最近在学hibernate,常见的教程都是搭配mysql,因为公司本地电脑用的是pg,所以就尝试着做个pg的小demo. 自己也是边学边写，只当是加深印象.话不多说，直接开始;
一) 准备工作;
1) 本地安装postgresql ,这个不多说，自己去网上下载;
注: 本次使用的为pg 9.4
2)下载pg的jdbc Driver;
网址: 可FQ的点此下载 ,不能FQ的自己百度吧。
说明一下,支持pg9.4的有4个版本,根据自己的jdk做选择:
JDBC3 Postgresql Driver, Version 9.3-1103 ( < jdk1.6)
JDBC4 Postgresql Driver, Version 9.4.1212 ( = jdk1.6)
JDBC41 Postgresql Driver, Version 9.4.1212 (= jdk1.7)
JDBC42 Postgresql Driver, Version 9.4.1212 (= jdk1.8)
3) 下载hibernate的jar包;
网址:FQ下载 (文件还挺大，248M);既然是学习，那就直接上最新版本: 5.2.4.Final(2016-10-26)
解压后目录：
required目录下的jar包是必须添加的( 比3.x版本的多了好多呀):
意外发现在spatial目录下已经包含有pg的驱动文件了，哈哈，考虑的果然周到:
二) 启程;
1) pg 创建一个用户反馈表(feedback);
orm框架连接数据库都有两种方式：code first和db first; db first 指提前建好数据库表格，在code中写好匹配的model类进行mapping,而code first指在代码中配置好表格的相关字段信息,项目运行时，再由框架根据你的model类及配置，自动在数据库执行表格的创建及修改操作;
如果你用db first的方式,可以用类似如下的sql语句在pg提前创建表格:
create table feedback (id serial not null primary key,//serial 相当于mysql中的int auto_increment,实现的是自增长效果username varchar(45) not null,content varchar(200) not null,sendtime timestamp not null )
2)创建数据表Feedback对应的持久化类Feedback, 及持久化类Feedback对应的映射文件Feedback.hbm.xml。需要注意的是,该映射文件与对应的持久化类应该在同一目录下。关键代码如下：
/*** Created by c-yangx on 11/16/2016.*/ public class Feedback {private Integer id;private String username;private String content;private Timestamp sendTime;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 getContent() {return content;}public void setContent(String content) {this.content = content;}public Timestamp getSendTime() {return sendTime;}public void setSendTime(Timestamp sendTime) {this.sendTime = sendTime;}}
<?xml version="1.0"?> <!--~ Hibernate, Relational Persistence for Idiomatic Java~~ License: GNU Lesser General Public License (LGPL), version 2.1 or later.~ See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.--> <!DOCTYPE hibernate-mapping PUBLIC"-//Hibernate/Hibernate Mapping DTD 3.0//EN""http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"><hibernate-mapping package="models"><class name="models.Feedback" table="feedback" catalog="hbstudy"><id name="id" column="id" type="java.lang.Integer"><generator class="increment"></generator></id><property name="username" type="java.lang.String"><column name="username" length="45" not-null="true"><comment>反馈人</comment></column></property><property name="content" type="java.lang.String"><column name="content" length="200" not-null="true"><comment>反馈内容</comment></column></property><property name="sendTime" type="java.sql.Timestamp"><column name="sendTime" length="19" not-null="false"><comment>反馈时间</comment></column></property></class> </hibernate-mapping>
3) 创建Hibernate的主配置文件src/hibernate.cfg.xml,该文件中存放着 数据库连接驱动程序类、登陆数据库的用户名/密码、映射实体类配置文件的位置...etc.
