ServletContext功能获取MIME类型和域对象和获取文件服务器路径
ServletContext功能
1.获取MIME类型
MIME类型:在互联网通信过程中定义的一种文件数据类型
格式:大类型/小类型 text/html image/jpeg
获取:String getMimeType(String file)
@WebServlet("/servletContextD2") public class ServletContextD2 extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //2.通过HTTPServlet获取 ServletContext context = this.getServletContext(); //定义文件名称 String str = "a.jpg"; //获取MIME类型 String mimeType = context.getMimeType(str); System.out.println(mimeType); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { this.doGet(req, resp); } }
获取出来的为image/jpeg
2.域对象:共享数据
1.setAttribute(String name,Object value)通过名称设置值
2.getAttribute(String name)通过名称获取值
3.removeAttribute(String name)通过名称移除对应的值键
ServletContext对象范围:所有用户所有请求的数据
ServletContextD3 :
@WebServlet("/servletContextD3") public class ServletContextD3 extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //2.通过HTTPServlet获取 ServletContext context = this.getServletContext(); //设置数据 context.setAttribute("msg","haha"); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { this.doGet(req, resp); } }
ServletContextD4:
@WebServlet("/servletContextD4") public class ServletContextD4 extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //2.通过HTTPServlet获取 ServletContext context = this.getServletContext(); //获取数据 Object msg = context.getAttribute("msg"); System.out.println(msg); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { this.doGet(req, resp); } }
先去访问3进行存入进数据
可以在换个浏览器访问4就可以获取到3的数据
3.获取文件服务器路径
获取文件的真实(服务器)路径
1.方法:String getRealPath(String path)
@WebServlet("/servletContextD5") public class ServletContextD5 extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //2.通过HTTPServlet获取 ServletContext context = this.getServletContext(); //获取文件的服务器路径 String realPath = context.getRealPath("/b.txt");//web目录下的资源访问 System.out.println(realPath); String c = context.getRealPath("/WEB-INF/c.txt");//WEB-INF目录资源访问 System.out.println(c); String a = context.getRealPath("/WEB-INF/classes/a.txt");//获取src下的a.txt的资源访问 System.out.println(a); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { this.doGet(req, resp); } }