Java Spring Boot项目中的存储过程返回null作为输出

经过数小时的尝试，我找到了使其工作的方法。

首先，我添加

@NamedStoredProcedureQuery

CompanyResource

CompanyResource.java

@Entity@Table(name = "company_resource")@NamedStoredProcedureQueries({        @NamedStoredProcedureQuery(name = "getAllmetalFromCompaniesByPlayerId",   procedureName = "getAllmetalFromCompaniesByPlayerId",   parameters = {       @StoredProcedureParameter(mode = ParameterMode.IN, name = "playerId", type = Integer.class),       @StoredProcedureParameter(mode = ParameterMode.OUT, name = "metalSum", type = BigDecimal.class)   })})@IdClass(CompanyResourcePK.class)public class CompanyResource {...}

然后我按如下

getmetalResourceByPlayerId()

CompanyResourceServiceImpl

CompanyResourceServiceImpl.java

@Servicepublic class CompanyResourceServiceImpl implements CompanyResourceService {@PersistenceContext    private EntityManager entityManager;...private int getmetalResourceByPlayerId(int theId) {        StoredProcedureQuery theQuery = entityManager.createNamedStoredProcedureQuery("getAllmetalFromCompaniesByPlayerId");        theQuery.setParameter("Param1", theId);        BigDecimal outAmount = (BigDecimal) theQuery.getSingleResult();        return  outAmount.intValue();    }...}