java - 使用 EntityManager 查询 Spring JPA NullPointerException

Question

我尝试使用 EntityManager 运行查询，但每次在 JPA 控制台中运行此查询时，我都会收到 NullPointerException。

但是当我直接在数据库中运行这个查询时，它可以工作。

@Repository
@Slf4j
public class MyCredentialRepositoryImpl implements MyCredentialRepository {

  @PersistenceContext
  private EntityManager entityManager;

  @Override
  public Set<PublicKeyCredentialDescriptor> getCredentialIdsForUsername(String username) {
        Query query1 = this.entityManager.createQuery("SELECT UserEntity.id FROM UserEntity");
    return null;
  }
}

这是我收到错误时的堆栈跟踪：

java.lang.NullPointerException: null
    at java.base/java.lang.String$CaseInsensitiveComparator.compare(String.java:1224) ~[na:na]
    at java.base/java.lang.String$CaseInsensitiveComparator.compare(String.java:1218) ~[na:na]
    at java.base/java.util.TreeMap.getEntryUsingComparator(TreeMap.java:374) ~[na:na]
    at java.base/java.util.TreeMap.getEntry(TreeMap.java:343) ~[na:na]
    at java.base/java.util.TreeMap.get(TreeMap.java:277) ~[na:na]
    at org.hibernate.dialect.function.SQLFunctionRegistry.findSQLFunction(SQLFunctionRegistry.java:45) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
    at org.hibernate.hql.internal.ast.util.SessionFactoryHelper.findSQLFunction(SessionFactoryHelper.java:385) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
    at org.hibernate.hql.internal.ast.tree.IdentNode.getDataType(IdentNode.java:366) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
    at org.hibernate.hql.internal.ast.HqlSqlWalker.lookupProperty(HqlSqlWalker.java:659) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.propertyRef(HqlSqlBaseWalker.java:1146) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.selectExpr(HqlSqlBaseWalker.java:2300) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.selectExprList(HqlSqlBaseWalker.java:2241) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.selectClause(HqlSqlBaseWalker.java:1507) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.query(HqlSqlBaseWalker.java:589) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.selectStatement(HqlSqlBaseWalker.java:317) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.statement(HqlSqlBaseWalker.java:265) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
    at org.hibernate.hql.internal.ast.QueryTranslatorImpl.analyze(QueryTranslatorImpl.java:272) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
    at org.hibernate.hql.internal.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:192) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
    at org.hibernate.hql.internal.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:144) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
    at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:113) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
    at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:73) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
    at org.hibernate.engine.query.spi.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:155) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
    at org.hibernate.internal.AbstractSharedSessionContract.getQueryPlan(AbstractSharedSessionContract.java:604) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
    at org.hibernate.internal.AbstractSharedSessionContract.createQuery(AbstractSharedSessionContract.java:716) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
    at org.hibernate.internal.AbstractSharedSessionContract.createQuery(AbstractSharedSessionContract.java:113) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
    at java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]
    at org.springframework.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:368) ~[spring-orm-5.2.4.RELEASE.jar:5.2.4.RELEASE]
    at com.sun.proxy.$Proxy109.createQuery(Unknown Source) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
    at java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]
    at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:314) ~[spring-orm-5.2.4.RELEASE.jar:5.2.4.RELEASE]
    at com.sun.proxy.$Proxy109.createQuery(Unknown Source) ~[na:na]
...
...

我找不到错误以及我的代码中可能缺少的内容

标签： javaspringspring-data-jpa

Answer 1

所以我在第一部分发表了评论，但我将给出一个答案，这样评论就不会失控并进入对话。

第一部分是从UserEntity.id到的变化id。

您在评论中问过的第二部分，即由于加入，您需要某种标识符，实际上我什至不确定这是真的。为了读者清楚起见，OP 在评论中放置的部分是

SELECT CredentialEntity.id FROM CredentialEntity
INNER JOIN UserEntity ON UserEntity.id = CredentialEntity.user.id
WHERE UserEntity.username = :username

所以基于此，看起来你有一个嵌入式 ID，这是你的问题。您必须提供嵌入字段名称以及可嵌入字段内的字段，例如

SELECT foo.user.id FROM CredentialEntity foo ...