接下来介绍Struts2中访问request,application,session对象的方式
在上面介绍了通过action访问用户输入，从而替代了访问HTTP Servlet Request，实现了与web层的解耦，但在某些特殊场景中，action中需要访问这些对象。Struts提供了多种方式访问这些对象，可以将这些方式大体分为两类：
与Servlet API解耦的方式和与Servlet API耦合的方式：
解耦方式：
1、为了避免与servlet API 耦合，struts用三个map来封装HttpServletRequest, HttpSession,ServletContext对象
在action中使用map来存储和访问数据，如下代码：
package Controller;
import java.util.Map;
import com.opensymphony.xwork2.Action;
import com.opensymphony.xwork2.ActionContext;
import model.User;
//与servlet解耦的方式，通过ActionContext获取三个类型对应的Map对象
public class LoginAction1 implements Action {
public User user;
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
@Override
public String execute() throws Exception {
if("aa".equals(user.getUserName())&&"123".equals(user.getPassWord())) {
{
ActionContext context =ActionContext.getContext();
Map request=(Map) context.get("request");
Map session=context.getSession();
Map application =context.getApplication();
request.put("greet", "欢迎");
session.put("user", user);
Integer cnt= (Integer) application.get("counter");
if(cnt==null) {
cnt=1;
}else {
cnt++;
}
application.put("counter", cnt);
}
return SUCCESS;
}
return ERROR;
}
}
首先通过ActionContext.getContext()的方法获取到context对象，然后通过context对象获取这三个对象，
其中，request需要context.get("request")的方式获取到，而其他两种使用getSession和getApplication便可以获取到。
修改success.jsp:
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<%@ taglib prefix="s" uri="/struts-tags" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Insert title here</title>
</head>
<body>
<s:property value="userName"/><br>
================<br>
${ requestScope.greet}<br>
${ sessionScope.user.userName}<br>
<%-- ${ contextScope.counter } --%>
本网站的访问量：${applicationScope.counter }<br>
</body>
</html>运行截图：
2、通过实现SessionAware, RequestAware, ApplicationAware来实现访问
代码如下：
package Controller;
import java.util.Map;
import org.apache.struts2.interceptor.ApplicationAware;
import org.apache.struts2.interceptor.RequestAware;
import org.apache.struts2.interceptor.SessionAware;
import com.opensymphony.xwork2.Action;
import com.opensymphony.xwork2.ActionContext;
import model.User;
public class LoginAction2 implements Action, SessionAware, RequestAware, ApplicationAware {
private User user;
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
private Map request;
private Map session;
private Map application;
public void setRequest(Map request) {
this.request = request;
}
public void setSession(Map session) {
this.session = session;
}
public void setApplication(Map application) {
this.application = application;
}
@Override
public String execute() throws Exception {
if ("aa".equals(user.getUserName()) && "123".equals(user.getPassWord())) {
{
request.put("greet", "欢迎");
session.put("user", user);
Integer cnt = (Integer) application.get("counter");
if (cnt == null) {
cnt = 1;
} else {
cnt++;
}
application.put("counter", cnt);
}
return SUCCESS;
}
return ERROR;
}
}
此种方式通过实现接口的方式，在Struts2框架运行时通过setter方法向Action实例注入这三个对象
运行截图：
耦合的方式：
耦合的方式即意味着直接访问ServletAPI，这种方式不方便进行单元测试，因为这三个对象是由servlet容器所创造，所以在测试时需要servlet容器。
1.通过ServletActionContext对象获取
代码如下：
package Controller;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import org.apache.struts2.ServletActionContext;
import com.opensymphony.xwork2.Action;
import model.User;
public class LoginAction3 implements Action{
private User user;
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
@Override
public String execute() throws Exception {
if("aaaa".equals(user.getUserName())&&"123".equals(user.getPassWord())) {
{
//通过ServletActionContext耦合的方式访问request,session,context
HttpServletRequest request =ServletActionContext.getRequest();
HttpSession session =request.getSession();
ServletContext context = ServletActionContext.getServletContext();
request.setAttribute("greet", "欢迎");
session.setAttribute("user", user);
Integer cnt= (Integer) context.getAttribute("counter");
if(cnt==null) {
cnt=1;
}else {
cnt++;
}
context.setAttribute("counter", cnt);
}
return SUCCESS;
}
return ERROR;
}
}
通过ServletActionContext对象来获取request和context对象，session对象需要通过request来获取
运行截图：
2.通过实现ServletContextAware, ServletRequestAware接口注入来获取
代码如下：
package Controller;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import org.apache.struts2.ServletActionContext;
import org.apache.struts2.interceptor.ServletRequestAware;
import org.apache.struts2.util.ServletContextAware;
import com.opensymphony.xwork2.Action;
import model.User;
public class LoginAction4 implements Action, ServletContextAware, ServletRequestAware {
private HttpServletRequest request;
private ServletContext context;
private User user;
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
@Override
public void setServletRequest(HttpServletRequest arg0) {
// TODO Auto-generated method stub
this.request=arg0;
}
@Override
public void setServletContext(ServletContext arg0) {
// TODO Auto-generated method stub
this.context=arg0;
}
@Override
public String execute() throws Exception {
if("a4".equals(user.getUserName())&&"123".equals(user.getPassWord())) {
{
//HttpServletRequest request =ServletActionContext.getRequest();
HttpSession session =request.getSession();
//ServletContext context = ServletActionContext.getServletContext();
request.setAttribute("greet", "欢迎");
session.setAttribute("user", user);
Integer cnt= (Integer) context.getAttribute("counter");
if(cnt==null) {
cnt=1;
}else {
cnt++;
}
context.setAttribute("counter", cnt);
}
return SUCCESS;
}
return ERROR;
}
}
运行截图：
3.通过ServletActionContext.HTTP_REQUEST与ServletActionContext.SERVLET_CONTEXT的方式获取
代码如下：
package Controller;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import org.apache.struts2.ServletActionContext;
import com.opensymphony.xwork2.Action;
import com.opensymphony.xwork2.ActionContext;
import model.User;
public class LoginAction5 implements Action {
private HttpServletRequest request;
private ServletContext context;
private User user;
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
@Override
public String execute() throws Exception {
if("a4".equals(user.getUserName())&&"123".equals(user.getPassWord())) {
{
request =(HttpServletRequest) ActionContext.getContext().get(ServletActionContext.HTTP_REQUEST);
context =(ServletContext) ActionContext.getContext().get(ServletActionContext.SERVLET_CONTEXT);
request.setAttribute("greet", "欢迎");
//session.setAttribute("user", user);
Integer cnt= (Integer) context.getAttribute("counter");
if(cnt==null) {
cnt=1;
}else {
cnt++;
}
context.setAttribute("counter", cnt);
}
return SUCCESS;
}
return ERROR;
}
}
运行截图：
这就是常用五种访问request，session,application对象的方式。
学习浅显，欢迎指正。
