标签:之间 eclips rect not meta 自动建表 ibatis ppi 名称
ORM即Object/Relation Mapping, 对象/关系数据库映射。ORM是一种规范,完成面向对象编程语言到关系数据库之间的映射。J2EE中的JPA就是一种ORM规范。
ORM框架有很多,例如JPA, Hibernate,iBATIS等。
Hibernate是JBoss旗下,同时也是RetHat组织的产品(JBoss加入了RetHat),是目前非常流行的ORM框架。
Hibernate中的重要概念为PO(Persistent Object), Hibernate采用低入侵的设计,这里的PO完全是一个普通的java类(POJO),其数据库操作功能完全由Hibernate实现,不需要POJO实现任何接口或者继承任何超类。
目前最新版是5.2.2,为了兼容和稳定起见我下载的是4.3.11版,hibernate-release-4.3.11.Final.zip ,解压后看到主要目录如下,
-project , 这个目录下放了很多demo project
-documentation 下面放了各种文档和教程,最重要的应该是Hibernate API, 即 javadocs
-lib 下面有很多二级目录,里面放了各种jar包,Hibernate是模块化的,其中required是Hibernate框架基础jar包,其他目录是一些扩展包,例如lib\optional\c3p0下面放了数据库连接池的jar包。
我下载的是1.6.1版本,可以在官网的数据仓库中找到 http://www.slf4j.org/dist/
先在Eclipse中新建一个project,然后新建一个user library,例如叫做 hibernate-4-3-11,注意不要勾选system library,否则后面在读取Hibernate配置文件时候一直会报 java.lang.NullPointerException 异常。
导入以下jar包
-hibernate下的 lib\require下的所有jar包(10个),这是框架基本jar包
-hibernate下的lib\optional\c3p0的所有jar包,这是数据库连接池jar包,为Hibernate框架提供数据源
-slf4框架下的slf4j-api-1.6.1.jar (这是api) 和 slf4j-nop-1.6.1.jar (这是具体实现) 两个包
我将所有jar包集中放在了一个目录里方便今后迁移,所有jar包如下,
将以上15个jar都添加进user library中去。
New类将要用来与数据库中的一张表对应,它只是一个普通类(POJO),我们放在src/hib路径下,后面Hibernate将会根据配置文件创建数据表
1 package hib; 2 3 public class News { 4 public int getId() { 5 return id; 6 } 7 public void setId(int id) { 8 this.id = id; 9 } 10 public String getTitle() { 11 return title; 12 } 13 public void setTitle(String title) { 14 this.title = title; 15 } 16 public String getContent() { 17 return content; 18 } 19 public void setContent(String content) { 20 this.content = content; 21 } 22 private int id; 23 private String title; 24 private String content; 25 26 }
在News类相同的路径下创建一个xml文件News.hbm.xml,这个文件与News.java对应,叫做映射文件,是一个Hibernate将依据这个文件操作数据库。
通过某些插件,可以依据实体类News.java 自动创建News.hbm.xml,不过我还是先收工创建一下。
1 <?xml version="1.0" encoding="UTF-8"?> 2 <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" 3 "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> 4 5 <hibernate-mapping package="hib"> 6 <class name="News" table="news_table"> 7 <id name="id" column="id"> 8 <generator class="identity" /> 9 </id> 10 <property name="title" type="string" column="title" /> 11 <property name="content" type="string" column="content" /> 12 </class> 13 </hibernate-mapping>
News.hbm.xml的语法在Hibernate提供的手册(hibernate-release-4.3.11.Final/documentation/manual/en-US/html_single/index.html)1.1.3. The mapping file 中已经有详细描述,
每一个持久化的实体类(例如上面的News.java),都需要有一个到数据表的映射,这里的<class>元素就是一个映射
表的主键用<id>元素表示,其他字段则用<property>元素表示,每个字段元素中可以添加name, colume, type属性,分别表示字段名称和类型
Hibernate配置文件的默认名称是Hibernate.cfg.xml,我们创建这个文件并放在src根目录,文件内容如下,
1 <?xml version="1.0" encoding="UTF-8"?> 2 <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" 3 "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> 4 5 <hibernate-configuration> 6 <session-factory> 7 8 <property name="connection.driver_class">com.mysql.jdbc.Driver</property> 9 <property name="connection.url">jdbc:mysql://127.0.0.1:3306/think_blog?useUnicode=true&characterEncoding=UTF-8</property> <!-- 指定字符集的方式--> 10 <property name="connection.username">root</property> 11 <property name="connection.password"></property> 12 13 <property name="hibernate.c3p0.max_size">20</property> 14 <property name="hibernate.c3p0.min_size">1</property> 15 16 <property name="hibernate.c3p0.timeout">5000</property> 17 18 <property name="hibernate.c3p0.max_statements">100</property> 19 <property name="hibernate.c3p0.idle_test_period">3000</property> 20 <property name="hibernate.c3p0.acquire_increment">2</property> 21 <property name="hibernate.c3p0.validate">true</property> 22 <property name="dialect">org.hibernate.dialect.MySQLDialect</property> <!--数据库方言--> 23 <!--自动建表及打印sql --> 24 <property name="hbm2ddl.auto">update</property> 25 <property name="show_sql">true</property> 26 <mapping resource="hib/News.hbm.xml" /> 27 </session-factory> 28 </hibernate-configuration>
对上面的关键点解释如下:
NewsManager也放在hib路径下,在这个类中初始化Hibernate执行数据库操作
1 package hib; 2 3 import org.hibernate.Session; 4 import org.hibernate.SessionFactory; 5 import org.hibernate.Transaction; 6 import org.hibernate.cfg.Configuration; 7 8 public class NewsManager { 9 public static void main(String[] args) { 10 //实例化Configuration 11 //configure()方法默认加载 /hibernate.cfg.xml 12 Configuration conf = new Configuration().configure(); 13 //用Configuration创建SessionFactory 14 SessionFactory sf = conf.buildSessionFactory(); 15 //用SessionFactory打开Session 16 Session sess = sf.openSession(); 17 //开始事务 18 Transaction tx = sess.beginTransaction(); 19 //创建消息实例 20 News n = new News(); 21 //设置消息标题和消息内容 22 n.setTitle("天王盖地虎"); 23 n.setContent("宝塔镇河妖"); 24 //保存消息 25 sess.save(n); 26 //提交事务 27 tx.commit(); 28 //关闭session 和 SessionFactory 29 sess.close(); 30 sf.close(); 31 System.out.println("执行完毕"); 32 } 33 }
注意上面的Configuration().configure()方法,是从默认的路径src下加载Hibernate配置文件Hibernate.cfg.xml。
启动mysql数据库(确保存在上面配置文件中的数据库名),再在Eclipse中执行NewsManager类结果如下,可以看到在末尾答应出了SQL语句,
1 Dec 23, 2016 2:57:38 PM org.hibernate.annotations.common.reflection.java.JavaReflectionManager <clinit> 2 INFO: HCANN000001: Hibernate Commons Annotations {4.0.5.Final} 3 Dec 23, 2016 2:57:38 PM org.hibernate.Version logVersion 4 INFO: HHH000412: Hibernate Core {4.3.11.Final} 5 Dec 23, 2016 2:57:38 PM org.hibernate.cfg.Environment <clinit> 6 INFO: HHH000206: hibernate.properties not found 7 Dec 23, 2016 2:57:38 PM org.hibernate.cfg.Environment buildBytecodeProvider 8 INFO: HHH000021: Bytecode provider name : javassist 9 Dec 23, 2016 2:57:38 PM org.hibernate.cfg.Configuration configure 10 INFO: HHH000043: Configuring from resource: /hibernate.cfg.xml 11 Dec 23, 2016 2:57:38 PM org.hibernate.cfg.Configuration getConfigurationInputStream 12 INFO: HHH000040: Configuration resource: /hibernate.cfg.xml 13 Dec 23, 2016 2:57:38 PM org.hibernate.internal.util.xml.DTDEntityResolver resolveEntity 14 WARN: HHH000223: Recognized obsolete hibernate namespace http://hibernate.sourceforge.net/. Use namespace http://www.hibernate.org/dtd/ instead. Refer to Hibernate 3.6 Migration Guide! 15 Dec 23, 2016 2:57:38 PM org.hibernate.cfg.Configuration addResource 16 INFO: HHH000221: Reading mappings from resource: hib/News.hbm.xml 17 Dec 23, 2016 2:57:39 PM org.hibernate.internal.util.xml.DTDEntityResolver resolveEntity 18 WARN: HHH000223: Recognized obsolete hibernate namespace http://hibernate.sourceforge.net/. Use namespace http://www.hibernate.org/dtd/ instead. Refer to Hibernate 3.6 Migration Guide! 19 Dec 23, 2016 2:57:39 PM org.hibernate.cfg.Configuration doConfigure 20 INFO: HHH000041: Configured SessionFactory: null 21 Dec 23, 2016 2:57:39 PM org.hibernate.c3p0.internal.C3P0ConnectionProvider configure 22 INFO: HHH010002: C3P0 using driver: com.mysql.jdbc.Driver at URL: jdbc:mysql://127.0.0.1:3306/think_blog?useUnicode=true&characterEncoding=UTF-8 23 Dec 23, 2016 2:57:39 PM org.hibernate.c3p0.internal.C3P0ConnectionProvider configure 24 INFO: HHH000046: Connection properties: {user=root, password=****} 25 Dec 23, 2016 2:57:39 PM org.hibernate.c3p0.internal.C3P0ConnectionProvider configure 26 INFO: HHH000006: Autocommit mode: false 27 Dec 23, 2016 2:57:39 PM com.mchange.v2.log.MLog <clinit> 28 INFO: MLog clients using java 1.4+ standard logging. 