I want to set all String members of an object to an empty string if they are null.
Pseudocode:
foreach member in object {
if (member instanceof String and member == null) {
member = '';
}
}
What is the simplest way to achieve that? Any framework / tool that I can use? Write my own solution via reflection?
public static void setEmpty(Object object) throws IllegalArgumentException, IllegalAccessException {
Class<?> clazz = object.getClass();
Field[] fields = clazz.getDeclaredFields();
for (Field field : fields) {
if (String.class.equals(field.getType())) {
field.setAccessible(true);
if (field.get(object) == null) {
field.set(object, "");
}
}
}
}
You can use reflection to list all fields of an object and then check and change it. You might have to modify the access level, if they are private. You can find a lot of tutorials on that when searching Google, e.g. this one.
Try to use AspectJ:
@Aspect
public class StringHandler {
@Around("execution(String com....YourClass.*(*))")
public Object handle(ProceedingJoinPoint thisJoinPoint) throws Throwable {
String s = (String) thisJoinPoint.proceed();
if (s == null){
return "";
}
return s;
}
}
This will be faster in run-time because this aspect will be compiled to byte-code, otherwise reflection will be used at run-time and slows your app.
Another way is to write an utility which generates code which sets empty strings to members of particular objects.
In favor of reusable design you should consider using a default value for null values just like Apache's common defaultString API, something like this:
public String getValue(String value){
return StringUtils.defaultString(value);
}
You can also consider using defaultString(String str,String defaultStr) so that you have the option of changing the default value to anything should there be any reason of doing so.
StringUtils documentation
.xsdto define the schema for JAXB2 you can definedefaultvalues direct in the.xsd.