使用类的字段自动生成地图

Question

I have the following class

@Data
public class CMC{

  String f1;
  String f2;
  String f3;      
  public Map<String, Supplier<String>> valuesMap() {
    return ImmutableMap.<String, Supplier<String>>builder()
        .put("f1", this::f1)
        .put("f2", this::f2)
        .put("f3", this::f3)
        .build();
  }

}

As you can see I have a few fields and a map for that contains each field pointing to a function that returns the value of that field.

The problem with this solution is that a developer may get here and add a new field but forgets to add it to a map.

Is there a way to automate this process?

I was hoping for something like lombok to help me with this case. It's a common thing to need a list of the field from a class and have access to their values.

To solve this I would create an annotation and then somehow use reflection to obtain my desired behavior but I suppose something like this has been already implemented in some tools.

Answer 1

You should look into: Class::getDeclaredFields ; Class::getSuperclass ; and Field . Together, they should be able to get pretty much what you're looking for... Something like:

final Map<String, Object> map = new HashMap<>();
Class<?> klass = this.getClass();
while (klass != null) {
    for (final Field field : klass.getDeclaredFields()) {
        if (!field.isAccessible()) {
            field.setAccessible(true);
        }
        map.put(field.getName(), field.get(this));
    }
    klass = klass.getSuperclass();
}

You'll need to handle exceptions, work out where to call this, and confirm if you want to do it for all fields ( private , etc.) or just some, whether to lazily cache the value somewhere, and whether everything needs converting to a String (in which case the Object in the map can be changed).