Package org.javers.core.diff.custom

Class NullAsBlankStringComparator

java.lang.Object

org.javers.core.diff.custom.NullAsBlankStringComparator

All Implemented Interfaces:

CustomValueComparator<String>

public class NullAsBlankStringComparator
extends Object
implements CustomValueComparator<String>

Compares Strings treating blank and null strings as equal.

Usage example:

 JaversBuilder.javers()
     .registerValue(String.class, new NullAsBlankStringComparator())
     .build();
 

See Also:

• JaversBuilder.registerValue(Class, CustomValueComparator)

Constructor Summary

Constructors

Constructor	Description
NullAsBlankStringComparator()

Method Summary

Modifier and Type	Method	Description
boolean	equals(String a, String b)	Called by Javers to compare two Values.
boolean	handlesNulls()	This flag is used to indicate to Javers whether a comparator implementation wants to handle nulls.
String	toString(String value)	This method has two roles.

Methods inherited from class java.lang.Object

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

Constructor Details

NullAsBlankStringComparator

public NullAsBlankStringComparator()

Method Details

equals

public boolean equals(String a,
 String b)

Description copied from interface: CustomValueComparator

Called by Javers to compare two Values.

Specified by:

equals in interface CustomValueComparator<String>

Parameters:

a - not null if CustomValueComparator.handlesNulls() returns false

b - not null if CustomValueComparator.handlesNulls() returns false

toString

public String toString(String value)

Description copied from interface: CustomValueComparator

This method has two roles. First, it is used when Values are compared in hashing contexts. Second, it is used to build Entity Ids from Values.

Hashcode role

When a Value class has custom toString(), it is used instead of Object.hashCode() when comparing Values in hashing contexts, so:

• Sets with Values
• Lists with Values compared as ListCompareAlgorithm.AS_SET
• Maps with Values as keys

Custom toString() implementation should be aligned with custom CustomValueComparator.equals(Object, Object) in the same way like Object.hashCode() should be aligned with Object.equals(Object).

Entity Id role

Each Value can serve as an Entity Id.
When a Value has custom toString() function, it is used for creating InstanceId for Entities. If a Value doesn't have a custom toString() , default ReflectionUtil.reflectiveToString(Object)) is used.

See full example CustomToStringExample.groovy.

Specified by:

toString in interface CustomValueComparator<String>

Parameters:

value - not null if CustomValueComparator.handlesNulls() returns false

handlesNulls

public boolean handlesNulls()

Description copied from interface: CustomValueComparator

This flag is used to indicate to Javers whether a comparator implementation wants to handle nulls.

By default, the flag is false and Javers checks if both values are non-null before calling a comparator.
If any of given values is null — Javers compares them using the standard Java logic:

• null == null
• null != non-null

If the flag is true — Javers skips that logic and allows a comparator to handle nulls on its own. In that case, a comparator holds responsibility for null-safety.

Specified by:

handlesNulls in interface CustomValueComparator<String>

See Also:

• NullAsBlankStringComparator