Singleton Bean实例通过泛型参数

本文介绍了Singleton Bean实例通过泛型参数的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述 我想通过基于单个 @Component 泛型类的泛型参数来创建单例bean实例。 我的代码： public interface Mapper< I， O> { ... } 它的多重实现是Spring @Component s（单身人士）。类似这样： @Component public class MapperA实现Mapper< ClazzAI，ClazzAO> { ... } 和 @Component public class MapperB实现Mapper< ClazzBI，ClazzBO> { ... } 其中 ClazzAI ， ClazzAO ， ClazzBI 和 ClazzBO @Component （singleton），它有一个 $ b $ pre $ $ $ $ $ $ $ $ $ $ $ $ $ $ code> @Component public class TransformerImpl< I，O，M扩展Mapper< I，O>> { / **映射器* / 保护的最终M映射器; @Inject private TransformerImpl（final M mapper）{ this.mapper = mapper; } ... } 我想这样使用它： @Inject private TransformerImpl< ClazzAI，ClazzAO，MapperA> transformerA; @Inject private TransformerImpl< ClazzBI，ClazzBO，MapperB> transformerB; 问题： 但Spring无法实例化这两个对象，因为它找到了两个 Mapper 实现： MapperA 和 MapperB ，即使我指定了我希望作为通用参数的实现。 任何想法如何无需在 @Configuration class ？ $ b $中实例化所有这些bean b 解决方案您需要一个单身人士，但需要两个注射点 @Inject private TransformerImpl< ClazzAI，ClazzAO，MapperA> transformerA; @Inject private TransformerImpl< ClazzBI，ClazzBO，MapperB> transformerB; 用于不同构造的对象。这没有什么意义。 你现在意识到你需要两个豆子。如果你不能（不想）在 @Configuration 类中使用 @Bean 工厂方法，你需要声明（并扫描）两个单独的 @Component 类。 （我把你的父构造器公开在这里）。 $ b $ p class MapperATransformerImpl extends TransformerImpl< ClazzAI，ClazzAO，MapperA> ; { @Inject public MapperATransformerImpl（MapperA mapper）{ super（mapper）; } } @Component class MapperBTransformerImpl扩展了TransformerImpl< ClazzBI，ClazzBO，MapperB> { @Inject public MapperBTransformerImpl（MapperB mapper）{ super（mapper）; } } 处理注入目标时 @Inject private TransformerImpl< ClazzAI，ClazzAO，MapperA> transformerA; Spring会找到 MapperATransformerImpl ，它是类型为 TransformerImpl 并注入。 I would like to have a singleton bean instance by generic parameter based on a single @Component generic class.(I am using Spring 4.)My code :I have an interface like this :public interface Mapper<I, O> { ...}And multiple implementation of it which are Spring @Components (singletons). Something like this :@Componentpublic class MapperA implements Mapper<ClazzAI, ClazzAO> { ...}and@Componentpublic class MapperB implements Mapper<ClazzBI, ClazzBO> { ...}where ClazzAI, ClazzAO, ClazzBI and ClazzBO are basic Java classes.I have another Spring @Component (singleton) which have a Mapper class as a generic parameter :@Componentpublic class TransformerImpl<I, O, M extends Mapper<I, O>> { /** The Mapper */ protected final M mapper; @Inject private TransformerImpl(final M mapper) { this.mapper= mapper; } ...}and I would like to use it like this :@Injectprivate TransformerImpl<ClazzAI, ClazzAO, MapperA> transformerA;@Injectprivate TransformerImpl<ClazzBI, ClazzBO, MapperB> transformerB;The problem :But Spring is not able to instantiate those 2 objects because it founds 2 implementations of Mapper : MapperA and MapperB even if I specify which implementation I want as a generic parameter.Any idea how to make it without the need of instantiate all of those beans in a @Configuration class ? 解决方案 You're asking for a singleton but requiring two injection points@Injectprivate TransformerImpl<ClazzAI, ClazzAO, MapperA> transformerA;@Injectprivate TransformerImpl<ClazzBI, ClazzBO, MapperB> transformerB;for differently constructed objects. That doesn't make much sense. You now realize you need two beans. If you can't (don't want to) do it in a @Configuration class with @Bean factory methods, you'll need to declare (and scan) two separate @Component classes. (I made your parent constructor public here.)@Componentclass MapperATransformerImpl extends TransformerImpl<ClazzAI, ClazzAO, MapperA> { @Inject public MapperATransformerImpl(MapperA mapper) { super(mapper); }}@Componentclass MapperBTransformerImpl extends TransformerImpl<ClazzBI, ClazzBO, MapperB> { @Inject public MapperBTransformerImpl(MapperB mapper) { super(mapper); }}When processing the injection target@Injectprivate TransformerImpl<ClazzAI, ClazzAO, MapperA> transformerA;Spring will find the MapperATransformerImpl, which is of type TransformerImpl<ClazzAI, ClazzAO, MapperA> and inject that. 这篇关于Singleton Bean实例通过泛型参数的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！