Class HashCodeMethod

java.lang.Object

net.bytebuddy.implementation.HashCodeMethod

All Implemented Interfaces:

InstrumentedType.Prepareable, Implementation

@Enhance
public class HashCodeMethod
extends Object
implements Implementation

An implementation of Object.hashCode() that takes a class's declared fields into consideration. A hash code is computed by transforming primitive field types to an int value and by summing those values up starting from a given offset after multiplying any previous value with a multiplier. Reference values are checked against null values unless specified otherwise.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
protected static class	HashCodeMethod.Appender	A byte code appender to implement a hash code method.
protected static interface	HashCodeMethod.NullValueGuard	A guard against null values for fields with reference types.
protected static interface	HashCodeMethod.OffsetProvider	An offset provider is responsible for supplying the initial hash code.
protected static enum	HashCodeMethod.ValueTransformer	A value transformer that is responsible for resolving a field value to an int value.

Nested classes/interfaces inherited from interface Implementation

Implementation.Composable, Implementation.Compound, Implementation.Context, Implementation.Simple, Implementation.SpecialMethodInvocation, Implementation.Target

Nested classes/interfaces inherited from interface InstrumentedType.Prepareable

InstrumentedType.Prepareable.NoOp

Field Summary

Fields

Modifier and Type	Field	Description
private static final int	DEFAULT_MULTIPLIER	The default multiplier for each value before adding a field's hash code value which should be a prime number.
private static final int	DEFAULT_OFFSET	The default offset which should be a prime number.
private static final MethodDescription.InDefinedShape	GET_CLASS	The Object.getClass() method.
private static final MethodDescription.InDefinedShape	HASH_CODE	The Object.hashCode() method.
private final ElementMatcher.Junction<? super FieldDescription.InDefinedShape>	identity	A matcher to determine that a field should be considered by its identity.
private final ElementMatcher.Junction<? super FieldDescription.InDefinedShape>	ignored	A matcher to filter fields that should not be used for a hash codes computation.
private final int	multiplier	A multiplier for each value before adding a field's hash code value.
private final ElementMatcher.Junction<? super FieldDescription.InDefinedShape>	nonNullable	A matcher to determine fields of a reference type that cannot be null.
private final HashCodeMethod.OffsetProvider	offsetProvider	The hash code's offset provider.

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	HashCodeMethod(HashCodeMethod.OffsetProvider offsetProvider)	Creates a new hash code method implementation.
private	HashCodeMethod(HashCodeMethod.OffsetProvider offsetProvider, int multiplier, ElementMatcher.Junction<? super FieldDescription.InDefinedShape> ignored, ElementMatcher.Junction<? super FieldDescription.InDefinedShape> nonNullable, ElementMatcher.Junction<? super FieldDescription.InDefinedShape> identity)	Creates a new hash code method implementation.

Method Summary

Modifier and Type	Method	Description
ByteCodeAppender	appender(Implementation.Target implementationTarget)	Creates a byte code appender that determines the implementation of the instrumented type's methods.
InstrumentedType	prepare(InstrumentedType instrumentedType)	Prepares a given instrumented type.
static HashCodeMethod	usingDefaultOffset()	Creates a hash code method implementation that bases the hash code on a fixed value.
static HashCodeMethod	usingOffset(int value)	Creates a hash code method implementation that bases the hash code on a fixed value.
static HashCodeMethod	usingSuperClassOffset()	Creates a hash code method implementation that bases the hash code on the instrumented type's super class's hash code value.
static HashCodeMethod	usingTypeHashOffset(boolean dynamic)	Creates a hash code method implementation that bases the hash code on the instrumented type's class constant's hash code..
HashCodeMethod	withIdentityFields(ElementMatcher<? super FieldDescription.InDefinedShape> identity)	Returns a new version of this hash code method implementation that considers the matched fields by their identity.
HashCodeMethod	withIgnoredFields(ElementMatcher<? super FieldDescription.InDefinedShape> ignored)	Returns a new version of this hash code method implementation that ignores the specified fields additionally to any previously specified fields.
HashCodeMethod	withMultiplier(int multiplier)	Returns a new version of this hash code method implementation that uses the given multiplier onto any given hash code before adding a field's hash code.
HashCodeMethod	withNonNullableFields(ElementMatcher<? super FieldDescription.InDefinedShape> nonNullable)	Returns a new version of this hash code method implementation that does not apply a null value check for the specified fields if they have a reference type additionally to any previously specified fields.

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

DEFAULT_OFFSET

private static final int DEFAULT_OFFSET

The default offset which should be a prime number.

See Also:

• Constant Field Values

DEFAULT_MULTIPLIER

private static final int DEFAULT_MULTIPLIER

The default multiplier for each value before adding a field's hash code value which should be a prime number.

See Also:

• Constant Field Values

HASH_CODE

private static final MethodDescription.InDefinedShape HASH_CODE

The Object.hashCode() method.

