我遇到了一个奇怪的问题，根据我的判断，还没有其他人报告过，使用createNativeQuery时可能会出现错误。我已经尝试了很多事情来理解为什么无济于事。
执行时：
Long total = (Long) em.createNativeQuery("Project.count").getSingleResult();
它抛出以下内容：
javax.persistence.PersistenceException: Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.7.3.v20180807-4be1041): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: org.postgresql.util.PSQLException: ERROR: syntax error at or near "Project"
Position: 1
Error Code: 0
Call: Project.count
Query: DataReadQuery(sql="Project.count")
at org.eclipse.persistence.internal.jpa.QueryImpl.getDetailedException(QueryImpl.java:391)
at org.eclipse.persistence.internal.jpa.QueryImpl.executeReadQuery(QueryImpl.java:264)
at org.eclipse.persistence.internal.jpa.QueryImpl.getSingleResult(QueryImpl.java:530)
at org.eclipse.persistence.internal.jpa.EJBQueryImpl.getSingleResult(EJBQueryImpl.java:404)
at com.bbandt.util.testers.ProjectTester.ProjectVersionMapping(ProjectTester.java:43)
at com.bbandt.util.testers.ProjectTester.main(ProjectTester.java:21)
Caused by: Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.7.3.v20180807-4be1041): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: org.postgresql.util.PSQLException: ERROR: syntax error at or near "Project"
Position: 1
Error Code: 0
Call: Project.count
Query: DataReadQuery(sql="Project.count")
at org.eclipse.persistence.exceptions.DatabaseException.sqlException(DatabaseException.java:342)
at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.basicExecuteCall(DatabaseAccessor.java:691)
at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.executeCall(DatabaseAccessor.java:567)
at org.eclipse.persistence.internal.sessions.AbstractSession.basicExecuteCall(AbstractSession.java:2096)
at org.eclipse.persistence.sessions.server.ServerSession.executeCall(ServerSession.java:603)
at org.eclipse.persistence.internal.queries.DatasourceCallQueryMechanism.executeCall(DatasourceCallQueryMechanism.java:275)
at org.eclipse.persistence.internal.queries.DatasourceCallQueryMechanism.executeCall(DatasourceCallQueryMechanism.java:261)
at org.eclipse.persistence.internal.queries.DatasourceCallQueryMechanism.executeSelectCall(DatasourceCallQueryMechanism.java:332)
at org.eclipse.persistence.internal.queries.DatasourceCallQueryMechanism.executeSelect(DatasourceCallQueryMechanism.java:314)
at org.eclipse.persistence.queries.DataReadQuery.executeNonCursor(DataReadQuery.java:199)
at org.eclipse.persistence.queries.DataReadQuery.executeDatabaseQuery(DataReadQuery.java:154)
at org.eclipse.persistence.queries.DatabaseQuery.execute(DatabaseQuery.java:914)
at org.eclipse.persistence.queries.DataReadQuery.execute(DataReadQuery.java:139)
at org.eclipse.persistence.queries.DatabaseQuery.executeInUnitOfWork(DatabaseQuery.java:813)
at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.internalExecuteQuery(UnitOfWorkImpl.java:2981)
at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1895)
at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1877)
at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1842)
at org.eclipse.persistence.internal.jpa.QueryImpl.executeReadQuery(QueryImpl.java:262)
... 4 more
Caused by: org.postgresql.util.PSQLException: ERROR: syntax error at or near "Project"
Position: 1
at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2440)
at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2183)
at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:308)
at org.postgresql.jdbc.PgStatement.executeInternal(PgStatement.java:441)
at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:365)
at org.postgresql.jdbc.PgPreparedStatement.executeWithFlags(PgPreparedStatement.java:143)
at org.postgresql.jdbc.PgPreparedStatement.executeQuery(PgPreparedStatement.java:106)
at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.executeSelect(DatabaseAccessor.java:1015)
at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.basicExecuteCall(DatabaseAccessor.java:651)
... 21 more
Persistence.xml（有目的地被截断了）
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
<persistence-unit name="LocalPostgreSQL" transaction-type="RESOURCE_LOCAL">
<mapping-file>META-INF/orm.xml</mapping-file>
<mapping-file>META-INF/Queries.xml</mapping-file>
<!-- <mapping-file>META-INF/ResultsetMappings.xml</mapping-file>
-->
<class>com.bbandt.jpa.converters.UUIDAttributeConverter</class>
<class>model.Component</class>
<class>model.ComponentVulnerability</class>
<class>model.ComponentVulnerabilityPK</class>
<class>model.Project</class>
<class>model.ProjectVersion</class>
<class>model.ProjectVersionPK</class>
ORM.xml内容：
<?xml version="1.0" encoding="UTF-8"?>
<entity-mappings version="2.1"
xmlns="http://xmlns.jcp.org/xml/ns/persistence/orm"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence/orm http://xmlns.jcp.org/xml/ns/persistence/orm_2_1.xsd">
<named-native-query name="Project.count">
<query>Select count(*) as total from public.project</query>
</named-native-query>
</entity-mappings>
据我所知，命名的本机查询没有被解析回实际的SQL内容。
执行此操作（并解析 命名为本地查询的名称“ Project.count” ）：
Long total = (Long) em.createNamedQuery("Project.count").getSingleResult();
这也有效：
Long total = (Long) em.createNativeQuery("Select count(*) from project").getSingleResult();
由于其他与该线程无关的原因，我不想求助于JPQL，我还需要实现SQL结果集映射。
任何对此的见解将不胜感激。我真的没有想法了。
答案 0 :(得分：1)
createNamedQuery ：用于通过映射文件或注释中的第一个名称定义查询 createNativeQuery ：用于执行本机/纯SQL查询
由于您对命名查询使用了createNativeQuery方法，因此遇到了错误