemo</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>  <!--设置全局参数 -->  <context-param>     <param-name>encoding</param-name>     <param-value>GB18030</param-value>  </context-param>  <servlet>     <servlet-name>InitServlet</servlet-name>     <servlet-class>servlets.InitServlet</servlet-class>     <!-- 设置局部参数 -->     <init-param>       <param-name>driverClassName</param-name>       <param-value>com.serversql.jdbc.Driver</param-value>     </init-param>  </servlet>  <servlet-mapping>    <servlet-name>InitServlet</servlet-name>    <url-pattern>/servlets/InitServlet</url-pattern>  </servlet-mapping>

获取参数

public class InitServlet extends HttpServlet {    @Override    protected void doGet(HttpServletRequest request,            HttpServletResponse response) throws IOException {        // 获取全局参数        ServletContext application = this.getServletContext();        String encoding = application.getInitParameter("encoding");        System.out.println("encoding参数是：" + encoding);        // 获取局部参数        String driverClassName = this.getInitParameter("driverClassName");        System.out.println("driverClassName的参数是：" + driverClassName);    }}

测试结果