Struts2中对Servlet API的访问

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1 通过接口进行对象注入，action必须是实现相应的接口，struts就可以将指定的对象传递给action类
ServletContextAware接口：可以获得ServletContext对象
ServletResponseAware接口：可以获得ServletResponse对象
ServletRequestAware接口：可以获得ServletRequest对象
request.getSession获得session对象

public class ServletAction extends ActionSupport implements ServletRequestAware{    private HttpServletRequest request;    @Override    public void setServletRequest(HttpServletRequest request) {        this.request = request;    }    @Override    public String execute() throws Exception {        System.out.println(request.getContextPath());        return SUCCESS;    }   }

执行结果：
这里写图片描述

2 ServletActionContext 工具类，struts 的action类中获得servlet的api
获得servlet 对象，可以操作域数据，可以调用其他api
HttpServletRequest ServletActionContext.getRequest();
HttpSession ServletActionContext.getRequest().getSession();
ServletContext ServletActionContext.getServletContext();

public class ServletAction extends ActionSupport {      @Override    public String execute() throws Exception {        ServletActionContext.getResponse();        ServletActionContext.getRequest().setAttribute("sac", "ServletActionContext_request");        ServletActionContext.getRequest().getSession().setAttribute("sac", "ServletActionContext_session");        ServletActionContext.getServletContext().setAttribute("sac", "ServletActionContext_application");        return SUCCESS;    }}

jsp代码：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <body>   <h3>获得3作用域内容 -- ServletActionContext</h3>    ${requestScope.sac} <br/>    ${sessionScope.sac} <br/>    ${applicationScope.sac} <br/>  </body></html>

执行结果：
这里写图片描述

3 通过Action上下文对象ActionContext，可以间接对servlet 域数据进行操作，实现了解耦，不依赖于servlet api
获得ActionContext实例：ActionContext.getContext()
间接操作域数据

public class ServletAction extends ActionSupport {    @Override    public String execute() throws Exception {              ActionContext.getContext().put("ac", "ActionContext_request");          ActionContext.getContext().getSession().put("ac", "ActionContext_session");        ActionContext.getContext().getApplication().put("ac", "ActionContext_application");        return SUCCESS;    }}

jsp代码：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <body>        <h3>获得3作用域内容-- ActionContext</h3>    ${requestScope.ac} <br/>    ${sessionScope.ac} <br/>    ${applicationScope.ac} <br/>  </body></html>

执行结果：
这里写图片描述

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