通过反思获得第一个父母的字段

时间:2011-11-01 12:30:24

标签: java reflection

我正在尝试获取对象的第一个父级的字段和值。我目前的代码是:

Class<? extends Object> cls = obj.getClass();
Field[] fields = cls.getDeclaredFields();
for ( Field field : fields )
{
    String fieldName = field.getName();
    String fieldValue = field.get(obj);
}

我的班级结构类似于:

class A
{
    int x;
}

class B extends A
{
    int y;
}

class C extends B
{
    int z;
}

现在,我将C对象传递给方法,我想从C和B获取所有字段,但不是从A获取。有没有办法做到这一点(使用反射,我不想实现其他方法)?

4 个答案:

答案 0 :(得分:13)

Luchian,使用getSuperclass()方法获取对Class对象的引用,该对象表示相关对象的超类类型。在此之后,您可以轻松地以与示例相同的方式获取字段。

答案 1 :(得分:7)

创建方法

public static void printFieldsFor(Class cls, Object obj) {
  Field[] fields = cls.getDeclaredFields();
  for ( Field field : fields ) {
    String fieldName = field.getName();
    String fieldValue = field.get(obj);
  }
}

printFieldsFor(object.getClass(), obj);
printFieldsFor(object.getClass().getSuperclass(), obj);

或使用循环

for(Class cls = object.getClass(); 
    cls!=null && cls!=A.class; 
    cls = cls.getSuperclass()) {
  for(Field field : cls.getDeclaredFields()) {
     String fieldName = field.getName();
     String fieldValue = field.get(obj);
     // do something with the field.
  }
}

答案 2 :(得分:0)

import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 * @author pablo.barbosa (2017-08-15)
 */
public class ReflectionUtil {

    /**
     * Hiding constructor. The methods are statics
     */
    private ReflectionUtil() {
        // Hiding constructor
    }

    public static List<Field> getInheritedDeclaredFields(Class<?> fromClass, Class<?> stopWhenClass) {
        if (stopWhenClass == null) {
            stopWhenClass = Object.class;
        }
        List<Field> fields = new ArrayList<>();
        List<Class<?>> classes = new ArrayList<>();

        Class<?> cls = fromClass;
        do {
            classes.add(cls);
            cls = cls.getSuperclass();
        } while (cls != null && !cls.equals(stopWhenClass));

        for (int i = classes.size() - 1; i >= 0; i--) {
            fields.addAll(Arrays.asList(classes.get(i).getDeclaredFields()));
        }

        return fields;
    }

    public static Field getInheritedDeclaredField(Class<?> fromClass, String fieldName, Class<?> stopWhenClass) throws NoSuchFieldException {
        if (stopWhenClass == null) {
            stopWhenClass = Object.class;
        }

        Class<?> cls = fromClass;
        do {
            Field field;
            try {
                field = cls.getDeclaredField(fieldName);
                if (field != null) {
                    return field;
                }
            } catch (NoSuchFieldException | SecurityException e) {
                // Nothing. We'll try to get field from superclass
            }
            cls = cls.getSuperclass();
        } while (cls != null && !cls.equals(stopWhenClass));

        // If we got here, we'll throw an exception
        throw new NoSuchFieldException(fieldName);
    }

    public static Object getInheritedDeclaredFieldValue(Object obj, String fieldName, Class<?> stopWhenClass) throws NoSuchFieldException, IllegalAccessException {
        Field field = getInheritedDeclaredField(obj.getClass(), fieldName, stopWhenClass);
        field.setAccessible(true);
        return field.get(obj);
    }

}

答案 3 :(得分:-3)

您可以使用此代码从任何类中获取字段,而不是其父类或子类

for (Field field : YourClassName.class.getDeclaredFields()) {
  //fields
}