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SpringBoot,如何从另一个类访问映射?

jpa spring-boot spring java
  •  0
  • Ryan S  · 技术社区  · 7 年前

    我有一个类,它允许我注册数据存储库以访问另一个组件。

    总体思路是,我有一个映射,可以通过一个关联的键(只是一个字符串)引用每个存储库。

    调试发现:

    从我的调试来看,当我希望映射中的值作为每个JpaRepository的引用时,映射中的值似乎为null,这让我相信它的连接没有正常工作。

    我的两个问题:

    1) 我希望地图是静态的,但仍然能够访问存储库而没有任何问题

    2) 这实际上在关联的使用者类中不起作用,我的spring引导服务器无法使用NPE启动。

    关联消费者类中的用法示例: 

    @Autowired private DataLoaderRegistrar loaderConstants;

    以上是我 认为 这应该申报吗?如果它变为静态,希望这可以改变。

    我在类中遍历对象并调用 DataLoaderRegistrar 使用以下内容初始化:

    forEach简介如下:

    我迭代了几个类型,这将获取每个关联数据类型的类名(这是映射中的键),然后调用关联JPA存储库上的save方法。 

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

    DataLoaderRegistrar类 

    @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]

    代码接近故障(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 回复  |  直到 7 年前
        1
  •  2
  •   Evgeny    7 年前

    reposByName 在Spring实例化时初始化 DataLoaderRegistrar 但目前回购尚未注入。要解决此问题,可以使用 @PostConstruct 注释。Spring将在注入所有依赖项后调用此方法。 

    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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