java :: getReference

ReflectionReference.java

/**
 * This method will return the reference to the internal private/protected/public/default fields of the given object.
 * This method can go as deeper as needed; with the passed `fields` parameter.
 * The parameter `fields` array follows order from outer `object variable name` to `inner variable name`
 * See below example:
 *    - getReference(obj, "var", "var", "var:list:0", "var:array:0", ">>var", "var:map:custom_key", "var:set:1")
 */
public static Object getReference(final Object obj, final String... fields) throws Exception {
  if (fields.length < 1 || fields[0] == null) {
    return obj;
  }

  String fieldName = fields[0];
  Class<?> cls = obj.getClass();
  while (fieldName.startsWith(">")) {
    cls = cls.getSuperclass();
    fieldName = fieldName.substring(1);
  }
  if ("".equals(fieldName)) {
    return obj;
  }

  final String fieldParts[] = fieldName.split(":");
  final Field field = cls.getDeclaredField(fieldParts[0]);
  field.setAccessible(true);
  Object child = field.get(obj);
  field.setAccessible(false);
  final String[] childFields = Arrays.copyOfRange(fields, 1, fields.length);
  if (fieldParts.length != 1) {
    int index = -1;
    try { index = Integer.parseInt(fieldParts[2]); } catch (final Exception e) {}
    if (fieldParts[1].equals("array") && index != -1) {
      if (child instanceof Object[]) {
        Object[] childArray = (Object[]) child;
        child = childArray[index];
      } else if (child instanceof int[]) {
        int[] childArray = (int[]) child;
        child = childArray[index];
      } else if (child instanceof short[]) {
        short[] childArray = (short[]) child;
        child = childArray[index];
      } else if (child instanceof byte[]) {
        byte[] childArray = (byte[]) child;
        child = childArray[index];
      } else if (child instanceof long[]) {
        long[] childArray = (long[]) child;
        child = childArray[index];
      } else if (child instanceof double[]) {
        double[] childArray = (double[]) child;
        child = childArray[index];
      } else if (child instanceof float[]) {
        float[] childArray = (float[]) child;
        child = childArray[index];
      } else if (child instanceof boolean[]) {
        boolean[] childArray = (boolean[]) child;
        child = childArray[index];
      }
    } else if (fieldParts[1].equals("list") && index != -1) {
      List<?> childList = (List) child;
      child = childList.get(index);
    } else if (fieldParts[1].equals("set") && index != -1) {
      List<?> childList = new ArrayList<Object>((Set) child);
      child = childList.get(index);
    } else if (fieldParts[1].equals("map") && index == -1) {
      Map<String, ?> childMap = (Map<String, ?>) child;
      child = childMap.get(fieldParts[2]);
    }
  }
  return getReference(child, childFields);
}

TestIt.java

public class TestIt {
  public static void main(String[] args) throws Exception {
    System.out.println(ReflectionReference.getReference(new A(), "var1"));
    System.out.println(ReflectionReference.getReference(new A(), "var"));
    System.out.println(ReflectionReference.getReference(new A(), "var", "var"));
    System.out.println(ReflectionReference.getReference(new A(), "var", "var", "var:list:0"));
    System.out.println(ReflectionReference.getReference(new A(), "var", "var", "var:list:0", "var"));
    System.out.println(ReflectionReference.getReference(new A(), "var", "var", "var:list:0", "var", "var:array:2"));
    System.out.println(ReflectionReference.getReference(new A(), "var", "var", "var:list:0", "var", "var1:set:1"));
    System.out.println(ReflectionReference.getReference(new A(), "var", "var", "var1:map:key2"));
    System.out.println(ReflectionReference.getReference(new A(), "var", "var"));
    System.out.println(ReflectionReference.getReference(new A(), "var", ">svar"));
    System.out.println(ReflectionReference.getReference(new A(), "var", ">>ssvar"));
  }
}

class A {
  private final B var;
  private final double var1;
  public A() {
    var = new B();
    var1 = 99.99d;
  }
  @Override
  public String toString() {
    return String.format("A={%s, s}", var, var1);
  }
}

class B extends F {
  private final C var;
  public B() {
    var = new C();
  }
  @Override
  public String toString() {
    return String.format("B={%s}", var);
  }
}

class C {
  private final List<D> var;
  private final Map<String, String> var1 = new HashMap<String, String>() {{
    put("key1", "Chandu's secret");put("key2", "Something else");
  }};
  public C() {
    var = Arrays.asList(new D(), new D());
  }
  @Override
  public String toString() {
    return String.format("C={%s}", var);
  }
}

class D {
  private final E var;
  public D() {
    var = new E();
  }
  @Override
  public String toString() {
    return String.format("D={%s}", var);
  }
}

class E {
  private final boolean[] var;
  private final Set<Integer> var1 = new LinkedHashSet<Integer>() {{
    add(123);add(546);
  }};
  public E() {
    var = new boolean[]{true, false, true};
  }
  @Override
  public String toString() {
    return String.format("E={%s}", Arrays.toString(var));
  }
}

class F extends G {
  private final String svar;
  public F() {
    svar = "haha";
  }
  @Override
  public String toString() {
    return String.format("F={%s}", svar);
  }
}

class G {
  private final String ssvar;
  public G() {
    ssvar = "hahahaha";
  }
  @Override
  public String toString() {
    return String.format("G={%s}", ssvar);
  }
}