Interface InstancioApi<T>
- Type Parameters:
T
- type to create
- All Superinterfaces:
BaseApi<T>
,LenientModeApi
,SettingsApi
,VerboseModeApi
- All Known Subinterfaces:
InstancioClassApi<T>
,InstancioCollectionsApi<C>
- Since:
- 1.0.1
-
Method Summary
Modifier and TypeMethodDescriptionapplyFeed
(TargetSelector selector, Feed feed) Applies the providedfeed
to the specifiedselector
.applyFeed
(TargetSelector selector, FeedProvider provider) Creates a feed and applies it to the specifiedselector
.default <R> R
A convenience method for mapping the result (as returned by thecreate()
method) to another object using afunction
.asResult()
Returns aResult
containing the created object and seed value used to generate its values.assign
(Assignment... assignments) Generates values based on given assignments.create()
Creates a new instance of a class and populates it with data.<V> InstancioApi
<T> filter
(TargetSelector selector, FilterPredicate<V> predicate) Filters generated values using givenpredicate
.<V> InstancioApi
<T> generate
(TargetSelector selector, GeneratorSpec<V> spec) Customises values using arbitrary generator specs.<V> InstancioApi
<T> generate
(TargetSelector selector, GeneratorSpecProvider<V> gen) Customises values using built-in generators provided by thegen
parameter, of typeGenerators
.ignore
(TargetSelector selector) Specifies that a class or field should be ignored.lenient()
Disables strict mode in which unused selectors trigger an error.<V> InstancioApi
<T> onComplete
(TargetSelector selector, OnCompleteCallback<V> callback) A callback that gets invoked after an object has been fully populated.<V> InstancioApi
<T> set
(TargetSelector selector, V value) Sets a value to matching selector targets.setBlank
(TargetSelector selector) Specifies that a blank object should be generated for the selected target.<V> InstancioApi
<T> setModel
(TargetSelector selector, Model<V> model) Applies givenmodel
to the specifiedselector
.stream()
Creates an infiniteStream
of objects.subtype
(TargetSelector selector, Class<?> subtype) Maps target field or class to the given subtype.<V> InstancioApi
<T> supply
(TargetSelector selector, Supplier<V> supplier) Supplies an object using aSupplier
.<V> InstancioApi
<T> supply
(TargetSelector selector, Generator<V> generator) Supplies an object using aGenerator
to matching selector targets.toModel()
Creates a model containing generation parameters for creating an object A model acts as a template for creating objects or other models.verbose()
Outputs debug information toSystem.out
.withMaxDepth
(int maxDepth) Specifies the maximum depth for populating an object.withNullable
(TargetSelector selector) Specifies that a field or class is nullable.withSeed
(long seed) Sets the seed value for the random number generator.<V> InstancioApi
<T> withSetting
(SettingKey<V> key, V value) Overrides the setting for the givenkey
with the specifiedvalue
.withSettings
(Settings settings) Merges the specifiedSettings
with the current settings, allowing for the addition and update of settings.withUnique
(TargetSelector selector) Specifies that the given selector's target(s) should have unique values.
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Method Details
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create
T create()Creates a new instance of a class and populates it with data.Example:
Person person = Instancio.of(Person.class) // snip... .create();
The returned object will have all its fields populated with random data, including collection and array fields.
