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Null Safe

In some cases, you might want to instantiate a @Parameter even though the end user has not provided a value, for example:


       
    
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@Parameter
@Optional
private List<Integer> numbers;

While interacting with numbers in your code, you will need to check if numbers == null at some point to avoid a NullPointerException.

The SDK supports the use of annotations like @NullSafe, which can provide an empty list instead of null. When you use it, the SDK can automatically create a value for you if the value was not configured.

There are many "flavors" of @NullSafe annotations. When used with List and Map interfaces, @NullSafe will provide a default implementation for those collections.

This example shows a POJO as a null safe type:


       
    
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@Parameter
@Optional
@NullSafe
private Foo foo;

As you might expect, the SDK will instantiate Foo and assign it to your foo parameter so that you do not have to manually check for null.

Note that if you use @NullSafe with a POJO, all the parameters declared inside the POJO must all be optional. If a parameter is required, there is no default value for the SDK to use. So, using @NullSafe to automatically instantiate required parameters makes no sense.

@NullSafe can be configured to instantiate a certain class instead of using the parameter’s type. This can be helpful in the cases where the parameter’s type cannot be instantiated (like an abstract class or an interface).

You specify the class to be instantiated by setting the defaultImplementingType attribute in the annotation, for example:


       
    
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@Parameter
@Optional
@NullSafe(defaultImplementingType = Foo.class)
private AbstractFoo foo;