Hibernate支持自动建表，在开发阶段很方便，可以保证hbm与数据库表结构的自动同步。
方法很简单，在hibernate.cfg.xml内加入
<property name="hibernate.hbm2ddl.auto">update</property>
update：(推荐使用) 自动生成表.如果已经存在不会再生成.如果表有变动.自动更新表(不会删除任何数据).
在这里还有其他几个参数：
create：自动建表.每次框架运行都会创建新的表.以前表将会被覆盖,表数据会丢失.(开发环境中测试使用)
create-drop： 自动建表.每次框架运行结束都会将所有表删除.(开发环境中测试使用)
validate： 校验.不自动生成表.每次启动会校验数据库中表是否正确.校验失败.
测试用例：
实体类User
package com.domain;
public class User {
private Integer id;
private String username;
private String password;
private Integer age;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
@Override
public String toString() {
return "User [id=" + id + ", username=" + username + ", password=" + password + ", age=" + age + "]";
}
}
User.hbm.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<!-- name: 完整类名 table:数据库表名 -->
<class name="com.domain.User" table="user">
<!-- id配置表的主键 name代表表中属性 -->
<id name="id" column="id">
<!-- 主键生成策略 -->
<generator class="native"></generator>
</id>
<property name="username" column="username" type="string"></property>
<property name="password" column="password" type="string"></property>
<property name="age" column="age" type="integer"></property>
</class>
</hibernate-mapping>
hibernate.cfg.xml
<?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>
<!-- 指定方言 -->
<property name="hibernate.dialect">org.hibernate.dialect.MySQL5InnoDBDialect</property>
<!-- 数据库驱动 -->
<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
<!-- 数据库url -->
<property name="hibernate.connection.url">jdbc:mysql://localhost:3306/hibernate02_1514010311</property>
<!-- 数据库连接用户名 -->
<property name="hibernate.connection.username">root</property>
<!-- 数据库连接密码 -->
<property name="hibernate.connection.password">0x3137</property>
<!-- 将hibernate生成的sql语句打印到控制台 -->
<property name="hibernate.show_sql">true</property>
<!-- 将hibernate生成的sql语句格式化(语法缩进) -->
<property name="hibernate.format_sql">true</property>
<!-- 配置getCurrentSession -->
<property name="hibernate.current_session_context_class">thread</property>
<!-- 配置sql语句生成方式 -->
<property name="hibernate.hbm2ddl.auto">update</property>
<mapping resource="com/domain/User.hbm.xml" />
</session-factory>
</hibernate-configuration>
HibernateUtil.java
package com.util;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class HibernateUtil {
private static Configuration cfg;
private static SessionFactory sessionFactory;
static {
try {
cfg = new Configuration().configure();
sessionFactory = cfg.buildSessionFactory();
}catch (Exception e) {
e.printStackTrace();
}
}
public static SessionFactory getSessionFactory() {
return sessionFactory;
}
}
TestUser.java
package com.test;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.junit.Test;
import com.domain.User;
import com.util.HibernateUtil;
public class TestUser {
@Test
public void saveUser() {
SessionFactory sessionFactory = null;
Session session = null;
Transaction transaction = null;
User user = new User();
user.setUsername("三哥无邪");
user.setPassword("1514010311");
user.setAge(21);
try {
sessionFactory = HibernateUtil.getSessionFactory();
session = sessionFactory.getCurrentSession();
transaction = session.beginTransaction();
session.save(user);
transaction.commit();
} catch (Exception e) {
if (transaction!=null) {
transaction.rollback();
}
e.printStackTrace();
}
}
@Test
public void updateUser() {
SessionFactory sessionFactory = null;
Session session = null;
Transaction transaction = null;
try {
sessionFactory = HibernateUtil.getSessionFactory();
session = sessionFactory.getCurrentSession();
transaction = session.beginTransaction();
User user = session.get(User.class, 1);
user.setUsername("三哥无邪啊");
user.setPassword("1514010311");
user.setAge(21);
session.update(user);
transaction.commit();
} catch (Exception e) {
if (transaction!=null) {
transaction.rollback();
}
e.printStackTrace();
}
}
@Test
public void queryUser() {
SessionFactory sessionFactory = null;
Session session = null;
Transaction transaction = null;
try {
sessionFactory = HibernateUtil.getSessionFactory();
session = sessionFactory.getCurrentSession();
transaction = session.beginTransaction();
User user = session.get(User.class, 2);
System.out.println("ID:"+user.getId()+" 用户名："+user.getUsername()+" 密码："+user.getPassword());
transaction.commit();
} catch (Exception e) {
if (transaction!=null) {
transaction.rollback();
}
e.printStackTrace();
}
}
@Test
public void deleteUser() {
SessionFactory sessionFactory = null;
Session session = null;
Transaction transaction = null;
try {
sessionFactory = HibernateUtil.getSessionFactory();
session = sessionFactory.getCurrentSession();
transaction = session.beginTransaction();
User user = session.get(User.class, 1);
session.delete(user);
transaction.commit();
} catch (Exception e) {
if (transaction!=null) {
transaction.rollback();
}
e.printStackTrace();
}
}
}
测试saveUser方法，测试结果如图
自动创建了user表，然后向表内插入数据
遇到的问题
运行时出现以下错误
23:37:12,245 WARN pooling:70 - HHH10001002: Using Hibernate built-in connection pool (not for production use!)