- Returns:
- a fully populated object
- Since:
- 1.0.1
-
asResult
Returns aResult
containing the created object and seed value used to generate its values. The seed value can be used to reproduce the same object again.Example:
Result<Person> result = Instancio.of(Person.class) .set(field(Person::getName), "Homer Simpson") .asResult(); Person person = result.get(); long seed = result.getSeed();
- Returns:
- result containing the created object
- Since:
- 1.5.1
-
as
A convenience method for mapping the result (as returned by thecreate()
method) to another object using afunction
.For example, this method can be used to return the result as JSON or other formats:
String json = Instancio.of(Person.class).as(json());
where
json()
is a user-defined method implemented using the preferred library, e.g. using Jackson:public static <T> Function<T, String> json() { return result -> new ObjectMapper() .writerWithDefaultPrettyPrinter() .writeValueAsString(result); }
- Type Parameters:
R
- the type of object the result is mapped to- Parameters:
function
- the function for mapping the result- Returns:
- the object returned by applying the mapping function to the result
- Since:
- 4.8.0
-
stream
Creates an infiniteStream
of objects. Ensurelimit()
is called on the returned stream to prevent an infinite loop.Each object is generated separately when using this method. For instance, if a stateful generator like a sequence generator is used, the sequence will restart from one for each object:
List<Person> persons = Instancio.of(Person.class) .generate(field(Person::getId), gen -> gen.longSeq()) .stream() .limit(3) .collect(Collectors.toList()); // Output: // [Person[id=1], Person[id=1], Person[id=1]]
Compared to using
ofList()
, where the sequence is continuous:List<Person> persons = Instancio.ofList(Person.class) .size(3) .generate(field(Person::getId), gen -> gen.longSeq()) .create(); // Output: // [Person[id=1], Person[id=2], Person[id=3]]
- Returns:
- an infinite stream of object instances
- Since:
- 1.1.9
-
toModel
Creates a model containing generation parameters for creating an object A model acts as a template for creating objects or other models.The example below illustrates how to create a reusable model with predefined attributes, which serves as a template for generating objects with base properties:
Model<Person> simpsons = Instancio.of(Person.class) .set(field(Person::getLastName), "Simpson") .set(field(Address::getCity), "Springfield") .generate(field(Person::getAge), gen -> gen.ints().range(40, 50)) .toModel(); Person homer = Instancio.of(simpsons) .set(field(Person::getFirstName), "Homer") .set(all(Gender.class), Gender.MALE) .create(); Person marge = Instancio.of(simpsons) .set(field(Person::getFirstName), "Marge") .set(all(Gender.class), Gender.FEMALE) .create();
For more information, see:
- The Using Models section of the user guide
- Creating Object Templates Using Models article at instancio.org
- Returns:
- a model that can be used as a template for creating objects
- Since:
- 1.0.1
- See Also:
-
ignore
Specifies that a class or field should be ignored.Example:
Person person = Instancio.of(Person.class) .ignore(field(Phone::getPhoneNumber)) .ignore(allStrings()) .create();
will create a fully populated person, but will ignore the
getPhoneNumber
field, and all strings.Precedence
This method has higher precedence than other API methods. Once a target is ignored, no other selectors will apply. For example, the following snippet will trigger an unused selector error because
field(Phone::getNumber)
is redundant:Person person = Instancio.of(Person.class) .ignore(all(Phone.class)) .set(field(Phone::getNumber), "123-45-56") .create();
Usage with Java records
If
ignore()
targets one of the required arguments of a record constructor, then a default value for the ignored type will be generated.Example:
record PersonRecord(String name, int age) {} PersonRecord person = Instancio.of(PersonRecord.class) .ignore(allInts()) .ignore(allStrings()) .create(); // will produce: PersonRecord[name=null, age=0]
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withNullable
Specifies that a field or class is nullable. By default, Instancio assigns non-null values to fields. If marked as nullable, Instancio will generate either a null or non-null value.Example:
Note: a type marked as nullable using this method is only nullable when declared as a field, but not as a collection element, or map key/value. For example,Person person = Instancio.of(Person.class) .withNullable(allStrings()) .withNullable(field(Person::getAddress)) .withNullable(fields().named("lastModified")) .create();
withNullable(allStrings())
will not generate nulls in aList<String>
.- Specified by:
withNullable
in interfaceBaseApi<T>
- Parameters:
selector
- for fields and/or classes this method should be applied to- Returns:
- API builder reference
- Since:
- 1.0.1
-
set
Sets a value to matching selector targets.Example: if
Person
class contains aList<Phone>
, the following snippet will set all the country code of all phone instances to "+1".Person person = Instancio.of(Person.class) .set(field(Phone::getCountryCode), "+1") .create();
Note: Instancio will not
- populate or modify objects supplied by this method
- apply other
set()
,supply()
, orgenerate()
} methods with matching selectors to the supplied object - invoke
onComplete()
callbacks on supplied instances
-
setModel
Applies givenmodel
to the specifiedselector
.For example, given the following classes and
Model
:record Foo(String value) {} record Container(Foo fooA, Foo fooB) {} Model<Foo> fooModel = Instancio.of(Foo.class) .set(field(Foo::value), "foo") .toModel();
The model can be applied to a specific
Foo
field declared by theContainer
:Container container = Instancio.of(Container.class) .setModel(field(Container::fooA), fooModel) .create();
Alternatively, to apply the model to all instances of
Foo
:Container container = Instancio.of(Container.class) .setModel(all(Foo.class), fooModel) .create();
Note: the following properties of the supplied model are not applied to the target object:
Settings
lenient()
mode- custom seed value
See the user guide for further details.
