Osgi guice-运行时选择不同的提供程序

我想在不停止JVM的情况下更改运行时使用的提供程序。例如，这不是我正试图做的，但是这个想法是一样的：比如，我想在运行的应用程序中间从Amazon S3切换到谷歌云存储。 这是我可以在guice内做的事吗

我必须在运行时提供所有JAR，并在启动时配置所有模块。然后，在应用程序启动之后，我必须使用一个提供程序来确定要注入@startup的实例，以及稍后它发生变化的时间

或者，在更新配置后重新启动应用程序是否更好，然后系统将继续该配置，如果需要更改，应用程序将再次需要重新启动

---

OSGI能帮上忙吗？

你不需要任何额外的东西：Guice可以开箱即用。但是您必须使用而不是直接实例

在您的模块中

bind(Cloud.class)
  .annotatedWith(Names.named("google"))
  .to(GoogleCloud.class);
bind(Cloud.class)
  .annotatedWith(Names.named("amazon"))
  .to(AmazonCloud.class);
bind(Cloud.class)
  .toProvider(SwitchingCloudProvider.class);

class SwitchingCloudProvider implements Provider<Cloud> {
  @Inject @Named("google") Provider<Cloud> googleCloudProvider;
  @Inject @Named("amazon") Provider<Cloud> amazonCloudProvider;
  @Inject Configuration configuration;        // used as your switch "commander"
  public Cloud get() {
    switch(configuration.getCloudName()) {
      case "google": return googleCloudProvider.get();
      case "amazon": return amazonCloudProvider.get();
      default: 
        // Whatever you want, usually an exception.
    }
  }
}

@Provides
Cloud provideCloud(
    @Named("google") Provider<Cloud> googleCloudProvider,
    @Named("amazon") Provider<Cloud> amazonCloudProvider,
    Configuration configuration) {
  switch(configuration.getCloudName()) {
    case "google": return googleCloudProvider.get();
    case "amazon": return amazonCloudProvider.get();
    default: 
      // Whatever you want, usually an exception.
  }
}

class Foo {
  @Inject Provider<Cloud> cloudProvider; // Do NOT inject Cloud directly or you won't get the changes as they come up.
  public void bar() {
    Cloud cloud = cloudProvider.get();
    // use cloud
  }
}

某处

bind(Cloud.class)
  .annotatedWith(Names.named("google"))
  .to(GoogleCloud.class);
bind(Cloud.class)
  .annotatedWith(Names.named("amazon"))
  .to(AmazonCloud.class);
bind(Cloud.class)
  .toProvider(SwitchingCloudProvider.class);

class SwitchingCloudProvider implements Provider<Cloud> {
  @Inject @Named("google") Provider<Cloud> googleCloudProvider;
  @Inject @Named("amazon") Provider<Cloud> amazonCloudProvider;
  @Inject Configuration configuration;        // used as your switch "commander"
  public Cloud get() {
    switch(configuration.getCloudName()) {
      case "google": return googleCloudProvider.get();
      case "amazon": return amazonCloudProvider.get();
      default: 
        // Whatever you want, usually an exception.
    }
  }
}

@Provides
Cloud provideCloud(
    @Named("google") Provider<Cloud> googleCloudProvider,
    @Named("amazon") Provider<Cloud> amazonCloudProvider,
    Configuration configuration) {
  switch(configuration.getCloudName()) {
    case "google": return googleCloudProvider.get();
    case "amazon": return amazonCloudProvider.get();
    default: 
      // Whatever you want, usually an exception.
  }
}

class Foo {
  @Inject Provider<Cloud> cloudProvider; // Do NOT inject Cloud directly or you won't get the changes as they come up.
  public void bar() {
    Cloud cloud = cloudProvider.get();
    // use cloud
  }
}

类切换CloudProvider实现提供程序{
@注入@Named（“谷歌”）提供商googleCloudProvider；
@注入@Named（“amazon”）提供者amazonCloudProvider；
@注入配置；//用作交换机“指挥官”
公共云get（）{
开关（configuration.getCloudName（））{
案例“google”：返回googleCloudProvider.get（）；
案例“amazon”：返回amazonCloudProvider.get（）；
违约：
//不管你想要什么，通常都是例外。
}
}
}

