App Engine Java SDK version 1.9.8

[gae.git] / java / src / main / com / google / appengine / api / datastore / Query.java

// Copyright 2007 Google Inc. All rights reserved.

package com.google.appengine.api.datastore;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.appengine.api.NamespaceManager;
import com.google.common.base.Joiner;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.Objects;

/**
 * {@link Query} encapsulates a request for zero or more {@link Entity} objects
 * out of the datastore.  It supports querying on zero or more properties,
 * querying by ancestor, and sorting.  {@link Entity} objects which match the
 * query can be retrieved in a single list, or with an unbounded iterator.
 *
 */
public final class Query implements Serializable {

  @Deprecated
  public static final String KIND_METADATA_KIND = Entities.KIND_METADATA_KIND;

  @Deprecated
  public static final String PROPERTY_METADATA_KIND = Entities.PROPERTY_METADATA_KIND;

  @Deprecated
  public static final String NAMESPACE_METADATA_KIND = Entities.NAMESPACE_METADATA_KIND;

  static final long serialVersionUID = 7090652715949085374L;

  /**
   * SortDirection controls the order of a sort.
   */
  public enum SortDirection {
    ASCENDING,
    DESCENDING
  }

  /**
   * Operators supported by {@link FilterPredicate}.
   */
  public enum FilterOperator {
    LESS_THAN("<"),
    LESS_THAN_OR_EQUAL("<="),
    GREATER_THAN(">"),
    GREATER_THAN_OR_EQUAL(">="),
    EQUAL("="),
    NOT_EQUAL("!="),
    IN("IN");

    private final String shortName;
    private FilterOperator(String shortName) {
      this.shortName = shortName;
    }

    @Override
    public String toString() {
      return shortName;
    }

    public FilterPredicate of(String propertyName, Object value) {
      return new FilterPredicate(propertyName, this, value);
    }
  }

  /**
   * Operators supported by {@link CompositeFilter}.
   */
  public enum CompositeFilterOperator {
    AND,
    OR;

    public static CompositeFilter and(Filter... subFilters) {
      return and(Arrays.asList(subFilters));
    }

    public static CompositeFilter and(Collection<Filter> subFilters) {
      return new CompositeFilter(AND, subFilters);
    }

    public static CompositeFilter or(Filter... subFilters) {
      return or(Arrays.asList(subFilters));
    }

    public static CompositeFilter or(Collection<Filter> subFilters) {
      return new CompositeFilter(OR, subFilters);
    }

    public CompositeFilter of(Filter... subFilters) {
      return new CompositeFilter(this, Arrays.asList(subFilters));
    }

    public CompositeFilter of(Collection<Filter> subFilters) {
      return new CompositeFilter(this, subFilters);
    }
  }

  private final String kind;
  private final List<SortPredicate> sortPredicates = Lists.newArrayList();
  private final List<FilterPredicate> filterPredicates = Lists.newArrayList();
  private Filter filter;
  private Key ancestor;
  private boolean keysOnly;
  private final Map<String, Projection> projectionMap = Maps.newHashMap();
  private boolean distinct;
  private AppIdNamespace appIdNamespace;

  private transient String fullTextSearch;

  /**
   * Create a new kindless {@link Query} that finds {@link Entity} objects.
   * Note that kindless queries are not yet supported in the Java dev
   * appserver.
   *
   * Currently the only operations supported on a kindless query are filter by
   * __key__, ancestor, and order by __key__ ascending.
   */
  public Query() {
    this(null, null);
  }

  /**
   * Create a new {@link Query} that finds {@link Entity} objects with
   * the specified {@code kind}. Note that kindless queries are not yet
   * supported in the Java dev appserver.
   *
   * @param kind the kind or null to create a kindless query
   */
  public Query(String kind) {
    this(kind, null);
  }

  /**
   * Copy constructor that performs a deep copy of the provided Query.
   *
   * @param query The Query to copy.
   */
  Query(Query query) {
    this(query.kind, query.ancestor, query.sortPredicates, query.filter, query.filterPredicates,
        query.keysOnly, query.appIdNamespace, query.projectionMap.values(), query.distinct,
        query.fullTextSearch);
  }

