struts2访问servlet的API

1.struts作为控制器，正常很多时候要访问到servlet的API，常用功能:

(1).获取请求参数,控制界面跳转

(2).把共享数据存储于request,session,servletContext中,获取作用域中的数据

宏观的来说，应该有三种访问方式。

2.第一种:实现接口，访问Action时完成注入

ServletContextAware

void setServletContext(javax.servlet.ServletContext context)

ServletRequestAware

void setServletRequest(javax.servlet.http.HttpServletRequest request)

ServletResponseAware

void setServletResponse(javax.servlet.http.HttpServletResponse response)

上述方式:Action和ServletAPI耦合太深了.

简单的示例代码：

package cn.wwh.www.web.servletapi;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.struts2.interceptor.ServletRequestAware;
import org.apache.struts2.interceptor.ServletResponseAware;

import com.opensymphony.xwork2.Action;
import com.opensymphony.xwork2.ActionSupport;

/**
*类的作用：
*
*
*@author 一叶扁舟
*@version 1.0
*@创建时间： 2014-8-16 上午07:54:05
*/
public class ParamAction1 extends ActionSupport implements ServletRequestAware,
ServletResponseAware {

private static final long serialVersionUID = 1L;
private HttpServletRequest request;
private HttpServletResponse response;

@Override
public String execute() throws Exception {
String name = request.getParameter("name");
String age = request.getParameter("age");
System.out.println("name:" + name);
System.out.println("age:" + age);
response.getWriter().write(name + "<br/>");
response.getWriter().write(age);
// 没有起到效果，很奇怪
request.getRequestDispatcher("/views/servletapi/result.jsp").forward(
request, response);
return Action.NONE;
}

public void setServletRequest(HttpServletRequest request) {
this.request = request;
}

public void setServletResponse(HttpServletResponse response) {
this.response = response;

}

}

3.第二种:使用ServletActionContext(开发中使用的很多,因为简单,直观)ServletActionContext: 通过该类提供了ServletAPI的环境,可以获取到Servlet的API信息static PageContext getPageContext()static HttpServletRequest getRequest()static HttpServletResponse getResponse()static
ServletContext getServletContext()

该方案可避免Action类实现XxxAware接口，但Action依然与Servlet API直接耦合但是该方式和ServletApi也有耦合.

简单的实例代码：

package cn.wwh.www.web.servletapi;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import org.apache.struts2.ServletActionContext;

import com.opensymphony.xwork2.ActionSupport;

/**
*类的作用：
*
*
*@author 一叶扁舟
*@version 1.0
*@创建时间： 2014-8-16 上午09:09:02
*/
public class ParamAction2 extends ActionSupport {

private static final long serialVersionUID = 1L;
public String execute() throws Exception {

HttpServletRequest req = ServletActionContext.getRequest();
String name = ServletActionContext.getRequest().getParameter("name");
String age = ServletActionContext.getRequest().getParameter("age");
HttpSession session = req.getSession();
session.getServletContext();
System.out.println(name);
System.out.println(age);
HttpServletResponse resp = ServletActionContext.getResponse();
return NONE;
}

}

4.第三种方式：使用ActionContext类(没有和ServletApi耦合,开发推荐使用方式)

Action的上下文,该类提供了Action存在的环境. 也就是说通过该类可以获取到Action相关的一切数据.

ActionContext

getContext() 返回ActionContext实例对象

get(key) 相当于 HttpServletRequest的getAttribute(String name)方法

put(String,Object) 相当于HttpServletRequest的setAttribute方法

getApplication() 返回一个Map对象，存取ServletContext属性

getSession() 返回一个Map对象，存取HttpSession属性

getParameters() 类似调用HttpServletRequest的getParameterMap()方法

setApplication(Map) 将该Map实例里key-value保存为ServletContext的属性名、属性值

setSession(Map) 将该Map实例里key-value保持为HttpSession的属性名、属性值

获取ActionContext对象: ActionContext context = ActionContext.getContext();

简单的示例代码：

package cn.wwh.www.web.servletapi;

import java.lang.reflect.Array;
import java.util.Map;

import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionSupport;

/**
*类的作用：
*
*
*@author 一叶扁舟
*@version 1.0
*@创建时间： 2014-8-16   上午09:31:42
*/
public class ParamAction3 extends ActionSupport {

private static final long serialVersionUID = 1L;

public String execute() throws Exception {
ActionContext ctx = ActionContext.getContext();
Map<String,Object> paramMap = ctx.getParameters();
System.out.println(paramMap);

//去paramMap.get("name")数组中索引为0的元素值
System.out.println(Array.get(paramMap.get("name"), 0));

//往request设置共享数据
ctx.put("name", "一叶扁舟");//request.setAttribute(key,Object)
Object requestValue  = ctx.get("name");
System.out.println(requestValue);

//往Session设置共享数据
//Map<String,Object> getSession()
Map<String,Object> sessionMap = ctx.getSession();
sessionMap.put("sessionKey", "sessionValue");

//往ServletContext中设置共享数据
//.Map<String,Object> getContextMap()
Map<String,Object> contextMap= ctx.getContextMap();
contextMap.put("appKey", "appValue");
return SUCCESS;
}

}

注意在jsp中读取数据为：

${requestScope.name}<br />

${sessionScope.sessionKey}<br />

${appKey}

5.通过ActionContext获取request、session、application解耦Map

(1) 对request域的操作

actionContext.put("name", "一叶扁舟") --> 相等与request.setAttribute("name", "一叶扁舟");

Object o = actionContext.get("name"); --> 等同与Object o = request.getAttribute("name");

(2).对session域的操作

Map<String,Object> sessionMap = ActionContext.getContext().getSession();

sessionMap.put("name", "一叶扁舟") --> 等同与session.setAttribute("name", "一叶扁舟");

Object o = sessionMap.get("name") --> 等同与Object o = session.getAttribute("name");

(3).对application域的操作

Map<String,Object> appMap = ActionContext.getContext().getApplication();

appMap.put("name", "一叶扁舟") --> 等同与servletContext.setAttribute("name", "一叶扁舟");

Object o = appMap.get("name") --> 等同与Object o = servletContext.getAttribute("name");

(4). 对请求参数的操作

Map<String,Object> paramMap = ActionContext.getContext().getParameters();

Object o = paramMap.get("username");

String[] values = (String[])o;

String username = values[0];