Question

I have an object that contains sub properties, which also have sub properties and so on.

I basically need to find the best way to retrieve the value of a particular field on the object, given it’s full hierarchical path as a string.

For example, if the object has the field company (Object) which has the field client (Object) which has the field id (String), this path will be represented as company.client.id. Therefore, given a path to the field i’m trying to get the value of on an object, how would I go about doing this?

Cheers.

Answer 1

Please find below Fieldhelper class with getFieldValue method.
It should allow you to solve your problem pretty quickly by
splitting your string and then applying the the getFieldValue recursively, taking the result object as input for the next step.

package com.bitplan.resthelper;
import java.lang.reflect.Field;

/**
 * Reflection help
 * @author wf
 *
 */
public class FieldHelper {

    /**
     * get a Field including superclasses
     * 
     * @param c
     * @param fieldName
     * @return
     */
    public Field getField(Class<?> c, String fieldName) {
        Field result = null;
        try {
            result = c.getDeclaredField(fieldName);
        } catch (NoSuchFieldException nsfe) {
            Class<?> sc = c.getSuperclass();
            result = getField(sc, fieldName);
        }
        return result;
    }

    /**
     * set a field Value by name
     * 
     * @param fieldName
     * @param Value
     * @throws Exception
     */
    public void setFieldValue(Object target,String fieldName, Object value) throws Exception {
        Class<? extends Object> c = target.getClass();
        Field field = getField(c, fieldName);
        field.setAccessible(true);
        // beware of ...
        // http://docs.oracle.com/javase/tutorial/reflect/member/fieldTrouble.html
        field.set(this, value);
    }

    /**
     * get a field Value by name
     * 
     * @param fieldName
     * @return
     * @throws Exception
     */
    public Object getFieldValue(Object target,String fieldName) throws Exception {
        Class<? extends Object> c = target.getClass();
        Field field = getField(c, fieldName);
        field.setAccessible(true);
        Object result = field.get(target);
        return result;
    }

}