Sweetener - Collection Restrictions - Part I

Search through the collection has always been a problem for developers and simple search enforced on the programmer writing many lines of code (Countless foreach, if-else constructions). Fortunately, class Collections solves this problem. The integral part of this class is Criteria and Restriction mechanism, which allows for complex query conditions. The restrictions can be joined in chain by add method. Example criteria is shown below:

Criteria.newCriteria().add(Restrictions.isNotNull("company.name"))
        .add(Restrictions.contains("categoriesOfDrivingLicense", "B","D"))
        .add(Restrictions.greaterOrEquals("age", 24))
        .add(Restrictions.equals("name", "marry", true));

Criteria object created in this way can be used in filter method on Collections

 public static <T> Collection<T> filter(Collection<T> collection, Criteria criteria) {

Many Restriction classes have been prepared in order to allow a smooth search through the collection. Some of them are intended for numbers, some of them are intended for Collections / Arrays and there are restrictions intended for any objects:

• Restrictions for any objects
  • equals(String field, Object value) Checks whether object is equals to object passed as second parameter
  • notEquals(String field, Object value) Checks whether object is not equals to object passed as second parameter
  • isNull(String field) Checks whether object is null
  • isNotNull(String field) Checks whether object is not null
• Restrictions for String
  • equals(String field, Object value, boolean ignoreCase) Checks whether object is equals to object passed as second parameter ignoring case sensitivity
  • notEquals(String field, Object value, boolean ignoreCase) Checks whether object is not equals to object from second parameter ignoring case sensitivity
  • like(String field, String value) Checks whether object contains substring passed as second parameter
  • notLike(String field, String value) Checks whether object does not contains substring passed as second parameter
• Restrictions for Number
  • greater(String field, Number value) Check whether object is greater than the number passed as second parameter
  • less(String field, Number value) Check whether object is less than the number passed as second parameter
  • greaterOrEquals(String field, Number value) Check whether object is greater or equals to the number passed as second parameter
  • lessOrEquals(String field, Number value) Check whether object is less or equals to the number passed as second parameter
  • between(String field, Number minValue, Number maxValue) Check whether value is between the numbers passed as second and third parameter
  • notBetween(String field, Number minValue, Number maxValue) Check whether value is not between the numbers passed as second and third parameter
  • between(String field, Number minValue, Number maxValue, boolean leftInclusive, boolean rightInclusive) Check whether value is between the numbers passed as second and third parameter. leftInclusive/rightInclusive indicates whether point in left range/ right range should or shouldn’t be taken into account
  • notBetween(String field, Number minValue, Number maxValue, boolean leftInclusive, boolean rightInclusive) Check whether value is not between the numbers passed as second and third parameter. leftInclusive/rightInclusive indicates whether point in left range/ right range should or shouldn’t be taken into account
• Restrictions for Collections / Arrays
  • contains(String field, Object... values) Checks whether object contains all objects passed as second parameter
  • containsAny(String field, Object... values) Checks whether object contains any of objects passed as second parameter
  • notContains(String field, Object... values) Checks whether object does not contain all objects passed as second parameter
  • notContainsAny(String field, Object... values) Checks whether object does not contain any objects passed as second parameter
  • in(String field, Object... values) Checks whether value is equals to one of objects passed as second, third … parameter
  • notIn(String field, Object... values) Checks whether value is not equals to any of objects passed as second, third … parameter

A bit of practice

Assume that we have Person object with the following properties

public class Person {

    private String name;
    private String lastName;
    private int age;
    private Company company;
    private List<String> categoriesOfDrivingLicense = Collections.newArrayList();

	// contructor, getters and setters
}

Let’s create lists of Person objects

private List<Person> prepareListOfPeople() {
  List<Person> people = new ArrayList<Person>();
  people.add(new Person("John", "Wolf", 27, null, null));
  people.add(new Person("John", "Sky", 31, new Company("Jsolve", new Address("street1", "city1")),   prepareListOfCategories("B")));
  people.add(new Person("Marry", "Duke", 45, new Company("Sweetener", new Address("street2", null)),  prepareListOfCategories("A", "B")));
  people.add(new Person("Peter", "Hunt", 41, null, prepareListOfCategories("B", "D")));
  return people;
}

Now, we can perform some searches by using filter methods on Collections object:

Collection<Person> filteredList = Collections.filter(people, Criteria.newCriteria()
  .add(Restrictions.isNotNull("company"))
  .add(Restrictions.containsAny("categoriesOfDrivingLicense", "A", "D")));

// As a result will be returned collection containing: Marry Duke

Collection<Person> filteredList = Collections.filter(people, Criteria.newCriteria()
  .add(Restrictions.greaterOrEquals("age", 31)));

// As a result will be returned collection containing: John Sky, Peter Hunt, Marry Duke

Collection<Person> filteredList = Collections.filter(people, Criteria.newCriteria()
  .add(Restrictions.like("company.address.street", "street")));

// As a result will be returned collection containing: John Sky, Marry Duke