For MAP access using jstl, the key is integer or long.

 

Refer to this article on stackoverflows.ArticleHttp://stackoverflow.com/questions/924451/jstl-access-a-map-value-by-key

 

Map <integer, string> map = new hashmap <integer, string> (); <br/> map. put (1, "one"); <br/> map. put (2, "two"); <br/> <C: Out value = "$ {map [1]}"/>The value cannot be obtained.

 

ChangeMap <long, string> map = new hashmap <long, string> (); <br/> map. Put (1l, "one ");That is, it is normal.

 

The reason is that jstl encapsulates numbers as long by default.

 

Another problem: type conversion

 

 

Map <long, string> map = new hashmap <long, string> ();

$ {Map [obj. ID]}

 

When obj. ID is defined as int type, the value cannot be obtained. Convert obj. ID to long.

On the JSP page, you can write

$ {Map [obj. ID + 0]}