使用Spring数据JPA和Hibernate延迟加载异常
使用Spring数据JPA和Hibernate延迟加载异常
提问于 2016-01-14 13:01:37
我正在尝试学习使用Hibernate的Spring，目前在一个独立项目中(不过稍后我将在Web中使用)，而且我得到了例外：
org.hibernate.LazyInitializationException:未能延迟初始化角色集合: com.dbprototype.domain.Crash.vehicles
我不知道为什么。
@Entity(name = "STAGING.TEST_CRASH")
public class Crash {
@Id
@Column(name = "C_TEST_CRASH_NUMBER")
private int crashNum;
@Column(name = "C_RECORD_NUMBER")
private int recordNum;
@Column(name = "C_TOTAL_UNITS")
private int totalUnits;
@Column(name = "C_TOTAL_INJURIES")
private int totalInjured;
@OneToMany(cascade=CascadeType.ALL, mappedBy="crash") // fails.
private List<Vehicle> vehicles;
@OneToOne(mappedBy="crash", cascade=CascadeType.ALL) // this works ok.
private Metadata metaData;
public void printCrash() {
// prints Crash fields, vehicles, and metadata.
}
// getters & setters
}
@Entity(name = "STAGING.TEST_VEHICLE")
public class Vehicle {
@Id
@Column(name = "V_TEST_VEHICLE_NUMBER")
private int vehicleNum;
//@Id
@Column(name = "C_TEST_CRASH_NUMBER")
private int crashNum;
@Column(name = "C_RECORD_NUMBER")
private int recordNum;
@Column(name = "V_VEH_MAKE")
private String vehicleMake;
@Column(name = "V_VEH_MODEL")
private String vehicleModel;
@Column(name = "V_VEH_YEAR")
private int year;
@ManyToOne(cascade=CascadeType.ALL)
private Crash crash;
// getters & setters
}我的服务层是：
@Service
@Transactional(propagation=Propagation.REQUIRED)
public class CrashService {
private CrashDao crashDao;
public void setCrashDao(CrashDao dao) {
crashDao = dao;
}
public void print() {
System.out.println("you called CrashService!");
}
// DAO layer will need all 4 CRUD operations on each table.
// read one Crash
public Crash readCrash(int id) {
return crashDao.findOne(1000);
}我的DAO层就是：
@Repository
public interface CrashDao extends CrudRepository<Crash, Integer>{ }我的spring.xml是：
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:p="http://www.springframework.org/schema/p"
xmlns:tx="http://www.springframework.org/schema/tx"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:jpa="http://www.springframework.org/schema/data/jpa"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-4.2.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-4.2.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-4.2.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx-4.2.xsd
http://www.springframework.org/schema/data/jpa
http://www.springframework.org/schema/data/jpa/spring-jpa.xsd
">
<!-- Scans the classpath for annotated components that will be auto-registered as Spring beans -->
<context:component-scan base-package="com.dbprototype" />
<!-- Activates various annotations to be detected in bean classes e.g: @Autowired -->
<context:annotation-config />
<jpa:repositories base-package="com.dbprototype.dao" />
<bean class="org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor" />
<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<!-- data source properties -->
</bean>
<bean id="jpaVendorAdapter" class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
<property name="generateDdl" value="false" />
<property name="showSql" value="true" />
<property name="databasePlatform" value="org.hibernate.dialect.OracleDialect" />
</bean>
<bean id="entityManagerFactory"
class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="dataSource" ref="dataSource" />
<property name="jpaVendorAdapter" ref="jpaVendorAdapter" />
<!-- Spring based scanning for @Entity classes -->
<property name="packagesToScan" value="com.dbprototype.domain" />
</bean>
<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
<property name="entityManagerFactory" ref="entityManagerFactory" />
</bean>
<tx:annotation-driven transaction-manager="transactionManager" />
</beans>我不理解做@OneToMany的正确方法，尽管从一些教程来看，我拥有的是“正确的”。虽然如果我将@OneToMany更改为使用急切加载而不是默认的惰性，但我得到了另一个例外：
org.springframework.dao.InvalidDataAccessResourceUsageException:无法提取ResultSet；SQL n/a；嵌套异常是org.hibernate.exception.SQLGrammarException:无法提取ResultSet
由: java.sql.SQLSyntaxErrorException: ORA-00904：“VEHICLES1_”引起。“CRASH_C_TEST_CRASH_NUMBER”：无效标识符
有人能帮我理解一下发生了什么，以及如何正确地做OneToMany吗？
谢谢克里斯
回答 1
Stack Overflow用户
发布于 2016-01-14 13:07:11
这种关系是以另一种方式起作用吗？如果您想从任何Crash访问Vechicle
Vechicle表中的联接列是什么？我认为，您忽略了类@JoinColumn中的Vechicle注释。
参见关于WikiBook ManyToOnes：Persistence/ManyToOne的JPA
代码：
@ManyToOne(cascade=CascadeType.ALL)
@JoinColumn(name = "join_column_in_table_of_vechicle", reverseJoinColumn="C_TEST_CRASH_NUMBER")
private Crash crash;如果没有，请提供表结构，打开SQL-日志记录，并提供select，这将导致异常。
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原文链接：
https://stackoverflow.com/questions/34799654
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