将varargs从Java代码传递到SQL或PL / SQL

Question

I need to bind at maximum 8 variables. Each one of them could be null . Is there any recommended way to achieve this? I know that I could simply check for null , but this seems tedious.

Additional details :
I'm going to call this sql from java code. It may be written using JPA 2.0 Criteria API , but most likely it's going to be a native query. The database is Oracle 10g , so I think I could make use of PL/SQL as well.

Edit1:
Maybe the title is a bit misleading, so I'll try to elaborate. The resulting SQL would be something like:
...
WHERE var1 = :var1
AND var2 = :var2
...
AND var = :var8
Now I need to bind parameters from java code in the way like:
nativeQuery.setParameter("var1", var1)
...
nativeQuery.setParameter("var8", var8)
Some parameters could be null, so there is no need to bind them. But I see no way I can omit them in SQL.

Edit2: I'm expecting to see SQL or PL/SQL procedure in your answers (if it's ever possible without null checking). In fact, all of these variables are of the same type. I think it's not possible to find a solution using ANSI SQL, but maybe there are some PL/SQL procedures which allow to work with varargs?

Answer 1

The use of a criteria query is appropriate in this case, because if I understood correctly, you need to construct the SQL query dynamically. If all the variables except var1 are null, the where clause would be

where var1 = :var1

and if all variables except var2 and var5 are non null you would have

where var2 = :var2 and var5 = :var5

Is that right?

If so, then do what you plan to do, and construct the query dynamically using a criteria query. Something like this must be done:

CriteriaBuilder builder = em.getCriteriaBuilder();
Predicate conjunction = builder.conjunction();
if (var1 != null) {
    conjunction = builder.and(conjunction,
                              builder.equal(root.get(MyEntity_.var1),
                                            var1));
}
if (var2 != null) {
    conjunction = builder.and(conjunction,
                              builder.equal(root.get(MyEntity_.var2),
                                            var2));
}
...
criteria.where(conjunction);

Answer 2

You don't specify the type of the objects you want to pass. So in this example I'm considering you will pass Object .

@Test(expected=IllegalArgumentException.class)
public void testMyMethod() {
    List<Object> testList = new ArrayList<Object>();
    testList.add("1");
    testList.add("2");
    testList.add(3);

    myMethod(testList);
}

public void myMethod(List<Object> limitedList) {
    final int MAX_SIZE = 2;
    if (limitedList.size() > MAX_SIZE) {
        throw new IllegalArgumentException("Size exceeded");
    }
    //my logic
}

In this example I'm passing the arguments as a List of Objects but you could use array ( varargs ) or another type of collection if you need to. If the client sends me more than the expected objects it will throw an IllegalArgumentException .

Also if you don't want to throw an exception you could just continue and iterate the list to bind the parameters but using the list size or MAX_SIZE as your limit. For example:

public void myMethod2(List<Object> limitedList) {
        final int MAX_SIZE = 2;

        int size = MAX_SIZE;
        if (limitedList.size() < MAX_SIZE) {
            size = limitedList.size();
        }

        //Iterate through the list
        for (int i = 0; i < size; i++) {
            Object obj = limitedList.get(i);
            //Logic to bind the obj to the criteria.            
        }
    }