Spring无法自动连线课程

Question

我有以下Spring @Configuration：

@Bean
@Qualifier("mongo")
public MongoFacade mongo(Environment env){
    final String host = env.getProperty("database.host");
    final MongoClient mongoClient = new MongoClient(host);
    return new MongoFacade(mongoClient, "test-db");
}

@Bean
public MessageStore<Event> eventStore(@Qualifier("mongo") MongoFacade mongo, ObjectMapper mapper) {
    return new MongoMessageStore<>(mongo, mapper);
}

当我启动应用程序时，会引发异常，原因是：

Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'eventStore' defined in it.m.MyConfiguration: Unsatisfied dependency expressed through constructor argument with index 0 of type [base.backend.persistence.impl.mongo.MongoFacade]: : No qualifying bean of type [base.backend.persistence.impl.mongo.MongoFacade] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Qualifier(value=mongo)}; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [base.backend.persistence.impl.mongo.MongoFacade] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Qualifier(value=mongo)}

MongoFacade类是一个真实的类，并且不实现接口，我也尝试从该方法中删除Environment依赖项，但仍然无法正常工作。

删除@Qualifier批注，错误是：

Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [base.backend.persistence.impl.mongo.MongoFacade] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {}

MongoFacade是适用于我的PersistenceId类的MongoClient类的简单外观：

public class MongoFacade {

public static final String DEFAULT_NAME = "default";

private final MongoClient mongo;
private final String defaultName;

public MongoFacade(MongoClient mongoClient) {
    this(mongoClient, DEFAULT_NAME);
}
public MongoFacade(MongoClient mongoClient, String defaultName) {
    this.mongo = mongoClient;
    this.defaultName = defaultName;
}

public Document findOne(PersistenceId id){
    final MongoCollection<Document> collection = collection(id);
    final String documentId = documentId(id);

    return collection.find(eq("_id", documentId)).first();
}

public UpdateResult updateOne(PersistenceId id, Document update) {
    final MongoCollection<Document> collection = collection(id);
    final String documentId = documentId(id);

    return collection.updateOne(eq("_id", documentId), update);
}

Answer 1

可以将环境作为字段而不是构造函数作为字段注入，我建议使用方法调用代替对依赖项的自动接线。

类似于以下内容

@Autowired
private Environment env;

@Bean
public MongoFacade mongoFacade(){
    final String host = env.getProperty("database.host");
    final MongoClient mongoClient = new MongoClient(host);
    return new MongoFacade(mongoClient, "test-db");
}

@Bean
public MessageStore<Event> eventStore(ObjectMapper mapper) {
    return new MongoMessageStore<>(mongoFacade(), mapper);
}

编辑：添加了Spring Boot MongoDB配置

从注释中可以明显看出您正在使用Spring Boot，这已经为您自动配置了MongoClient 。 除了自己做之外，您还可以进一步减少配置。 （另请MongoAutoConfiguration ）。

在您的application.properties添加

spring.data.mongodb.host=<value of current database.host>

还是完整的URI

spring.data.mongodb.uri=<value of current database.host>

然后更改您的配置类。

@Bean
public MongoFacade mongoFacade(MongoClient mongoClient){
    return new MongoFacade(mongoClient, "test-db");
}

@Bean
public MessageStore<Event> eventStore(ObjectMapper mapper) {
    return new MongoMessageStore<>(mongoFacade(null), mapper);
}

Spring Boot现在将构造一个MongoClient 。

Answer 2

您可以在声明bean定义时使用@Service而不是@qualifier吗

@Service("mongo")
public MongoFacade mongoFacade()

让我知道它是否对您有用。