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;           
    }
}