在struts2中获取Servlet API有三种方式：
1.通过ActionContext来获取
1.获取一个ActionContext对象。
ActionContext context=ActionContext.getContext();
2.获取servlet api
注意:通过ActionContext获取的不是真正的Servlet API,而是一个Map集合。
1.context.getApplication()
2.context.getSession()
3.context.getParameter();---得到的就相当于request.getParameterMap()
4.context.put(String,Object) 相当于request.setAttribute(String,String);
public class Demo01Action extends ActionSupport{ @Override public String execute() throws Exception { ActionContext context = ActionContext.getContext(); Map<String, Object> application = context.getApplication(); Map<String, Object> session = context.getSession(); Map<String, Object> parameters = context.getParameters(); context.put(key, value); return null; } }
2.注入方式获取(这种方式是真正的获取到了Servlet API)
1.要求action类必须实现提定接口。
ServletContextAware ： 注入ServletContext对象
ServletRequestAware ：注入 request对象
ServletResponseAware ： 注入response对象
2.重定接口中的方法。
private HttpServletRequest request;
3.声明一个web对象，使用接口中的方法的参数对声明的web对象赋值.
public void setServletRequest(HttpServletRequest request) {
this.request = request;
}
public class Demo01Action extends ActionSupport implements ServletContextAware, ServletRequestAware, ServletResponseAware { private ServletContext context; private HttpServletRequest request; private HttpServletResponse response; @Override public String execute() throws Exception { return null; } @Override public void setServletContext(ServletContext context) { this.context = context; } @Override public void setServletRequest(HttpServletRequest request) { this.request = request; } @Override public void setServletResponse(HttpServletResponse response) { this.response = response; } }
扩展:分析其实现：
是使用struts2中的一个interceptor完成的.
<interceptor/>
源码:
public class ServletConfigInterceptor extends AbstractInterceptor implements StrutsStatics {
private static final long serialVersionUID = 605261777858676638L;
/**
* Sets action properties based on the interfaces an action implements. Things like application properties,
* parameters, session attributes, etc are set based on the implementing interface.
*
* @param invocation an encapsulation of the action execution state.
* @throws Exception if an error occurs when setting action properties.
*/
public String intercept(ActionInvocation invocation) throws Exception {
final Object action = invocation.getAction();
final ActionContext context = invocation.getInvocationContext();
//判断当前的action是否继承指定方法
if (action instanceof ServletRequestAware) {
//获取reqeust对象，，并将request对象封装到action中
HttpServletRequest request = (HttpServletRequest) context.get(HTTP_REQUEST);
((ServletRequestAware) action).setServletRequest(request);
}
if (action instanceof ServletResponseAware) {
HttpServletResponse response = (HttpServletResponse) context.get(HTTP_RESPONSE);
((ServletResponseAware) action).setServletResponse(response);
}
if (action instanceof ParameterAware) {
((ParameterAware) action).setParameters((Map)context.getParameters());
}
if (action instanceof ApplicationAware) {
((ApplicationAware) action).setApplication(context.getApplication());
}
if (action instanceof SessionAware) {
((SessionAware) action).setSession(context.getSession());
}
if (action instanceof RequestAware) {
((RequestAware) action).setRequest((Map) context.get("request"));
}
if (action instanceof PrincipalAware) {
HttpServletRequest request = (HttpServletRequest) context.get(HTTP_REQUEST);
if(request != null) {
// We are in servtlet environment, so principal information resides in HttpServletRequest
((PrincipalAware) action).setPrincipalProxy(new ServletPrincipalProxy(request));
}
}
if (action instanceof ServletContextAware) {
ServletContext servletContext = (ServletContext) context.get(SERVLET_CONTEXT);
((ServletContextAware) action).setServletContext(servletContext);
}
return invocation.invoke();
}
}