【发布时间】：2020-03-06 14:15:30
【问题描述】：
我正在学习 Java EE，这两天我一直在努力配置 Hibernate，以便在一个简单的 Java EE Web 应用程序中使用 TomEE 服务器上的 MySQL 数据库。
- Hibernate 版本：5.4.10.Final（核心和实体管理器依赖项）
- Java EE API：8.0
- MySQL 版本：8.0.19
- TomEE 版本：8.0.1（TomEE 嵌入在 tomee-embedded-maven-plugin 中）
我有 2 个简单的实体：Car 和 Seat，具有从 Car 到 Seat 的单向 @OneToMany 关系。 Color 和 EngineType 是普通枚举，而 Specification 是这两个枚举的值对象）。注意：FetchType.EAGER 在@OneToMany 中用于学习目的，我知道这通常不是一个好的解决方案。
当我尝试配置persistence.xml 文件时，alghouth 指定了“与 MySQL 一样”的所有内容，似乎 Hibernate 仍然使用默认的 HSQLDB 语法/方言/引擎，因此，我在架构创建过程中收到错误：
[INFO] TomEE embedded started on localhost:8080
INFO: HHH000400: Using dialect: org.hibernate.dialect.MySQL8Dialect
Hibernate: alter table Seat drop foreign key FKkkm9pdx9e1t9jva76n9tqhhqv
mar 06, 2020 1:48:31 PM org.hibernate.tool.schema.internal.ExceptionHandlerLoggedImpl handleException
WARN: GenerationTarget encountered exception accepting command : Error executing DDL "alter table Seat drop foreign key FKkkm9pdx9e1t9jva76n9tqhhqv" via JDBC Statement
org.hibernate.tool.schema.spi.CommandAcceptanceException: Error executing DDL "alter table Seat drop foreign key FKkkm9pdx9e1t9jva76n9tqhhqv" via JDBC Statement
(...)
Caused by: java.sql.SQLSyntaxErrorException: user lacks privilege or object not found: PUBLIC.SEAT
(...)
Caused by: org.hsqldb.HsqlException: user lacks privilege or object not found: PUBLIC.SEAT // what is going on here???
对于以后创建 DDL 时的 Hibernate SQL 命令，我也有：
Hibernate: create table Car (identifier bigint not null auto_increment, color varchar(255), engineType varchar(255), primary key (identifier)) engine=InnoDB
mar 06, 2020 1:48:31 PM org.hibernate.tool.schema.internal.ExceptionHandlerLoggedImpl handleException
WARN: GenerationTarget encountered exception accepting command : Error executing DDL "create table Car (identifier bigint not null auto_increment, color varchar(255), engineType varchar(255), primary key (identifier)) engine=InnoDB" via JDBC Statement
org.hibernate.tool.schema.spi.CommandAcceptanceException: Error executing DDL "create table Car (identifier bigint not null auto_increment, color varchar(255), engineType varchar(255), primary key (identifier)) engine=InnoDB" via JDBC Statement
(...)
Caused by: java.sql.SQLSyntaxErrorException: unexpected token: AUTO_INCREMENT
(...)
Caused by: org.hsqldb.HsqlException: unexpected token: AUTO_INCREMENT // definitely something messed up, this is a correct MySQL token
当我省略所有“MySQL 的东西”（驱动程序和方言）并让 Hibernate 使用默认的 HSQLDB 时，它工作正常...... HSQLDB 的 DDL 已创建良好。
我尝试了许多不同的配置和替换，通过网络和 SO 搜索它，但没有找到任何提示为什么 Hibernate 仍然使用非 MySQL 语法（但我不能 100% 确定这是问题的直接原因）。
我试图在 webapp 下的 resources.xml 文件中指定数据源，但它并没有改变任何东西。 此外，我检查了是否可以从 Maven 构建中排除 HSQLDB，但它附带了 hibernate -core，所以它不容易实现，也许也无济于事。
我之前使用过 Hibernate 和 Spring 和 SpringBoot，但是对于 Java EE，我完全迷失了，这就是我问这个问题的原因。
谁能帮助解决这个问题并就所有这些的正确配置提供一些建议？
resources/META-INF下我的persistence.xml是这样的：
<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://xmlns.jcp.org/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="2.2"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_2.xsd">
<persistence-unit name="my-persistence-unit" transaction-type="JTA">
<provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
<jta-data-source>java:openejb/Resource/myJtaDatabase</jta-data-source>
<!-- Entity classes -->
<class>com.example.javaeecourse.entity.Car</class>
<class>com.example.javaeecourse.entity.Seat</class>
<exclude-unlisted-classes>false</exclude-unlisted-classes>
<properties>
<property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver" />
<property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/javaeecourse?serverTimezone=UTC" />
<property name="hibernate.connection.username" value="root" />
<property name="hibernate.connection.password" value="admin" />
<property name="hibernate.dialect" value="org.hibernate.dialect.MySQL8Dialect" />
<property name="hibernate.show_sql" value="true" />
<property name="hibernate.hbm2ddl.auto" value="create"/>
<property name="tomee.jpa.factory.lazy" value="true" />
<!--<property name="tomee.jpa.cdi=false" value="false" />-->
</properties>
</persistence-unit>
</persistence>
汽车实体：
package com.example.javaeecourse.entity;
import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;
import javax.persistence.*;
import java.util.HashSet;
import java.util.Set;
import static com.example.javaeecourse.entity.Car.FIND_ALL;
@Getter
@Setter
@Entity
@Table(name = "cars")
@NamedQuery(name = FIND_ALL, query = "SELECT car FROM Car car")
@NoArgsConstructor
public class Car {