  Query(String kind, Key ancestor, Filter filter, boolean keysOnly, AppIdNamespace appIdNamespace,
      boolean distinct, String fullTextSearch) {
    this.kind = kind;
    this.keysOnly = keysOnly;
    this.appIdNamespace = appIdNamespace;
    this.fullTextSearch = fullTextSearch;
    this.distinct = distinct;
    this.filter = filter;
    if (ancestor != null) {
      setAncestor(ancestor);
     }
  }

  Query(String kind, Key ancestor, Collection<SortPredicate> sortPreds,
      Filter filter,
      Collection<FilterPredicate> filterPreds, boolean keysOnly, AppIdNamespace appIdNamespace,
      Collection<Projection> projections, boolean distinct, String fullTextSearch) {
    this(kind, ancestor, filter, keysOnly, appIdNamespace, distinct, fullTextSearch);
    this.sortPredicates.addAll(sortPreds);
    this.filterPredicates.addAll(filterPreds);
    for (Projection projection : projections) {
      addProjection(projection);
    }
  }

  private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
    in.defaultReadObject();
    if (appIdNamespace == null) {
      if (ancestor != null) {
        appIdNamespace = ancestor.getAppIdNamespace();
      } else {
        appIdNamespace = new AppIdNamespace(DatastoreApiHelper.getCurrentAppId(), "");
      }
    }
  }

  /**
   * Create a new {@link Query} that finds {@link Entity} objects with
   * the specified {@code Key} as an ancestor.
   *
   * @param ancestor the ancestor key or null
   * @throws IllegalArgumentException If ancestor is not complete.
   */
  public Query(Key ancestor) {
    this(null, ancestor);
  }

  /**
   * Create a new {@link Query} that finds {@link Entity} objects with
   * the specified {@code kind} and the specified {@code ancestor}. Note that
   * kindless queries are not yet supported in the Java dev appserver.
   *
   * @param kind the kind or null to create a kindless query
   * @param ancestor the ancestor key or null
   * @throws IllegalArgumentException If the ancestor is not complete.
   */
  public Query(String kind, Key ancestor) {
    this(kind, ancestor, null, false, DatastoreApiHelper.getCurrentAppIdNamespace(), false, null);
  }

  /**
   * Only {@link Entity} objects whose kind matches this value will be
   * returned.
   */
  public String getKind() {
    return kind;
  }

  /**
   * Returns the AppIdNamespace that is being queried.
   * <p>The AppIdNamespace is set at construction time of this
   * object using the {@link NamespaceManager} to retrieve the
   * current namespace.
   */
  AppIdNamespace getAppIdNamespace() {
    return appIdNamespace;
  }

  /**
   * Returns the appId for this {@link Query}.
   */
  public String getAppId() {
    return appIdNamespace.getAppId();
  }

  /**
   * Returns the namespace for this {@link Query}.
   */
  public String getNamespace() {
    return appIdNamespace.getNamespace();
  }

  /**
   * Gets the current ancestor for this query, or null if there is no
   * ancestor specified.
   */
  public Key getAncestor() {
    return ancestor;
  }

  /**
   * Sets an ancestor for this query.
   *
   * This restricts the query to only return result entities that are
   * descended from a given entity. In other words, all of the results
   * will have the ancestor as their parent, or parent's parent, or
   * etc.
   *
   * If null is specified, unsets any previously-set ancestor.  Passing
   * {@code null} as a parameter does not query for entities without
   * ancestors (this type of query is not currently supported).
   *
   * @return {@code this} (for chaining)
   *
   * @throws IllegalArgumentException If the ancestor key is incomplete, or if
   * you try to unset an ancestor and have not set a kind, or if you try to
   * unset an ancestor and have not previously set an ancestor.
   */
  public Query setAncestor(Key ancestor) {
    if (ancestor != null && !ancestor.isComplete()) {
      throw new IllegalArgumentException(ancestor + " is incomplete.");
    } else if (ancestor == null) {
      if (this.ancestor == null) {
        throw new IllegalArgumentException(
            "Cannot clear ancestor unless ancestor has already been set");
      }
    }
    if (ancestor != null) {
      if (!ancestor.getAppIdNamespace().equals(appIdNamespace)) {
        throw new IllegalArgumentException(
            "Namespace of ancestor key and query must match.");
      }
    }
    this.ancestor = ancestor;
    return this;
  }

