为什么hibernate会在创建表之前删除关键约束？

时间：2017-04-11 15:00:58

标签： java hibernate many-to-one

这是我简单的hibernate.cfg.xml文件：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
 "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
 "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <!-- Database connection settings -->
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://localhost/UserDB</property>
        <property name="connection.username">root</property>
        <property name="connection.password"></property>

        <!-- JDBC connection pool (use the built-in) -->
        <property name="connection.pool_size">1</property>

        <!-- SQL dialect -->
        <property name="dialect">org.hibernate.dialect.MySQL5Dialect</property>

        <!-- Enable Hibernate's automatic session context management -->
        <property name="current_session_context_class">thread</property>

        <!-- Disable the second-level cache -->
        <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>

        <!-- Echo all executed SQL to stdout -->
        <property name="show_sql">true</property>
        <property name="format_sql">true</property>

        <!-- Drop and re-create the database schema on startup -->
        <property name="hbm2ddl.auto">create-drop</property>

        <!-- Mapping files -->
        <mapping class="com.stackoverflow.model.Person" />
        <mapping class="com.stackoverflow.model.Phone" />

    </session-factory>

这是简单的Person实体：

@Entity(name = "Person")
public class Person {

    @Id
    @GeneratedValue
    private Long id;

    public Person() {
    }
}

这是简单的电话实体：

@Entity(name = "Phone")
public class Phone {

    @Id
    @GeneratedValue
    private Long id;

    @Column(name = "`number`")
    private String number;

    @ManyToOne(cascade=CascadeType.ALL,optional=false)
    @JoinColumn(name = "person_id",
            foreignKey = @ForeignKey(name = "PERSON_ID_FK")
    )
    private Person person;

    public Phone() {
    }

    public Phone(String number) {
        this.number = number;
    }

    public Long getId() {
        return id;
    }

    public String getNumber() {
        return number;
    }

    public Person getPerson() {
        return person;
    }

    public void setPerson(Person person) {
        this.person = person;
    }
}

这是试图将此关系保存到数据库中的junit测试类：

    public class TestManyToOne {
    private static SessionFactory sessionFactory;
    private Session session;

    @BeforeClass
    public static void setUp() throws Exception {
        // A SessionFactory is set up once for an application!
        final StandardServiceRegistry registry = new StandardServiceRegistryBuilder().configure("hibernate.cfg.xml")
                .build();
        try {
            sessionFactory = new MetadataSources(registry).buildMetadata().buildSessionFactory();
        } catch (Exception e) {
            // The registry would be destroyed by the SessionFactory, but we had
            // trouble building the SessionFactory
            // so destroy it manually.
            StandardServiceRegistryBuilder.destroy(registry);
            System.out.println("Exception\n" + e);
        }
        assertNotNull(sessionFactory);
    }

    @AfterClass
    public static void tearDown() throws Exception {
        sessionFactory.close();
    }

    @Before
    public void beforeEach() {
        session = sessionFactory.getCurrentSession();
        session.beginTransaction();

    }

    @After
    public void afterEach() {
        session.getTransaction().commit();
        session.close();
    }

    @Test
    public void testSave() {
        Person person = new Person();
        Phone phone1 = new Phone("93283287832");
        Phone phone2 = new Phone("0987654321");

        phone1.setPerson(person);
        phone2.setPerson(person);

        session.save(phone1);
        session.save(phone2);
    }
}

它只有一个名为testSave的@Test方法。当我在刚刚创建的数据库上运行它时出现错误：

Hibernate: 

    alter table Phone 
        drop 
        foreign key PERSON_ID_FK
апр 11, 2017 5:50:54 PM org.hibernate.resource.transaction.backend.jdbc.internal.DdlTransactionIsolatorNonJtaImpl getIsolatedConnection
INFO: HHH10001501: Connection obtained from JdbcConnectionAccess [org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator$ConnectionProviderJdbcConnectionAccess@6f2cfcc2] for (non-JTA) DDL execution was not in auto-commit mode; the Connection 'local transaction' will be committed and the Connection will be set into auto-commit mode.
апр 11, 2017 5:50:54 PM org.hibernate.tool.schema.internal.ExceptionHandlerLoggedImpl handleException
WARN: GenerationTarget encountered exception accepting command : Error executing DDL via JDBC Statement
org.hibernate.tool.schema.spi.CommandAcceptanceException: Error executing DDL via JDBC Statement
    at org.hibernate.tool.schema.internal.exec.GenerationTargetToDatabase.accept(GenerationTargetToDatabase.java:62)
    at org.hibernate.tool.schema.internal.SchemaDropperImpl.applySqlString(SchemaDropperImpl.java:374)
    at org.hibernate.tool.schema.internal.SchemaDropperImpl.applySqlStrings(SchemaDropperImpl.java:359)
    at org.hibernate.tool.schema.internal.SchemaDropperImpl.applyConstraintDropping(SchemaDropperImpl.java:331)
    at org.hibernate.tool.schema.internal.SchemaDropperImpl.dropFromMetadata(SchemaDropperImpl.java:230)
    at org.hibernate.tool.schema.internal.SchemaDropperImpl.performDrop(SchemaDropperImpl.java:154)
    at org.hibernate.tool.schema.internal.SchemaDropperImpl.doDrop(SchemaDropperImpl.java:126)
    at org.hibernate.tool.schema.internal.SchemaDropperImpl.doDrop(SchemaDropperImpl.java:112)
    at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.performDatabaseAction(SchemaManagementToolCoordinator.java:137)
    at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.process(SchemaManagementToolCoordinator.java:65)
    at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:307)
    at org.hibernate.boot.internal.SessionFactoryBuilderImpl.build(SessionFactoryBuilderImpl.java:490)
    at org.hibernate.boot.internal.MetadataImpl.buildSessionFactory(MetadataImpl.java:170)
    at com.stackoverflow.dao.TestDao.setUp(TestDao.java:37)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:24)
    at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
    at org.apache.maven.surefire.junit4.JUnit4Provider.execute(JUnit4Provider.java:283)
    at org.apache.maven.surefire.junit4.JUnit4Provider.executeWithRerun(JUnit4Provider.java:173)
Hibernate: 

    drop table if exists hibernate_sequence
    at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:153)
    at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:128)
    at org.apache.maven.surefire.booter.ForkedBooter.invokeProviderInSameClassLoader(ForkedBooter.java:203)
    at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:155)
    at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:103)
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Table 'userdb.phone' doesn't exist
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
    at com.mysql.jdbc.Util.getInstance(Util.java:381)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1030)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3491)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3423)
    at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1936)
    at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2060)
    at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2536)
    at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2465)
    at com.mysql.jdbc.StatementImpl.execute(StatementImpl.java:734)
    at org.hibernate.tool.schema.internal.exec.GenerationTargetToDatabase.accept(GenerationTargetToDatabase.java:49)
    ... 30 more

错误的这一行非常重要：

Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Table 'userdb.phone' doesn't exist

如何告诉hibernate在创建表之前不删除外键约束？

谢谢。

1 个答案:

答案 0 :(得分：0)

我不相信，但问题是连接池大小设置为1.我将其设置为10 

<property name="connection.pool_size">10</property>
junit test成功运行，但错误并没有消失。它被eclipse忽略了。

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