学习Netflix管理员

最近几天，我一直在与Netflix Governator合作，并尝试使用Governator尝试一个小样本，以将其与Spring Framework的依赖项注入功能集进行比较。以下内容并不全面，我将在下一系列文章中对此进行扩展。

因此，对于没有经验的人来说，Governorator是Google Guice的扩展，通过一些类似于Spring的功能对其进行了增强，引用Governator网站：

类路径扫描和自动绑定，生命周期管理，配置到字段映射，字段验证和并行化的对象预热。

在这里，我将演示两个功能，类路径扫描和自动绑定。

基本依赖注入

考虑一个BlogService，具体取决于BlogDao：

public class DefaultBlogService implements BlogService {private final BlogDao blogDao;public DefaultBlogService(BlogDao blogDao) {this.blogDao = blogDao;}@Overridepublic BlogEntry get(long id) {return this.blogDao.findById(id);}
}

如果我使用Spring定义这两个组件之间的依赖关系，则将使用以下配置：

package sample.spring;import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import sample.dao.BlogDao;
import sample.service.BlogService;@Configuration
public class SampleConfig {@Beanpublic BlogDao blogDao() {return new DefaultBlogDao();}@Beanpublic BlogService blogService() {return new DefaultBlogService(blogDao());}
}

在Spring中，依赖项配置是在带有@Configuration注释的类中指定的。 @Bean注释的方法返回组件，请注意如何通过blogService方法中的构造函数注入来注入blogDao。

此配置的单元测试如下：

package sample.spring;import org.junit.Test;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import sample.service.BlogService;import static org.hamcrest.MatcherAssert.*;
import static org.hamcrest.Matchers.*;public class SampleSpringExplicitTest {@Testpublic void testSpringInjection() {AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();context.register(SampleConfig.class);context.refresh();BlogService blogService = context.getBean(BlogService.class);assertThat(blogService.get(1l), is(notNullValue()));context.close();}}

请注意，Spring为单元测试提供了良好的支持，更好的测试如下：

package sample.spring;package sample.spring;import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import sample.service.BlogService;import static org.hamcrest.MatcherAssert.*;
import static org.hamcrest.Matchers.*;@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration
public class SampleSpringAutowiredTest {@Autowiredprivate BlogService blogService;@Testpublic void testSpringInjection() {assertThat(blogService.get(1l), is(notNullValue()));}@Configuration@ComponentScan("sample.spring")public static class SpringConig {}}

这是基本的依赖项注入，因此不需要指定这种依赖关系，Governator本身就是必需的，Guice就足够了，这就是使用Guice Modules时配置的外观：

package sample.guice;import com.google.inject.AbstractModule;
import sample.dao.BlogDao;
import sample.service.BlogService;public class SampleModule extends AbstractModule{@Overrideprotected void configure() {bind(BlogDao.class).to(DefaultBlogDao.class);bind(BlogService.class).to(DefaultBlogService.class);}
}

此配置的单元测试如下：

package sample.guice;import com.google.inject.Guice;
import com.google.inject.Injector;
import org.junit.Test;
import sample.service.BlogService;import static org.hamcrest.Matchers.*;
import static org.hamcrest.MatcherAssert.*;public class SampleModuleTest {@Testpublic void testExampleBeanInjection() {Injector injector = Guice.createInjector(new SampleModule());BlogService blogService = injector.getInstance(BlogService.class);assertThat(blogService.get(1l), is(notNullValue()));}}

类路径扫描和自动绑定

类路径扫描是一种通过在类路径中查找标记来检测组件的方法。使用Spring的样本应该澄清这一点：

@Repository
public class DefaultBlogDao implements BlogDao {....
}@Service
public class DefaultBlogService implements BlogService {private final BlogDao blogDao;@Autowiredpublic DefaultBlogService(BlogDao blogDao) {this.blogDao = blogDao;}...
}

在这里，注释@ Service，@ Repository用作标记，以指示它们是组件，并且依赖项由DefaultBlogService的构造函数上的@Autowired注释指定。

鉴于现在已经简化了配置，我们只需要提供应该为此类带注释的组件进行扫描的软件包名称，这就是完整测试的样子：

package sample.spring;
...
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration
public class SampleSpringAutowiredTest {@Autowiredprivate BlogService blogService;@Testpublic void testSpringInjection() {assertThat(blogService.get(1l), is(notNullValue()));}@Configuration@ComponentScan("sample.spring")public static class SpringConig {}
}

总督提供了类似的支持：

@AutoBindSingleton(baseClass = BlogDao.class)
public class DefaultBlogDao implements BlogDao {....
}@AutoBindSingleton(baseClass = BlogService.class)
public class DefaultBlogService implements BlogService {private final BlogDao blogDao;@Injectpublic DefaultBlogService(BlogDao blogDao) {this.blogDao = blogDao;}....
}

在这里，@ AutoBindSingleton批注用作标记批注来定义guice绑定，考虑到以下是对类路径扫描的测试：

package sample.gov;import com.google.inject.Injector;
import com.netflix.governator.guice.LifecycleInjector;
import com.netflix.governator.lifecycle.LifecycleManager;
import org.junit.Test;
import sample.service.BlogService;import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.is;
import static org.hamcrest.Matchers.notNullValue;public class SampleWithGovernatorTest {@Testpublic void testExampleBeanInjection() throws Exception {Injector injector  = LifecycleInjector.builder().withModuleClass(SampleModule.class).usingBasePackages("sample.gov").build().createInjector();LifecycleManager manager = injector.getInstance(LifecycleManager.class);manager.start();BlogService blogService = injector.getInstance(BlogService.class);assertThat(blogService.get(1l), is(notNullValue()));}}

查看如何使用Governator的LifecycleInjector组件指定要扫描的软件包，这将自动检测这些组件并将它们连接在一起。

只是为了包装类路径扫描和自动绑定功能，像Spring这样的Governor提供了对junit测试的支持，更好的测试如下：

package sample.gov;import com.google.inject.Injector;
import com.netflix.governator.guice.LifecycleTester;
import org.junit.Rule;
import org.junit.Test;
import sample.service.BlogService;import static org.hamcrest.MatcherAssert.*;
import static org.hamcrest.Matchers.*;public class SampleWithGovernatorJunitSupportTest {@Rulepublic LifecycleTester tester = new LifecycleTester();@Testpublic void testExampleBeanInjection() throws Exception {tester.start();Injector injector = tester.builder().usingBasePackages("sample.gov").build().createInjector();BlogService blogService = injector.getInstance(BlogService.class);assertThat(blogService.get(1l), is(notNullValue()));}}