Struts transmits data from the background to the foreground

Before writing it, The get and set methods should be provided for the instantiated objects in the action, and data can be obtained through the struts tag at the front end.

 

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Instead of passing values to the JSP page by action, the JSP page obtains the values in the property values or ranges (such as request, session, and application) of the action. Therefore, there are two methods: 1. Obtain the value of the action attribute. You can use the struts2 tag and ognl to obtain the value, for example, <s: property value = "property name. property name... "/> In this Form 2, get the value in the range and directly use the El expression, for example, $ {name} is the attribute named name bound to the requestscope range, omit requestscope because this is the default range $ {sessionscope. name} is the name attribute bound to the sessionscope.

 

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1 ) Action defines getpersons () 2 ) getname () and getage () are defined in person () 3 ): "U" value = "persons" > '# U. getname () ' /> '# U. getage () ' />

总结来说是2中方式：如下 

1、一般是在Action中定义一个成员变量，然后对这个成员变量提供get/set方法，在JSP页面就可以取到这个变量的值了。

　　1）在Action中定义成员变量

//定义一个成员变量 private String message;       //提供get/set方法 public String getMessage() {     return message; } public void setMessage(String message) {     this.message = message; }

　2）在JSP页面中取值

${message} 或者 <s:property value="message"/>

2、但是定义的成员变量多了，感觉整个Action的代码就很长了。这个时候可以使用一些Servlet API进行值的存取操作：HttpServletRequest、HttpSession和ServletContext。Struts2对这个三个对象用Map进行了封装，我们就可以使用Map对象来存取数据了。

　　1)在Action中存值

ActionContext actionContext = ActionContext.getContext();           //get HttpServletRequest Map<String,Object> request = (Map) actionContext.get("request"); request.put("a", "a is in request");           //get HttpSession //Map<String,Object> session = (Map) actionContext.get("session"); Map<String,Object> session = actionContext.getSession(); session.put("b", "b is in session");           //get ServletContext //Map<String,Object> application  = (Map) actionContext.get("application"); Map<String,Object> application  = actionContext.getApplication(); application.put("c", "c is in application");

　2）在JSP页面上取值

${a} ${b} ${c} or               ${requestScope.a} ${sessionScope.b} ${applicationScope.c}

struts transfers data from the background to the foreground