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From: angelochen960 on 12 Mar 2010 09:02
Hi,

I have this bean:

public class Item {
private String type;
private Boolean pub;

public String getType() { return type;}

public Boolean isPub() { return pub;}
}


I can use item.getType() to get the type value, but I'm looking for a
generic way, say I have a string 'Type', then I'd like to get the
value of type of a certain object, any idea how to achieve this?
Thanks.

A.C.
From: Daniel Pitts on 12 Mar 2010 11:25
On 3/12/2010 6:02 AM, angelochen960(a)gmail.com wrote:
> Hi,
>
> I have this bean:
>
> public class Item {
> private String type;
> private Boolean pub;
This should probably be a "boolean", not a Boolean.
>
> public String getType() { return type;}
>
> public Boolean isPub() { return pub;}
Same as above. Boolean is an object reference type, which may end up
being null. Most of the time, you don't want a null for a boolean
value. This is true of most of the primitive types.
> }
>
>
> I can use item.getType() to get the type value, but I'm looking for a
> generic way, say I have a string 'Type', then I'd like to get the
> value of type of a certain object, any idea how to achieve this?
> Thanks.
>
> A.C.
Actually, it would be if you had the string "type", because that is the
name of the property. You can use introspection, or use a third-party
library (which uses reflection/introspection).

Spring has some good classes for this.

I often prefer OGNL for an embedded expression language.

So, the Big Question is, what are you *really* trying to do? If you
have to ask about reflection, then you are hopefully not working on a
production system. Reflection is useful for framework-type development,
but developing a useful and maintainable framework requires experience.
If you're playing around with reflection for fun and/or homework, then
have at it.



--
Daniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/>
From: Arne Vajhøj on 12 Mar 2010 20:29
On 12-03-2010 11:25, Daniel Pitts wrote:
> On 3/12/2010 6:02 AM, angelochen960(a)gmail.com wrote:
>> I have this bean:
>>
>> public class Item {
>> private String type;
>> private Boolean pub;
> This should probably be a "boolean", not a Boolean.
>>
>> public String getType() { return type;}
>>
>> public Boolean isPub() { return pub;}
> Same as above. Boolean is an object reference type, which may end up
> being null. Most of the time, you don't want a null for a boolean value.
> This is true of most of the primitive types.

Data classes frequently have the requirement to support
null for data not available or not applicable.

Arne
From: Daniel Pitts on 12 Mar 2010 20:52
On 3/12/2010 5:29 PM, Arne Vajh�j wrote:
> On 12-03-2010 11:25, Daniel Pitts wrote:
>> On 3/12/2010 6:02 AM, angelochen960(a)gmail.com wrote:
>>> I have this bean:
>>>
>>> public class Item {
>>> private String type;
>>> private Boolean pub;
>> This should probably be a "boolean", not a Boolean.
>>>
>>> public String getType() { return type;}
>>>
>>> public Boolean isPub() { return pub;}
>> Same as above. Boolean is an object reference type, which may end up
>> being null. Most of the time, you don't want a null for a boolean value.
>> This is true of most of the primitive types.
>
> Data classes frequently have the requirement to support
> null for data not available or not applicable.
Which is why I used the phrase "Most of the time" as opposed to "All of
the time".

In my experience, it is more common for someone mistakenly choose a
wrapper than for someone meaningfully choose a wrapper. It is also less
common that someone mistakenly chooses a primitive over a wrapper.

--
Daniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/>
From: Arne Vajhøj on 16 Mar 2010 21:56
On 12-03-2010 20:52, Daniel Pitts wrote:
> On 3/12/2010 5:29 PM, Arne Vajh�j wrote:
>> On 12-03-2010 11:25, Daniel Pitts wrote:
>>> On 3/12/2010 6:02 AM, angelochen960(a)gmail.com wrote:
>>>> I have this bean:
>>>>
>>>> public class Item {
>>>> private String type;
>>>> private Boolean pub;
>>> This should probably be a "boolean", not a Boolean.
>>>>
>>>> public String getType() { return type;}
>>>>
>>>> public Boolean isPub() { return pub;}
>>> Same as above. Boolean is an object reference type, which may end up
>>> being null. Most of the time, you don't want a null for a boolean value.
>>> This is true of most of the primitive types.
>>
>> Data classes frequently have the requirement to support
>> null for data not available or not applicable.
> Which is why I used the phrase "Most of the time" as opposed to "All of
> the time".
>
> In my experience, it is more common for someone mistakenly choose a
> wrapper than for someone meaningfully choose a wrapper. It is also less
> common that someone mistakenly chooses a primitive over a wrapper.

Data classes and CRUD are a big part of IT.

And choosing a wrapper unnecessary have very small consequences
while mistakenly choosing a primitive is a real data integrity
problem.

Arne

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