Elasticsearch 源代码中使用了Guice框架进行依赖注入. 为了方便阅读源码, 此处我先通过模仿ES guice的使用方式简单写了一个基本Demo 方便理解, 之后再来理一下ES的Guice使用. 编写的测试类原理图如下:
总共有两个Module,一个是ToolModule, 用于绑定 IAnimal接口、ITool接口以及Map对象. 另一个是HumanModule 用于绑定Person对象。
其中Person的构造函数通过 @Inject
注解注入其他实例
gradle 需要引入的 Jar 包
compile group: 'com.google.inject.extensions', name: 'guice-multibindings', version: '4.2.0' compile group: 'com.google.inject', name: 'guice', version: '4.2.0' 复制代码
public interface ITool { public void doWork(); } 复制代码
import com.whirly.guice.example.ITool; public class IToolImpl implements ITool { @Override public void doWork() { System.out.println("use tool to work"); } } 复制代码
public interface IAnimal { void work(); } 复制代码
public class IAnimalImpl implements IAnimal { @Override public void work() { System.out.println("animals can also do work"); } } 复制代码
public class ToolModule extends AbstractModule { @Override protected void configure() { //此处注入的实例可以注入到其他类的构造函数中, 只要那个类使用@Inject进行注入即可 bind(IAnimal.class).to(IAnimalImpl.class); bind(ITool.class).to(IToolImpl.class); // 注入Map实例 MapBinder<String, String> mapBinder = MapBinder.newMapBinder(binder(), String.class, String.class); mapBinder.addBinding("test1").toInstance("test1"); mapBinder.addBinding("test2").toInstance("test2"); } } 复制代码
bind(IAnimal.class).to(IAnimalImpl.class);bind(ITool.class).to(IToolImpl.class);
是将接口与其具体实现绑定起来
MapBinder<String,String> mapBinder =MapBinder.newMapBinder(binder(), String.class, String.class);mapBinder.addBinding("test1").toInstance("test1");mapBinder.addBinding("test2").toInstance("test2");
则是完成Map的绑定.
后面来看看Person类和HumanModule
public class Person { private IAnimal iAnimal; private ITool iTool; private Map<String, String> map; @Inject public Person(IAnimal iAnimal, ITool iTool, Map<String, String> map) { this.iAnimal = iAnimal; this.iTool = iTool; this.map = map; } public void startwork() { iTool.doWork(); iAnimal.work(); for (Map.Entry entry : map.entrySet()) { System.out.println("注入的map 是 " + entry.getKey() + " value " + entry.getValue()); } } } 复制代码
Person 类中由 IAnimal
、 ITool
和 Map<String, String>
这三个接口定义的变量,对象将通过 @Inject
从构造方法中注入进来
public class HumanModule extends AbstractModule { @Override protected void configure() { bind(Person.class).asEagerSingleton(); } } 复制代码
Person类的构造函数是通过注入的方式,注入对象实例的
最后 CustomModuleBuilder
进行 统一管理所有的Module ,实例化所有Module中的对象. 完成依赖注入。
这里的CustomModuleBuilder是修改自Elasticsearch中的ModulesBuilder,其原理是一样的。
就是一个迭代器, 内部封装的是Module集合, 统一管理所有的Module
public class CustomModuleBuilder implements Iterable<Module> { private final List<Module> modules = new ArrayList<>(); public CustomModuleBuilder add(Module... newModules) { for (Module module : newModules) { modules.add(module); } return this; } @Override public Iterator<Module> iterator() { return modules.iterator(); } public Injector createInjector() { Injector injector = Guice.createInjector(modules); return injector; } } 复制代码
这样就可以从Main方法是如何进行使用的
public class Main { public static void main(String[] args) { CustomModuleBuilder moduleBuilder = new CustomModuleBuilder(); moduleBuilder.add(new ToolModule()); moduleBuilder.add(new HumanModule()); Injector injector = moduleBuilder.createInjector(); Person person = injector.getInstance(Person.class); person.startwork(); } } 复制代码
运行结果
use tool to work animals can also do work 注入的map 是 test1 value test1 注入的map 是 test2 value test2 复制代码
通过CustomModuleBuilder 的createInjector获取Injector 对象, 根据Injector 对象取相应的具体实例对象.
