# 3.6. 配置全局日期和时间格式

默认情况下，未使用`@DateTimeFormat`注解的日期和时间字段是使用`DateFormat.SHORT`样式从字符串转换而来的。如果您愿意，可以通过定义自己的全局格式来更改它。

为此，请确保 Spring 不注册默认格式化程序。相反，请在以下帮助下手动注册格式化程序：

* `org.springframework.format.datetime.standard.DateTimeFormatterRegistrar`
* `org.springframework.format.datetime.DateFormatterRegistrar`

例如，以下 Java 配置注册了一种全局`yyyyMMdd`格式：

```java
@Configuration
public class AppConfig {

    @Bean
    public FormattingConversionService conversionService() {

        // Use the DefaultFormattingConversionService but do not register defaults
        DefaultFormattingConversionService conversionService = new DefaultFormattingConversionService(false);

        // Ensure @NumberFormat is still supported
        conversionService.addFormatterForFieldAnnotation(new NumberFormatAnnotationFormatterFactory());

        // Register JSR-310 date conversion with a specific global format
        DateTimeFormatterRegistrar registrar = new DateTimeFormatterRegistrar();
        registrar.setDateFormatter(DateTimeFormatter.ofPattern("yyyyMMdd"));
        registrar.registerFormatters(conversionService);

        // Register date conversion with a specific global format
        DateFormatterRegistrar registrar = new DateFormatterRegistrar();
        registrar.setFormatter(new DateFormatter("yyyyMMdd"));
        registrar.registerFormatters(conversionService);

        return conversionService;
    }
}
```

如果您更喜欢基于 XML 的配置，可以使用 `FormattingConversionServiceFactoryBean`. 以下示例显示了如何执行此操作：

```xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd>

    <bean id="conversionService" class="org.springframework.format.support.FormattingConversionServiceFactoryBean">
        <property name="registerDefaultFormatters" value="false" />
        <property name="formatters">
            <set>
                <bean class="org.springframework.format.number.NumberFormatAnnotationFormatterFactory" />
            </set>
        </property>
        <property name="formatterRegistrars">
            <set>
                <bean class="org.springframework.format.datetime.standard.DateTimeFormatterRegistrar">
                    <property name="dateFormatter">
                        <bean class="org.springframework.format.datetime.standard.DateTimeFormatterFactoryBean">
                            <property name="pattern" value="yyyyMMdd"/>
                        </bean>
                    </property>
                </bean>
            </set>
        </property>
    </bean>
</beans>
```

请注意，在 Web 应用程序中配置日期和时间格式时有额外的注意事项。请参阅 [WebMVC 转换和格式化](https://docs.spring.io/spring-framework/docs/current/reference/html/web.html#mvc-config-conversion)或 [WebFlux 转换和格式化](https://docs.spring.io/spring-framework/docs/current/reference/html/web-reactive.html#webflux-config-conversion)。


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