public static final String FIND_ALL = "Car.findAll";
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long identifier;
@Enumerated(EnumType.STRING)
private Color color;
@Enumerated(EnumType.STRING)
private EngineType engineType;
@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
@JoinColumn(name = "car", nullable = false)
private Set<Seat> seats = new HashSet<>();
}
座位实体：
package com.example.javaeecourse.entity;
import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;
import javax.persistence.*;
@Entity
@Table(name = "seats")
@NoArgsConstructor
@Getter
@Setter
public class Seat {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String seatMaterial;
public Seat(String seatMaterial) {
this.seatMaterial = seatMaterial;
}
}
CarManufacturer 类（@Stateless EJB，其中调用了 EntityManager）：
package com.example.javaeecourse.boundary;
import com.example.javaeecourse.control.CarFactory;
import com.example.javaeecourse.entity.Car;
import com.example.javaeecourse.entity.CarCreatedEvent;
import com.example.javaeecourse.entity.Specification;
import javax.ejb.Stateless;
import javax.enterprise.event.Event;
import javax.inject.Inject;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import java.util.List;
@Stateless
public class CarManufacturer {
@Inject
CarFactory carFactory;
@Inject
Event<CarCreatedEvent> carCreatedEvent;
@PersistenceContext
EntityManager entityManager;
public Car manufactureCar(Specification specification) {
Car car = carFactory.createCar(specification);
entityManager.persist(car);
carCreatedEvent.fire(new CarCreatedEvent(car.getIdentifier()));
return car;
}
public List<Car> retrieveCars() {
return entityManager.createNamedQuery(Car.FIND_ALL, Car.class).getResultList();
}
}
CarFactory 类，实例化实体：
package com.example.javaeecourse.control;
import com.example.javaeecourse.entity.*;
import javax.inject.Inject;
public class CarFactory {
@Inject
@DefaultCarColor
Color randomCarColor;
@Inject
@DefaultCarEngineType
EngineType randomCarEngineType;
public Car createCar(Specification specification) {
Car car = new Car();
car.setColor(specification.getColor() == null ? randomCarColor : specification.getColor());
car.setEngineType(specification.getEngineType() == null ? randomCarEngineType : specification.getEngineType());
Seat seat = new Seat("Leather");
car.getSeats().add(seat);
return car;
}
}
pom.xml：
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.example</groupId>
<artifactId>javaeecourse</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>war</packaging>
<name>Java EE Course App</name>
<!-- FIXME change it to the project's website -->
<url>http://www.example.com</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
<failOnMissingWebXml>false</failOnMissingWebXml>
</properties>
<dependencies>
<dependency>
<groupId>javax</groupId>
<artifactId>javaee-api</artifactId>
<version>8.0</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
<version>8.0.19</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>5.4.10.Final</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-entitymanager</artifactId>
<version>5.4.10.Final</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.12</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.jaxrs</groupId>
<artifactId>jackson-jaxrs-json-provider</artifactId>
<version>2.9.0</version>
</dependency>
</dependencies>
<build>
<finalName>javaeecourse</finalName>
<pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
<plugins>
<plugin>
<groupId>org.apache.tomee.maven</groupId>
<artifactId>tomee-embedded-maven-plugin</artifactId>
<version>8.0.1</version>
</plugin>
<plugin>
<artifactId>maven-clean-plugin</artifactId>
<version>3.1.0</version>
</plugin>
<!-- see http://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_war_packaging -->
<plugin>
<artifactId>maven-resources-plugin</artifactId>
<version>3.0.2</version>
</plugin>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.0</version>
</plugin>
<plugin>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.22.1</version>
</plugin>
<plugin>
<artifactId>maven-war-plugin</artifactId>
<version>3.2.2</version>
</plugin>
<plugin>
<artifactId>maven-install-plugin</artifactId>
<version>2.5.2</version>
</plugin>
<plugin>
<artifactId>maven-deploy-plugin</artifactId>
<version>2.8.2</version>
</plugin>
</plugins>
</pluginManagement>
</build>
</project>
如果有任何帮助，我将不胜感激。
【问题讨论】：
-
当您为数据源提供
jta-datasource元素时，您不必提供任何hibernate.connection属性。检查数据源在 TomeEE 上的配置是否正确，并且 jdbc 驱动程序在那里。 -
@areus 非常感谢您的提示！我能够解决此案（为该问题的未来读者发布了答案）。
标签： mysql hibernate jpa apache-tomee java-ee-8