ES中TransportClient初始化时的Guice的使用是这样的, 如下图所示
Elasticsearch 6.3.2
private static ClientTemplate buildTemplate(Settings providedSettings, Settings defaultSettings, Collection<Class<? extends Plugin>> plugins, HostFailureListener failureListner) { // 省略 ... try { // 省略 ... // 创建一个迭代器, 然后将各个Module通过add方法加入进去 ModulesBuilder modules = new ModulesBuilder(); // plugin modules must be added here, before others or we can get crazy injection errors... for (Module pluginModule : pluginsService.createGuiceModules()) { modules.add(pluginModule); } modules.add(b -> b.bind(ThreadPool.class).toInstance(threadPool)); ActionModule actionModule = new ActionModule(true, settings, null, settingsModule.getIndexScopedSettings(), settingsModule.getClusterSettings(), settingsModule.getSettingsFilter(), threadPool, pluginsService.filterPlugins(ActionPlugin.class), null, null, null); modules.add(actionModule); CircuitBreakerService circuitBreakerService = Node.createCircuitBreakerService(settingsModule.getSettings(), settingsModule.getClusterSettings()); resourcesToClose.add(circuitBreakerService); PageCacheRecycler pageCacheRecycler = new PageCacheRecycler(settings); BigArrays bigArrays = new BigArrays(pageCacheRecycler, circuitBreakerService); resourcesToClose.add(bigArrays); modules.add(settingsModule); NetworkModule networkModule = new NetworkModule(settings, true, pluginsService.filterPlugins(NetworkPlugin.class), threadPool, bigArrays, pageCacheRecycler, circuitBreakerService, namedWriteableRegistry, xContentRegistry, networkService, null); final Transport transport = networkModule.getTransportSupplier().get(); final TransportService transportService = new TransportService(settings, transport, threadPool, networkModule.getTransportInterceptor(), boundTransportAddress -> DiscoveryNode.createLocal(settings, new TransportAddress(TransportAddress.META_ADDRESS, 0), UUIDs.randomBase64UUID()), null, Collections.emptySet()); modules.add((b -> { b.bind(BigArrays.class).toInstance(bigArrays); b.bind(PluginsService.class).toInstance(pluginsService); b.bind(CircuitBreakerService.class).toInstance(circuitBreakerService); b.bind(NamedWriteableRegistry.class).toInstance(namedWriteableRegistry); b.bind(Transport.class).toInstance(transport); b.bind(TransportService.class).toInstance(transportService); b.bind(NetworkService.class).toInstance(networkService); })); // 注入所有module下的实例 Injector injector = modules.createInjector(); final TransportClientNodesService nodesService = new TransportClientNodesService(settings, transportService, threadPool, failureListner == null ? (t, e) -> {} : failureListner); // construct the list of client actions final List<ActionPlugin> actionPlugins = pluginsService.filterPlugins(ActionPlugin.class); final List<GenericAction> clientActions = actionPlugins.stream().flatMap(p -> p.getClientActions().stream()).collect(Collectors.toList()); // add all the base actions final List<? extends GenericAction<?, ?>> baseActions = actionModule.getActions().values().stream().map(ActionPlugin.ActionHandler::getAction).collect(Collectors.toList()); clientActions.addAll(baseActions); final TransportProxyClient proxy = new TransportProxyClient(settings, transportService, nodesService, clientActions); List<LifecycleComponent> pluginLifecycleComponents = new ArrayList<>(pluginsService.getGuiceServiceClasses().stream() .map(injector::getInstance).collect(Collectors.toList())); resourcesToClose.addAll(pluginLifecycleComponents); // 启动服务 transportService.start(); transportService.acceptIncomingRequests(); ClientTemplate transportClient = new ClientTemplate(injector, pluginLifecycleComponents, nodesService, proxy, namedWriteableRegistry); resourcesToClose.clear(); return transportClient; } finally { IOUtils.closeWhileHandlingException(resourcesToClose); } } 复制代码
可以看到确实是先通 过ModulesBuilder modules = new ModulesBuilder()
创建一个迭代器, 然后将各个Module通过add方法加入进去, 最后通过 Injector injector = modules.createInjector();
创建Injector对象, 之后便可根据Injector对象去获取实例了 .
各个Module会绑定自己所需要的实例, 这里以 SettingsModule 举例:
public class SettingsModule extends AbstractModule { private final Settings settings; private final Set<String> settingsFilterPattern = new HashSet<>(); private final Map<String, Setting<?>> nodeSettings = new HashMap<>(); private final Map<String, Setting<?>> indexSettings = new HashMap<>(); private final Logger logger; private final IndexScopedSettings indexScopedSettings; private final ClusterSettings clusterSettings; private final SettingsFilter settingsFilter; public SettingsModule(Settings settings, Setting<?>... additionalSettings) { this(settings, Arrays.asList(additionalSettings), Collections.emptyList()); } @Override public void configure(Binder binder) { binder.bind(Settings.class).toInstance(settings); binder.bind(SettingsFilter.class).toInstance(settingsFilter); binder.bind(ClusterSettings.class).toInstance(clusterSettings); binder.bind(IndexScopedSettings.class).toInstance(indexScopedSettings); } //... } 复制代码
可以看到它绑定了四个,分别是 Settings.class,SettingsFilter.class,ClusterSettings.class,IndexScopedSettings.class
它们的实例对象都可以通过Injector来获取