最近在學hibernate,常見的教程都是搭配mysql,因為公司本地電腦用的是pg,所以就嘗試著做個pg的小demo. 自己也是邊學邊寫，只當是加深印象.話不多說，直接開始;
1) 本地安裝postgresql ,這個不多說，自己去網上下載;
注: 本次使用的為pg 9.4
2)下載pg的jdbc Driver;
網址: 可FQ的點此下載 ,不能FQ的自己百度吧。
說明一下,支持pg9.4的有4個版本,根據自己的jdk做選擇:
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) 下載hibernate的jar包;
網址:FQ下載 (文件還挺大，248M);既然是學習，那就直接上最新版本: 5.2.4.Final(2016-10-26)
解壓後目錄：
required目錄下的jar包是必須添加的( 比3.x版本的多了好多呀):
意外發現在spatial目錄下已經包含有pg的驅動文件了，哈哈，考慮的果然周到:
1) pg 創建一個用戶反饋表(feedback);
orm框架連接數據庫都有兩種方式：code first和db first; db first 指提前建好數據庫表格，在code中寫好匹配的model類進行mapping,而code first指在代碼中配置好表格的相關字段信息,項目運行時，再由框架根據你的model類及配置，自動在數據庫執行表格的創建及修改操作;
如果你用db first的方式,可以用類似如下的sql語句在pg提前創建表格:
create table feedback
(
id serial not null primary key,
//serial 相當於mysql中的int auto_increment,實現的是自增長效果
username varchar(45) not null,
content varchar(200) not null,
sendtime timestamp not null
)
2)創建數據表Feedback對應的持久化類Feedback, 及持久化類Feedback對應的映射文件Feedback.hbm.xml。需要注意的是,該映射文件與對應的持久化類應該在同一目錄下。關鍵代碼如下：
/**
* 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;}
}
Feedback.java
<?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>反饋人</comment>
</column>
</property>
<property name="content" type="java.lang.String">
<column name="content" length="200" not-null="true">
<comment>反饋內容</comment>
</column>
</property>
<property name="sendTime" type="java.sql.Timestamp">
<column name="sendTime" length="19" not-null="false">
<comment>反饋時間</comment>
</column>
</property>
</class>
</hibernate-mapping>
Feedback.hbm.xml
3) 創建Hibernate的主配置文件src/hibernate.cfg.xml,該文件中存放著 數據庫連接驅動程序類、登陸數據庫的用戶名/密碼、映射實體類配置文件的位置...etc.
Hibernate在初始化時,會自動在classes路徑下尋找該主配置文件,並且讀取配置信息，用於後期的數據庫操作;
那麼問題就來了,hinernate.cfg.xml的格式是什麼呢?不要怕,你能想到的，官方也都考慮到了，直接在文件路徑下搜索，ctrl+C=>ctrl+V 就是這麼簡單;
打開文件如下,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>
<!-- 是否自動創建數據庫表 他主要有一下幾個值:validate:當sessionFactory創建時，
自動驗證或者schema定義導入數據庫。 create:每次啟動都drop掉原來的schema，創建新的。 create-drop:
當sessionFactory明確關閉時，drop掉schema。update(常用):如果沒有schema就創建，有就更新。 -->
<!--此處配置來實現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)編寫HibernateUtil.java,用於構建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 Hibernate
static{
try{
Configuration config=new Configuration().configure();
sessionFactory=config.buildSessionFactory();
}catch(Exception e){
String msg=e.getMessage();
e.printStackTrace();
System.out.println(msg);
}
}
//Start Session
public static Session openSession(){
return sessionFactory.openSession();
}
}
HibernateUtil.java
數據庫Feedback表的操作類FeedbackDaoImpl及接口IFeedbackDao定義：
package IDao;
import models.Feedback;
/**
* Created by c-yangx on 11/16/2016.
*/
public interface IFeedbackDao {
void save(Feedback item);
}
IFeedbackDao
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 {
@Override
public 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();
}
}
}
FeedbackDaoImpl.java
5)最後寫一個測試類Test
import dao.FeedbackDaoImpl;
import models.Feedback;
import java.sql.Timestamp;
/**
* Created by c-yangx on 11/16/2016.
*/
public class Test {
@org.junit.Test
public 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);
}
}
Test
項目啟動運行，遇到一些bug,一起做個記錄:
a)Error msg如下; 是配置的密碼有誤，干脆給數據庫加了一個新的role和密碼
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#connect
at 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)添加賬號之後，又遇到新的Bug,原來是忘了給賬號配置數據庫權限了，在pg端配置一下就ok了
org.hibernate.exception.SQLGrammarException: could not extract ResultSet
at 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
運行Test.java中的testSave方法,執行成功，再查看下數據庫，數據也已成功插入;
最後放一個項目結構圖：(說明一下，因為後續打算學習全部的ssh,所以用了個web項目)
樓主也是剛開始學習java中的ssh框架，所以後面也會繼續寫一些hibernate的crud,Spring及struct2的文章記錄自己的學習過程,並在最後整理成一個小系列.如果感興趣，歡迎大家關注;
大家有覺得可以優化的地方,也歡迎指正.
(...未完待續)
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