The only way we have to get only inherited fields is to use the getDeclaredFields() method, as we just did, and filter its results using the Field::getModifiers method. This one returns an int representing the modifiers of the current field. Each possible modifier is assigned a power of two between 2^0 and 2^7.
Reflection is a feature in the Java programming language. It allows an executing Java program to examine or "introspect" upon itself, and manipulate internal properties of the program. For example, it's possible for a Java class to obtain the names of all its members and display them.
The list of all declared fields can be obtained using the java. lang. Class. getDeclaredFields() method as it returns an array of field objects.
A field is a class, interface, or enum with an associated value. Methods in the java. lang. reflect. Field class can retrieve information about the field, such as its name, type, modifiers, and annotations.
no, you need to write it yourself. It is a simple recursive method called on Class.getSuperClass():
public static List<Field> getAllFields(List<Field> fields, Class<?> type) {
fields.addAll(Arrays.asList(type.getDeclaredFields()));
if (type.getSuperclass() != null) {
getAllFields(fields, type.getSuperclass());
}
return fields;
}
@Test
public void getLinkedListFields() {
System.out.println(getAllFields(new LinkedList<Field>(), LinkedList.class));
}
public static List<Field> getAllFields(Class<?> type) {
List<Field> fields = new ArrayList<Field>();
for (Class<?> c = type; c != null; c = c.getSuperclass()) {
fields.addAll(Arrays.asList(c.getDeclaredFields()));
}
return fields;
}
If instead you wanted to rely upon a library to accomplish this, Apache Commons Lang version 3.2+ provides FieldUtils.getAllFieldsList
:
import java.lang.reflect.Field;
import java.util.AbstractCollection;
import java.util.AbstractList;
import java.util.AbstractSequentialList;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;
import org.apache.commons.lang3.reflect.FieldUtils;
import org.junit.Assert;
import org.junit.Test;
public class FieldUtilsTest {
@Test
public void testGetAllFieldsList() {
// Get all fields in this class and all of its parents
final List<Field> allFields = FieldUtils.getAllFieldsList(LinkedList.class);
// Get the fields form each individual class in the type's hierarchy
final List<Field> allFieldsClass = Arrays.asList(LinkedList.class.getFields());
final List<Field> allFieldsParent = Arrays.asList(AbstractSequentialList.class.getFields());
final List<Field> allFieldsParentsParent = Arrays.asList(AbstractList.class.getFields());
final List<Field> allFieldsParentsParentsParent = Arrays.asList(AbstractCollection.class.getFields());
// Test that `getAllFieldsList` did truly get all of the fields of the the class and all its parents
Assert.assertTrue(allFields.containsAll(allFieldsClass));
Assert.assertTrue(allFields.containsAll(allFieldsParent));
Assert.assertTrue(allFields.containsAll(allFieldsParentsParent));
Assert.assertTrue(allFields.containsAll(allFieldsParentsParentsParent));
}
}
You need to call:
Class.getSuperclass().getDeclaredFields()
Recursing up the inheritance hierarchy as necessary.
Use Reflections library:
public Set<Field> getAllFields(Class<?> aClass) {
return org.reflections.ReflectionUtils.getAllFields(aClass);
}
getFields():
Gets all the public fields up the entire class hierarchy and
getDeclaredFields():
Gets all the fields, regardless of their modifiers but only for the current class. So, you have to get for all the hierarchy involved.
I recently saw this code from org.apache.commons.lang3.reflect.FieldUtils
public static List<Field> getAllFieldsList(final Class<?> cls) {
Validate.isTrue(cls != null, "The class must not be null");
final List<Field> allFields = new ArrayList<>();
Class<?> currentClass = cls;
while (currentClass != null) {
final Field[] declaredFields = currentClass.getDeclaredFields();
Collections.addAll(allFields, declaredFields);
currentClass = currentClass.getSuperclass();
}
return allFields;
}
The recursive solutions are OK, the only small issue is that they return a superset of declared and inherited members. Note that getDeclaredFields() method returns also private methods. So given that you navigate the whole superclass hierarchy you will include all private fields declared in the superclasses, and those don't get inherited.
A simple filter with a Modifier.isPublic || Modifier.isProtected predicate would do:
import static java.lang.reflect.Modifier.isPublic;
import static java.lang.reflect.Modifier.isProtected;
(...)
List<Field> inheritableFields = new ArrayList<Field>();
for (Field field : type.getDeclaredFields()) {
if (isProtected(field.getModifiers()) || isPublic(field.getModifiers())) {
inheritableFields.add(field);
}
}
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