如何测试使用外部程序包与数据库交互的方法

Question

I am trying to test a function, which is part of the business logic layer of a struts application. I am facing problem because the code is dependent on external functions in a organization wide used jar.

public CustomObject getCustomObject(String id){
        CustomObject customObject = new CustomObject();
        QueryObject sql = createSqlStatement(id); // EXTERNAL jar
        Result result = execute(sql); // EXTERNAL jar
        ArrayList list = result.getResulList(); // EXTERNAL jar

        // Logic to use the list object to fill the customObject
        // I can see an error here, that could have been 
        // caught in unit test

            return customObject ;
        }

Now the problem is testing the logic of filling up the object.
The Junit4 test that I have written is:

    @Test
    public void testCustomObject()  {
        CustomObject customObjectwActual = new CustomObject();
        CustomObject customObjectExpected = new CustomObject();

           // set properties of customObjectExpected here

        customObjectwActual = getCustomObject(id); // Exception here

        assertEquals(customObjectExpected , customObjectwActual );
    }

The exception is thrown because "the external jar classes are loaded at the time of startup of struts application" as per the developers explanation. I am new to Java and struts. Is my approach wrong? Is there a way to "load" these external jar classes in the setUpBeforeClass() in someway?
Please let me know if anything is unclear.

EDIT 2: Sorry, my question is unclear. I have these external jars in my classpath. It compiles fine, and it actually loads the external jar's classes. The SQL queries are stored in an xml file. These external jars have their own xml file with SQL statements as well. It is failing to load one of these two xml files.
Further, even if they load correctly, I actually dont want to call the database. Is there some way to mock these calls?

Answer 1

Is there a way to "load" these external jar classes in the setUpBeforeClass() in someway?

You just need to include these jars in your class path. Classes are loaded at runtime automatically when you use them

I am new to Java and struts. Is my approach wrong?

There is nothing specific to Struts. Its plain core java that external classes you are using in your project must be included in your class path

Is there some way to mock these calls?

Well if you mock these calls ,whats the use of writing the DB testcases which does test DB Interaction

I also suggest using IDE like eclipse as its very helpful for development like providing compilation issues upfront, formatting etc