JPA:名称的命名查询:..找不到

Question

我正在公司用JPA开发一个多租户应用程序。因此，我使用TABLE_PER_TENANT特性将租户特定的数据分离为不同的模式。将数据推入数据库是没有问题的，这很好。问题是只是从数据库中读取数据，应用程序找不到我的命名查询。

我已经尝试过不同的东西：

• 重新编译和部署应用程序
• 将persistence.xml移动到不同的文件夹中
• 已检查错误日志并调试了整个应用程序，找不到原因
• 看了看我在谷歌上能找到的所有可能的解决方案，并尝试了一下

我这里缺少什么？有什么想法吗？

BaseObject.java

@MappedSuperclass
@Multitenant(MultitenantType.TABLE_PER_TENANT)
@TenantTableDiscriminator(type = TenantTableDiscriminatorType.SCHEMA, contextProperty="tenant.id")
public abstract class BaseObject {
/**
* The (globally unique) ID of the object.
*/
@Id
@Column(name = "GUID", length = 36)
private String guid = UUID.randomUUID().toString();
/**
* The {@link Date} the object was created at.
*/
@Temporal(TemporalType.TIMESTAMP)
@Column(name = "CREATION_DATE", updatable = false)
private Date createdAt = null;
/**
* The {@link Date} the object was last modified at.
*/
@Temporal(TemporalType.TIMESTAMP)
@Column(name = "MODIFICATION_DATE")
private Date lastModifiedAt = null;
/**
* ID of the user who created the object.
*/
@Column(name = "CREATED_BY", updatable = false, length = 20)
private String createdBy = null;
/**
* ID of the user who was the last to modify the object.
*/
@Column(name = "MODIFIED_BY", length = 20)
private String lastModifiedBy = null;
// Methods...
}

Plant.java

@Entity
@Table(name = "PLANT_POLLUTION_DATA")
@NamedQueries({ @NamedQuery(name = "Plant.getPlants", query = "SELECT c FROM Plant c"),
@NamedQuery(name = "Plant.getPlantById", query = "SELECT c FROM Plant c WHERE c.id = :id") })
@XmlRootElement(name = "plantlist")
@XmlAccessorType(XmlAccessType.FIELD)
public class Plant extends BaseObject implements Serializable {
/**
* The <code>serialVersionUID</code> of the {@link Plant} class.
*/
private static final long serialVersionUID = 1L;
@Column(name = "ID", length = 36, nullable = true)
String id = null;
@Column(name = "O3", length = 10, nullable = true)
String o3 = null;
@Column(name = "DATE_FIELD")
java.sql.Date dateField = null;
@Column(name = "location", length = 36, nullable = true)
String location = null;
// Methods...
}

NamedQuery调用

String tenantId = getTenantId();
Map<String, String> props = new HashMap<String, String>();
props.put("tenant.id", tenantId);
EntityManager em = this.getEntityManagerFactory().createEntityManager(props);
Query query = em.createNamedQuery("Plant.getPlantById");
query.setParameter("id", id);
retVal = query.getResultList();

persistence.xml(位于"file.war/WEB-INF/classes/META-INF/persistence.xml"(

<?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="pollutionmonitoring" transaction-type="RESOURCE_LOCAL">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
<class>com.company.cloud.samples.pollutionmonitoring.model.BaseObject</class>
<class>com.company.cloud.samples.pollutionmonitoring.model.Plant</class>
<properties>
<property name="eclipselink.ddl-generation" value="create-or-extend-tables"/>
</properties>
</persistence-unit>
</persistence>

Answer 1

我可以通过添加以下两行代码来自己解决这个问题：

...
EntityManager em = this.getEntityManagerFactory().createEntityManager(props);
em.getTransaction().begin();
em.getTransaction().commit();
Query query = em.createNamedQuery("Plant.getPlantById");
...

我不知道这个改变到底有什么作用，但它对我有效：(也许有人知道为什么这个解决方案有效？

附言：我刚刚从我的另一个类复制了它，在那里我必须向DB添加数据，这是两个类之间唯一的区别。