這是什麼Eclipselink錯誤，以及如何解決它？

Question

下面是相關堆棧跟蹤：

[EL Warning]: 2017-05-11 16:35:34.18--ServerSession(4115088)--Exception [EclipseLink-32] (Eclipse Persistence Services - 2.0.2.v20100323-r6872): org.eclipse.persistence.exceptions.DescriptorException 
Exception Description: Trying to set value [0] for instance variable [EmpInd] of type [char] in the object. The specified object is not an instance of the class or interface declaring the underlying field, or an unwrapping conversion has failed. 
Internal Exception: java.lang.IllegalArgumentException: Can not set char field com.MyProj.entity.EmployeeTask.empInd to java.lang.Integer 
Mapping: org.eclipse.persistence.mappings.DirectToFieldMapping[EmpInd-->EMPLOYEE_TASK.EMP_IND] 
Descriptor: RelationalDescriptor(com.MyProj.entity.EmployeeTask --> [DatabaseTable(EMPLOYEE_TASK)]) 

at org.eclipse.persistence.exceptions.DescriptorException.illegalArgumentWhileSettingValueThruInstanceVariableAccessor(DescriptorException.java:682) 
    at org.eclipse.persistence.internal.descriptors.InstanceVariableAttributeAccessor.setAttributeValueInObject(InstanceVariableAttributeAccessor.java:184) 
    at org.eclipse.persistence.mappings.DatabaseMapping.setAttributeValueInObject(DatabaseMapping.java:1368) 
    at org.eclipse.persistence.mappings.DatabaseMapping.readFromRowIntoObject(DatabaseMapping.java:1259) 
    at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildAttributesIntoObject(ObjectBuilder.java:332) 
    at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildObject(ObjectBuilder.java:661) 
    at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildObject(ObjectBuilder.java:494) 
    at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildObject(ObjectBuilder.java:444) 
    at org.eclipse.persistence.queries.ObjectLevelReadQuery.buildObject(ObjectLevelReadQuery.java:635) 
    at org.eclipse.persistence.queries.ReadObjectQuery.executeObjectLevelReadQuery(ReadObjectQuery.java:441) 
    at org.eclipse.persistence.queries.ObjectLevelReadQuery.executeDatabaseQuery(ObjectLevelReadQuery.java:997) 
    at org.eclipse.persistence.queries.DatabaseQuery.execute(DatabaseQuery.java:675) 
    at org.eclipse.persistence.queries.ObjectLevelReadQuery.execute(ObjectLevelReadQuery.java:958) 
    at org.eclipse.persistence.queries.ReadObjectQuery.execute(ReadObjectQuery.java:399) 
    at org.eclipse.persistence.internal.sessions.AbstractSession.internalExecuteQuery(AbstractSession.java:2322) 
    at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1225) 
    at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1207) 
    at org.eclipse.persistence.internal.indirection.NoIndirectionPolicy.valueFromQuery(NoIndirectionPolicy.java:299) 
    at org.eclipse.persistence.mappings.ForeignReferenceMapping.valueFromRowInternal(ForeignReferenceMapping.java:1624) 
    at org.eclipse.persistence.mappings.OneToOneMapping.valueFromRowInternal(OneToOneMapping.java:1563) 
    at org.eclipse.persistence.mappings.ForeignReferenceMapping.valueFromRow(ForeignReferenceMapping.java:1534) 
    at org.eclipse.persistence.mappings.DatabaseMapping.readFromRowIntoObject(DatabaseMapping.java:1258) 
    at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildAttributesIntoObject(ObjectBuilder.java:332) 
    at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildObject(ObjectBuilder.java:661) 
    at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildWorkingCopyCloneNormally(ObjectBuilder.java:583) 
    at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildObjectInUnitOfWork(ObjectBuilder.java:552) 
    at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildObject(ObjectBuilder.java:492) 
    at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildObject(ObjectBuilder.java:444) 
    at org.eclipse.persistence.queries.ObjectLevelReadQuery.buildObject(ObjectLevelReadQuery.java:635) 
    at org.eclipse.persistence.queries.ReadAllQuery.registerResultInUnitOfWork(ReadAllQuery.java:838) 
    at org.eclipse.persistence.queries.ReadAllQuery.executeObjectLevelReadQuery(ReadAllQuery.java:464) 
    at org.eclipse.persistence.queries.ObjectLevelReadQuery.executeDatabaseQuery(ObjectLevelReadQuery.java:997) 
    at org.eclipse.persistence.queries.DatabaseQuery.execute(DatabaseQuery.java:675) 
    at org.eclipse.persistence.queries.ObjectLevelReadQuery.execute(ObjectLevelReadQuery.java:958) 
    at org.eclipse.persistence.queries.ReadAllQuery.execute(ReadAllQuery.java:432) 
    at org.eclipse.persistence.queries.ObjectLevelReadQuery.executeInUnitOfWork(ObjectLevelReadQuery.java:1021) 
    at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.internalExecuteQuery(UnitOfWorkImpl.java:2898) 
    at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1225) 
    at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1207) 
    at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1181) 
    at org.eclipse.persistence.internal.jpa.EJBQueryImpl.executeReadQuery(EJBQueryImpl.java:453) 
    at org.eclipse.persistence.internal.jpa.EJBQueryImpl.getResultList(EJBQueryImpl.java:681) 

Answer 1

最關鍵的是這句話：

Can not set char field com.MyProj.entity.EmployeeTask.empInd to java.lang.Integer Mapping: org.eclipse.persistence.mappings.DirectToFieldMapping[EmpInd-->EMPLOYEE_TASK.EMP_IND] Descriptor: RelationalDescriptor(com.MyProj.entity.EmployeeTask --> [DatabaseTable(EMPLOYEE_TASK)]) 

的數據庫字段EMPLOYEE_TASK.EMP_IND是一個整數，而在Java領域com.MyProj.entity.EmployeeTask.empInd是char。 EclipseLink無法將從數據庫返回的整數轉換爲char，因此可以在您的EmployeeTask對象中設置它。