Module org.eclipse.persistence.core
Package org.eclipse.persistence.internal.oxm

Class ReferenceResolver

java.lang.Object
org.eclipse.persistence.internal.oxm.ReferenceResolver
public final class ReferenceResolver extends Object
This class is leveraged by reference mappings. It plays 3 roles:
  • Stores objects with an ID
  • Stores key based relationships
  • Resolves key based relationships based on the objects stored by ID

  • Constructor Details

    • ReferenceResolver

      public ReferenceResolver()
      The default constructor initializes the list of References.

  • Method Details

    • addReference

      public void addReference(Reference ref)
      Add a Reference object to the list - these References will be resolved after unmarshalling is complete.

      ############################# # Strategy - Hash Collision # ############################# Suppose that hashing function is h(k) = k % 9; __________Input 9 entries_________________________ Key k | 0, 8, 7, 5, 5, 5, 1, 14, 3 | Position# p | 0, 1, 2, 3, 4, 5, 6, 7, 8 | Value = p * 3 | 0, 3, 6, 9, 12, 15, 18, 21, 24 | -------------------------------------------------- e.g. eighth entry is Entry#7{ key = 14, value = 21 } #################################### # Insert element - O(1) guaranteed # #################################### Processing the 9th key: 1. Attempt to insert Entry#7 with key '14' into map of references. > h(14) = 5; HashMap buckets: position | 0 1 2 3 4 5 6 7 8 entry(key) | 0 1 3 5 7 8 ^ > Bucket 5 is taken. 2. Store the entry in a separate list. List for unlucky references: position | 0 1 2 entry(key) | 5 5 ^ position | 0 1 2 entry(key) | 5 5 14 ^ 3. Store the position # p of this element, i.e. what spot it would have taken if all entries were stored in a position list, counting from zero. List storing position # of unlucky references: position | 0 1 2 entry # (p) | 4 5 ^ position | 0 1 2 entry # (p) | 4 5 7 ^ ##################################################### # Retrieve element - O(1) expected, O(n) worst case # ##################################################### Retrieve entry with key '14' 1. Attempt to retrieve it from map > h(14) = 5; HashMap buckets: position | 0 1 2 3 4 5 6 7 8 entry(key) | 0 1 3 5 7 8 ^ Hash function points to bucket # 5. Stored key is 5. > key 5 != 14. 2. Iterate through list of unluckyReferences, comparing key to all keys in the list. position | 0 1 2 entry(key) | 5 5 14 ^ > key 5 != 14 position | 0 1 2 entry(key) | 5 5 14 ^ > key 5 != 14 position | 0 1 2 entry(key) | 5 5 14 ^ > key 14 = 14, retrieve entry. ################################################## # Iterate through all elements - O(n) guaranteed # ################################################## 1. Create boolean array of size n that keeps track of unlucky positions: > boolean[] a = new boolean[lastPosition + 1]; 2. Set a[p] = true for elements that did not fit into hash map, p = position # of element. > for (Integer p : unluckyRefPositions) { > a[p] = true; > } 3. Iterate through LinkedMap and List as if they were one joined collection of size s = map.size() + list.size(), ordered by p = position # of element: > for (p = 0; p < s; p ++) { > if a[p] = false, take next element from linked map iterator, > if a[p] = true, take next element from list iterator, > }

    • getReference

      public Reference getReference(ObjectReferenceMapping mapping, Object sourceObject)
      Retrieve the reference for a given mapping instance. If more keys match, returns the first occurrence.

    • getReference

      public Reference getReference(ObjectReferenceMapping mapping, Object sourceObject, Field xmlField)
      Return a reference for the given mapping and source object, that doesn't already contain an entry for the provided field.

    • putValue

      public void putValue(Class<?> clazz, Object key, Object object)
      Store an instance by key based on a mapped class. These values will be used when it comes time to resolve the references.
      Since:
      EclipseLink 2.5.0

    • resolveReferences

      public void resolveReferences(CoreAbstractSession session, IDResolver userSpecifiedResolver, ErrorHandler handler)
      INTERNAL: Iterates through all references. Resolves them. Resets containers.
      Parameters:
      session - typically will be a unit of work
      userSpecifiedResolver - a user-provided subclass of IDResolver, may be null