GET_CLASS

private static final MethodDescription.InDefinedShape GET_CLASS

The Object.getClass() method.

offsetProvider

private final HashCodeMethod.OffsetProvider offsetProvider

The hash code's offset provider.

multiplier

private final int multiplier

A multiplier for each value before adding a field's hash code value.

ignored

private final ElementMatcher.Junction<? super FieldDescription.InDefinedShape> ignored

A matcher to filter fields that should not be used for a hash codes computation.

nonNullable

private final ElementMatcher.Junction<? super FieldDescription.InDefinedShape> nonNullable

A matcher to determine fields of a reference type that cannot be null.

identity

private final ElementMatcher.Junction<? super FieldDescription.InDefinedShape> identity

A matcher to determine that a field should be considered by its identity.

Constructor Details

HashCodeMethod

protected HashCodeMethod(HashCodeMethod.OffsetProvider offsetProvider)

Creates a new hash code method implementation.

Parameters:

offsetProvider - The hash code's offset provider.

HashCodeMethod

private HashCodeMethod(HashCodeMethod.OffsetProvider offsetProvider,
 int multiplier,
 ElementMatcher.Junction<? super FieldDescription.InDefinedShape> ignored,
 ElementMatcher.Junction<? super FieldDescription.InDefinedShape> nonNullable,
 ElementMatcher.Junction<? super FieldDescription.InDefinedShape> identity)

Creates a new hash code method implementation.

Parameters:

offsetProvider - The hash code's offset provider.

multiplier - A multiplier for each value before adding a field's hash code value

ignored - A matcher to filter fields that should not be used for a hash codes computation.

nonNullable - A matcher to determine fields of a reference type that cannot be null.

identity - A matcher to determine that a field should be considered by its identity.

Method Details

usingSuperClassOffset

public static HashCodeMethod usingSuperClassOffset()

Creates a hash code method implementation that bases the hash code on the instrumented type's super class's hash code value.

Returns:

A hash code method implementation that bases the hash code on the instrumented type's super class's hash code value.

usingTypeHashOffset

public static HashCodeMethod usingTypeHashOffset(boolean dynamic)

Creates a hash code method implementation that bases the hash code on the instrumented type's class constant's hash code..

Parameters:

dynamic - true if the type should be resolved from the instance and not be set as the declaring class.

Returns:

A hash code method implementation that bases the hash code on the instrumented type's class constant's hash code.

usingDefaultOffset

public static HashCodeMethod usingDefaultOffset()

Creates a hash code method implementation that bases the hash code on a fixed value.

Returns:

A hash code method implementation that bases the hash code on a fixed value.

usingOffset

public static HashCodeMethod usingOffset(int value)

Creates a hash code method implementation that bases the hash code on a fixed value.

Parameters:

value - The fixed value.

Returns:

A hash code method implementation that bases the hash code on a fixed value.

withIgnoredFields

public HashCodeMethod withIgnoredFields(ElementMatcher<? super FieldDescription.InDefinedShape> ignored)

Returns a new version of this hash code method implementation that ignores the specified fields additionally to any previously specified fields.

Parameters:

ignored - A matcher to specify any fields that should be ignored.

Returns:

A new version of this hash code method implementation that also ignores any fields matched by the provided matcher.

withNonNullableFields

public HashCodeMethod withNonNullableFields(ElementMatcher<? super FieldDescription.InDefinedShape> nonNullable)

Returns a new version of this hash code method implementation that does not apply a null value check for the specified fields if they have a reference type additionally to any previously specified fields.

Parameters:

nonNullable - A matcher to specify any fields that should not be guarded against null values.

Returns:

A new version of this hash code method implementation that also does not apply null value checks to any fields matched by the provided matcher.

withIdentityFields

public HashCodeMethod withIdentityFields(ElementMatcher<? super FieldDescription.InDefinedShape> identity)

Returns a new version of this hash code method implementation that considers the matched fields by their identity.

Parameters:

identity - A matcher to specify any fields that should be considered by their identity.

Returns:

A new version of this hash code method implementation that also considers the matched fields by their identity.

withMultiplier

public HashCodeMethod withMultiplier(int multiplier)

Returns a new version of this hash code method implementation that uses the given multiplier onto any given hash code before adding a field's hash code.

Parameters:

multiplier - The multiplier to use for any hash code before adding any field's hash code.

Returns:

A new version of this hash code method implementation that uses the given multiplier onto any given hash code before adding a field's hash code.

prepare

public InstrumentedType prepare(InstrumentedType instrumentedType)

Prepares a given instrumented type.

Specified by:

prepare in interface InstrumentedType.Prepareable

Parameters:

instrumentedType - The instrumented type in its current form.

Returns:

The prepared instrumented type.

appender

public ByteCodeAppender appender(Implementation.Target implementationTarget)

Creates a byte code appender that determines the implementation of the instrumented type's methods.

Specified by:

appender in interface Implementation

Parameters:

implementationTarget - The target of the current implementation.

Returns:

A byte code appender for implementing methods delegated to this implementation. This byte code appender is also responsible for handling methods that were added by this implementation on the call to InstrumentedType.Prepareable.prepare(InstrumentedType).