1. 概念
代表整个web应用,可以和程序的容器(服务器)来通信
2. 获取
1. 通过request对象获取
request.getServletContext();
2. 通过HttpServlet获取
this.getServletContext();
package cn.itcast.web.servletcontext; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; @WebServlet("/servletContextDemo1") public class ServletContextDemo1 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { /* ServletContext对象获取: 1. 通过request对象获取 request.getServletContext(); 2. 通过HttpServlet获取 this.getServletContext(); */ //1. 通过request对象获取 ServletContext context1 = request.getServletContext(); //2. 通过HttpServlet获取 ServletContext context2 = this.getServletContext(); System.out.println(context1); System.out.println(context2); System.out.println(context1 == context2);//true } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } }
3. 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)
package cn.itcast.web.servletcontext; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; @WebServlet("/servletContextDemo2") public class ServletContextDemo2 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { /* 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) 2. 域对象:共享数据 3. 获取文件的真实(服务器)路径 */ //2. 通过HttpServlet获取 ServletContext context = this.getServletContext(); //3. 定义文件名称 String filename = "a.jpg";//image/jpeg //4.获取MIME类型 String mimeType = context.getMimeType(filename); System.out.println(mimeType); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } }
2. 域对象:共享数据
1. setAttribute(String name,Object value)
2. getAttribute(String name)
3. removeAttribute(String name)
ServletContext对象范围:所有用户所有请求的数据
package cn.itcast.web.servletcontext; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; @WebServlet("/servletContextDemo3") public class ServletContextDemo3 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { /* ServletContext功能: 1. 获取MIME类型: 2. 域对象:共享数据 3. 获取文件的真实(服务器)路径 */ //2. 通过HttpServlet获取 ServletContext context = this.getServletContext(); //设置数据 context.setAttribute("msg","haha"); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } }
package cn.itcast.web.servletcontext; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; @WebServlet("/servletContextDemo4") public class ServletContextDemo4 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { /* ServletContext功能: 1. 获取MIME类型: 2. 域对象:共享数据 3. 获取文件的真实(服务器)路径 */ //2. 通过HttpServlet获取 ServletContext context = this.getServletContext(); //获取数据 Object msg = context.getAttribute("msg"); System.out.println(msg); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } }
3. 获取文件的真实(服务器)路径
方法:String getRealPath(String path)
package cn.itcast.web.servletcontext; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.File; import java.io.IOException; @WebServlet("/servletContextDemo5") public class ServletContextDemo5 extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { /* ServletContext功能: 1. 获取MIME类型: 2. 域对象:共享数据 3. 获取文件的真实(服务器)路径 */ // 通过HttpServlet获取 ServletContext context = this.getServletContext(); // 获取文件的服务器路径 String b = context.getRealPath("/b.txt");//web目录下资源访问 System.out.println(b); // File file = new File(realPath); String c = context.getRealPath("/WEB-INF/c.txt");//WEB-INF目录下的资源访问 System.out.println(c); String a = context.getRealPath("/WEB-INF/classes/a.txt");//src目录下的资源访问 System.out.println(a); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } }