如何使用 google Guice 创建多个相同类型的实例

Question

我们使用 Google Guice 框架进行依赖注入。我需要在java中创建一个接口的多个实例。

从这里开始执行：下面代码中的KfhRecordValidator.java类：

public class KfhRecordValidator implements RequestHandler<Request, Response> {
       public Response handleRequest(Request request, Context context) 
        {
     // Resolve the necessary dependencies, and process the request.
       Injector injector = Guice.createInjector(new 
                      DependencyModule());
            Processor processor = 
                 injector.getInstance(Processor.class);
              return processor.process(request, context);
}}

流程类引用了 RecordValidationHelper 类，并且注入是通过构造函数进行的。 IRecordValidationService.java 是一个具有 validate 方法的接口。

public interface IRecordValidationService {
              void validate(Record record) throws ValidationException;}

类处理器有一个名为 process 的方法，该方法在 RecordValidationHelper 类中被调用。

class Processor {
   private final RecordValidationHelper recordValidationHelper;
@Inject
@SuppressWarnings({"WeakerAccess"})
public Processor(IRecordValidationService recordValidationService, 
IRecordService<ErrorRecord> recordService,
                 S3UtilsInterface s3Utils, IEnvironmentVariableReader 
                 environmentVariableReader) {
                 this.recordValidationHelper = new 
                 RecordValidationHelper(recordValidationService);
                 this.errorRecordHelper = new 
                 ErrorRecordHelper(recordService, environmentVariableReader);
}

public Response process(Request request, @SuppressWarnings("unused") Context context) {

    // Validate records
    List<LambdaRecord> records = recordValidationHelper.processRecords(request.getRecords());}

Class DependencyModule.java extneds 具有配置方法的 Guice 注入的 AbstractModule 类。

class DependencyModule extends AbstractModule {
@Override
protected void configure() {
    String validationType = System.getenv("ValidationType");

    validationType= validationType.toLowerCase(Locale.ENGLISH);

    String valType[]= validationType.split(",");
    int length= valType.length;

    for(int i=0;i<length;i++){

        switch(valType[i]){
         case "json":
             bind(IRecordValidationService.class).to(JsonValidationService.class);
             break;
         case "avro":
             bind(IRecordValidationService.class).to(AvroSchemaValidationService.class);
             break;
         case "clientlogging":
             bind(IRecordValidationService.class).to(ClientLoggingValidationService.class);
             break;
         case "servicelogs":
             bind(IRecordValidationService.class).to(ServiceLoggingValidationService.class);
             break;
         default:
             throw new UnsupportedOperationException(String.format("Encountered an unsupported ValidationType of '%s'.", valType[i]));
        }

    } } }

所以问题是，如果我将验证类型设为 AVRO、JSON，那么它会将 IRecordValidationService 绑定到相应的 JsonValidationService/AvroSchemaValidationService 类。我需要为此创建多个实例，但它一次只支持一个实例。 下面是 RecordValidationHelper.java 类

公共类 RecordValidationHelper 扩展 AbstractModule { private final IRecordValidationService recordValidationService;

@Inject
public RecordValidationHelper(IRecordValidationService recordValidationService) {
    this.recordValidationService = recordValidationService;
}

public List processRecords(List requestRecords) { 列出记录 = new ArrayList();

    for (RequestRecord record : requestRecords) {
        try {

            Record domainRecord = new Record();
            domainRecord.setKey(record.getRecordId());
            domainRecord.setValue(new String(Base64.getDecoder().decode(record.getData())));

            // Use the injected logic to validate the record.
            ((IRecordValidationService) 
           recordValidationService).validate(domainRecord);}
           catch (ValidationException ex) {}}}
           return records;}

任何对如何实现它以获得适合此的多个实例有任何想法的人。

Answer 1

使用@Named 绑定

在您的 DependencyModule 中，使用名称绑定：

bind(IRecordValidationService.class)
  .annotatedWith(Names.named("json"))
  .to(JsonValidationService.class);
bind(IRecordValidationService.class)
  .annotatedWith(Names.named("avro"))
  .to(AvroSchemaValidationService.class);
bind(IRecordValidationService.class)
  .annotatedWith(Names.named("clientlogging"))
  .to(ClientLoggingValidationService.class);
bind(IRecordValidationService.class)
  .annotatedWith(Names.named("servicelogs"))
  .to(ServiceLoggingValidationService.class);

然后在你的被注射者中：

@Inject
public RecordValidationHelper(
    @Named("json") IRecordValidationService jsonValidation,
    @Named("avro") IRecordValidationService avroValidation,
    @Named("clientlogging") IRecordValidationService clientLoggingValidation,
    @Named("servicelogs") IRecordValidationService serviceLogsValidation,
  ) {
    this.jsonValidation = jsonValidation;
    this.avroValidation = avroValidation;
    this.clientLoggingValidation = clientLoggingValidation;
    this.serviceLogsValidation = serviceLogsValidation;
}

请参阅Guice's BindingAnnotation wiki page 了解更多信息。