Elasticsearch 中的 Guice-白红宇

前言

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

1、Demo

iTool接口与实现类

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

IAnimal 接口与实现类

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

ToolModule的实现, 它绑了三个实例

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
    
      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

Person 类

public class Person {    private IAnimal iAnimal;    private ITool iTool;    private Map
    
      map;    @Inject    public Person(IAnimal iAnimal, ITool iTool, Map
     
       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

CustomModuleBuilder 统一管理 Module

public class CustomModuleBuilder implements Iterable
    
      {    private final List
     
       modules = new ArrayList<>();    public CustomModuleBuilder add(Module... newModules) {        for (Module module : newModules) {            modules.add(module);        }        return this;    }    @Override    public Iterator
      
        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

Main 方法

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 workanimals 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.

2、ES 中Guice的使用

ES中TransportClient初始化时的Guice的使用是这样的, 如下图所示

TransportClient的初始化代码

Elasticsearch 6.3.2

private static ClientTemplate buildTemplate(Settings providedSettings, Settings defaultSettings,                                            Collection
    
     > 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
     
       actionPlugins = pluginsService.filterPlugins(ActionPlugin.class);        final List
      
        clientActions =                actionPlugins.stream().flatMap(p -> p.getClientActions().stream()).collect(Collectors.toList());        // add all the base actions        final List
       > 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
       
         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
    
      settingsFilterPattern = new HashSet<>();    private final Map
     
      > nodeSettings = new HashMap<>();    private final Map
      
       > 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

小结

示例代码可在处下载

参考：
kason_zhang

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