java 中获取ServletContext中常用的方法

1.在javax.servlet.Filter中直接获取 

ServletContext context = config.getServletContext(); 

2.在HttpServlet中直接获取 

this.getServletContext() 

3.在其他方法中，通过HttpRequest获得 

request.getSession().getServletContext(); 

当然struts2中还有常见的两种方法获得 
获取HttpServletRequest / HttpSession / ServletContext / HttpServletResponse对象 

方法一，通过ServletActionContext.类直接获取： 
public String rsa() throws Exception{ 
HttpServletRequest request = ServletActionContext.getRequest(); 
ServletContext servletContext = ServletActionContext.getServletContext(); 
request.getSession() 
HttpServletResponse response = ServletActionContext.getResponse(); 
return "scope"; 
} 
方法二，实现指定接口，由struts框架运行时注入： 
public class HelloWorldAction implements ServletRequestAware, ServletResponseAware,
ServletContextAware{ 
private HttpServletRequest request; 
private ServletContext servletContext; 
private HttpServletResponse response; 
public void setServletRequest(HttpServletRequest req) { 
this.request=req; 
} 
public void setServletResponse(HttpServletResponse res) { 
this.response=res; 
} 
public void setServletContext(ServletContext ser) { 
this.servletContext=ser; 
}