或在模块中的提供程序方法中

bind(Cloud.class)
  .annotatedWith(Names.named("google"))
  .to(GoogleCloud.class);
bind(Cloud.class)
  .annotatedWith(Names.named("amazon"))
  .to(AmazonCloud.class);
bind(Cloud.class)
  .toProvider(SwitchingCloudProvider.class);

class SwitchingCloudProvider implements Provider<Cloud> {
  @Inject @Named("google") Provider<Cloud> googleCloudProvider;
  @Inject @Named("amazon") Provider<Cloud> amazonCloudProvider;
  @Inject Configuration configuration;        // used as your switch "commander"
  public Cloud get() {
    switch(configuration.getCloudName()) {
      case "google": return googleCloudProvider.get();
      case "amazon": return amazonCloudProvider.get();
      default: 
        // Whatever you want, usually an exception.
    }
  }
}

@Provides
Cloud provideCloud(
    @Named("google") Provider<Cloud> googleCloudProvider,
    @Named("amazon") Provider<Cloud> amazonCloudProvider,
    Configuration configuration) {
  switch(configuration.getCloudName()) {
    case "google": return googleCloudProvider.get();
    case "amazon": return amazonCloudProvider.get();
    default: 
      // Whatever you want, usually an exception.
  }
}

class Foo {
  @Inject Provider<Cloud> cloudProvider; // Do NOT inject Cloud directly or you won't get the changes as they come up.
  public void bar() {
    Cloud cloud = cloudProvider.get();
    // use cloud
  }
}

@提供
云提供云(
@命名（“谷歌”）提供商google CloudProvider，
@命名（“亚马逊”）提供商amazonCloudProvider，
配置（配置）{
开关（configuration.getCloudName（））{
案例“google”：返回googleCloudProvider.get（）；
案例“amazon”：返回amazonCloudProvider.get（）；
违约：
//不管你想要什么，通常都是例外。
}
}

用法

bind(Cloud.class)
  .annotatedWith(Names.named("google"))
  .to(GoogleCloud.class);
bind(Cloud.class)
  .annotatedWith(Names.named("amazon"))
  .to(AmazonCloud.class);
bind(Cloud.class)
  .toProvider(SwitchingCloudProvider.class);

class SwitchingCloudProvider implements Provider<Cloud> {
  @Inject @Named("google") Provider<Cloud> googleCloudProvider;
  @Inject @Named("amazon") Provider<Cloud> amazonCloudProvider;
  @Inject Configuration configuration;        // used as your switch "commander"
  public Cloud get() {
    switch(configuration.getCloudName()) {
      case "google": return googleCloudProvider.get();
      case "amazon": return amazonCloudProvider.get();
      default: 
        // Whatever you want, usually an exception.
    }
  }
}

@Provides
Cloud provideCloud(
    @Named("google") Provider<Cloud> googleCloudProvider,
    @Named("amazon") Provider<Cloud> amazonCloudProvider,
    Configuration configuration) {
  switch(configuration.getCloudName()) {
    case "google": return googleCloudProvider.get();
    case "amazon": return amazonCloudProvider.get();
    default: 
      // Whatever you want, usually an exception.
  }
}

class Foo {
  @Inject Provider<Cloud> cloudProvider; // Do NOT inject Cloud directly or you won't get the changes as they come up.
  public void bar() {
    Cloud cloud = cloudProvider.get();
    // use cloud
  }
}

class-Foo{
@injectprovider cloudProvider；//不要直接注入云，否则在出现更改时将无法获得更改。
公共空白栏（）{
Cloud=cloudProvider.get（）；
//使用云
}
}

