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 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 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 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.
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 github.com/whirlys/ela… 处下载
参考：
kason_zhang Elasticsearch Guice 的使用
更多内容请访问我的个人博客：laijianfeng.org/
打开微信扫一扫，关注【小旋锋】微信公众号，及时接收博文推送