  /**
   * @param distinct if this query should be distinct. This may only be used
   * when the query has a projection.
   * @return {@code this} (for chaining)
   */
  public Query setDistinct(boolean distinct) {
    this.distinct = distinct;
    return this;
  }

  /**
   * @return if this query is distinct
   * @see #setDistinct(boolean)
   */
  public boolean getDistinct() {
    return distinct;
  }

  /**
   * @param filter the filter to use for this query, or {@code null}
   * @return {@code this} (for chaining)
   * @see CompositeFilter
   * @see FilterPredicate
   */
  public Query setFilter(Filter filter) {
    this.filter = filter;
    return this;
  }

  /**
   * @return the filter for this query or {@code null}
   * @see #setFilter(Filter)
   */
  public Filter getFilter() {
    return filter;
  }

  /**
   * Add a {@link FilterPredicate} on the specified property.
   *
   * <p>All {@link FilterPredicate}s added using this message are combined using
   * {@link CompositeFilterOperator#AND}.
   *
   * <p>Cannot be used in conjunction with {@link #setFilter(Filter)} which sets
   * a single {@link Filter} instead of many {@link FilterPredicate}s.
   *
   * @param propertyName The name of the property to which the filter applies.
   * @param operator The filter operator.
   * @param value An instance of a supported datastore type.  Note that
   * entities with multi-value properties identified by {@code propertyName}
   * will match this filter if the multi-value property has at least one
   * value that matches the condition expressed by {@code operator} and
   * {@code value}.  For more information on multi-value property filtering
   * please see the
   * <a href="http://code.google.com/appengine/docs/java/datastore">
   * datastore documentation</a>.
   *
   * @return {@code this} (for chaining)
   *
   * @throws NullPointerException If {@code propertyName} or {@code operator}
   * is null.
   * @throws IllegalArgumentException If {@code value} is not of a
   * type supported by the datastore.  See
   * {@link DataTypeUtils#isSupportedType(Class)}.  Note that unlike
   * {@link Entity#setProperty(String, Object)}, you cannot provide
   * a {@link Collection} containing instances of supported types
   * to this method.
   * @deprecated Use {@link #setFilter(Filter)}
   */
  @Deprecated
  public Query addFilter(String propertyName, FilterOperator operator, Object value) {
    filterPredicates.add(operator.of(propertyName, value));
    return this;
  }

  /**
   * Returns a mutable list of the current filter predicates.
   *
   * @see #addFilter(String, FilterOperator, Object)
   * @deprecated Use {@link #setFilter(Filter)} and {@link #getFilter()} instead
   */
  @Deprecated
  public List<FilterPredicate> getFilterPredicates() {
    return filterPredicates;
  }

  /**
   * Specify how the query results should be sorted.
   *
   * The first call to addSort will register the property that will
   * serve as the primary sort key.  A second call to addSort will set
   * a secondary sort key, etc.
   *
   * This method will always sort in ascending order.  To control the
   * order of the sort, use {@link #addSort(String,SortDirection)}.
   *
   * Note that entities with multi-value properties identified by
   * {@code propertyName} will be sorted by the smallest value in the list.
   * For more information on sorting properties with multiple values please see
   * the <a href="http://code.google.com/appengine/docs/java/datastore">
   * datastore documentation</a>.
   *
   * @return {@code this} (for chaining)
   *
   * @throws NullPointerException If any argument is null.
   */
  public Query addSort(String propertyName) {
    return addSort(propertyName, SortDirection.ASCENDING);
  }

  /**
   * Specify how the query results should be sorted.
   *
   * The first call to addSort will register the property that will
   * serve as the primary sort key.  A second call to addSort will set
   * a secondary sort key, etc.
   *
   * Note that if {@code direction} is {@link SortDirection#ASCENDING},
   * entities with multi-value properties identified by
   * {@code propertyName} will be sorted by the smallest value in the list.  If
   * {@code direction} is {@link SortDirection#DESCENDING}, entities with
   * multi-value properties identified by {@code propertyName} will be sorted
   * by the largest value in the list.  For more information on sorting
   * properties with multiple values please see
   * the <a href="http://code.google.com/appengine/docs/java/datastore">
   * datastore documentation</a>.
   *
   * @return {@code this} (for chaining)
   *
   * @throws NullPointerException If any argument is null.
   */
  public Query addSort(String propertyName, SortDirection direction) {
    sortPredicates.add(new SortPredicate(propertyName, direction));
    return this;
  }

  /**
   * Returns a mutable list of the current sort predicates.
   */
  public List<SortPredicate> getSortPredicates() {
    return sortPredicates;
  }

  /**
   * Makes this query fetch and return only keys, not full entities.
   *
   * @return {@code this} (for chaining)
   */
  public Query setKeysOnly() {
    keysOnly = true;
    return this;
  }

  /**
   * Clears the keys only flag.
   *
   * @see #setKeysOnly()
   * @return {@code this} (for chaining)
   */
  public Query clearKeysOnly() {
    keysOnly = false;
    return this;
  }

  /**
   * Adds a projection for this query.
   *
   * <p>Projections are limited in the following ways:
   * <ul>
   * <li>Un-indexed properties cannot be projected and attempting to do so will
   * result in no entities being returned.
   * <li>Projection {@link Projection#getName() names} must be unique.
   * <li>Properties that have an equality filter on them cannot be projected. This includes
   * the operators {@link FilterOperator#EQUAL} and {@link FilterOperator#IN}.
   * </ul>
   *
   * @see #getProjections()
   * @param projection the projection to add
   * @return {@code this} (for chaining)
   * @throws IllegalArgumentException if the query already contains a projection with the same name
   */
  public Query addProjection(Projection projection) {
    Preconditions.checkArgument(!projectionMap.containsKey(projection.getName()),
        "Query already contains projection with name: " + projection.getName());
    projectionMap.put(projection.getName(), projection);
    return this;
  }

  /**
   * Returns a mutable collection properties included in the projection for this query.
   *
   * <p>If empty, the full or keys only entities are returned. Otherwise
   * partial entities are returned. A non-empty projection is not compatible
   * with setting keys-only. In this case a {@link IllegalArgumentException}
   * will be thrown when the query is {@link DatastoreService#prepare(Query) prepared}.
   *
   * <p>Projection queries are similar to SQL statements of the form:
   * <pre>SELECT prop1, prop2, ...</pre>
   * As they return partial entities, which only contain the properties
   * specified in the projection. However, these entities will only contain
   * a single value for any multi-valued property and, if a multi-valued
   * property is specified in the order, an inequality property, or the
   * projected properties, the entity will be returned multiple times.
   * Once for each unique combination of values.
   *
   * <p>Specifying a projection:
   * <ul>
   * <li>May change the type of any property returned in a projection.
   * <li>May change the index requirements for the given query.
   * <li>Will cause a partial entity to be returned.
   * <li>Will cause only entities that contain those properties to be returned.
   * </ul>
   * However, projection queries are significantly faster than normal queries.
   *
   * @return a mutable collection properties included in the projection for this query
   * @see #addProjection(Projection)
   */
  public Collection<Projection> getProjections() {
    return projectionMap.values();
  }

  /**
   * Returns true if this query will fetch and return keys only, false if it
   * will fetch and return full entities.
   */
  public boolean isKeysOnly() {
    return keysOnly;
  }

  /**
   * Creates a query sorted in the exact opposite direction as the current one.
   *
   * This function requires a sort order on {@link Entity#KEY_RESERVED_PROPERTY}
   * to guarantee that each entity is uniquely identified by the set of properties
   * used in the sort (which is required to exactly reverse the order of a query).
   * Advanced users can reverse the sort orders manually if they know the set of
   * sorted properties meets this requirement without a order on {@link
   * Entity#KEY_RESERVED_PROPERTY}.
   *
   * The results of the reverse query will be the same as the results of the forward
   * query but in reverse direction.
   *
   * {@link Cursor Cursors} from the original query can be converted for use with
   * the reverse query through {@link Cursor#reverse()}.
   *
   * @return A new query with the sort order reversed.
   * @throws IllegalStateException if the current query is not sorted by
   * {@link Entity#KEY_RESERVED_PROPERTY}.
   */
  public Query reverse() {
    List<SortPredicate> order = new ArrayList<SortPredicate>(sortPredicates.size());
    boolean hasKeyOrder = false;
    for (SortPredicate sort : sortPredicates) {
      if (Entity.KEY_RESERVED_PROPERTY.equals(sort.getPropertyName())) {
        hasKeyOrder = true;
      }
      if (!distinct || projectionMap.containsKey(sort.getPropertyName())) {
        order.add(sort.reverse());
      } else {
        order.add(sort);
      }
    }
    Preconditions.checkState(hasKeyOrder, "A sort on " + Entity.KEY_RESERVED_PROPERTY +
        " is required to reverse a Query");

    return new Query(kind, ancestor, order, filter, filterPredicates, keysOnly, appIdNamespace,
        projectionMap.values(), distinct, fullTextSearch);
  }

  /**
   * Returns the query's full text search string.
   */
  String getFullTextSearch() {
    return fullTextSearch;
  }

  /**
   * Sets the query's full text search string.
   *
   * @return {@code this} (for chaining)
   */
  Query setFullTextSearch(String fullTextSearch) {
    this.fullTextSearch = fullTextSearch;
    return this;
  }

  @Override
  public boolean equals(Object o) {
    if (this == o) {
      return true;
    }
    if (o == null || getClass() != o.getClass()) {
      return false;
    }

    Query query = (Query) o;

    if (keysOnly != query.keysOnly) {
      return false;
    }

    if (!Objects.equals(ancestor, query.ancestor)) {
      return false;
    }
    if (!appIdNamespace.equals(query.appIdNamespace)) {
      return false;
    }
    if (!Objects.equals(filter, query.filter)) {
      return false;
    }
    if (!filterPredicates.equals(query.filterPredicates)) {
      return false;
    }
    if (!Objects.equals(kind, query.kind)) {
      return false;
    }
    if (!sortPredicates.equals(query.sortPredicates)) {
      return false;
    }
    if (!projectionMap.equals(query.projectionMap)) {
      return false;
    }
    if (distinct != query.distinct) {
      return false;
    }
    if (!Objects.equals(fullTextSearch, query.fullTextSearch)) {
      return false;
    }

    return true;
  }

  @Override
  public int hashCode() {
    return Objects.hash(kind, sortPredicates, filterPredicates, filter, ancestor, keysOnly,
        appIdNamespace, projectionMap, distinct, fullTextSearch);
  }

  /**
   * Obtains a hash code of the {@code Query} ignoring any 'value' arguments associated with
   * any query filters.
   */
  int hashCodeNoFilterValues() {
    int filterHashCode = 1;
    for (FilterPredicate filterPred : filterPredicates) {
      filterHashCode = 31 * filterHashCode + filterPred.hashCodeNoFilterValues();
    }
    filterHashCode = 31 * filterHashCode + ((filter == null) ? 0 : filter.hashCodeNoFilterValues());
    return Objects.hash(kind, sortPredicates, filterHashCode, ancestor, keysOnly,
        appIdNamespace, projectionMap, distinct, fullTextSearch);
  }

