java 从 HttpSession 检索 ArrayList 时获取无法将对象转换为 ArrayList 错误
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Getting cannot convert object to ArrayList error when retrieving ArrayList from HttpSession
提问by Ankur
I have saved an ArrayList to the session object. I am trying to retrieve it using
我已经将一个 ArrayList 保存到会话对象中。我正在尝试使用
sriList = session.getAttribute("scannedMatches");
I am getting the compile time error "Cannot convert from Object to ArrayList". How can I get my ArrayList back from the session object.
我收到编译时错误“无法从对象转换为 ArrayList”。如何从会话对象中取回我的 ArrayList。
回答by Pascal Thivent
The HttpSession#getAttribute()method returns java.lang.Object:
该HttpSession#getAttribute()方法返回java.lang.Object：
public java.lang.Object getAttribute(java.lang.String name)
Did you try to cast the returned object?
您是否尝试投射返回的对象？
sriList = (ArrayList)session.getAttribute("scannedMatches");
回答by Vincent Ramdhanie
You have to cast it.
你必须投它。
sriList = (ArrayList)session.getAttribute("scannedMatches");
回答by Rakesh Juyal
try this:
试试这个：
Object scannedMatchesObj = session.getAttribute("scannedMatches");
if ( scannedmatchesObj instanceOf List ){
sriList = (ArrayList)scannedMatchesObj;
//Do your stuff...
}
