servlet中的ServletContext

设置、获取ServletContext配置信息

与ServletConfig不同的是，所有Servlet共享一份ServletContext

1. 在web.xml中设置配置信息

   <?xml version="1.0" encoding="UTF-8"?>
   <web-app xmlns="https://jakarta.ee/xml/ns/jakartaee"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="https://jakarta.ee/xml/ns/jakartaee https://jakarta.ee/xml/ns/jakartaee/web-app_6_0.xsd"
            version="6.0">
       <context-param>
           <param-name>key1</param-name>
           <param-value>a</param-value>
       </context-param>
       <context-param>
           <param-name>key2</param-name>
           <param-value>b</param-value>
       </context-param>
   </web-app>
   

2. 在service方法中读取

   public class ServletTest extends HttpServlet {
   	public void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
   		ServletContext servletContext = this.getServletContext();
   		
   		// 获取指定的配置信息
   		String value = servletContext.getInitParameter("key2");
   		System.out.println(value);
   		
   		// 批量获取配置信息
   		Enumeration<String> initParameterNames = servletContext.getInitParameterNames();
   		while(initParameterNames.hasMoreElements()) {
   			String key = initParameterNames.nextElement();
   			System.out.println(key + "=" + servletContext.getInitParameter(key));
   		}
   	}
   } 
   

通过ServletContext获取项目实际部署的根路径：getRealPath()

ServletContext servletContext = this.getServletContext();
// 获取项目实际部署的根路径(绝对路径)
String rootPath = servletContext.getRealPath(""); // D:\workspace\javawebproject\out\artifacts\demo1_war_exploded\
// 获取项目实际部署的根目录下的static路径（绝对路径）
String staticPath = servletContext.getRealPath("static"); // D:\workspace\javawebproject\out\artifacts\demo1_war_exploded\static

通过ServletContext获取项目的访问路径：getContextPath()

ServletContext servletContext = this.getServletContext();
// 获取项目的访问路径
String accessPath = servletContext.getContextPath(); // /demo1