Hibernate在初始化时,会自动在classes路径下寻找该主配置文件,并且读取配置信息，用于后期的数据库操作;
那么问题就来了,hinernate.cfg.xml的格式是什么呢?不要怕,你能想到的，官方也都考虑到了，直接在文件路径下搜索，ctrl+C=>ctrl+V 就是这么简单;
打开文件如下,自己修改配置：
<?xml version='1.0' encoding='UTF-8'?> <!-- ~ Hibernate, Relational Persistence for Idiomatic Java ~ ~ License: GNU Lesser General Public License (LGPL), version 2.1 or later. ~ See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>. --> <!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><property name="hibernate.dialect">org.hibernate.dialect.HSQLDialect</property><property name="hibernate.connection.driver_class">org.hsqldb.jdbcDriver</property><property name="hibernate.connection.username">sa</property><property name="hibernate.connection.password"></property><property name="hibernate.connection.url">jdbc:hsqldb:.</property><property name="hibernate.cache.use_query_cache">true</property><property name="hibernate.cache.region_prefix">hibernate.test</property><property name="hibernate.jdbc.use_streams_for_binary">true</property><property name="hibernate.jdbc.batch_size">0</property><property name="hibernate.max_fetch_depth">3</property><!-- 是否自动创建数据库表 他主要有一下几个值:validate:当sessionFactory创建时，自动验证或者schema定义导入数据库。 create:每次启动都drop掉原来的schema，创建新的。 create-drop:当sessionFactory明确关闭时，drop掉schema。update(常用):如果没有schema就创建，有就更新。 --><!--此处配置来实现code first--><property name="hibernate.hbm2ddl.auto">create-drop</property><property name="hibernate.generate_statistics">true</property><property name="hibernate.cache.region.factory_class">org.hibernate.testing.cache.CachingRegionFactory</property><mapping class="org.hibernate.jpa.test.Item"/><mapping class="org.hibernate.jpa.test.Cat"/><mapping class="org.hibernate.jpa.test.Kitten"/><mapping class="org.hibernate.jpa.test.Distributor"/><class-cache class="org.hibernate.jpa.test.Item" usage="read-write"/><collection-cache collection="org.hibernate.jpa.test.Item.distributors" usage="read-write" region="RegionName"/></session-factory> </hibernate-configuration>
4)编写HibernateUtil.java,用于构建SessionFactory
package utils;import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.cfg.Configuration;/*** Created by c-yangx on 11/16/2016.*/ public class HibernateUtil {static SessionFactory sessionFactory;//Init Hibernatestatic{try{Configuration config=new Configuration().configure();sessionFactory=config.buildSessionFactory();}catch(Exception e){String msg=e.getMessage();e.printStackTrace();System.out.println(msg);}}//Start Sessionpublic static Session openSession(){return sessionFactory.openSession();} }
数据库Feedback表的操作类FeedbackDaoImpl及接口IFeedbackDao定义：
package IDao;import models.Feedback;/*** Created by c-yangx on 11/16/2016.*/ public interface IFeedbackDao {void save(Feedback item); }
package dao;import IDao.IFeedbackDao; import models.Feedback; import org.hibernate.Session; import org.hibernate.Transaction; import utils.HibernateUtil;/*** Created by c-yangx on 11/16/2016.*/ public class FeedbackDaoImpl implements IFeedbackDao {@Overridepublic void save(Feedback item) {Session session=null;Transaction tx=null;try{session= HibernateUtil.openSession();tx=session.beginTransaction();session.save(item);tx.commit();}catch(Exception e){tx.rollback();e.printStackTrace();throw new RuntimeException(e);}finally {session.close();}} }
5)最后写一个测试类Test
import dao.FeedbackDaoImpl; import models.Feedback; import java.sql.Timestamp;/*** Created by c-yangx on 11/16/2016.*/ public class Test {@org.junit.Testpublic void testSave(){Feedback newItem=new Feedback();newItem.setUsername("Andrew");newItem.setContent("test content one");newItem.setSendTime(new Timestamp(System.currentTimeMillis()));FeedbackDaoImpl feedbackDao=new FeedbackDaoImpl();feedbackDao.save(newItem);} }
三)路途坎坷;
项目启动运行，遇到一些bug,一起做个记录:
a)Error msg如下; 是配置的密码有误，干脆给数据库加了一个新的role和密码
org.hibernate.service.spi.ServiceException: Unable to create requested service [org.hibernate.engine.jdbc.env.spi.JdbcEnvironment]at org.hibernate.service.internal.AbstractServiceRegistryImpl.createService(AbstractServiceRegistryImpl.java:267)at org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:231)at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:210)at org.hibernate.engine.jdbc.internal.JdbcServicesImpl.configure(JdbcServicesImpl.java:51)at org.hibernate.boot.registry.internal.StandardServiceRegistryImpl.configureService(StandardServiceRegistryImpl.java:94)at org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:240)at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:210)at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.handleTypes(MetadataBuildingProcess.java:352)at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.complete(MetadataBuildingProcess.java:111)at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.build(MetadataBuildingProcess.java:83)at org.hibernate.boot.internal.MetadataBuilderImpl.build(MetadataBuilderImpl.java:418)at org.hibernate.boot.internal.MetadataBuilderImpl.build(MetadataBuilderImpl.java:87)at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:691)at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:726)at utils.HibernateUtil.