08 Struts2 访问Servlet API

Struts2 提供了三种方式访问本地Servlet API
1. ActionContext【推荐、非耦合】
2. XxxAware接口【推荐、非耦合】
3. ServletActionContext【不推荐、耦合】

1. ActionContext

ActionContext是Action执行的上下文对象，在ActionContext中保存了Action执行所需要的所有对象，包括parameters，request，session，application等。

ActionContext类访问Servlet API的常用方法，要访问Servlet API，可以通过如下方式进行，具体示例代码如下：

ActionContext context = ActionContext.getContext();
context.put("name", "张三");
context.getApplication().put("name", "李四");
context.getSession().put("name", "王五");

2. XxxAware 接口

XxxAware 接口获取的对象分两种，一种Servlet和非Servlet

2.1 非耦合Servlet

• RequestAware 接口
• SessionAware 接口
• ApplicationAware 接口

实现RequestAware，SessionAware，ApplicationAware 三个接口需要重写下面三个方法：

setRequest(Map<String, Object> request)  
setSession(Map<String, Object> session)  
setApplication(Map<String, Object> application)  

这三个方法给我们注入了一个Map 集合，我们只需要把数据存储在对应Map集合中就可以了。

public class UserinfoAction implements RequestAware, SessionAware, ApplicationAware {

    Map<String, Object> application;
    Map<String, Object> session;
    Map<String, Object> request;

    public String userLogin() {
        request.put("awareRequest", "赵云");
        session.put("awareSession", "黄盖");
        application.put("awareApplaction", "周瑜");
        return "success";
    }

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

${requestScope.awareRequest }<hr/>
${sessionScope.awareSession }<hr/>
${applicationScope.awareApplaction }<hr/>

2.2 耦合方式访问Servlet

Struts2 虽然提供了 RequestAware,SessionAwareApplicationAware 接口来访问 Servlet API。虽然这种方法可以访问Servlet API，但是无法直接获得Servlet API实例。为了在Action中直接访问Servlet API，Struts2还提供了下面三个接口:
- ServletRequestAware：实现该接口的Action可以直接访问Web应用的HttpServletRequest实例。
- ServletResponseAware：实现该接口的Action可以直接访问Web应用的HttpServletResponse实例。
- SessionAware：实现该接口的Action可以直接访问Web应用的HttpSession实例。
- ServletContextAware：实现该接口的Action可以直接访问Web应用的ServletContext实例。

public class UserinfoAction implements ServletRequestAware, ServletResponseAware, ServletContextAware, SessionAware {

    HttpServletRequest request;
    Map<String, Object> session;
    ServletContext context;
    HttpServletResponse response;

    public String userLogin() {

        request.setAttribute("servletResponseAware", "貂蝉");
        request.getSession().setAttribute("sessionKey", "吕布");

        session.put("sessionMap", "董卓");

        context.setAttribute("contextMap", "项羽");

        response.setCharacterEncoding("UTF-8");

        return "success";
    }
    @Override
    public void setServletRequest(HttpServletRequest request) {
        this.request = request;
    }
    @Override
    public void setSession(Map<String, Object> session) {
        this.session = session;
    }
    @Override
    public void setServletContext(ServletContext context) {
        this.context = context;
    }
    @Override
    public void setServletResponse(HttpServletResponse response) {
        this.response = response;
    }
}

3. ServletActionContext

为了直接访问Servlet API，Struts2框架还提供了ServletActionContext类，该类包含了几个常用的静态方法，具体如下：

• static HttpServletRequest getRequest()：获取Web应用的HttpServletRequest对象
• static HttpServletResponse getResponse()：获取Web应用的HttpServletResponse对象
• static ServletContext getServletContext()：获取Web应用的ServletContext对象
• static PageContext getPageContext()：获取Web应用的PageContext对象

3.1 HttpServletRequest

HttpServletRequest request = ServletActionContext.getRequest();

3.2 HttpServletResponse

HttpServletResponse response = ServletActionContext.getResponse();

3.3 ServletContext

ServletContext context = ServletActionContext.getServletContext();

3.4 PageContext

PageContext pageContext = ServletActionContext.getPageContext();

HttpServletRequest request = ServletActionContext.getRequest();
HttpSession session = request.getSession();
request.setAttribute("requesttKey","千年等一回")
session.setAttribute("userName", "赵雅芝");