ServletContext

Web容器再启动的时候，会为每个Web程序创建一个对应的ServletContext对象，它代表了当前的Web应用；

共享数据

在这个Servlet中保存的数据可以在另外一个Servlet中拿到:

public class HelloServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //this.getInitParameter() 初始化参数 //this.getServletConfig() Servlet配置 //this.getServletContext() Servlet上下文 ServletContext context = this.getServletContext(); String username = "顾家明";//数据 context.setAttribute("username",username);//将一个数据保存在ServletContext中，名字为：username，值为username System.out.println("Hello"); } } public class GetServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { ServletContext context = this.getServletContext(); String username = (String) context.getAttribute("username"); resp.setContentType("text/html"); resp.setCharacterEncoding("utf-8"); resp.getWriter().print("名字"+username); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doGet(req, resp); } } <servlet> <servlet-name>hello</servlet-name> <servlet-class>com.weng.servlet.HelloServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>hello</servlet-name> <url-pattern>/hello</url-pattern> </servlet-mapping> <servlet> <servlet-name>getc</servlet-name> <servlet-class>com.weng.servlet.GetServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>getc</servlet-name> <url-pattern>/getc</url-pattern> </servlet-mapping>

获取初始化参数

<!--配置一些Web应用的初始化参数--> <context-param> <param-name>url</param-name> <param-value>jdbc:mysql://localhost:3306/mybatis</param-value> </context-param> public class ServletDemo03 extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { ServletContext context = this.getServletContext(); String url = context.getInitParameter("url"); resp.getWriter().print(url); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doGet(req, resp); } }

请求转发

public class ServletDemo04 extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { ServletContext context = this.getServletContext(); System.out.println("进入了ServletDemo04"); //RequestDispatcher requestDispatcher = context.getRequestDispatcher("/gp");//转发的请求路径 //requestDispatcher.forward(req,resp);//调用forward实现请求转发 context.getRequestDispatcher("/gp").forward(req,resp);//合并以上两句 } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doGet(req, resp); } }

读取资源文件

Properties

在java目录下新建properties在resources目录下新建properties

发现:都被打包到了同一个路径下: classes，我们称这个路径为classpath:

思路:需要一个文件流

public class ServletDemo05 extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { InputStream is = this.getServletContext().getResourceAsStream("/WEB-INF/classes/db.properties"); Properties prop = new Properties(); prop.load(is); String user = prop.getProperty("username"); String pwd = prop.getProperty("password"); resp.getWriter().print(user+":"+pwd); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doGet(req, resp); } }