前言
Elasticsearch 原始碼中使用了Guice框架進行依賴注入. 為了方便閱讀原始碼, 此處我先通過模仿ES guice的使用方式簡單寫了一個基本Demo 方便理解, 之後再來理一下ES的Guice使用. 編寫的測試類原理圖如下:
總共有兩個Module，一個是ToolModule，用於繫結IAnimal介面、ITool介面以及Map物件. 另一個是HumanModule 用於繫結Person物件。
其中Person的建構函式通過 @Inject 註解注入其他例項
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'
複製程式碼1、Demo
iTool介面與實現類
public interface ITool {
public void doWork();
}
複製程式碼import com.whirly.guice.example.ITool;
public class IToolImpl implements ITool {
@Override
public void doWork() {
System.out.println("use tool to work");
}
}
複製程式碼IAnimal 介面與實現類
public interface IAnimal {
void work();
}
複製程式碼public class IAnimalImpl implements IAnimal {
@Override
public void work() {
System.out.println("animals can also do work");
}
}
複製程式碼ToolModule的實現, 它綁了三個例項
public class ToolModule extends AbstractModule {
@Override
protected void configure() {
//此處注入的例項可以注入到其他類的建構函式中, 只要那個類使用@Inject進行注入即可
bind(IAnimal.class).to(IAnimalImpl.class);
bind(ITool.class).to(IToolImpl.class);
// 注入Map例項
MapBinder<String, String> mapBinder = MapBinder.newMapBinder(binder(), String.class, String.class);
mapBinder.addBinding("test1").toInstance("test1");
mapBinder.addBinding("test2").toInstance("test2");
}
}
複製程式碼bind(IAnimal.class).to(IAnimalImpl.class);bind(ITool.class).to(IToolImpl.class); 是將介面與其具體實現繫結起來
MapBinder<String,String> mapBinder =MapBinder.newMapBinder(binder(), String.class, String.class);mapBinder.addBinding("test1").toInstance("test1");mapBinder.addBinding("test2").toInstance("test2"); 則是完成Map的繫結.
後面來看看Person類和HumanModule
Person 類
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());
}
}
}
複製程式碼Person 類中由 IAnimal、ITool 和 Map<String, String> 這三個介面定義的變數，物件將通過 @Inject 從構造方法中注入進來
public class HumanModule extends AbstractModule {
@Override
protected void configure() {
bind(Person.class).asEagerSingleton();
}
}
複製程式碼Person類的建構函式是通過注入的方式，注入物件例項的
最後 CustomModuleBuilder 進行統一管理所有的Module，例項化所有Module中的物件. 完成依賴注入。
這裡的CustomModuleBuilder是修改自Elasticsearch中的ModulesBuilder，其原理是一樣的。
就是一個迭代器，內部封裝的是Module集合, 統一管理所有的Module
CustomModuleBuilder 統一管理 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;
}
}
複製程式碼這樣就可以從Main方法是如何進行使用的
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();
}
}
複製程式碼執行結果
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
複製程式碼通過CustomModuleBuilder 的createInjector獲取Injector 物件, 根據Injector 物件取相應的具體例項物件.
2、ES 中Guice的使用
ES中TransportClient初始化時的Guice的使用是這樣的, 如下圖所示
TransportClient的初始化程式碼
Elasticsearch 6.3.2
private static ClientTemplate buildTemplate(Settings providedSettings, Settings defaultSettings,
Collection<Class<? extends Plugin>> plugins, HostFailureListener failureListner) {
// 省略 ...
try {
// 省略 ...
// 建立一個迭代器, 然後將各個Module通過add方法加入進去
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下的例項
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);
// 啟動服務
transportService.start();
transportService.acceptIncomingRequests();
ClientTemplate transportClient = new ClientTemplate(injector, pluginLifecycleComponents, nodesService, proxy, namedWriteableRegistry);
resourcesToClose.clear();
return transportClient;
} finally {
IOUtils.closeWhileHandlingException(resourcesToClose);
}
}
複製程式碼可以看到確實是先通 過ModulesBuilder modules = new ModulesBuilder() 建立一個迭代器, 然後將各個Module通過add方法加入進去, 最後通過 Injector injector = modules.createInjector(); 建立Injector物件, 之後便可根據Injector物件去獲取例項了.
各個Module會繫結自己所需要的例項, 這裡以 SettingsModule 舉例:
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);
}
//...
}
複製程式碼可以看到它繫結了四個,分別是 Settings.class，SettingsFilter.class，ClusterSettings.class，IndexScopedSettings.class
它們的例項物件都可以通過Injector來獲取
小結
示例程式碼可在 github.com/whirlys/ela… 處下載
參考：
kason_zhang Elasticsearch Guice 的使用
更多內容請訪問我的個人部落格：laijianfeng.org/
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