  /**
   * Outputs a SQL like string representing the query.
   */
  @Override
  public String toString() {
    StringBuilder result = new StringBuilder("SELECT ");
    if (distinct) {
      result.append("DISTINCT ");
    }
    if (!projectionMap.isEmpty()) {
      Joiner.on(", ").appendTo(result, projectionMap.values());
    } else if (keysOnly) {
      result.append("__key__");
    } else {
      result.append('*');
    }

    if (kind != null) {
      result.append(" FROM ");
      result.append(kind);
    }

    if (ancestor != null || !filterPredicates.isEmpty() || filter != null) {
      result.append(" WHERE ");
      final String AND_SEPARATOR = " AND ";

      if (filter != null) {
        result.append(filter);
      } else if (!filterPredicates.isEmpty()) {
        Joiner.on(AND_SEPARATOR).appendTo(result, filterPredicates);
      }

      if (ancestor != null) {
        if (!filterPredicates.isEmpty() || filter != null) {
          result.append(AND_SEPARATOR);
        }
        result.append("__ancestor__ is ");
        result.append(ancestor);
      }
    }

    if (!sortPredicates.isEmpty()) {
      result.append(" ORDER BY ");
      Joiner.on(", ").appendTo(result, sortPredicates);
    }
    return result.toString();
  }

  /**
   * SortPredicate is a data container that holds a single sort
   * predicate.
   */
  public static final class SortPredicate implements Serializable {
    @SuppressWarnings("hiding")
    static final long serialVersionUID = -623786024456258081L;
    private final String propertyName;
    private final SortDirection direction;

    public SortPredicate(String propertyName, SortDirection direction) {
      if (propertyName == null) {
        throw new NullPointerException("Property name was null");
      }

      if (direction == null) {
        throw new NullPointerException("Direction was null");
      }

      this.propertyName = propertyName;
      this.direction = direction;
    }

    /**
     * @return A sort predicate with the direction reversed.
     */
    public SortPredicate reverse() {
      return new SortPredicate(propertyName,
          direction == SortDirection.ASCENDING ?
              SortDirection.DESCENDING : SortDirection.ASCENDING);
    }

    /**
     * Gets the name of the property to sort on.
     */
    public String getPropertyName() {
      return propertyName;
    }

    /**
     * Gets the direction of the sort.
     */
    public SortDirection getDirection() {
      return direction;
    }

    @Override
    public boolean equals(Object o) {
      if (this == o) {
        return true;
      }
      if (o == null || getClass() != o.getClass()) {
        return false;
      }

      SortPredicate that = (SortPredicate) o;

      if (direction != that.direction) {
        return false;
      }
      if (!propertyName.equals(that.propertyName)) {
        return false;
      }

      return true;
    }

    @Override
    public int hashCode() {
      int result;
      result = propertyName.hashCode();
      result = 31 * result + direction.hashCode();
      return result;
    }

    @Override
    public String toString() {
      return propertyName + (direction == SortDirection.DESCENDING ? " DESC" : "");
    }
  }

  /**
   * The base class for a query filter.
   *
   * All sub classes should be immutable.
   */
  public abstract static class Filter implements Serializable {
    @SuppressWarnings("hiding")
    static final long serialVersionUID = -845113806195204425L;

    Filter() {}

    /**
     * Obtains the hash code for the {@code Filter} ignoring any value parameters associated
     * with the filter.
     */
    abstract int hashCodeNoFilterValues();
  }

  /**
   * A {@link Filter} that combines several sub filters using a {@link CompositeFilterOperator}.
   *
   * For example, to construct a filter of the form <code>a = 1 AND (b = 2 OR c = 3)</code> use:
   * <pre> {@code
   * new CompositeFilter(CompositeFilterOperator.AND, Arrays.asList(
   *     new FilterPredicate("a", FilterOperator.EQUAL, 1),
   *     new CompositeFilter(CompositeFilterOperator.OR, Arrays.<Filter>asList(
   *         new FilterPredicate("b", FilterOperator.EQUAL, 2),
   *         new FilterPredicate("c", FilterOperator.EQUAL, 3)))));
   * }</pre>
   * or
   * <pre> {@code
   * CompositeFilterOperator.and(
   *     FilterOperator.EQUAL.of("a", 1),
   *     CompositeFilterOperator.or(
   *         FilterOperator.EQUAL.of("b", 2),
   *         FilterOperator.EQUAL.of("c", 3)));
   * }</pre>
   */
  public static final class CompositeFilter extends Filter {
    @SuppressWarnings("hiding")
    static final long serialVersionUID = 7930286402872420509L;

    private final CompositeFilterOperator operator;
    private final ImmutableList<Filter> subFilters;

    public CompositeFilter(CompositeFilterOperator operator, Collection<Filter> subFilters) {
      Preconditions.checkArgument(subFilters.size() >= 2, "At least two sub filters are required.");
      this.operator = checkNotNull(operator);
      this.subFilters = ImmutableList.copyOf(subFilters);
    }

