Struts2 访问web元素

访问web元素的四种方法（耦合，依赖注入）、（耦合，非依赖注入）、（非耦合，依赖注入）、（非耦合，非依赖注入）

耦合：可以得到HttpServletResponse，HttpServletRequest，HttpSession等类型对象。能直接操作到真正的web元素。

非耦合：得到的是由struts封装好的Map类型,只能对范围进行存取值操作。

依赖注入：对象由struts2从外部注入。Action类不需要关心对象是如何得到的。

非依赖注入：对象由Action类自己提供初始化。

耦合

　　非依赖注入

 public class UserAction extends ActionSupport{
     //类型为真实的web元素:HttpServletResponse,HttpServletRequest等..
     private HttpServletResponse resp;
     private HttpServletRequest req;
     private HttpSession session;
     private ServletContext app;

     public String execute() throws IOException{
         req = ServletActionContext.getRequest();     //得到request
         resp = ServletActionContext.getResponse();    //得到response
         app = ServletActionContext.getServletContext();   //得到application
         session = ServletActionContext.getRequest().getSession();  //得到session
         //操作
         req.setAttribute("req", "write req..");    //往request里存值
         session.setAttribute("session", "write session");    //住session里存值
         session.getAttribute("session");         //从session里取值
         resp.getWriter();      //得到response的 PrintWriter
         return "test";
     }
 }

　　依赖注入

 //实现ServletRequestAware,ServletResponseAware接口
 public class UserAction extends ActionSupport implements ServletRequestAware,ServletResponseAware{
     private HttpServletResponse resp;
     private HttpServletRequest req;
     private HttpSession session;
     private ServletContext app;

     public String execute() throws IOException{
         //操作
         req.setAttribute("req", "write req..");              //往request里存值
         session.setAttribute("session", "write session");    //住session里存值
         session.getAttribute("session");                     //从session里取值
         resp.getWriter();                                    //得到response的 PrintWriter
         return "test";
     }

     //重写setServletResponse方法，Response对象不需要自己得到，由struts2从外部注入
     public void setServletResponse(HttpServletResponse resp) {
         this.resp=resp;                                      //得到response
     }
     //重写setServletRequest方法，Request对象不需要自己得到，由struts2从外部注入
     public void setServletRequest(HttpServletRequest req) {
         this.req=req;                                         //得到request
         this.session = req.getSession();                      //得到session
         this.app = session.getServletContext();               //得到application
     }
 }

非耦合

　　非依赖注入

 public class UserAction extends ActionSupport{
     //得到的是由struts封装好的Map类型,只能对范围进行存取值操作
     private Map<String,Object> req;
     private Map<String,Object> session;
     private Map<String,Object> app;

     public String execute() throws IOException{
         req= (Map<String,Object>)ActionContext.getContext().get("request");    //得到request
         session = ActionContext.getContext().getSession();                     //得到session
         app = ActionContext.getContext().getApplication();                     //得到application
         //操作
         req.put("req", "write req..");                    //存值到request
         session.put("session", "write session..");        //存值到session
         app.put("app", "write application..");            //存值到application
         session.get("session");                           //从session存值
         return "test";
     }
 }

　　依赖注入（推荐）

 //实现RequestAware,SessionAware,ApplicationAware等接口
 public class UserAction extends ActionSupport implements RequestAware,SessionAware,ApplicationAware{
     //得到的是由struts封装好的Map类型,只能对范围进行存取值操作
     private Map<String,Object> req;
     private Map<String,Object> session;
     private Map<String,Object> app;

     public String execute() throws IOException{
         //操作
         req.put("req", "write req..");                    //存值到request
         session.put("session", "write session..");        //存值到session
         app.put("app", "write application..");            //存值到application
         session.get("session");                           //从session存值
         return "test";
     }
     //得到application
     public void setApplication(Map<String, Object> app) {
         this.app=app;
     }
     //得到session
     public void setSession(Map<String, Object> session) {
         this.session=session;
     }
     //得到request
     public void setRequest(Map<String, Object> req) {
         this.req= req;
     }
 }