servlet与Web.xml配置关联

Dear 丶 2022-08-21 06:57 177阅读 0赞

【servlet与Web.xml配置】

【关联01:处理类与请求的关联】

web.xml配置为：

<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>
    	
      	<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：

<servlet>
      	<servlet-name>Gconfig</servlet-name>
      	<servlet-class>GServletConfig</servlet-class>
      	
      	<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：

<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>
      
      
      <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：

<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>
      
      
      <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);
    	}
    }