Java EL expression report null pointer exception (NULLPOINTEXCEPTION)

Recently in the use of El expression, the use of the int variable, because, many times, the variable will not be assigned to the initial value, after consideration, should be declared from int to Integer, after the change has been reported null pointer exception, after careful review, my getter and setter method, either set int or return int, which has been tested before, declares an integer variable, does not initialize, and returns a null pointer exception with an int. The reason should be an integer (null) to int times error. Therefore, the data of the El expression background must be at the same time the class or the same basic type, (the basic type of the number type, return is 0 or 0.0,char type of return null character, what is inside, no scrutiny, Boolean variable return false), if you need the foreground no initial value, You need to use the object type data (such as the bound input box to display no data, i.e. the data is null)

2018-05-04 Update

In fact, the El expression is called by the Get method to get the value.

Java EL expression report null pointer exception (NULLPOINTEXCEPTION)