Struts2：前后台的数据交互

Struts2：前后台的数据交互

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<span class="link_postdate">2016-07-18 11:08</span>
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目录(?)[+]
页面获取action传来的值
方法一使用Java代码
方法二使用EL表达式
方法三使用Struts2标签
action向页面传值
方法一放在request里
方法二放在session里面
方法三使用ValueStack
附ActionContext
get and go

页面获取action传来的值:

方法一：使用Java代码

<%= request.getParameter("str")%><%=request.getAttribute("str")%>

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方法二：使用EL表达式

${str}

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方法三：使用Struts2标签

从ValueStack取值：

<s:property value="name"/>
<s:property value="user"/>
<s:property value="user.id"/>

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从ActionContext中取值.

取值的时候需要加上一个符号:#

<s:property value="#user"/>
<s:property value="#user.id"/>

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<s:property value="#parameters.name"/><br>

//获得request中key为MyName的值
<s:property value="#request.MyName"/><br>
//获得session中key为MyName的值的值
<s:property value="#session.MyName"/><br>
//获得application中key为MyName的值的值
<s:property value="#application.MyName"/><br>

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action向页面传值：

方法一：放在request里：

1、通过ActionContext的实例化对象的put：

ActionContext context = ActionContext.getContext();
cotenxt.put(key, value);

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对应前端取值的4种方式：

<%=request.getAttribute("str") %>

${str}

<s:property value="str"/>

<s:property value="#request.str"/>

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2、通过ActionContext的实例化对象的get：

Map request = (Map)ActionContext.getContext().get("request");
request.put(key,value);

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获取方法同上（不可用S标签）

3、通过ServletActionContext获取request：

HttpServletRequest request = ServletActionContext.getRequest(); request.setAttribute(key, value);

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方法二：放在session里面：

1、通过request获取session

HttpServletRequest request = ServletActionContext.getRequest();

HttpSession session = request.getSession(); session.setAttribute(key, value);

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2、通过ActionContext获取session

HttpSession session =ActionContext.getContext().getSession();
session.setAttribute(key, value);

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方法三：使用ValueStack

ValueStack vs = ActionContext.getContext().getValueStack();
User user = new User();
vs.push(user);

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附：ActionContext

1、每一次请求都会创建一个ActionContext对象（也会创建一个ValueStack），struts框架默认向这个对象里面存放的对象(数据)很多,包括request、session、application、ValueStack、parameters等。

2、request session application的map类型获取：

（1）手动获取

ActionContext ac = ActionContext.getContext();
//获得Map类型request
Map<String,Object> request =
(Map<String, Object>) ac.get("request");

//获得Map类型session
Map<String, Object> session = ac.getSession();

//获得Map类型application
Map<String, Object> application = ac.getApplication();

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（2）自动获取（通过继承接口）

三个接口依次为:

RequestAware,SessionAware,ApplicationAware

public class WebActionTest extends ActionSupport implements RequestAware,SessionAware,ApplicationAware{
private Map<String, Object> request;
private Map<String, Object> session;
private Map<String, Object> application;

@Override
public String execute() throws Exception {
//页面中用原类型的对象取正常值就可以了
request.put("MyName", "tom");
session.put("YourName", "zhansan");
application.put("HerName", "lily");
return SUCCESS;
}
public void setRequest(Map<String, Object> request) {
this.request = request;
}

public void setSession(Map<String, Object> session) {
this.session = session;
}

public void setApplication(Map<String, Object> application) {
this.application = application;
}
}

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get and go!

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