我有这个属性类:
import java.util.List;
import org.springframework.boot.context.properties.ConfigurationProperties;
@ConfigurationProperties("some")
public class SomeProperties {
private List<String> stuff;
public List<String> getStuff() {
return stuff;
}
public void setStuff(List<String> stuff) {
this.stuff = stuff;
}
}
我在@Configuration类中启用配置属性,如下所示:
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Configuration;
@Configuration
@EnableConfigurationProperties(SomeProperties.class)
public class SomeAutoConfiguration {
}
在同一个类(“SomeAutoConfiguration”)中,我想创建另一个bean,具体取决于SomeProperties中的list属性是否为空。我以为我可以使用@ConditionalExpression和以下SpEl:
@Bean
@ConditionalOnExpression("!(#someProperties.stuff?.isEmpty()?:true)")
public Object someBean(final SomeProperties someProperties) {
return new Object();
}
SpEl是正确的,但我无法控制包含我的属性的bean。使用上面的表达式我遇到了
EL1007E:(pos 43):无法找到属性或字段'stuff' 空
尝试通过其名称获取bean,如
@Bean
@ConditionalOnExpression("!(@'some.CONFIGURATION_PROPERTIES'.stuff?.isEmpty()?:true)")
public Object someBean(final SomeProperties someProperties) {
return new Object();
}
结束于
NoSuchBeanDefinitionException:没有定义名为'some.CONFIGURATION_PROPERTIES'的bean
有什么想法吗?我已经尝试在另一个类中启用ConfigurationProperties,但这也不起作用。
答案 0 :(得分:2)
我认为您遇到的问题是@Conditions
在解析@Configuration
类时进行评估,因此不保证SomeProperties
bean已定义。即使它被定义了,你可能也不希望它提前初始化,所以我建议采用不同的方法。
您可以尝试@ConditionalOnPropety
,这是Spring Boot内部使用的注释,只要它有条件地想要根据属性启用自动配置。如果这不够灵活,您可以创建自己的Condition
并直接访问Environment
以判断属性值是否为空。如果要支持灵活绑定,可以使用RelaxedPropertyResolver
。 Here's an example
答案 1 :(得分:0)
为了补充有关Spring Boot 2+的@PhilWebb答案,RelaxedPropertyResolver
已被删除,取而代之的是更强大的名为 Binder
的替代方法。这是一个非常简单的示例:
@Configuration
@AutoConfigureBefore(JacksonAutoConfiguration.class)
@ConditionalOnMissingBean(ObjectMapper.class)
@Conditional(SpringJacksonPropertiesMissing.class)
public class ObjectMapperConfiguration {
@Bean
public ObjectMapper objectMapper() {
return new ObjectMapper()
.disable(FAIL_ON_UNKNOWN_PROPERTIES)
.setSerializationInclusion(JsonInclude.Include.NON_NULL);
}
static class SpringJacksonPropertiesMissing extends SpringBootCondition {
@Override
public ConditionOutcome getMatchOutcome(ConditionContext context,
AnnotatedTypeMetadata metadata) {
return new ConditionOutcome(hasJacksonPropertiesDefined(context),
"Spring Jackson property based configuration missing");
}
private boolean hasJackonPropertiesDefined(ConditionContext context) {
return Binder.get(context.getEnvironment())
.bind(ConfigurationPropertyName.of("spring.jackson"),
Bindable.of(Map.class))
.orElse(Collections.emptyMap())
.isEmpty();
}
}
}
免责声明:该代码用于逐步淘汰关于杰克逊对象映射器的一些不良做法,以便将某些代码过渡到spring boot way to configure an object mapper。
答案 2 :(得分:0)
基于Brice's answer,我提出了一个抽象条件:
public abstract class ConfigurationPropertyCondition<T> extends SpringBootCondition {
private final Class<T> propertiesClass;
private final Supplier<T> constructor;
private final String prefix;
private final Predicate<T> predicate;
public ConfigurationPropertyCondition(
Class<T> propertiesClass, Supplier<T> constructor, String prefix, Predicate<T> predicate) {
this.propertiesClass = propertiesClass;
this.constructor = constructor;
this.prefix = prefix;
this.predicate = predicate;
}
@Override
public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
return new ConditionOutcome(predicate.test(properties(context)), (String) null);
}
private T properties(ConditionContext context) {
return Binder.get(context.getEnvironment())
.bind(ConfigurationPropertyName.of(prefix), Bindable.of(propertiesClass))
.orElseGet(constructor);
}
}
现在我可以做类似的事情了
...
@ConfigurationProperties(prefix = MY_FEATURE_SETTINGS)
@Bean
public MyFeatureProperties myFeatureProperties() {
return new MyFeatureProperties();
}
...
@Conditional(MyFeatureConfiguration.MyFeatureEnabled.class)
@Configuration
public class MyFeatureConfiguration {
...
static class MyFeatureEnabled extends ConfigurationPropertyCondition<MyFeatureProperties> {
public MyFeatureEnabled() {
super(MyFeatureProperties.class, MyFeatureProperties::new, MY_FEATURE_SETTINGS, MyFeatureProperties::isEnabled);
}
}
}