29 Dec 23, 2016 2:57:39 PM com.mchange.v2.c3p0.C3P0Registry banner 30 INFO: Initializing c3p0-0.9.2.1 [built 20-March-2013 10:47:27 +0000; debug? true; trace: 10] 31 Dec 23, 2016 2:57:39 PM com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource getPoolManager 32 INFO: Initializing c3p0 pool... com.mchange.v2.c3p0.PoolBackedDataSource@49eb2a4c [ connectionPoolDataSource -> com.mchange.v2.c3p0.WrapperConnectionPoolDataSource@92efcc58 [ acquireIncrement -> 2, acquireRetryAttempts -> 30, acquireRetryDelay -> 1000, autoCommitOnClose -> false, automaticTestTable -> null, breakAfterAcquireFailure -> false, checkoutTimeout -> 0, connectionCustomizerClassName -> null, connectionTesterClassName -> com.mchange.v2.c3p0.impl.DefaultConnectionTester, debugUnreturnedConnectionStackTraces -> false, factoryClassLocation -> null, forceIgnoreUnresolvedTransactions -> false, identityToken -> 1hgeby99lbs898r1pl3km1|187a62fa, idleConnectionTestPeriod -> 3000, initialPoolSize -> 1, maxAdministrativeTaskTime -> 0, maxConnectionAge -> 0, maxIdleTime -> 5000, maxIdleTimeExcessConnections -> 0, maxPoolSize -> 20, maxStatements -> 100, maxStatementsPerConnection -> 0, minPoolSize -> 1, nestedDataSource -> com.mchange.v2.c3p0.DriverManagerDataSource@e332f0e7 [ description -> null, driverClass -> null, factoryClassLocation -> null, identityToken -> 1hgeby99lbs898r1pl3km1|4a84466d, jdbcUrl -> jdbc:mysql://127.0.0.1:3306/think_blog?useUnicode=true&characterEncoding=UTF-8, properties -> {user=******, password=******} ], preferredTestQuery -> null, propertyCycle -> 0, statementCacheNumDeferredCloseThreads -> 0, testConnectionOnCheckin -> false, testConnectionOnCheckout -> false, unreturnedConnectionTimeout -> 0, usesTraditionalReflectiveProxies -> false; userOverrides: {} ], dataSourceName -> null, factoryClassLocation -> null, identityToken -> 1hgeby99lbs898r1pl3km1|2c6d9d9c, numHelperThreads -> 3 ] 33 Dec 23, 2016 2:57:40 PM org.hibernate.dialect.Dialect <init> 34 INFO: HHH000400: Using dialect: org.hibernate.dialect.MySQLDialect 35 Dec 23, 2016 2:57:40 PM org.hibernate.engine.jdbc.internal.LobCreatorBuilder useContextualLobCreation 36 INFO: HHH000424: Disabling contextual LOB creation as createClob() method threw error : java.lang.reflect.InvocationTargetException 37 Dec 23, 2016 2:57:40 PM org.hibernate.engine.transaction.internal.TransactionFactoryInitiator initiateService 38 INFO: HHH000399: Using default transaction strategy (direct JDBC transactions) 39 Dec 23, 2016 2:57:40 PM org.hibernate.hql.internal.ast.ASTQueryTranslatorFactory <init> 40 INFO: HHH000397: Using ASTQueryTranslatorFactory 41 Dec 23, 2016 2:57:40 PM org.hibernate.tool.hbm2ddl.SchemaUpdate execute 42 INFO: HHH000228: Running hbm2ddl schema update 43 Dec 23, 2016 2:57:40 PM org.hibernate.tool.hbm2ddl.SchemaUpdate execute 44 INFO: HHH000102: Fetching database metadata 45 Dec 23, 2016 2:57:40 PM org.hibernate.tool.hbm2ddl.SchemaUpdate execute 46 INFO: HHH000396: Updating schema 47 Dec 23, 2016 2:57:40 PM org.hibernate.tool.hbm2ddl.DatabaseMetadata getTableMetadata 48 INFO: HHH000262: Table not found: news_table 49 Dec 23, 2016 2:57:40 PM org.hibernate.tool.hbm2ddl.DatabaseMetadata getTableMetadata 50 INFO: HHH000262: Table not found: news_table 51 Dec 23, 2016 2:57:40 PM org.hibernate.tool.hbm2ddl.DatabaseMetadata getTableMetadata 52 INFO: HHH000262: Table not found: news_table 53 Dec 23, 2016 2:57:40 PM org.hibernate.tool.hbm2ddl.SchemaUpdate execute 54 INFO: HHH000232: Schema update complete 55 Hibernate: insert into news_table (title, content) values (?, ?) 56 执行完毕
同时我们查看mysql数据库,发现在think_blog库下多了一张表News_table,同时在表中我们插入了一条数据,
到此,我们的Hibernate环境就算是配置成功了,并且成功执行了一个基本的demo。
从测试类中可以总结Hibernate的一般步骤,
以上步骤完全是面向对象的编程方式,不直接操作数据库,但是通过Hibernate完成了数据库操作,这便是Hibernate的基本原理。
标签:之间 eclips rect not meta 自动建表 ibatis ppi 名称
原文地址:http://www.cnblogs.com/fysola/p/6215051.html