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Java expressions

In the test data table of the test suite editor, you can set the format of variable values to Java expressions. The type of the expressions must be compatible with the type of the variables. The Java context is the variables themselves and any imports defined in the Imports page of the Test Data Table view.


Questions and answers about Java expressions

This section contains some questions and answers about the use of Java expressions in the test data table of the test suite editor.


Question: Why is there a null value for a variable used in a Java expression?


Answer: The variable is not being initialized in the request message because it is not being used in an invocation. You must use the variable in a test step in order for it to be initialized correctly, such as an Invocation, Wait on, or Wait step.


Question: I want to develop a test scenario where I can perform the following steps:

  1. Send a request for a new customer ID.
  2. Receive a response with the new customer ID.
  3. Send a new request using the customer ID received in step 2.
Is it possible to perform step 3? In other words, does the test data table provide a way to capture the customer ID from Step 2 and then use it in a request in Step 3?


Answer: Yes, this is a typical way to reuse the variables in the test data table. In this scenario, the customer ID is expressed as an expected variable in the test data table and the variable can be used in a subsequent request.


Question: I have a returned response that contains a Customer ID value. I want to populate an input parameter of a new request with the Customer ID. I assume that this requires a Java expression in the new request to populate a value with the Customer ID value of the initial response, but it is not obvious how to use a Java expression to accomplish this task. The test data table defines the response as a DOM Document type and there does not seem to be a simple way to write a single Java expression to obtain a reference to the Customer ID that is contained in one of the nodes in the DOM Document. Is there any way to accomplish this with a Java expression?


Answer: Yes. There is a utility class named com.ibm.wbit.comptest.ctnative.runtime.utils.DOMHelper that is used internally to extract the values in a DOM Document type object. You can use the utility method getSelectedNode(target, xpathExpr, nsInfo) to extract the field that you want to reference in your other variables. In your scenario, the target will return your DOM Document object and the xpathExpr will be the XPath to the Customer ID value. The nsInfo is not relevant in your scenario and you can simply set it to null. The following code fragment shows how to use the utility class: 

DOMHelper.getSelectedNode(responseDocument, "soap:Envelope/soap:Body/ns5:operation1/input1/field1", null)

If that the namespace prefix in your XPath must match the namespace prefix in your response message. To use the helper class, you need to import it into your test suite using the Import page in the Test Data Table view. You can simply switch to the Import page and add the DOMHelper class in the list. This enables you to reference the utility class in your variables using the Java Expression format.

Alternatively, you can also create a utility method yourself that takes a DOM Document type as a parameter to extract the value that you want and save your Java class in your component test project.

You can then switch to the Import page in the Test Data Table view and add your custom Java class in the list. Now you can reference your Java class in your variables using the Java expression format.


Question: I notice that DOMHelper.getSelectedNode returns a Java object. Does the object represent the String value of the element value or is it a node from which I need to extract the String?

For example, assume that the message looks like the following code fragment: 

<soap:Envelope>
  <soap:Body>
    <ns5:operation1>
       <input1>
          <field1>hello world</field>

Does the call to DOMHelper.getSelectedNode return a Java object that I can cast to a String that contains "hello world"? Or is it a node object of some type that I need to perform a further operation on?


Answer: It either returns a String or a DOM Node. In your example, it returns the "hello world" string and it will return a Node type if the node does not have a text value (such as input1 in your example). If you want to get the "hello world" string, you actually need to append "/text()" at the end of your XPath. Otherwise, you will get the DOM Node type instead. Similarly, if the field you want to extract is an attribute, you will need to insert "@" before the node name in your XPath.


Question: What do I do if I need multiple Java expressions to determine if a test passed?


Answer: In cases where the test logic is complex and cannot be expressed in a single Java expression, it may be helpful to create an expression that calls a method in a Java class, as shown.

  1. Create a Java class in the test project (if you want, it can be in a new Java package).

  2. Create a public static method that returns a boolean that will perform the verification logic.
  3. Typically, the logic will need the variable from the data table, so the method argument will usually be a DataObject.
  4. Write the verification logic.

  5. In the test data table, right-click the variable and select Add Operator > Condition.
  6. Edit the expression so that it calls your test method.
, When the test runs, the condition will pass or fail depending on whether the method returns true or false.


Example: You have a variable, myVar, of type MyVar, which contains the field, myData, of type MyData, which contains the field data1 of type String: 

myVar:MyVar
-- myData:MyData
----data1:String
----data2:String

You want to check whether the value of data2 is what is expected, depending on what the value of data1 is.

  1. In a Component Test project, create a class mytestpackage.Tester: 
    package mytestpackage;

import commonj.sdo.DataObject;

public class Tester {
    public static boolean checkValues(DataObject dObj) {
        boolean isPassed = true;
        System.out.println("Checking values");
        String d1 = dObj.getDataObject("myData").getString("data1");
        String d2 = dObj.getDataObject("myData").getString("data2");
        if (d1.startsWith("a123"))
        {
            if (s.equals("b456")) isPassed = true;
            else isPassed = false;
        }         return isPassed
    } }
  2. Save the class and ensure there are no compile errors.

  3. In the test data table, right click the myVar variable and select Add Operation -> Condition.
  4. Edit the condition (default is the expression, true), so that it calls Tester. 
     mytestpackage.Tester.checkValues(myVar)
Run the test case that uses myVar and the checkValues method will be called.


Question: How can I determine if an array has the required number of elements?


Answer: When specifying the values for array elements, if there are more elements in the actual data than are specified in the data table, no error is reported. If you want the test to fail in this case it is necessary to add a condition.

For example given a Business Object bo1 of type BO1 containing an array of bo2 of type BO2, if you want the test to pass only when five array elements are received, do the following:

  1. In the data table, under bo1, right-click bo2 and select Add Operator > Condition.

  2. Click the expected cell to put it in edit mode, and then change the value null to bo1.getList("bo2").size() == 5.

  3. Optional: Enter expected values for the fields of up to five bo2 elements. Checking the values of nested array data can be done in addition to setting a condition on the size of the array.

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