Question

我正在将Spring Boot与Hibernate一起使用。当我尝试在新线程中加载数据（来自PostgreSQL）时，hibernate给出了异常。但是，如果我在单个线程中执行代码，则效果很好。下面是此代码段。

Customer.java

@Entity
public class Customer {

    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Long id;

    private String name;

    @OneToMany(cascade=CascadeType.ALL)
    private List<UserEntity> entityList = new ArrayList<UserEntity>();
}

UserEntity.java

@Entity
public class UserEntity {
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Long id;

    @ManyToOne
    private Customer customer;
}

服务层

public class EmailServiceImpl {

    public void someFunction() {
        Customer cus = customerRepo.findOne(1l);
        new Thread(() -> {
            cus.getEntityList().isEmpty(); // Below mentioned exception is pointing to this line
            // executing some operations based on the size of above list
        }).start();
    }

}

尝试执行上述方法时出现异常/错误

org.hibernate.exception.GenericJDBCException: could not extract ResultSet
    at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:47) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:109) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:95) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:79) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.getResultSet(AbstractLoadPlanBasedLoader.java:434) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeQueryStatement(AbstractLoadPlanBasedLoader.java:186) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeLoad(AbstractLoadPlanBasedLoader.java:121) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeLoad(AbstractLoadPlanBasedLoader.java:86) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.loader.collection.plan.AbstractLoadPlanBasedCollectionInitializer.initialize(AbstractLoadPlanBasedCollectionInitializer.java:88) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:688) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.event.internal.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:75) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.internal.SessionImpl.initializeCollection(SessionImpl.java:1991) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection$4.doWork(AbstractPersistentCollection.java:570) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:252) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:566) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:135) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection$1.doWork(AbstractPersistentCollection.java:164) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection$1.doWork(AbstractPersistentCollection.java:149) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:252) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.readSize(AbstractPersistentCollection.java:148) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.collection.internal.PersistentBag.isEmpty(PersistentBag.java:266) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at com.e2log.service.impl.EmailServiceImpl.lambda$3(EmailServiceImpl.java:505) ~[classes/:na]
    at java.lang.Thread.run(Thread.java:748) ~[na:1.8.0_161]
Caused by: org.postgresql.util.PSQLException: This statement has been closed.
    at org.postgresql.jdbc.PgStatement.checkClosed(PgStatement.java:649) ~[postgresql-9.4.1212.jre7.jar:9.4.1212.jre7]
    at org.postgresql.jdbc.PgStatement.getMaxRows(PgStatement.java:485) ~[postgresql-9.4.1212.jre7.jar:9.4.1212.jre7]
    at org.postgresql.jdbc.PgStatement.createResultSet(PgStatement.java:158) ~[postgresql-9.4.1212.jre7.jar:9.4.1212.jre7]
    at org.postgresql.jdbc.PgStatement$StatementResultHandler.handleResultRows(PgStatement.java:210) ~[postgresql-9.4.1212.jre7.jar:9.4.1212.jre7]
    at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2092) ~[postgresql-9.4.1212.jre7.jar:9.4.1212.jre7]
    at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:288) ~[postgresql-9.4.1212.jre7.jar:9.4.1212.jre7]
    at org.postgresql.jdbc.PgStatement.executeInternal(PgStatement.java:430) ~[postgresql-9.4.1212.jre7.jar:9.4.1212.jre7]
    at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:356) ~[postgresql-9.4.1212.jre7.jar:9.4.1212.jre7]
    at org.postgresql.jdbc.PgPreparedStatement.executeWithFlags(PgPreparedStatement.java:168) ~[postgresql-9.4.1212.jre7.jar:9.4.1212.jre7]
    at org.postgresql.jdbc.PgPreparedStatement.executeQuery(PgPreparedStatement.java:116) ~[postgresql-9.4.1212.jre7.jar:9.4.1212.jre7]
    at sun.reflect.GeneratedMethodAccessor144.invoke(Unknown Source) ~[na:na]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_161]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_161]
    at org.apache.tomcat.jdbc.pool.StatementFacade$StatementProxy.invoke(StatementFacade.java:114) ~[tomcat-jdbc-8.5.27.jar:na]
    at com.sun.proxy.$Proxy215.executeQuery(Unknown Source) ~[na:na]
    at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:70) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]

正在执行代码但不适合我的场景

单线程执行（即注释/删除new Thread(() -> {和}).start();两行）
热切地加载数据（即将@OneToMany(cascade=CascadeType.ALL)中的行@OneToMany(cascade=CascadeType.ALL, fetch = FetchType.EAGER)更改为Customer.java）
1. 在行cus.getEntityList().isEmpty();上方写行cus.getEntityList().size();或new Thread(() -> {。（我认为，如果我们尝试在启动新线程之前先找到大小，则休眠将加载数据）

是否有任何方法可以使并发代码正常工作，而无需使用Eager加载？

仅供参考，春季启动版本：1.5.10.RELEASE 爪哇：1.8 PostgreSQL：9.5

Answer 1

Spring使用的事务上下文存储在线程局部变量中。因此，如果您启动一个新线程，或使用可调用对象在另一个线程中执行代码，则该代码将不会成为Spring事务方面启动的事务的一部分。

相反，如果您想使用从数据库中提取的某些数据来处理某些异步操作，则应首先将数据库中的数据加载到变量中，然后将加载的数据传递给异步线程以进行进一步处理。

Hibernate不在新线程{org.hibernate.exception.GenericJDBCException：无法提取ResultSet}中从数据库加载数据

1 个答案: