SpringBoot，如何从另一个类访问一个地图？

时间：2018-04-20 18:03:38

标签： java spring spring-boot jpa

我有这个类允许我注册数据存储库以便在另一个组件中访问。

总的想法是我有一张地图，我可以通过一个关联的键（只是一个字符串）引用每个单独的存储库。

我发现调试：

从我的调试开始，当我希望它成为每个JpaRepository的引用时，看起来map中的值为null，这使我相信它的连线无法正常工作。

我的两个问题：

1）我想使地图静态，但仍然能够访问存储库而没有问题

2）这实际上不适用于关联的消费者类，我的spring-boot服务器无法启动NPE。

关联消费者类​​中的用法示例：

@Autowired private DataLoaderRegistrar loaderConstants;

以上是我认为应该如何宣布？希望如果它变得静止，这可能会改变。

我循环遍历我的类中的对象并使用以下方法调用此DataLoaderRegistrar类：

  

以下每个的简要说明：

     

我有几种我正在迭代的类型，它抓取每个关联数据类型的类名（这是映射中的键）然后在关联的JPA存储库上调用save方法。 

.forEach(
    dataType -> {
      loaderConstants.getRepo(dataType.toString()).save(dataType);
    });

DataLoaderRegistrar Class 

@Component
public class DataLoaderRegistrar {

  /** Auto wired all {@link JpaRepository} references here to support storing test data in DB */
  @Autowired public UserRepository userRepo;

  @Autowired public GoalRepository goalRepo;

  /**
   * All registered entities can go here with an association to their repository as the value
   * Examples can be seen in {@link com.habicus.core.data GoalRepository} as well as {@link
   * com.habicus.core.entities.Goal}
   */
  private Map<String, JpaRepository> reposByName =
      new HashMap<String, JpaRepository>() {
        {
          put(User.class.getSimpleName(), userRepo);
          put(Goal.class.getSimpleName(), userRepo);
        }
      };

  public DataLoaderRegistrar() {}

  /**
   * Returns the requested repository that is stored in the
   *
   * @param className
   * @return {@link JpaRepository} that is associated with a particular class name
   */
  public JpaRepository getRepo(String className) {
    return reposByName.get(className);
  }

  /**
   * Method returns a {@link Map} which has a {@link String} as the key and an associated {@link
   * JpaRepository} as the value, which represents a CRUD repository for all supported data types in
   * our system
   */
  public Map<String, JpaRepository> retrieveAllDataRepositories() {
    return reposByName;
  }
}

堆栈跟踪

* Exception is:
org.gradle.api.tasks.TaskExecutionException: Execution failed for task ':bootRun'.
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:103)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:73)
        at org.gradle.api.internal.tasks.execution.OutputDirectoryCreatingTaskExecuter.execute(OutputDirectoryCreatingTaskExecuter.java:51)
        at org.gradle.api.internal.tasks.execution.SkipUpToDateTaskExecuter.execute(SkipUpToDateTaskExecuter.java:59)
        at org.gradle.api.internal.tasks.execution.ResolveTaskOutputCachingStateExecuter.execute(ResolveTaskOutputCachingStateExecuter.java:54)
        at org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute(ValidatingTaskExecuter.java:59)
        at org.gradle.api.internal.tasks.execution.SkipEmptySourceFilesTaskExecuter.execute(SkipEmptySourceFilesTaskExecuter.java:101)
        at org.gradle.api.internal.tasks.execution.FinalizeInputFilePropertiesTaskExecuter.execute(FinalizeInputFilePropertiesTaskExecuter.java:44)
        at org.gradle.api.internal.tasks.execution.CleanupStaleOutputsExecuter.execute(CleanupStaleOutputsExecuter.java:91)
        at org.gradle.api.internal.tasks.execution.ResolveTaskArtifactStateTaskExecuter.execute(ResolveTaskArtifactStateTaskExecuter.java:62)
        at org.gradle.api.internal.tasks.execution.SkipTaskWithNoActionsExecuter.execute(SkipTaskWithNoActionsExecuter.java:59)
        at org.gradle.api.internal.tasks.execution.SkipOnlyIfTaskExecuter.execute(SkipOnlyIfTaskExecuter.java:54)
        at org.gradle.api.internal.tasks.execution.ExecuteAtMostOnceTaskExecuter.execute(ExecuteAtMostOnceTaskExecuter.java:43)
        at org.gradle.api.internal.tasks.execution.CatchExceptionTaskExecuter.execute(CatchExceptionTaskExecuter.java:34)
        at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker$1.run(DefaultTaskGraphExecuter.java:256)
        at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:336)
        at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:328)
        at org.gradle.internal.progress.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:199)
        at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:110)
        at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker.execute(DefaultTaskGraphExecuter.java:249)
        at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker.execute(DefaultTaskGraphExecuter.java:238)
        at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker.processTask(DefaultTaskPlanExecutor.java:123)
        at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker.access$200(DefaultTaskPlanExecutor.java:79)
        at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker$1.execute(DefaultTaskPlanExecutor.java:104)
        at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker$1.execute(DefaultTaskPlanExecutor.java:98)
        at org.gradle.execution.taskgraph.DefaultTaskExecutionPlan.execute(DefaultTaskExecutionPlan.java:663)
        at org.gradle.execution.taskgraph.DefaultTaskExecutionPlan.executeWithTask(DefaultTaskExecutionPlan.java:597)
        at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker.run(DefaultTaskPlanExecutor.java:98)
        at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:63)
        at org.gradle.internal.concurrent.ManagedExecutorImpl$1.run(ManagedExecutorImpl.java:46)
        at org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:55)
Caused by: org.gradle.process.internal.ExecException: Process 'command '/Library/Java/JavaVirtualMachines/jdk1.8.0_151.jdk/Contents/Home/bin/java'' finished with non-zero exit value 1
        at org.gradle.process.internal.DefaultExecHandle$ExecResultImpl.assertNormalExitValue(DefaultExecHandle.java:389)
        at org.gradle.process.internal.DefaultJavaExecAction.execute(DefaultJavaExecAction.java:36)
        at org.gradle.api.tasks.JavaExec.exec(JavaExec.java:75)
        at org.springframework.boot.gradle.tasks.run.BootRun.exec(BootRun.java:51)
        at org.gradle.internal.reflect.JavaMethod.invoke(JavaMethod.java:73)
        at org.gradle.api.internal.project.taskfactory.StandardTaskAction.doExecute(StandardTaskAction.java:46)
        at org.gradle.api.internal.project.taskfactory.StandardTaskAction.execute(StandardTaskAction.java:39)
        at org.gradle.api.internal.project.taskfactory.StandardTaskAction.execute(StandardTaskAction.java:26)
        at org.gradle.api.internal.AbstractTask$TaskActionWrapper.execute(AbstractTask.java:788)
        at org.gradle.api.internal.AbstractTask$TaskActionWrapper.execute(AbstractTask.java:755)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$1.run(ExecuteActionsTaskExecuter.java:124)
        at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:336)
        at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:328)
        at org.gradle.internal.progress.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:199)
        at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:110)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeAction(ExecuteActionsTaskExecuter.java:113)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:95)
        ... 30 more

错误

java.lang.NullPointerException: null
        at com.habicus.repository.Loader.lambda$loadTestContainers$0(Loader.java:155) ~[main/:na]
        at java.util.ArrayList.forEach(ArrayList.java:1255) ~[na:1.8.0_151]
        at com.habicus.repository.Loader.loadTestContainers(Loader.java:153) ~[main/:na]
        at com.habicus.repository.Loader.onApplicationEvent(Loader.java:120) ~[main/:na]
        at com.habicus.repository.Loader.onApplicationEvent(Loader.java:49) ~[main/:na]
        at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:172) ~[spring-context-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:165) ~[spring-context-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139) ~[spring-context-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:400) ~[spring-context-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:354) ~[spring-context-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        at org.springframework.boot.context.event.EventPublishingRunListener.running(EventPublishingRunListener.java:103) ~[spring-boot-2.0.1.RELEASE.jar:2.0.1.RELEASE]
        at org.springframework.boot.SpringApplicationRunListeners.running(SpringApplicationRunListeners.java:78) ~[spring-boot-2.0.1.RELEASE.jar:2.0.1.RELEASE]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:343) [spring-boot-2.0.1.RELEASE.jar:2.0.1.RELEASE]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1255) [spring-boot-2.0.1.RELEASE.jar:2.0.1.RELEASE]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1243) [spring-boot-2.0.1.RELEASE.jar:2.0.1.RELEASE]
        at com.habicus.CoreApplication.main(CoreApplication.java:29) [main/:na]

代码接近失败（L155）：

    Arrays.stream(resources)
        .map(this::ingestFromFile)
        .collect(Collectors.toList())
        .stream()
        .map(Container.class::cast)
        .map(Container::getAll)
        .flatMap(Collection::stream)
        .collect(Collectors.toList())
        .forEach(
            dataType -> {
              loaderConstants.getRepo(dataType.toString()).save(dataType);
              LOGGER.log(Level.INFO, "Saved: " + dataType);
            });
  }

1 个答案:

答案 0 :(得分：2)

当Spring实例化reposByName时，

DataLoaderRegistrar被初始化，但此时repos是mot注入的。要解决它，您可以使用@PostConstruct注释来注释某些方法。在注入所有依赖项之后，Spring将调用此方法。

Component
public class DataLoaderRegistrar {

  @Autowired public UserRepository userRepo;

  @Autowired public GoalRepository goalRepo;

  @PostConstruct  
  public void registerRepos() {
    reposByName = new HashMap<String, JpaRepository>();
    reposByName.put(User.class.getSimpleName(), userRepo);
    reposByName.put(Goal.class.getSimpleName(), userRepo);
  }

  ...
}

更多信息https://docs.spring.io/spring/docs/current/spring-framework-reference/core.html#beans-factory-lifecycle

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