JSP基础语法之十三：Servlet取得内置对象和跳转

一：取得内置对象：

req.setCharacterEncoding("GBK");//解决乱码
String p = req.getParameter("param");
PrintWriter out = resp.getWriter();
out.println("<h1>"+"参数：" + p+"</h1>");
out.close();

//1.request和response直接从传参中取得
//2.session通过req取得
HttpSession se = req.getSession();
se.setAttribute("Aname","rt");
System.out.println("SessionID:"+se.getId());
System.out.println("SessionAttribute"+se.getAttribute("Aname"));

//3.application通过servletContext取得
ServletContext appl = super.getServletContext();
System.out.println("真实路径" + appl.getRealPath("/"));

//4.从这里拿不到pageContext

//5.config通过init（）方法获得
public void init(ServletConfig config)
{
String initParam = config.getInitParameter("confParam");
System.out.println("initParam:"+initParam);
}

web.xml中，初始化参数（confParam）的配置

<servlet>
<servlet-name>sl2</servlet-name>
<servlet-class>com.rt.demo.testServlet.servletTableInput</servlet-class><!-- 包.类名称 -->
<init-param>  <!-- init参数 -->
<param-name>confParam</param-name>
<param-value>confInitParamValue</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>sl2</servlet-name>
<url-pattern>/servletTableInput/servletTableInput</url-pattern>
</servlet-mapping>

二：两种跳转：

//1.客户端跳转(地址改变)：无法传递“request属性”，所以不能用在request上
resp.sendRedirect("*.jsp");
//2.服务器端跳转(地址不改变)，servlet中没有<jsp:forward>，用此接口
RequestDispatcher rd = req.getRequestDispatcher("*.jsp");
rd.forward(req,resp);