Shared DefaultConversionService instance e.g. for BeanPropertyRowMapper [SPR-14948]

[spring-projects-issues]

Yanming Zhou opened SPR-14948 and commented

Creating DefaultConversionService instance is not so cheap, it's thread-safe, so we can create a default instance.

class DefaultConversionService{
private static volatile ConversionService defaultConversionService;
public static DefaultConversionService getDefaultInstance(){
if (defaultConversionService == null) {
			synchronized (DefaultConversionService.class) {
				if (defaultConversionService == null) {
					defaultConversionService = new DefaultConversionService();
				}
			}
		}
return defaultConversionService;
}
}

It could be used by other class, for example BeanPropertyRowMapper

//private ConversionService conversionService = new DefaultConversionService();
private ConversionService conversionService = DefaultConversionService.getDefaultInstance();

---

Affects: 4.3.4

Issue Links:

• Ineffective synchronization in StandardTypeConverter constructor [SPR-14465] #19034 Ineffective synchronization in StandardTypeConverter constructor
• BeanPropertyRowMapper should use ConversionService for date-time support [SPR-13888] #18461 BeanPropertyRowMapper should use ConversionService for date-time support
• Update JdbcUtils to improve enum support [SPR-14990] #19556 Update JdbcUtils to improve enum support

Referenced from: commits spring-projects/spring-integration@d96b8e0

[spring-projects-issues]

Juergen Hoeller commented

Good point, provided that we're lazily initializing it, such a common shared DefaultConversionService makes sense these days, in particular with further use of it in 4.3 here.

So as of 4.3.5, we're reusing such a shared DefaultConversionService instance in BeanPropertyRowMapper, PropertySourcesPropertyResolver, StandardTypeConverter, GenericMessageConverter and also in our common MVC argument resolvers, if no specific ConversionService has been configured otherwise.

[spring-projects-issues]

Tim Lenz commented

My webapp no longer starts up after upgrading from 4.3.3 to 4.3.7. I think it's related to this issue. The stack trace is

Caused by: java.lang.NoSuchMethodError: org.springframework.core.convert.support.DefaultConversionService.getSharedInstance()Lorg/springframework/core/convert/ConversionService;
at org.springframework.jdbc.core.BeanPropertyRowMapper.<init>(BeanPropertyRowMapper.java:91)
at org.springframework.jdbc.core.BeanPropertyRowMapper.newInstance(BeanPropertyRowMapper.java:380)

I have two static BeanPropertyRowMapper instances in my class, created using BeanPropertyRowMapper.newInstance(Class<?> mappedClass)

[spring-projects-issues]

Juergen Hoeller commented

Tim Lenz, this is a new method introduced in 4.3.5. Please make sure that you're actually running against spring-core-4.3.7.jar; it looks like there's an old 4.3.3 jar in your classpath still.

[spring-projects-issues]

Tim Lenz commented

Thank you, somehow I had a dependency in my pom.xml that was still forcing 4.3.3 for spring-core. All good now.