Can not configuring a Global Date and Time Format - spring

Question

I wrote a DateTimeFormatAnnotationFormatterFactory to use for global conversion of LocalDateTime, imitating LocalDateTimeFormatAnnotationFormatterFactory
package com.taimi.localdatetimedemo.format.date;
import java.time.LocalDateTime;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
import org.springframework.format.AnnotationFormatterFactory;
import org.springframework.format.Formatter;
import org.springframework.format.Parser;
import org.springframework.format.Printer;
/**
* LocalDateTimeFormatAnnotationFormatterFactory
*/
public class LocalDateTimeFormatAnnotationFormatterFactory implements AnnotationFormatterFactory<LocalDateTimeFormat> {
private static final Set<Class<?>> FIELD_TYPES;
static {
Set<Class<?>> fieldTypes = new HashSet<>(1);
fieldTypes.add(LocalDateTime.class);
FIELD_TYPES = Collections.unmodifiableSet(fieldTypes);
}
#Override
public Set<Class<?>> getFieldTypes() {
return FIELD_TYPES;
}
#Override
public Printer<?> getPrinter(LocalDateTimeFormat annotation, Class<?> fieldType) {
return getFormatter(annotation, fieldType);
}
#Override
public Parser<?> getParser(LocalDateTimeFormat annotation, Class<?> fieldType) {
return getFormatter(annotation, fieldType);
}
protected Formatter<LocalDateTime> getFormatter(LocalDateTimeFormat annotation, Class<?> fieldType) {
LocalDateTimeFormater localDateTimeFormater=new LocalDateTimeFormater(annotation.pattern());
return localDateTimeFormater;
}
}
public #interface LocalDateTimeFormat {
String pattern() default "";
}
package com.taimi.localdatetimedemo.format.date;
import java.text.ParseException;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Locale;
import org.springframework.format.Formatter;
import org.springframework.util.StringUtils;
/**
* LocalDateFormater
*/
public class LocalDateTimeFormater implements Formatter<LocalDateTime> {
private String pattern;
public LocalDateTimeFormater(String pattern) {
if (StringUtils.isEmpty(pattern)) {
throw new IllegalArgumentException("Pattern can't be empty.", null);
}
this.pattern = pattern;
}
#Override
public String print(LocalDateTime localDateTime, Locale locale) {
return createDateTimeFormatter(locale).format(localDateTime);
}
#Override
public LocalDateTime parse(String text, Locale locale) throws ParseException {
return LocalDateTime.parse(text, createDateTimeFormatter(locale));
}
private DateTimeFormatter createDateTimeFormatter(Locale locale) {
return DateTimeFormatter.ofPattern(pattern, locale);
}
}
The configuration is
#Configuration
public class TimeConfig extends WebMvcConfigurationSupport {
#Override
public FormattingConversionService mvcConversionService() {
// DefaultFormattingConversionService conversionService = new DefaultFormattingConversionService(false);
FormattingConversionService conversionService=new FormattingConversionService();
conversionService.addFormatterForFieldAnnotation(new LocalDateTimeFormatAnnotationFormatterFactory());
return conversionService;
}
}
But it always failed in conversion because converterCache can not find a suitable converter or is empty.
The source code of finding converter is showing down below from GenericConversionService
#Nullable
protected GenericConverter getConverter(TypeDescriptor sourceType, TypeDescriptor targetType) {
ConverterCacheKey key = new ConverterCacheKey(sourceType, targetType);
GenericConverter converter = this.converterCache.get(key);
if (converter != null) {
return (converter != NO_MATCH ? converter : null);
}
converter = this.converters.find(sourceType, targetType);
if (converter == null) {
converter = getDefaultConverter(sourceType, targetType);
}
if (converter != null) {
this.converterCache.put(key, converter);
return converter;
}
this.converterCache.put(key, NO_MATCH);
return null;
}

Answer 1

I've found out where I was wrong, the #Interface should be
#Target(ElementType.FIELD)
#Retention(RetentionPolicy.RUNTIME)
public #interface LocalDateTimeFormat {
String pattern() default "";
}