如何在OQL中对字符串排序

Question

I have tried:

select sort(obj.displayName, 'lhs < rhs') from my.org.BusinessClass obj

and

select sort(obj.displayName, 'lhs.toString() < rhs.toString()') from my.org.BusinessClass obj

Both give me character array results, but none of them are sorted by String. I think it's sorting by object id.

I have also tried:

select sort(obj.displayName, lhs < rhs) from my.org.BusinessClass obj 
select sort(obj.displayName, lhs.toString() < rhs.toString()) from my.org.BusinessClass obj

But these result in errors because sort second argument is suppose to a string expression.

The examples on the VisualVM documentation are only for numbers: Analyzing a Heap Dump Using Object Query Language (OQL)

The class is structured as follows:

package my.org;
public class BusinessClass {
    private String displayName;
    // rest of class omitted for brevity 
}

Answer 1

You can use the following query to sort strings in OQL:

select sort(heap.objects('java.lang.String'), 'lhs.toString().localeCompare(rhs.toString())')

in your case use this OQL query to sort your business object by displayName:

select sort(heap.objects('my.org.BusinessClass'), 'lhs.displayName.toString().localeCompare(rhs.displayName.toString())')

if you want to see your business object and actual displayName in the output use this OQL query:

select map(sort(heap.objects('my.org.BusinessClass'), 'lhs.displayName.toString().localeCompare(rhs.displayName.toString())'), 'toHtml(it)+" "+it.displayName.toString()')

Answer 2

This is the workaround I used:

1. Increase the max number of rows returned by OQL
   1. (see: Increasing the Max Size of OQL Result )
2. Copy and paste the result of the unsorted query to a text file
3. Use vim or similar text processor to remove the object id
4. sort using unix sort