Top Description Inners Fields Constructors Methods
org.hibernate.transform

public Class DistinctResultTransformer

extends BasicTransformerAdapter
implements Serializable
Class Inheritance
All Implemented Interfaces
java.io.Serializable
Imports
java.util.List, .ArrayList, .Set, .HashSet, java.io.Serializable, org.slf4j.Logger, .LoggerFactory
Distinctions the result tuples in the final result based on the defined equality of the tuples.

Since this transformer is stateless, all instances would be considered equal. So for optimization purposes we limit it to a single, singleton instance.

Author
Steve Ebersole

Nested and Inner Type Summary

Modifier and TypeClass and Description
private static class
DistinctResultTransformer.Identity

Helper class to handle distincting

Field Summary

Modifier and TypeField and Description
public static final DistinctResultTransformer
INSTANCE

private static final Logger
log

Constructor Summary

AccessConstructor and Description
private
DistinctResultTransformer()

Disallow instantiation of DistinctResultTransformer.

Method Summary

Modifier and TypeMethod and Description
private Object

Returns:

The singleton instance : INSTANCE
readResolve()

Serialization hook for ensuring singleton uniqueing.

public List<E>
transformList(List<E>
The result.
list)

Overrides org.hibernate.transform.BasicTransformerAdapter.transformList.

Implements org.hibernate.transform.ResultTransformer.transformList.

Uniquely distinct each tuple row here.
Inherited from org.hibernate.transform.BasicTransformerAdapter:
transformTuple

Field Detail

INSTANCEback to summary
public static final DistinctResultTransformer INSTANCE
logback to summary
private static final Logger log

Constructor Detail

DistinctResultTransformerback to summary
private DistinctResultTransformer()

Disallow instantiation of DistinctResultTransformer.

Method Detail

readResolveback to summary
private Object readResolve()

Serialization hook for ensuring singleton uniqueing.

Returns:Object

The singleton instance : INSTANCE

transformListback to summary
public List<E> transformList(List<E> list)

Overrides org.hibernate.transform.BasicTransformerAdapter.transformList.

Implements org.hibernate.transform.ResultTransformer.transformList.

Uniquely distinct each tuple row here.

Parameters
list:List<E>

Doc from org.hibernate.transform.ResultTransformer.transformList.

The result.

Returns:List<E>

Doc from org.hibernate.transform.ResultTransformer.transformList.

The transformed result.

org.hibernate.transform back to summary

private final Class DistinctResultTransformer.Identity

extends Object
Class Inheritance
Helper class to handle distincting

Field Summary

Modifier and TypeField and Description
pack-priv final Object
entity

Constructor Summary

AccessConstructor and Description
private
Identity(Object entity)

Method Summary

Modifier and TypeMethod and Description
public boolean
equals(Object
the reference object with which to compare.
other)

Overrides java.lang.Object.equals.

Indicates whether some other object is "equal to" this one.
public int
hashCode()

Overrides java.lang.Object.hashCode.

Returns a hash code value for the object.
Inherited from java.lang.Object:
clonefinalizegetClassnotifynotifyAlltoStringwaitwaitwait

Field Detail

entityback to summary
pack-priv final Object entity

Constructor Detail

Identityback to summary
private Identity(Object entity)

Method Detail

equalsback to summary
public boolean equals(Object other)

Overrides java.lang.Object.equals.

Doc from java.lang.Object.equals.

Indicates whether some other object is "equal to" this one.

The equals method implements an equivalence relation on non-null object references:

  • It is reflexive: for any non-null reference value x, x.equals(x) should return true.
  • It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.
  • It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.
  • It is consistent: for any non-null reference values x and y, multiple invocations of x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified.
  • For any non-null reference value x, x.equals(null) should return false.

An equivalence relation partitions the elements it operates on into equivalence classes; all the members of an equivalence class are equal to each other. Members of an equivalence class are substitutable for each other, at least for some purposes.

Parameters
other:Object

the reference object with which to compare.

Returns:boolean

true if this object is the same as the obj argument; false otherwise.

hashCodeback to summary
public int hashCode()

Overrides java.lang.Object.hashCode.

Doc from java.lang.Object.hashCode.

Returns a hash code value for the object. This method is supported for the benefit of hash tables such as those provided by java.util.HashMap.

The general contract of hashCode is:

  • Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
  • If two objects are equal according to the equals method, then calling the hashCode method on each of the two objects must produce the same integer result.
  • It is not required that if two objects are unequal according to the equals method, then calling the hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hash tables.
Returns:int

a hash code value for this object.