您不需要任何额外的东西：Guice可以开箱即用。但是您必须使用而不是直接实例

在您的模块中

bind(Cloud.class)
  .annotatedWith(Names.named("google"))
  .to(GoogleCloud.class);
bind(Cloud.class)
  .annotatedWith(Names.named("amazon"))
  .to(AmazonCloud.class);
bind(Cloud.class)
  .toProvider(SwitchingCloudProvider.class);

class SwitchingCloudProvider implements Provider<Cloud> {
  @Inject @Named("google") Provider<Cloud> googleCloudProvider;
  @Inject @Named("amazon") Provider<Cloud> amazonCloudProvider;
  @Inject Configuration configuration;        // used as your switch "commander"
  public Cloud get() {
    switch(configuration.getCloudName()) {
      case "google": return googleCloudProvider.get();
      case "amazon": return amazonCloudProvider.get();
      default: 
        // Whatever you want, usually an exception.
    }
  }
}

@Provides
Cloud provideCloud(
    @Named("google") Provider<Cloud> googleCloudProvider,
    @Named("amazon") Provider<Cloud> amazonCloudProvider,
    Configuration configuration) {
  switch(configuration.getCloudName()) {
    case "google": return googleCloudProvider.get();
    case "amazon": return amazonCloudProvider.get();
    default: 
      // Whatever you want, usually an exception.
  }
}

class Foo {
  @Inject Provider<Cloud> cloudProvider; // Do NOT inject Cloud directly or you won't get the changes as they come up.
  public void bar() {
    Cloud cloud = cloudProvider.get();
    // use cloud
  }
}

某处

bind(Cloud.class)
  .annotatedWith(Names.named("google"))
  .to(GoogleCloud.class);
bind(Cloud.class)
  .annotatedWith(Names.named("amazon"))
  .to(AmazonCloud.class);
bind(Cloud.class)
  .toProvider(SwitchingCloudProvider.class);

class SwitchingCloudProvider implements Provider<Cloud> {
  @Inject @Named("google") Provider<Cloud> googleCloudProvider;
  @Inject @Named("amazon") Provider<Cloud> amazonCloudProvider;
  @Inject Configuration configuration;        // used as your switch "commander"
  public Cloud get() {
    switch(configuration.getCloudName()) {
      case "google": return googleCloudProvider.get();
      case "amazon": return amazonCloudProvider.get();
      default: 
        // Whatever you want, usually an exception.
    }
  }
}

@Provides
Cloud provideCloud(
    @Named("google") Provider<Cloud> googleCloudProvider,
    @Named("amazon") Provider<Cloud> amazonCloudProvider,
    Configuration configuration) {
  switch(configuration.getCloudName()) {
    case "google": return googleCloudProvider.get();
    case "amazon": return amazonCloudProvider.get();
    default: 
      // Whatever you want, usually an exception.
  }
}

class Foo {
  @Inject Provider<Cloud> cloudProvider; // Do NOT inject Cloud directly or you won't get the changes as they come up.
  public void bar() {
    Cloud cloud = cloudProvider.get();
    // use cloud
  }
}

类切换CloudProvider实现提供程序{
@注入@Named（“谷歌”）提供商googleCloudProvider；
@注入@Named（“amazon”）提供者amazonCloudProvider；
@注入配置；//用作交换机“指挥官”
公共云get（）{
开关（configuration.getCloudName（））{
案例“google”：返回googleCloudProvider.get（）；
案例“amazon”：返回amazonCloudProvider.get（）；
违约：
//不管你想要什么，通常都是例外。
}
}
}

或在模块中的提供程序方法中

bind(Cloud.class)
  .annotatedWith(Names.named("google"))
  .to(GoogleCloud.class);
bind(Cloud.class)
  .annotatedWith(Names.named("amazon"))
  .to(AmazonCloud.class);
bind(Cloud.class)
  .toProvider(SwitchingCloudProvider.class);

class SwitchingCloudProvider implements Provider<Cloud> {
  @Inject @Named("google") Provider<Cloud> googleCloudProvider;
  @Inject @Named("amazon") Provider<Cloud> amazonCloudProvider;
  @Inject Configuration configuration;        // used as your switch "commander"
  public Cloud get() {
    switch(configuration.getCloudName()) {
      case "google": return googleCloudProvider.get();
      case "amazon": return amazonCloudProvider.get();
      default: 
        // Whatever you want, usually an exception.
    }
  }
}

