【Struts2复习知识点十二】web元素request session application等

有四种方法可以得到request session application等web元素。
方法一

LoginAction1.java

public class LoginAction1 extends ActionSupport {
    
    private Map request;
    private Map session;
    private Map application;
    
    public LoginAction1() {
        request = (Map)ActionContext.getContext().get("request");
        session = ActionContext.getContext().getSession();
        application = ActionContext.getContext().getApplication();
    }
    
    public String execute() {
        request.put("r1", "r1");
        session.put("s1", "s1");
        application.put("a1", "a1");
        return SUCCESS; 
    }
    
    
}

方法二

LoginAction2.java

public class LoginAction2 extends ActionSupport implements RequestAware,SessionAware, ApplicationAware {
    
    private Map<String, Object> request;
    private Map<String, Object> session;
    private Map<String, Object> application;
    
    //DI dependency injection
    //IoC inverse of control
    public String execute() {
        request.put("r1", "r1");
        session.put("s1", "s1");
        application.put("a1", "a1");
        return SUCCESS; 
    }

    @Override
    public void setRequest(Map<String, Object> request) {
        this.request = request;
    }

    @Override
    public void setSession(Map<String, Object> session) {
        this.session = session;
    }

    @Override
    public void setApplication(Map<String, Object> application) {
        this.application = application;
    }
    
    
}

方法三

LoginAction3.java

public class LoginAction3 extends ActionSupport {
    
    private HttpServletRequest request;
    private HttpSession session;
    private ServletContext application;
    
    public LoginAction3() {
        request = ServletActionContext.getRequest();
        session = request.getSession();
        application = session.getServletContext();
    }
    
    public String execute() {
        request.setAttribute("r1", "r1");
        session.setAttribute("s1", "s1");
        application.setAttribute("a1", "a1");
        return SUCCESS; 
    }
    
}

方法四

LoginAction4.java

public class LoginAction4 extends ActionSupport implements ServletRequestAware {
    
    private HttpServletRequest request;
    private HttpSession session;
    private ServletContext application;
    
    
    
    public String execute() {
        request.setAttribute("r1", "r1");
        session.setAttribute("s1", "s1");
        application.setAttribute("a1", "a1");
        return SUCCESS; 
    }



    @Override
    public void setServletRequest(HttpServletRequest request) {
        this.request = request;
        this.session = request.getSession();
        this.application = session.getServletContext();
    }
    
}

JSP中的访问代码

<s:property value="#request.r1"/> | <%=request.getAttribute("r1") %> <br />
    <s:property value="#session.s1"/> | <%=session.getAttribute("s1") %> <br />
    <s:property value="#application.a1"/> | <%=application.getAttribute("a1") %> <br />
    <s:property value="#attr.a1"/><br />
    <s:property value="#attr.s1"/><br />
    <s:property value="#attr.r1"/><br />

总结 ：

前两种方法取得Map类型request,session,application

后两种方法真实类型 HttpServletRequest, HttpSession, ServletContext

方法1和方法3是依赖容器的。（ActionContext，ServletActionContext）

方法2和方法4是 IOC 的。具体用的时候用 方法2。

JSP中 用attr取值 是检查request session等地方 取值的，不建议用。<s:debug></s:debug>

application占资源，具体应用的时候可以通过javabean 或者数据库代替。

开发时用<s:debug></s:debug>调试跟踪request session中的值。