    /**
     * @return the operator
     */
    public CompositeFilterOperator getOperator() {
      return operator;
    }

    /**
     * @return an immutable list of sub filters
     */
    public List<Filter> getSubFilters() {
      return subFilters;
    }

    @Override
    public String toString() {
      StringBuilder builder = new StringBuilder();
      builder.append('(');
      Joiner.on(" " + operator + " ").appendTo(builder, subFilters);
      builder.append(')');
      return builder.toString();
    }

    @Override
    public int hashCode() {
      return Objects.hash(operator, subFilters);
    }

    @Override
    int hashCodeNoFilterValues() {
      int result = 1;
      result = 31 * result + operator.hashCode();
      for (Filter filter : subFilters) {
          result = 31 * result + filter.hashCodeNoFilterValues();
      }
      return result;
    }

    @Override
    public boolean equals(Object obj) {
      if (this == obj) return true;
      if (!(obj instanceof CompositeFilter)) return false;
      CompositeFilter other = (CompositeFilter) obj;
      if (operator != other.operator) return false;
      return subFilters.equals(other.subFilters);
    }
  }

  /**
   * A {@link Filter} on a single property.
   */
  public static final class FilterPredicate extends Filter {
    @SuppressWarnings("hiding")
    static final long serialVersionUID = 7681475799401864259L;
    private final String propertyName;
    private final FilterOperator operator;
    private final Object value;

    /**
     * Constructs a filter predicate from the given parameters.
     *
     * @param propertyName the name of the property on which to filter
     * @param operator the operator to apply
     * @param value A single instances of a supported type or if {@code
     * operator} is {@link FilterOperator#IN} a non-empty {@link Iterable}
     * object containing instances of supported types.
     *
     * @throws IllegalArgumentException If the provided filter values are not
     * supported.
     *
     * @see DataTypeUtils#isSupportedType(Class)
     */

    public FilterPredicate(String propertyName, FilterOperator operator, Object value) {
      if (propertyName == null) {
        throw new NullPointerException("Property name was null");
      } else if (operator == null) {
        throw new NullPointerException("Operator was null");
      } else if (operator == FilterOperator.IN) {
        if (!(value instanceof Collection<?>) && value instanceof Iterable<?>) {
          List<Object> newValue = new ArrayList<Object>();
          Iterables.addAll(newValue, (Iterable<?>) value);
          value = newValue;
        }
        DataTypeUtils.checkSupportedValue(propertyName, value, true, true);
      } else {
        DataTypeUtils.checkSupportedValue(propertyName, value, false, false);
      }
      this.propertyName = propertyName;
      this.operator = operator;
      this.value = value;
    }

    /**
     * Gets the name of the property to be filtered on.
     */
    public String getPropertyName() {
      return propertyName;
    }

    /**
     * Gets the operator describing how to apply the filter.
     */
    public FilterOperator getOperator() {
      return operator;
    }

    /**
     * Gets the argument to the filter operator.
     */
    public Object getValue() {
      return value;
    }

    @Override
    public boolean equals(Object o) {
      if (this == o) {
        return true;
      }
      if (o == null || getClass() != o.getClass()) {
        return false;
      }

      FilterPredicate that = (FilterPredicate) o;

      if (operator != that.operator) {
        return false;
      }
      if (!propertyName.equals(that.propertyName)) {
        return false;
      }
      if (!Objects.equals(value, that.value)) {
        return false;
      }

      return true;
    }

    @Override
    public int hashCode() {
      return Objects.hash(propertyName, operator, value);
    }

    @Override
    int hashCodeNoFilterValues() {
      return Objects.hash(propertyName, operator);
    }

    @Override
    public String toString() {
      return propertyName + " " + operator + " " + (value != null ? value : "NULL");
    }
  }
}