@Provides
Cloud provideCloud(
    @Named("google") Provider<Cloud> googleCloudProvider,
    @Named("amazon") Provider<Cloud> amazonCloudProvider,
    Configuration configuration) {
  switch(configuration.getCloudName()) {
    case "google": return googleCloudProvider.get();
    case "amazon": return amazonCloudProvider.get();
    default: 
      // Whatever you want, usually an exception.
  }
}

class Foo {
  @Inject Provider<Cloud> cloudProvider; // Do NOT inject Cloud directly or you won't get the changes as they come up.
  public void bar() {
    Cloud cloud = cloudProvider.get();
    // use cloud
  }
}

@提供
云提供云(
@命名（“谷歌”）提供商google CloudProvider，
@命名（“亚马逊”）提供商amazonCloudProvider，
配置（配置）{
开关（configuration.getCloudName（））{
案例“google”：返回googleCloudProvider.get（）；
案例“amazon”：返回amazonCloudProvider.get（）；
违约：
//不管你想要什么，通常都是例外。
}
}

用法

bind(Cloud.class)
  .annotatedWith(Names.named("google"))
  .to(GoogleCloud.class);
bind(Cloud.class)
  .annotatedWith(Names.named("amazon"))
  .to(AmazonCloud.class);
bind(Cloud.class)
  .toProvider(SwitchingCloudProvider.class);

class SwitchingCloudProvider implements Provider<Cloud> {
  @Inject @Named("google") Provider<Cloud> googleCloudProvider;
  @Inject @Named("amazon") Provider<Cloud> amazonCloudProvider;
  @Inject Configuration configuration;        // used as your switch "commander"
  public Cloud get() {
    switch(configuration.getCloudName()) {
      case "google": return googleCloudProvider.get();
      case "amazon": return amazonCloudProvider.get();
      default: 
        // Whatever you want, usually an exception.
    }
  }
}

@Provides
Cloud provideCloud(
    @Named("google") Provider<Cloud> googleCloudProvider,
    @Named("amazon") Provider<Cloud> amazonCloudProvider,
    Configuration configuration) {
  switch(configuration.getCloudName()) {
    case "google": return googleCloudProvider.get();
    case "amazon": return amazonCloudProvider.get();
    default: 
      // Whatever you want, usually an exception.
  }
}

class Foo {
  @Inject Provider<Cloud> cloudProvider; // Do NOT inject Cloud directly or you won't get the changes as they come up.
  public void bar() {
    Cloud cloud = cloudProvider.get();
    // use cloud
  }
}

class-Foo{
@injectprovider cloudProvider；//不要直接注入云，否则在出现更改时将无法获得更改。
公共空白栏（）{
Cloud=cloudProvider.get（）；
//使用云
}
}

好的，这是有道理的。这是个好主意吗？我想我实现它的方法是避免将自己限制在2或3个，等等。我想我可以在这里使用multibinder查找每个实现，然后通过从列表中选择与配置匹配的正确实现（或在该点引发异常）来确定我想要哪个实现。@WalterWhite是的，这是个好主意，在这里使用多重绑定也很好。考虑到问题中的任何内容都不允许我在Guice中评估您的级别，我不认为最好将其提出来，但是是的，如果您现在能够做到这一点，多绑定完全是最好的工具。我在这里只强调，如果某个云具有非单例作用域，您需要使用

Provider

s来避免意外。因此，您应该插入一个

映射

。注意，这只在Guice 4之后才起作用。好的，这是有意义的。这是个好主意吗？我想我实现它的方法是避免将自己限制在2或3个，等等。我想我可以在这里使用multibinder查找每个实现，然后通过从列表中选择与配置匹配的正确实现（或在该点引发异常）来确定我想要哪个实现。@WalterWhite是的，这是个好主意，在这里使用多重绑定也很好。考虑到问题中的任何内容都不允许我在Guice中评估您的级别，我不认为最好将其提出来，但是是的，如果您现在能够做到这一点，多绑定完全是最好的工具。我在这里只强调，如果某个云具有非单例作用域，您需要使用

Provider

s来避免意外。因此，您应该插入一个

映射

。请注意，这仅在Guice 4之后起作用。