java 怎么更新session值_java – 如何更新session.setAttribute(name,value)值,其中名称相同？…「建议收藏」

我有一种情况,我需要更新名称保持不变的setAttribute的值.考虑以下情况作为示例 – 假设我有三个JSP：abc.jsp,xyz.jsp,pqr.jsp.现在首先运行abc.jsp然后控制前进到xyz.jsp&然后转发到pqr.jsp.现在执行pqr.jspt后,再次使用setAttribute中的更新值控制回xyz.jsp.

abc.jsp：

ArrayList getSupplyStatus=new ArrayList();

JavaBean javaBean=new JavaBean();

session=request.getSession(false);

getSupplyStatus=javaBean.getSupplyStatus(memberID); //It returns a ArrayList

if(!getSupplyStatus.isEmpty())

{

session.setAttribute(“UpdatedBooklist”, getSupplyStatus);

request.getRequestDispatcher(“xyz.jsp”).forward(request, response);

}

xyz.jsp：

session=request.getSession(false);

ArrayList getSupplyStatus=(ArrayList) session.getAttribute(“UpdatedBooklist”);

// some operations & forward to pqr.jsp

pqr.jsp：

// in this jsp new ArrayList will be prodeuced

// & I need to bound the value of “UpdatedBooklist” with

// which is set in abc.jsp,

// and previous value must be override & then forward to xyz.jsp again

// In xyz.jsp we recieve the updated value.

解决方法:

再次使用setAttribute()将replace the value并调用必要的生命周期方法.

If an object was already bound to this session of this name that implements HttpSessionBindingListener, its HttpSessionBindingListener.valueUnbound method is called.

您也可以使用removeAttribute()并再次设置具有相同名称的属性.如果通过’update’表示您希望对象更新而不是替换,则使用getAttribute()获取属性并在其上调用将改变对象的方法.

标签：java,servlets

来源： https://codeday.me/bug/20190823/1696017.html