Reflection question

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Dave - 09 Dec 2005 19:23 GMT

I am using glazed lists to create JTables from simple POJO objects.
With my understanding of glazed lists you basically need to create a
TableFormat and TextFilterator for each POJO in order to create the
table (with filtering). I am trying to use reflection to dynamically
determine the column count, column names and column values. Here is
how I access the POJO objects in order to get the column values:

/* */
public Object getColumnValue(Object baseObject, int column)
{
Object columnValue = null;
Class c = baseObject.getClass();
Field [] fields = c.getDeclaredFields();
try
{
columnValue = fields[column].get(baseObject);
}
catch (IllegalAccessException e)
{

TalonAuditTrails.getInstance(this.getClass().toString()).exceptionThrown(e);
}
catch (Exception e)
{

TalonAuditTrails.getInstance(this.getClass().toString()).exceptionThrown(e);
}
return columnValue;
}

Here's the rub:

The attributes must be declared as public in the POJO to use this
method; which I don't want to because I feel this is bad design.

Is there a better way to do this with reflection?

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Oliver Wong - 09 Dec 2005 19:29 GMT

>I am using glazed lists to create JTables from simple POJO objects.
> With my understanding of glazed lists you basically need to create a
[quoted text clipped - 32 lines]
>
> Is there a better way to do this with reflection?

I believe the typical approach to this is to only get the fields which
are public (there may be zero of these), and then additionally get values
from all the getters that can be found.

That is, after getting all the declared fields, you then get all the
declared methods which take no arguments, which return something, and whose
name starts with "get" (or "is" in the case where the method returns a
boolean).

So if I had a class like this:

<code>
public class myClass {
private int x, y, z;

public int getX() {
return this.x;
}

public void doubleX() {
x = x * 2;
}

public int getY() {
return this.y;
}

public void setY(int value) {
this.y = value;
}
}
</code>

Then the reflection code would know to use getX() and getY() to populate the
column values, but to not expose the value of z.

- Oliver

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