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supply
Supplies an object using aSupplier
.Example:
Person person = Instancio.of(Person.class) .supply(all(LocalDateTime.class), () -> LocalDateTime.now()) .supply(field(Address::getPhoneNumbers), () -> List.of( new PhoneNumber("+1", "123-45-67"), new PhoneNumber("+1", "345-67-89"))) .create();
Note: Instancio will not
- populate or modify objects supplied by this method
- apply other
set()
,supply()
, orgenerate()
} methods with matching selectors to the supplied object - invoke
onComplete()
callbacks on supplied instances
If you require the supplied object to be populated and/or selectors to be applied, use the
BaseApi.supply(TargetSelector, Generator)
method instead. -
supply
Supplies an object using aGenerator
to matching selector targets. By default, Instancio will populate uninitialised fields of the supplied object. This includes fields withnull
or default primitive values.This method supports the following use cases.
Generate random objects
This method provides an instance of
Random
that can be used to randomise generated objects. For example, if Instancio did not support creation ofjava.time.Year
, it could be generated as follows:List<Year> years = Instancio.ofList(Year.class) .supply(all(Year.class), random -> Year.of(random.intRange(1900, 2000))) .create();
Provide a partially initialised instance
In some cases, an object may need to be created in a certain state or instantiated using a specific constructor to be in a valid state. A partially initialised instance can be supplied using this method, and Instancio will populate remaining fields that are
null
:Person person = Instancio.of(Person.class) .supply(field(Person::getAddress), random -> new Address("Springfield", "USA")) .create();
This behaviour is controlled by the
AfterGenerate
hint specified byGenerator.hints()
. Refer to theGenerator.hints()
Javadoc for details, or Custom Generators section of the user guide. -
generate
Customises values using built-in generators provided by thegen
parameter, of typeGenerators
.Example:
Person person = Instancio.of(Person.class) .generate(field(Person::getAge), gen -> gen.ints().range(18, 100)) .generate(all(LocalDate.class), gen -> gen.temporal().localDate().past()) .generate(field(Address::getPhoneNumbers), gen -> gen.collection().size(5)) .generate(field(Address::getCity), gen -> gen.oneOf("Burnaby", "Vancouver", "Richmond")) .create();
- Specified by:
generate
in interfaceBaseApi<T>
- Type Parameters:
V
- type of object to generate- Parameters:
selector
- for fields and/or classes this method should be applied togen
- provider of customisable built-in generators (also known as specs)- Returns:
- API builder reference
- Since:
- 2.2.0
- See Also:
-
generate
Customises values using arbitrary generator specs.Example:
Person person = Instancio.of(Person.class) .generate(field(Person::getAge), Instancio.ints().range(18, 100)) .generate(all(LocalDate.class), Instancio.temporal().localDate().past()) .generate(field(Phone::getNumber), MyCustomGenerators.phones().northAmerican()) .create();
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onComplete
A callback that gets invoked after an object has been fully populated.Example:
// Sets countryCode field on all instances of Phone to the specified value Person person = Instancio.of(Person.class) .onComplete(all(Phone.class), (Phone phone) -> phone.setCountryCode("+1")) .create();
Note: callbacks are never invoked on objects provided using:
Person person = Instancio.of(Person.class) .set(field(Phone::getCountryCode), "+1") .onComplete(field(Phone::getCountryCode), ...) // will not be invoked! .create();
- Specified by:
onComplete
in interfaceBaseApi<T>
- Type Parameters:
V
- type of object handled by the callback- Parameters:
selector
- for fields and/or classes this method should be applied tocallback
- to invoke after object has been populated- Returns:
- API builder reference
- Since:
- 1.0.4
-
filter
Filters generated values using givenpredicate
. If a value is rejected, a new value will be generated, which will also be tested against thepredicate
. If no value is accepted afterKeys.MAX_GENERATION_ATTEMPTS
, an exception will be thrown.A simple example is to generate a list of even numbers:
List<Integer> evenNumbers = Instancio.ofList(Integer.class) .filter(allInts(), (Integer i) -> i % 2 == 0) .create();
Note that customising objects using this method is less efficient than
BaseApi.generate(TargetSelector, GeneratorSpecProvider)
. The latter should be preferred where possible.- Specified by:
filter
in interfaceBaseApi<T>
- Type Parameters:
V
- the type of object the predicate is evaluated against- Parameters:
selector
- for fields and/or classes this method should be applied topredicate
- that must be satisfied by the generated value- Returns:
- API builder reference
- Since:
- 4.6.0
- See Also:
-
setBlank
Specifies that a blank object should be generated for the selected target.A blank object has the following properties:
- value fields (strings, numbers, dates, etc) are
null
