java - 如何在构造函数接受类的情况下使用 Guice `Module` 进行注入(inject)？

Question

标题描述了我的问题。

例如

public class EntryDAOModule extends AbstractModule {

    @Override
    protected void configure() {
        bind(EntryDAO.class).to(EntryDTOMongoImpl.class); // what should this be?       
    }
}

如图所示，.to 的参数应该是什么，如下所示:

public class GenericDAOMongoImpl<T, K extends Serializable> extends BasicDAO<T, K> {
    public GenericDAOMongoImpl(Class<T> entityClass) throws UnknownHostException {
        super(entityClass, ConnectionManager.getDataStore());
    }
}

public class EntryDAOMongoImpl extends GenericDAOMongoImpl<EntryDTOMongoImpl, ObjectId> implements EntryDAO<EntryDTOMongoImpl> {
    private static final Logger logger = Logger.getLogger(EntryDAOMongoImpl.class);

    @Inject
    public EntryDAOMongoImpl(Class<EntryDTOMongoImpl> entityClass) throws UnknownHostException {
        super(entityClass);
    }
    ...
}

如何实例化 EntryDAOMongoImpl 类，如下所示:

Injector injector = Guice.createInjector(new EntryDAOModule());
this.entryDAO = injector.getInstance(EntryDAO.class); // what should this be?

Answer 1

这里您需要创建一个工厂。使用辅助注入(inject)可以帮助您。

你可以看到我的previous post regarding assisted injection

但这是适合您的情况的确切解决方案:

入口DAOMongoImpl:

public class EntryDAOMongoImpl extends GenericDAOMongoImpl<EntryDTOMongoImpl, ObjectId> implements EntryDAO<EntryDTOMongoImpl> {
    private static final Logger logger = Logger.getLogger(EntryDAOMongoImpl.class);

    @Inject
    public EntryDAOMongoImpl(@Assisted Class<EntryDTOMongoImpl> entityClass) throws UnknownHostException {
        super(entityClass);
    }
    ...
}

工厂:

public interface EntryDAOFactory {
    public EntryDAOMongoImpl buildEntryDAO(Class<EntryDTOMongoImpl> entityClass);
}

模块:

public class EntryDAOModule extends AbstractModule {

    @Override
    protected void configure() {
        //bind(EntryDAO.class).to(EntryDAOMongoImpl.class); // what should this be?

        FactoryModuleBuilder factoryModuleBuilder = new FactoryModuleBuilder();
        install(factoryModuleBuilder.build(EntryDAOFactory.class));
    }
}

用法:

Injector injector = Guice.createInjector(new EntryDAOModule());
EntryDAOFactory factory = injector.getInstance(EntryDAOFactory.class);
this.entryDAO = factory.buildEntryDAO(entityClass);

如果您打算将 EntryDAOMongoImpl 作为单例使用(在我看来单例的自然用法)，那么您可以执行以下操作，而无需在模块内进行辅助注入(inject):

public class EntryDAOModule extends AbstractModule {

    @Override
    protected void configure() {
        EtnryDTOMongoImpl dto = new EntryDTOMongoImpl(TargetEntry.class); //guessing here
        bind(EntryDAO.class).toInstance(new EntryDAOMongoImpl(dto)); // singleton   
    }
}

如果有帮助请告诉我