Generics problem in JSP?

[makpandian]

Hi,

List<Man> list=new ArrayList<Man>();
		
		Man raja=new Man("Raja",25);
		
		Man pandian=new Man("pandian",23);

                Iterator<Man> ite=list.iterator();
		
		while(ite.hasNext()){			
			Man obj=ite.next();
			System.out.println(obj);			
		}

The above code does work too good in my servlet. But in JSP its throws NullPointerException.
Does any one know why this happens in JSP ?

[masijade]

Because you shouldn't be using scriptlets?

I don't know that scriptlets even allow 1.5 or later syntax (yet another reason not to use them).

[makpandian]

Hi,

FYI, I have put my code inside the scriptlets. One more thing I have to say here is that if I did not use generics in Iterator, It s works pretty well.

List<Man> list=new ArrayList<Man>();
		
		Man raja=new Man("Raja",25);
		
		Man pandian=new Man("pandian",23);

                Iterator ite=list.iterator();
		
		while(ite.hasNext()){			
			Man obj=(Man)ite.next();
			System.out.println(obj);			
		}

The above code works well in JSP..

[masijade]

Hi,

FYI, I have put my code inside the scriptlets.

Which is exactly what I said you should not be doing. Do not use scriptlets they are no longer recommended. That was one of the first ways of getting "dynamic" content in a JSP, and was quickly gotten rid of. It is only supported for backwards compatability (and you don't want to be backwards, do you?).

One more thing I have to say here is that if I did not use generics in Iterator, It s works pretty well.

List<Man> list=new ArrayList<Man>();
		
		Man raja=new Man("Raja",25);
		
		Man pandian=new Man("pandian",23);

                Iterator ite=list.iterator();
		
		while(ite.hasNext()){			
			Man obj=(Man)ite.next();
			System.out.println(obj);			
		}

The above code works well in JSP..

And did I not also just say that I don't believe 1.5 syntax (i.e. Generics, the new for "each" loop, etc) is supported in Scriptlets?

Edit: Or maybe you're just using an out of date container that doesn't support 1.5.

[JosAH]

Edit: Or maybe you're just using an out of date container that doesn't support 1.5.

Nope, afaik (and my knowledge may be outdated as well), the type parameters <T> in generic classes confuse the JSP compiler (they look too much like html tags), that's why JSPs only support Java up to version 1.4 (or no generics in later versions). imho, that entire http technology (and all of its paraphernalia) sucks big times.

kind regards,

Jos

[makpandian]

The conclution of this Thread is: The type parameters <T> in generic classes confuse the JSP compiler. that's why JSPs only support Java up to version 1.4.

If any one of you has any objection in this conclusion, We can continue. Otherwise I will mark this as SOLVED.

[masijade]

No, the conclusion of this thread is that you should read the JEE 5 and/or JEE 6 tutorials, so that you can learn to do them right and not use scriptlets anymore.