- arrays, collections, and maps are empty
- nested POJOs are blank
Example:
Person person = Instancio.of(Person.class) .setBlank(field(Person::getAddress)) .create(); // Output: // Person[ // name="GNQTXA", // dateOfBirth=1988-04-09, // address=Address[street=null, city=null, country=null] // blank Address //]
- value fields (strings, numbers, dates, etc) are
-
subtype
Maps target field or class to the given subtype. This can be used in the following cases:- to specify an implementation for interfaces or abstract classes
- to override default implementations used by Instancio
When Instancio encounters an interface or an abstract type it is not aware of (for example, that is not part of the JDK), it will not be able to instantiate it. This method can be used to specify an implementation to use in such cases. For example:
WidgetContainer container = Instancio.of(WidgetContainer.class) .subtype(all(AbstractWidget.class), ConcreteWidget.class) .create();
Override default implementations
By default, Instancio uses certain defaults for collection classes, for example
ArrayList
forList
. If an alternative implementation is required, this method allows to specify it:Person person = Instancio.of(Person.class) .subtype(all(List.class), LinkedList.class) .create();
will use the
LinkedList
implementation for allList
s. -
assign
Generates values based on given assignments. AnAssignment
can be created using one of the builder patterns provided by theAssign
class.Assign.valueOf(originSelector).to(destinationSelector)
Assign.given(originSelector).satisfies(predicate).set(destinationSelector, value)
Assign.given(originSelector, destinationSelector).set(predicate, value)
For example, the following snippet uses
Assign.given(TargetSelector, TargetSelector)
to create an assignment that setsPhone.countryCode
based on the value of theAddress.country
field:Assignment assignment = Assign.given(field(Address::getCountry), field(Phone::getCountryCode)) .set(When.isIn("Canada", "USA"), "+1") .set(When.is("Italy"), "+39") .set(When.is("Poland"), "+48") .set(When.is("Germany"), "+49"); Person person = Instancio.of(Person.class) .generate(field(Address::getCountry), gen -> gen.oneOf("Canada", "USA", "Italy", "Poland", "Germany")) .assign(assignment) .create();
The above API allows specifying different values for a given origin/destination pair. An alternative for creating a conditional is provided by
Assign.given(TargetSelector)
. This method allows specifying different destination selectors for a given origin:Assignment shippedOrderAssignment = Assign.given(Order::getStatus) .is(OrderStatus.SHIPPED) .supply(field(Order::getDeliveryDueDate), () -> LocalDate.now().plusDays(2)); Assignment cancelledOrderAssignment = Assign.given(Order::getStatus) .is(OrderStatus.CANCELLED) .set(field(Order::getCancellationReason), "Shipping delays") .generate(field(Order::getCancellationDate), gen -> gen.temporal().instant().past()); List<Order> orders = Instancio.ofList(Order.class) .generate(all(OrderStatus.class), gen -> gen.oneOf(OrderStatus.SHIPPED, OrderStatus.CANCELLED)) .assign(shippedOrderAssignment, cancelledOrderAssignment) .create();
Limitations of assignments
Using assignments has a few limitations to be aware of.
- The origin selector must match a single target.
It must not be a
SelectorGroup
created viaSelect.all(GroupableSelector...)
or primitive/wrapper selector, such asSelect.allInts()
- An assignment where the origin selector's target is within a collection element must have a destination selector within the same collection element.
- Circular assignments will produce an error.
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withMaxDepth
Specifies the maximum depth for populating an object. The root object is at depth zero. Children of the root object are at depth 1, grandchildren at depth 2, and so on.Instancio will populate values up to the maximum depth. Beyond that, values will be
null
unless the maximum depth is set to a higher value.The default maximum depth is defined by
Keys.MAX_DEPTH
.Note: this method is a shorthand for:
int maxDepth = 5; Person person = Instancio.of(Person.class) .withSettings(Settings.create().set(Keys.MAX_DEPTH, maxDepth)) .create();
If the maximum depth is specified using
Settings
and this method, then this method takes precedence.- Specified by:
withMaxDepth
in interfaceBaseApi<T>
- Parameters:
maxDepth
- the maximum depth, must not be negative- Returns:
- API builder reference
- Since:
- 2.9.0
-
withSetting
Overrides the setting for the givenkey
with the specifiedvalue
.- Specified by:
withSetting
in interfaceSettingsApi
- Type Parameters:
V
- the setting value type- Parameters:
key
- the setting key to overridevalue
- the setting value- Returns:
- API builder reference
- Since:
- 4.3.1
- See Also:
-
withSettings
Merges the specifiedSettings
with the current settings, allowing for the addition and update of settings.Use this method to apply custom settings to override the default ones. The provided settings will be combined with the existing settings, updating any overlapping values and adding any new ones.
