我正在使用Spring Boot 1.4.3的@AutoConfiguration，可以根据用户指定的属性自动创建bean。用户可以指定一组服务，其中名称和版本是必填字段：
service[0].name=myServiceA
service[0].version=1.0
service[1].name=myServiceB
service[1].version=1.2
...
@ConditionalOnProperty实现这个功能吗？我想要像这样的东西：@Configuration
@ConditionalOnProperty({"service[i].name", "service[i].version"})
class AutoConfigureServices {
....
}
org.springframework.boot.autoconfigure.condition.OnPropertyListCondition 类。例如，假设你想检查 service 属性是否至少有一个值：class MyListCondition extends OnPropertyListCondition {
MyListCondition() {
super("service", () -> ConditionMessage.forCondition("service"));
}
}
@Configuration
@Condition(MyListCondition.class)
class AutoConfigureServices {
}
Condition。它需要一些改进，使其更加通用(即不硬编码字符串)，但对我来说效果很好。@Conditional(RequiredRepeatablePropertiesCondition.class)。public class RequiredRepeatablePropertiesCondition extends SpringBootCondition {
private static final Logger LOGGER = LoggerFactory.getLogger(RequiredRepeatablePropertiesCondition.class.getName());
public static final String[] REQUIRED_KEYS = {
"my.services[i].version",
"my.services[i].name"
};
@Override
public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
List<String> missingProperties = new ArrayList<>();
RelaxedPropertyResolver resolver = new RelaxedPropertyResolver(context.getEnvironment());
Map<String, Object> services = resolver.getSubProperties("my.services");
if (services.size() == 0) {
missingProperties.addAll(Arrays.asList(REQUIRED_KEYS));
return getConditionOutcome(missingProperties);
}
//gather indexes to check: [0], [1], [3], etc
Pattern p = Pattern.compile("\\[(\\d+)\\]");
Set<String> uniqueIndexes = new HashSet<String>();
for (String key : services.keySet()) {
Matcher m = p.matcher(key);
if (m.find()) {
uniqueIndexes.add(m.group(1));
}
}
//loop each index and check required props
uniqueIndexes.forEach(index -> {
for (String genericKey : REQUIRED_KEYS) {
String multiServiceKey = genericKey.replace("[i]", "[" + index + "]");
if (!resolver.containsProperty(multiServiceKey)) {
missingProperties.add(multiServiceKey);
}
}
});
return getConditionOutcome(missingProperties);
}
private ConditionOutcome getConditionOutcome(List<String> missingProperties) {
if (missingProperties.isEmpty()) {
return ConditionOutcome.match(ConditionMessage.forCondition(RequiredRepeatablePropertiesCondition.class.getCanonicalName())
.found("property", "properties")
.items(Arrays.asList(REQUIRED_KEYS)));
}
return ConditionOutcome.noMatch(
ConditionMessage.forCondition(RequiredRepeatablePropertiesCondition.class.getCanonicalName())
.didNotFind("property", "properties")
.items(missingProperties)
);
}
}
RelaxedPropertyResolver已不再存在，也没有直接替代RelaxedPropertyResolver.getSubProperties(...)或PropertySourceUtils.getSubProperties(...)。 - bric3Binder.get(context.getEnvironment()).bind("my.services", List.class).orElse(null);它返回 List<String>。我没有尝试将其解析为 POJO（像 AutoConfigureService 那样），但对于简单的字符串很有帮助。 - zegee29关于在Spring自动配置中使用自定义条件的问题，我有一些看法。与@Strumbels提出的类似，但更具可重用性。
@Conditional注释在应用程序启动期间非常早就执行了。属性源已经加载，但是ConfigurationProperties bean尚未创建。但是，我们可以通过将属性绑定到Java POJO来解决这个问题。
首先，我介绍一个函数接口，它将使我们能够定义任何自定义逻辑，检查属性是否实际存在。在您的情况下，此方法将负责检查属性列表是否为空/ null以及其中所有项目是否有效。
public interface OptionalProperties {
boolean isPresent();
}
@Conditional进行元注释，并允许我们定义自定义参数。prefix表示属性命名空间，targetClass表示应将属性映射到的配置属性模型类。@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Conditional(OnConfigurationPropertiesCondition.class)
public @interface ConditionalOnConfigurationProperties {
String prefix();
Class<? extends OptionalProperties> targetClass();
}
现在进入主要部分，自定义条件的实现。
public class OnConfigurationPropertiesCondition extends SpringBootCondition {
@Override
public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
MergedAnnotation<ConditionalOnConfigurationProperties> mergedAnnotation = metadata.getAnnotations().get(ConditionalOnConfigurationProperties.class);
String prefix = mergedAnnotation.getString("prefix");
Class<?> targetClass = mergedAnnotation.getClass("targetClass");
// type precondition
if (!OptionalProperties.class.isAssignableFrom(targetClass)) {
return ConditionOutcome.noMatch("Target type does not implement the OptionalProperties interface.");
}
// the crux of this solution, binding properties to Java POJO
Object bean = Binder.get(context.getEnvironment()).bind(prefix, targetClass).orElse(null);
// if properties are not present at all return no match
if (bean == null) {
return ConditionOutcome.noMatch("Binding properties to target type resulted in null value.");
}
OptionalProperties props = (OptionalProperties) bean;
// execute method from OptionalProperties interface
// to check if condition should be matched or not
// can include any custom logic using property values in a type safe manner
if (props.isPresent()) {
return ConditionOutcome.match();
} else {
return ConditionOutcome.noMatch("Properties are not present.");
}
}
}
现在，您应该创建自己的配置属性类，实现 OptionalProperties 接口。
@ConfigurationProperties("your.property.prefix")
@ConstructorBinding
public class YourConfigurationProperties implements OptionalProperties {
// Service is your POJO representing the name and version subproperties
private final List<Service> services;
@Override
public boolean isPresent() {
return services != null && services.stream().all(Service::isValid);
}
}
然后在Spring的@Configuration类中。
@Configuration
@ConditionalOnConfigurationProperties(prefix = "", targetClass = YourConfigurationProperties.class)
class AutoConfigureServices {
....
}
这种解决方案有两个缺点：
@ConfigurationProperties注释和@ConditionalOnConfigurationProperties注释上。您可以通过在配置属性POJO中定义public static final String PREFIX = "namespace"来部分缓解这个问题。虽然这是一个旧问题，但我希望我的答案能够对Spring2.x有所帮助： 感谢@Brian，我查看了迁移指南，并从示例代码中获得了灵感。这段代码对我很有效：
final List<String> services = Binder.get(context.getEnvironment()).bind("my.services", List.class).orElse(null);
我尝试获取POJO列表（作为AutoConfigureService），但我的类与AutoConfigureServices不同。 为此，我使用了：
final Services services = Binder.get(context.getEnvironment()).bind("my.services", Services.class).orElse(null);
嗨，继续玩吧 :-D
@Getter
@Validated
@RequiredArgsConstructor
@ConfigurationProperties("root")
public class YourProperties {
private final Set<Item> service;
@Getter
@Validated
@RequiredArgsConstructor
public static class Item {
@NotNull
private final String name;
@NotNull
private final String version;
}
}
@ConditionalOnExpression("#{T(org.springframework.util.StringUtils).hasText('${service[0].name}')}")
@Autoconfiguration和@Conditionals会阻止bean被创建。这个想法是用户依赖于具有自动配置的jar包，但它不应该通过抛出致命错误来阻止他们的应用程序加载。 - Strumbles