Initialize all String members with an empty String

Question

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?

For what purpose? It's easier to do that in the corresponding get() method, if you always call it, than it is to affect the actual value. — user207421, Nov 28 '11 at 09:05
The classes are generated by JAXB2, so I don't want to change them. — Sebi, Nov 28 '11 at 09:13
If you are using an `.xsd` to define the schema for JAXB2 you can define `default` values direct in the `.xsd`. — ante, Nov 28 '11 at 09:32
Unfortunately the schema is not under my control.. But I agree that it would be better to solve the problem there. — Sebi, Nov 28 '11 at 09:54

score 7 · Accepted Answer · answered Nov 28 '11 at 09:09

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, "");
            }
        }
    }
}

score 1 · Answer 2 · answered Nov 28 '11 at 09:02

1

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.

answered Nov 28 '11 at 09:02

Till Helge

9,253
2
40
56

score 1 · Answer 3 · answered Nov 28 '11 at 09:48

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.

score 0 · Answer 4 · answered Nov 28 '11 at 09:17

0

Another way is to write an utility which generates code which sets empty strings to members of particular objects.

answered Nov 28 '11 at 09:17

Lavir the Whiolet

1,006
9
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score 0 · Answer 5 · answered Nov 28 '11 at 09:24

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

Initialize all String members with an empty String

5 Answers5

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