- Specified by:
withSettings
in interfaceSettingsApi
- Parameters:
settings
- the custom settings to merge with the current settings- Returns:
- API builder reference
- Since:
- 1.0.1
- See Also:
-
withSeed
Sets the seed value for the random number generator. If the seed is not specified, a random seed will be used. Specifying the seed is useful for reproducing test results. By specifying the seed value, the same random data will be generated again.Example:
// Generates a different UUID each time UUID result = Instancio.create(UUID.class); // Generates the same UUID each time UUID result = Instancio.of(UUID.class) .withSeed(1234) .create();
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lenient
InstancioApi<T> lenient()Disables strict mode in which unused selectors trigger an error. In lenient mode unused selectors are simply ignored.This method is a shorthand for:
Example example = Instancio.of(Example.class) .withSetting(Keys.MODE, Mode.LENIENT) .create();
- Specified by:
lenient
in interfaceLenientModeApi
- Returns:
- API builder reference
- Since:
- 1.4.1
-
verbose
Outputs debug information toSystem.out
. This includes:- current
Settings
- node hierarchy, including the type and depth of each node
- seed used to create the object
Warning: this method has a significant performance impact. It is recommended to remove the call to
verbose()
after troubleshooting is complete.- Specified by:
verbose
in interfaceVerboseModeApi
- Returns:
- API builder reference
- Since:
- 3.0.0
- current
-
applyFeed
Applies the providedfeed
to the specifiedselector
. Theselector
targets must be POJOs or Javarecord
s. Properties from thefeed
will be automatically mapped to the selected objects.For example, we can generate instances of the following record:
record Person(String firstName, String lastName, String fullName, int age, String username, String email) {}
using data from a CSV file (formatted for readability):
firstName, lastName, age, username John, Doe, 24, john_doe Alice, Smith, 55, alice_s # more entries...
by defining the following feed:
@Feed.Source(resource = "persons.csv") interface PersonFeed extends Feed { @TemplateSpec("${firstName} ${lastName}") FeedSpec<String> fullName(); @GeneratedSpec(CustomEmailGenerator.class) FeedSpec<String> email(); }
and applying the feed using the
all(Person.class)
selector:Feed personFeed = Instancio.createFeed(PersonFeed.class); List<Person> persons = Instancio.ofList(Person.class) .applyFeed(all(Person.class), personFeed) .create();
Data from the CSV will be mapped to
Person
fields by matching field names to property names in the data file.- Note that
PersonFeed
does not need to declarefirstName()
andlastName()
methods (they are mapped automatically). fullName()
andemail()
can also be mapped to thePerson
object, even though these are generated and not present in the data file.
- Note that
-
applyFeed
Creates a feed and applies it to the specifiedselector
. The selector's target must be a POJO or a Javarecord
. Properties from the feed will be automatically mapped to the selected object.For example, given the following CSV file (formatted for readability):
firstName, lastName, age, username John, Doe, 24, john_doe Alice, Smith, 55, alice_s # more entries...
and a record with matching properties:
class Person(String firstName, String lastName, int age, String username) {}
a feed can be applied as follows:
List<Person> persons = Instancio.ofList(Person.class) .applyFeed(all(Person.class), feed -> feed.ofResource("data/persons.csv")) .create(); // Output: // [Person[firstName=John, lastName=Doe, age=24, username=john_doe], // Person[firstName=Alice, lastName=Smith, age=55, username=alice_s]]
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withUnique
Specifies that the given selector's target(s) should have unique values.Example:
record Data(int foo, int bar) {} List<Data> results = Instancio.ofList(Data.class) .size(100) .withUnique(field(Data::foo)) .create();
The above snippet generates a list of
Data
instances with uniquefoo
values. Note that values will be unique across all targets that match the selector. For instance, the following usages:withUnique(allInts())
withUnique(all(field(Data::foo), field(Data::bar))
would result in unique values for
foo
andbar
with no overlap (i.e.foo
andbar
are disjoint). To generate unique values per field (with potential overlap), thewithUnique()
method must be specified per field:List<Data> results = Instancio.ofList(Data.class) .size(100) .withUnique(field(Data::foo)) // e.g. { 601, 42, 573, ...} .withUnique(field(Data::bar)) // e.g. { 888, 251, 42, ...} .create();
If it is impossible to generate a sufficient number of unique values after a certain number of attempts, an exception will be thrown:
List<Boolean> results = Instancio.ofList(Boolean.class) .size(10) // will fail as it's impossible to generate 10 unique booleans .withUnique(allBooleans()) .create();
- Specified by:
withUnique
in interfaceBaseApi<T>
- Parameters:
selector
- for fields and/or classes this method should be applied to- Returns:
- API builder reference
- Since:
- 4.8.0
-