I'm using Javers to compare two object having a String attribute. Since in my application an empty String and a null value in that attribute must be treated equal, I wrote a CustomValueComparator and registered it for the java.lang.String class.
But that comparator is not used, when the attribute is null in the old (or left) version. I wrote a JUnit test to show the issue, see below.
Of course, I could run through my old object and set the null attribute to empty string before comparing it, but probably you guys know a better solution. Neither can I change or override the equals method of MyClass.
Java 1.8.0_144; Javers 3.9.0
@Test
public void test() {
MyClass old = MyClass.getBuilder()
.anAttribute(null)
.build();
MyClass current = MyClass.getBuilder()
.anAttribute("")
.build();
Javers javers = JaversBuilder.javers()
.registerValueObject(ValueObjectDefinitionBuilder.valueObjectDefinition(MyClass.class)
.withIncludedProperties(Arrays.asList("anAttribute"))
.build())
.registerValue(String.class, new StringValueComparator())
.build();
Diff diff = javers.compare(old, current);
System.out.println(diff.prettyPrint());
Assert.assertFalse(diff.hasChanges());
}
class MyClass {
private String anAttribute;
public static Builder getBuilder() {
return new Builder();
}
static class Builder {
MyClass resp = new MyClass();
Builder anAttribute(String arg) {
resp.anAttribute = arg;
return this;
}
public MyClass build() {
return resp;
}
}
}
class StringValueComparator implements CustomValueComparator<String> {
@Override
public boolean equals(String left, String right) {
String defaultLeft = StringUtils.defaultString(left);
String defaultRight = StringUtils.defaultString(right);
return defaultLeft.equals(defaultRight);
}
}
The output in the console is:
Diff:
* changes on com.test.TestJavers$MyClass/ :
- 'anAttribute' changed from '' to ''
