Optimize ObjectToStringConverter to ensure copies are not made when source is already a String [SPR-7109]

[spring-projects-issues]

Keith Donald opened SPR-7109 and commented

The existing String should be returned as-is unless their is some specific transformation that needs to be applied by some other converter.

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Affects: 3.0.2

[spring-projects-issues]

Keith Donald commented

Moved the CharSequence assignable check first in canConvert and added a test.

[spring-projects-issues]

Keith Donald commented

Just to give an idea here, consider the amount of work that currently goes into converting simple objects to string, where no specific toString converter is registered:

DEBUG: org.springframework.core.convert.support.GenericConversionService - Converting value true of [TypeDescriptor java.lang.Boolean] to [TypeDescriptor java.lang.String]
TRACE: org.springframework.core.convert.support.GenericConversionService - Looking for converters indexed by sourceType [java.lang.Boolean]
TRACE: org.springframework.core.convert.support.GenericConversionService - and indexed by targetType [java.lang.String]
TRACE: org.springframework.core.convert.support.GenericConversionService - and indexed by targetType [java.io.Serializable]
TRACE: org.springframework.core.convert.support.GenericConversionService - and indexed by targetType [java.lang.Comparable]
TRACE: org.springframework.core.convert.support.GenericConversionService - and indexed by targetType [java.lang.CharSequence]
TRACE: org.springframework.core.convert.support.GenericConversionService - and indexed by targetType [java.lang.Object]
TRACE: org.springframework.core.convert.support.GenericConversionService - Looking for converters indexed by sourceType [java.io.Serializable]
TRACE: org.springframework.core.convert.support.GenericConversionService - and indexed by targetType [java.lang.String]
TRACE: org.springframework.core.convert.support.GenericConversionService - and indexed by targetType [java.io.Serializable]
TRACE: org.springframework.core.convert.support.GenericConversionService - and indexed by targetType [java.lang.Comparable]
TRACE: org.springframework.core.convert.support.GenericConversionService - and indexed by targetType [java.lang.CharSequence]
TRACE: org.springframework.core.convert.support.GenericConversionService - and indexed by targetType [java.lang.Object]
TRACE: org.springframework.core.convert.support.GenericConversionService - Looking for converters indexed by sourceType [java.lang.Comparable]
TRACE: org.springframework.core.convert.support.GenericConversionService - and indexed by targetType [java.lang.String]
TRACE: org.springframework.core.convert.support.GenericConversionService - and indexed by targetType [java.io.Serializable]
TRACE: org.springframework.core.convert.support.GenericConversionService - and indexed by targetType [java.lang.Comparable]
TRACE: org.springframework.core.convert.support.GenericConversionService - and indexed by targetType [java.lang.CharSequence]
TRACE: org.springframework.core.convert.support.GenericConversionService - and indexed by targetType [java.lang.Object]
TRACE: org.springframework.core.convert.support.GenericConversionService - Looking for converters indexed by sourceType [java.lang.Object]
TRACE: org.springframework.core.convert.support.GenericConversionService - and indexed by targetType [java.lang.String]
TRACE: org.springframework.core.convert.support.GenericConversionService - Found matchable converters org.springframework.core.convert.support.ObjectToStringConverter@a19b1de
TRACE: org.springframework.core.convert.support.GenericConversionService - Matching org.springframework.core.convert.support.ObjectToStringConverter@a19b1de
DEBUG: org.springframework.core.convert.support.GenericConversionService - Matched converter org.springframework.core.convert.support.ObjectToStringConverter@a19b1de
DEBUG: org.springframework.core.convert.support.GenericConversionService - Converted to 'true'