Hibernate:
drop table if exists user
Hibernate:
create table user (
id integer not null auto_increment,
username varchar(255),
password varchar(255),
age integer,
primary key (id)
) type=MyISAM
23:37:13,303 WARN ExceptionHandlerLoggedImpl:27 - 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:67)
at org.hibernate.tool.schema.internal.SchemaCreatorImpl.applySqlString(SchemaCreatorImpl.java:440)
at org.hibernate.tool.schema.internal.SchemaCreatorImpl.applySqlStrings(SchemaCreatorImpl.java:424)
at org.hibernate.tool.schema.internal.SchemaCreatorImpl.createFromMetadata(SchemaCreatorImpl.java:315)
at org.hibernate.tool.schema.internal.SchemaCreatorImpl.performCreation(SchemaCreatorImpl.java:166)
at org.hibernate.tool.schema.internal.SchemaCreatorImpl.doCreation(SchemaCreatorImpl.java:135)
at org.hibernate.tool.schema.internal.SchemaCreatorImpl.doCreation(SchemaCreatorImpl.java:121)
at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.performDatabaseAction(SchemaManagementToolCoordinator.java:155)
at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.process(SchemaManagementToolCoordinator.java:72)
at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:309)
at org.hibernate.boot.internal.SessionFactoryBuilderImpl.build(SessionFactoryBuilderImpl.java:452)
at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:710)
at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:726)
at com.util.HibernateUtil.<clinit>(HibernateUtil.java:12)
at com.test.TestUser.saveUser(TestUser.java:23)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:678)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'type=MyISAM' at line 7
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.Util.getInstance(Util.java:386)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1054)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4237)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4169)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2617)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2778)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2819)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2768)
at com.mysql.jdbc.StatementImpl.execute(StatementImpl.java:894)
at com.mysql.jdbc.StatementImpl.execute(StatementImpl.java:732)
at org.hibernate.tool.schema.internal.exec.GenerationTargetToDatabase.accept(GenerationTargetToDatabase.java:54)
... 37 more
Hibernate:
insert
into
user
(username, password, age)
values
(?, ?, ?)
23:37:13,441 WARN SqlExceptionHelper:129 - SQL Error: 1146, SQLState: 42S02
23:37:13,441 ERROR SqlExceptionHelper:131 - Table 'hibernate02_1514010311.user' doesn't exist
org.hibernate.exception.SQLGrammarException: could not execute statement
at org.hibernate.exception.internal.SQLExceptionTypeDelegate.convert(SQLExceptionTypeDelegate.java:63)
at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:42)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:111)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:97)
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:208)
at org.hibernate.dialect.identity.GetGeneratedKeysDelegate.executeAndExtract(GetGeneratedKeysDelegate.java:57)
at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:42)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2909)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3480)
at org.hibernate.action.internal.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:81)
at org.hibernate.engine.spi.ActionQueue.execute(ActionQueue.java:626)
at org.hibernate.engine.spi.ActionQueue.addResolvedEntityInsertAction(ActionQueue.java:280)
at org.hibernate.engine.spi.ActionQueue.addInsertAction(ActionQueue.java:261)
at org.hibernate.engine.spi.ActionQueue.addAction(ActionQueue.java:306)
at org.hibernate.event.internal.AbstractSaveEventListener.addInsertAction(AbstractSaveEventListener.java:318)
at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:275)
at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:182)
at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:113)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:192)
at org.hibernate.event.internal.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:38)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:177)
at org.hibernate.event.internal.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:32)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:73)
at org.hibernate.internal.SessionImpl.fireSave(SessionImpl.java:689)
at org.hibernate.internal.SessionImpl.save(SessionImpl.java:681)
at org.hibernate.internal.SessionImpl.save(SessionImpl.java:676)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.hibernate.context.internal.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:355)
at com.sun.proxy.$Proxy26.save(Unknown Source)
at com.test.TestUser.saveUser(TestUser.java:26)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:678)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Table 'hibernate02_1514010311.user' doesn't exist
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.Util.getInstance(Util.java:386)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1054)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4237)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4169)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2617)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2778)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2825)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2156)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2459)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2376)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2360)
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:205)
... 51 more
在网络上查询得到结果
目前配置的mysql方言
<property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
根据错误内容提示很显然得知：这是MySQL的版本问题导致的问题。
实际上，在MySQL5.0以前，type=InnoDB是有效的SQL语句，但是自己用的是MySQL5.7版本，type=InnoDB不再有效了。
对于出现的错误，解决方法就是将mysql的方言改为如下
<property name="hibernate.dialect">org.hibernate.dialect.MySQL5InnoDBDialect</property>
就此再次运行就可以自动建表了。