在 Action 中访问 WEB 资源(struts2获取HttpServletRequest, HttpSession, ServletContext)

浅浅的花香味﹌ 2022-06-07 06:38 172阅读 0赞

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   <td><font> &nbsp;面向对象面向君，不负代码不负卿。 *^o^* </font> </td> 
  </tr> 
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在 Action 中访问 WEB 资源

**1). 什么是 WEB 资源 ?**

HttpServletRequest, HttpSession, ServletContext 等原生的 Servlet API。

**2). 为什么访问 WEB 资源?**

B\S 的应用的 Controller 中必然需要访问 WEB 资源: 向域对象中读写属性, 读写 Cookie, 获取 realPath ....

**3). 如何访问 ?**

*I. 和 Servlet API 解耦的方式: 只能访问有限的 Servlet API 对象, 且只能访问其有限的方法(读取请求参数, 读写域对象的属性, 使 session 失效…).*

***注意:struts版本为2.5.13***

1.使用 ActionContext

package com.struts2.actionpage;
    
    import com.opensymphony.xwork2.ActionContext;
    import org.apache.struts2.dispatcher.HttpParameters;
    
    import java.util.Map;
    
    public class TestAction {
        public String execute(){
          ActionContext actionContext = ActionContext.getContext() ;
          Map<String,Object> applicationMap = actionContext.getApplication() ; 
            applicationMap.put("applicationKey","applicationValue") ;
         Map<String,Object> sessionMap = actionContext.getSession() ;
        sessionMap.put("sessionKey","sessionValue") ;
        Map<String,Object> requestMap = (Map<String, Object>) actionContext.get("request");
        requestMap.put("requestKey","requestValue");
         HttpParameters paramterMap = actionContext.getParameters() ;
          //System.out.println("1+1"+paramterMap.get("name"));
                        return  "OK" ;
                }
    }

2.实现 XxxAware 接口

package com.struts2.awarepage;
    
    import org.apache.struts2.dispatcher.HttpParameters;
    import org.apache.struts2.interceptor.*;
    
    import java.util.Map;
    
    public class TestAwareAction implements ApplicationAware,RequestAware,SessionAware,HttpParametersAware { 
        //ParameterAware弃用，推荐HttpParametersAware
    
        private Map<String,Object> applicationMap ;
        private Map<String,Object> sessionMap ;
        private Map<String,Object> requestMap ;
        private HttpParameters parameter ;
    
        public String execute(){
            applicationMap.put("applicationKey","applicationValue") ;
            sessionMap.put("sessionKey","sessionValue") ;
            requestMap.put("requestKey","requestValue") ;
            System.out.println(parameter.get("name"));
            return "OK" ;
    
        }
        @Override
        public void setApplication(Map<String, Object> map) {
            applicationMap = map ;
        }
    
        @Override
        public void setRequest(Map<String, Object> map) {
            requestMap = map ;
        }
    
        @Override
        public void setSession(Map<String, Object> map) {
            sessionMap = map ;
        }
    
        @Override
        public void setParameters(HttpParameters httpParameters) {
             parameter = httpParameters ;
        }
    }

选用的建议: 若一个 Action 类中有多个 action 方法, 且多个方法都需要使用域对象的 Map 或 parameters, 则建议使用Aware 接口的方式
    
     session 对应的 Map 实际上是 SessionMap 类型的! 强转后若调用其 invalidate() 方法, 可以使其 session 失效!如:

((SessionMap)session).invalidate();

*II. 和 Servlet API 耦合的方式: 可以访问更多的 Servlet API 对象, 且可以调用其原生的方法.*

使用 ServletActionContext

package com.struts2.servletaction;
    
    import org.apache.struts2.ServletActionContext;
    
    import javax.servlet.ServletContext;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpSession;
    
    public class TestServletActionContext {
    
        public String execute(){
            HttpServletRequest request = ServletActionContext.getRequest() ;
            HttpSession session = request.getSession() ;
            ServletContext servletContext = ServletActionContext.getServletContext() ;
    
    
            request.setAttribute("requestKey","requestValue");
            session.setAttribute("sessionKey","sessionValue");
            servletContext.setAttribute("applicationKey","applicationValue");
            System.out.println("execute...");
    
    
            return "OK" ;
        }
    }

实现 ServletXxxAware 接口

package com.struts2.servletawareaction;
    
    import org.apache.struts2.interceptor.ServletRequestAware;
    import org.apache.struts2.interceptor.ServletResponseAware;
    import org.apache.struts2.util.ServletContextAware;
    
    import javax.servlet.ServletContext;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    public class TestServletContextAwareAction implements ServletContextAware,ServletResponseAware,ServletRequestAware { 
        //同上一个实现 XxxAware 接口
        @Override
        public void setServletContext(ServletContext servletContext) {
    
        }
    
            @Override
            public void setServletRequest(HttpServletRequest httpServletRequest) {
    
            }
    
            @Override
            public void setServletResponse(HttpServletResponse httpServletResponse) {
    
            }
        }

struts.xml配置

<!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.5//EN" "http://struts.apache.org/dtds/struts-2.5.dtd">
    
    <struts>
    <package name="servletActionContext" extends="struts-default">
            <action name="servletActionContext" class="com.struts2.servletaction.TestServletActionContext">
                <result name="OK">/servletActionContext_page.jsp</result>
            </action>
        </package>
    
        <package name="aware_action" extends="struts-default">
            <action name="aware_page" class="com.struts2.awarepage.TestAwareAction">
                <result name="OK">/aware_page.jsp</result>
            </action>
        </package>
    
        <package name="action-page" extends="struts-default">
            <action name="action-page" class="com.struts2.actionpage.TestAction">
                <result name="OK">/action-page.jsp</result>
            </action>
    
        </package>
    </struts>

jsp示例片段：

<a href="aware_page.action"> to action-page</a>

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   <td><font> &nbsp;&nbsp;&nbsp;大牛，别默默看了。快登陆帮我评论吧！ *^o^* </font> </td> 
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