2013/11/18 Nick Williams <nicho...@nicholaswilliams.net>:
>
>>
>> Regarding the list() example,
>> "map(u -> [u.username, u.firstName, u.lastName])" creates a
>> List<Object> with 3 elements and you are asking for "lastName"
>> property on that list.
>
> No, this is not correct. The lambda expression "u -> [u.username,
> u.firstName, u.lastName]" RETURNS a List<Object>. But "u" is a User. I am
> creating a List<Object> where the first element is the user's username, the
> second element is the user's first name, and the third element is the user's
> last name. That is completely valid. It is also essentially identical to
> Section 2.3.6.4's example "p->[p.name, p.unitPrice]."
>
>>
>> It is no wonder that it results in NumberFormatException. (Whether
>> there should be other handling for wrong property name here, I do not
>> know. One should look into what resolvers are being used here).
>
> It should not result in any exception. It should work, because the syntax is
> valid, as explained above. :-)
>
You apply map() which replaces each user with a list [u.username,
u.firstName, u.lastName].
Then you try to apply sorted() to that list. That sorted() fails as it
cannot evaluate "u1.lastName.compareTo(u2.lastName)".
As I said - provide a simple example.
>>
>>>>> Section 2.3.6.4 of the specification uses the following example, where a
>>>>> LIST literal is used as the right-hand side of the mapping lambda
>>>>> expression:
>>>>>
>>>>> products.stream().filter(p->p.unitPrice >= 10).
>>>>> .map(p->[p.name, p.unitPrice])
>>>>> .toList()
>>>>>
>>>>> I tried to use this exact syntax, as shown in the spec, with my example:
>>>>>
>>>>> ${users.stream()
>>>>> .filter(u -> fn:contains(u.username, '1'))
>>>>> .map(u -> [u.username, u.firstName, u.lastName])
>>>>> .sorted((u1, u2) -> u1.lastName.compareTo(u2.lastName) == 0
>>>>> ? u1.firstName.compareTo(u2.firstName) :
>>>>> u1.lastName.compareTo(u2.lastName))
>>>>> .toList()}
>>>>>
>>>>> And now I get this lovely error:
>>>>>
>>>>> javax.el.ELException: java.lang.NumberFormatException: For input string:
>>>>> "lastName"
>>>>> javax.el.BeanELResolver.invoke(BeanELResolver.java:185)
>>>>>
>>>>> org.apache.jasper.el.JasperELResolver.invoke(JasperELResolver.java:147)
>>>>> org.apache.el.parser.AstValue.getValue(AstValue.java:158)
>>>>> ...
>>>>>
>>
>> Best regards,
>> Konstantin Kolinko
>
> Thanks,
>
> Nick
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