servlet与Web.xml配置关联

【servlet与Web.xml配置】

【关联01:处理类与请求的关联】

web.xml配置为：

<!--  定义如何在浏览器中访问此serlvet 如下即：通过/abc可以访问到demo类去处理-->  
  <servlet-mapping>
    <servlet-name>demo</servlet-name>
    <url-pattern>*.gdy</url-pattern>
  </servlet-mapping>
  <servlet>
    <servlet-name>GenericServletone</servlet-name>
    <servlet-class>ServerByGenerServlet</servlet-class>
  <!-- 启动时加载，即服务器启动时就加载该类，数组代表启动时，启动的顺序 -->
    <load-on-startup>3</load-on-startup>
  </servlet>

java对应的类代码为：

public class GServletConfig extends HttpServlet {
  public void service(ServletRequest req, ServletResponse res)
      throws ServletException, IOException {
  }
 }

【关联02：通过ServletConfig获取配置信息】

web.xml配置为：

<!-- GServletConig处理类 -->
  <servlet>
    <servlet-name>Gconfig</servlet-name>
    <servlet-class>GServletConfig</servlet-class>
    <!-- 定义类的全局变量 -->
    <init-param>
      <param-name>name</param-name>
      <param-value>你猜猜我是谁</param-value>
    </init-param>
    <init-param>
      <param-name>gdy</param-name>
      <param-value>我是gdy</param-value>
    </init-param>
    <load-on-startup>5</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>Gconfig</servlet-name>
    <url-pattern>*.gan</url-pattern>
  </servlet-mapping>

对应的java获取配置代码为：

/**
 * 处理【*.gan】请求
 * 功能：学习ServletConfig
 * @author Administrator
 * 
 * 获取ServletConfig的方法
 *     1.采用带参数的init方法
 *     2.采用servlet实例获取，（但不要写在带参数的init方法里面）
 *
 */
public class GServletConfig extends HttpServlet {
  @Override
  public void service(ServletRequest req, ServletResponse res)
      throws ServletException, IOException {
//    //获取web.xml配置文件中的单个配置信息
//    String name=this.getServletConfig().getInitParameter("name");
//    System.out.println(name);
    
    //获取多个配置信息
    Enumeration<String> enumer = this.getInitParameterNames();
    while (enumer.hasMoreElements()) {
      String wname = (String) enumer.nextElement();
      System.out.println(wname+":"+this.getServletConfig().getInitParameter(wname));
    }
    
  }
}

【关联03：通过ServletContext获取定义的全局变量】

web.xml配置为：

<!-- 定义应用程序的全局的变量 -->
  <context-param>
    <param-name>name1</param-name>
    <param-value>全局标量01</param-value>
  </context-param>
  <context-param>
    <param-name>name2</param-name>
    <param-value>全局变量02</param-value>
  </context-param>
  
  <!-- com.gdy.Servlet.GServletContext 处理类 处理请求为*.ggt -->
  <servlet>
    <servlet-name>Gggt</servlet-name>
    <servlet-class>com.gdy.Servlet.GServletContext</servlet-class>
    <load-on-startup>7</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>Gggt</servlet-name>
    <url-pattern>*.ggt</url-pattern>
  </servlet-mapping>

java类获取方法为：

/**
 * 通过ServletContext获取定义的全局变量
 * @author Administrator
 *
 */
public class GServletContext extends HttpServlet {
  
  @Override
  protected void service(HttpServletRequest req, HttpServletResponse resp)
      throws ServletException, IOException {
    Enumeration<String> genum = this.getServletConfig().getServletContext().getInitParameterNames();
    while (genum.hasMoreElements()) {
      String str = (String) genum.nextElement();
      System.out.println(str + ":" +this.getServletContext().getInitParameter(str));
    }
  }
}

【关联04：请求转发处理】

web.xml代码为：

<!-- com.gdy.Servlet.GservletRealy类的创建 -->
  <servlet>
    <servlet-name>Grealy</servlet-name>
    <servlet-class>com.gdy.Servlet.GservletRealy</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>Grealy</servlet-name>
    <url-pattern>*.realy</url-pattern>
  </servlet-mapping>
  
  <!-- com.gdy.Servlet.GservletGetRealy类的创建 -->
  <servlet>
    <servlet-name>Gdd</servlet-name>
    <servlet-class>com.gdy.Servlet.GservletGetRealy</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>Gdd</servlet-name>
    <url-pattern>*.gdd</url-pattern>
  </servlet-mapping>

Java请求转发，和转发后处理代码为：

[请求转发类]

/**
 * 请求转发实例，
 * 处理请求为【*.realy】
 * 功能：将带*。realy的请求转发到*。getregly上处理
 *
 */
public class GservletRealy extends HttpServlet{
  @Override
  protected void service(HttpServletRequest req, HttpServletResponse resp)
      throws ServletException, IOException {
    //获取全局变量
    ServletContext context = this.getServletContext();
    //添加值
    context.setAttribute("age", "13");
    req.setAttribute("gname", "你猜我是什么");
    System.out.println("开始转发");
    //获取请求转发器
    RequestDispatcher rd = context.getRequestDispatcher("/aa.gdd");
    //转发请求
    rd.forward(req, resp);
    
  }
}

[转发后处理类为]

/**
 * 处理请求类为【*.gdd】
 * @author Administrator
 *
 */
public class GservletGetRealy extends HttpServlet{

  @Override
  protected void service(HttpServletRequest req, HttpServletResponse resp)
      throws ServletException, IOException {
    System.out.println("成功接收");
    //获取context传递过来的值
    String contname=(String)this.getServletContext().getAttribute("age");
    //获取servletrequest传递过来的值
    String sername=(String)req.getAttribute("gname");
    System.out.println("context传递过来的值:"+contname);
    System.out.println("servletrequest传递过来的值："+sername);
  }
}