<clinit>(HibernateUtil.java:17)at dao.FeedbackDaoImpl.save(FeedbackDaoImpl.java:18)at Test.testSave(Test.java:19)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.InvokeMethod.evaluate(InvokeMethod.java:17)at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)at org.junit.runners.ParentRunner.run(ParentRunner.java:309)at org.junit.runner.JUnitCore.run(JUnitCore.java:160)at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:117)at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:42)at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:262)at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:84) Caused by: org.hibernate.exception.JDBCConnectionException: Error calling Driver#connectat org.hibernate.engine.jdbc.connections.internal.BasicConnectionCreator$1$1.convert(BasicConnectionCreator.java:105)at org.hibernate.engine.jdbc.connections.internal.BasicConnectionCreator.convertSqlException(BasicConnectionCreator.java:123)at org.hibernate.engine.jdbc.connections.internal.DriverConnectionCreator.makeConnection(DriverConnectionCreator.java:41)at org.hibernate.engine.jdbc.connections.internal.BasicConnectionCreator.createConnection(BasicConnectionCreator.java:58)at org.hibernate.engine.jdbc.connections.internal.PooledConnections.addConnections(PooledConnections.java:123)at org.hibernate.engine.jdbc.connections.internal.PooledConnections.<init>(PooledConnections.java:42)at org.hibernate.engine.jdbc.connections.internal.PooledConnections.<init>(PooledConnections.java:20)at org.hibernate.engine.jdbc.connections.internal.PooledConnections$Builder.build(PooledConnections.java:161)at org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl.buildPool(DriverManagerConnectionProviderImpl.java:109)at org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl.configure(DriverManagerConnectionProviderImpl.java:72)at org.hibernate.boot.registry.internal.StandardServiceRegistryImpl.configureService(StandardServiceRegistryImpl.java:94)at org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:240)at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:210)at org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator.buildJdbcConnectionAccess(JdbcEnvironmentInitiator.java:145)at org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator.initiateService(JdbcEnvironmentInitiator.java:66)at org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator.initiateService(JdbcEnvironmentInitiator.java:35)at org.hibernate.boot.registry.internal.StandardServiceRegistryImpl.initiateService(StandardServiceRegistryImpl.java:88)at org.hibernate.service.internal.AbstractServiceRegistryImpl.createService(AbstractServiceRegistryImpl.java:257)... 38 more Caused by: org.postgresql.util.PSQLException: FATAL: password authentication failed for user "postgres"at org.postgresql.core.v3.ConnectionFactoryImpl.doAuthentication(ConnectionFactoryImpl.java:443)at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:217)at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:52)at org.postgresql.jdbc.PgConnection.<init>(PgConnection.java:216)at org.postgresql.Driver.makeConnection(Driver.java:404)at org.postgresql.Driver.connect(Driver.java:272)at org.hibernate.engine.jdbc.connections.internal.DriverConnectionCreator.makeConnection(DriverConnectionCreator.java:38)... 53 more
b)添加账号之后，又遇到新的Bug,原来是忘了给账号配置数据库权限了，在pg端配置一下就ok了
org.hibernate.exception.SQLGrammarException: could not extract ResultSetat org.hibernate.exception.internal.SQLStateConversionDelegate.convert(SQLStateConversionDelegate.java:106)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.extract(ResultSetReturnImpl.java:79)at org.hibernate.id.IncrementGenerator.initializePreviousValueHolder(IncrementGenerator.java:113)at org.hibernate.id.IncrementGenerator.generate(IncrementGenerator.java:52)at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:105)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:674)at org.hibernate.internal.SessionImpl.save(SessionImpl.java:666)at org.hibernate.internal.SessionImpl.save(SessionImpl.java:661)at dao.FeedbackDaoImpl.save(FeedbackDaoImpl.java:20)at Test.testSave(Test.java:18)at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:42)at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:262)at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:84)
Caused by: org.postgresql.util.PSQLException: ERROR: permission denied for relation feedback... 35 more 四) 抵达;
运行Test.java中的testSave方法,执行成功，再查看下数据库，数据也已成功插入;
最后放一个项目结构图：(说明一下，因为后续打算学习全部的ssh,所以用了个web项目)
后言:
楼主也是刚开始学习java中的ssh框架，所以后面也会继续写一些hibernate的crud,Spring及struct2的文章记录自己的学习过程,并在最后整理成一个小系列.如果感兴趣，欢迎大家关注;
大家有觉得可以优化的地方,也欢迎指正.
(...未完待续)
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本文出自:博客园--别问是谁
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