玩耍Hibernate系列(一)--基础知识
Hibernate框架介绍：
Hibernate ORM 主要用于持久化对象（最常用的框架）
Hibernate Search 用于对对象进行搜索，底层基于Apache Lucene做的
Hibernate Validator 用于进行校验
Hibernate OGM 用于Nosql的持久化
Hibernate Tools 是一款基于Eclipse的插件，用于快捷生成xxx.hbm.xml以及hibernate配置文件等
Hibernate产生的背景
在最古老的编程模式还没出现的时候，程序猿会把所有的内容都写在一起，比如一个jsp文件，既有前台页面又有后台逻辑，甚至数据查询，对于开发者而言，苦不堪言，这样分层的架构应运而生
通常的web应用都会采用后者的模型来设计，展现层用于显示页面以及用户的交互，比如Struts，webwork,springmvc等，业务逻辑层用于对业务逻辑进行处理，这里负责复杂的逻辑设计，数据层用于与数据库进行交互。
经过这样的一个演变，层次化区分清晰了，但是编程却比较痛苦。
业务逻辑或者前台数据都是存储在内存中的，如果想要存储在数据库中，需要进行复杂的处理。比如JDBC来说，需要加载驱动，申请链接，创建执行计划，最后还要不断的释放，操作数据经常变动，就要经常性的进行上述的处理，而且，内存中的数据，有可能因为断电或者关机没来得及存储，导致丢失。
在这种情况下，持久化应运而生，一方面负责把内存中的对象，随时的与本地文件或者数据库存储关联，另一方面帮助管理JDBC连接，避免每次复杂的操作。
Hibernate入门使用
Hibernate跟JDBC一样需要进行一些操作步骤：
1） 创建Configuration对象，配置Hibernate
2） 创建SessionFactory，初始化Hibernate，这个SessionFactory是重量级的，也就是说一个应用可以用这一个SessionFactory，因为SessionFactory通常作为缓存存储了实体对象的关系映射，因此进来不要频繁的申请释放SessionFactory
3）Session，保存更新删除加载查询对象，这个session就是一个相对轻量级的了，而且不是线程安全的，所以每次结束操作之后应该释放
4）Transaction，用于事务管理
5）Query，Criteria，用于进行Hql等的查询
Eclipse在线安装使用Hibernate Tools
在Eclipse的Help-->Install new Software
点击Add,输入下面网址：http://download.jboss.org/jbosstools/updates/stable/
点击OK
查找Jboss tools里面，点击Hibernate Tools下载即可。
Hibernate用的包及作用
最小量的hibernate，需要以下几个jar包：
hibernate.jar_hibernate核心包
actlr.jar_hql语法解析
asm.jar _ 字节码相关
cglib.jar _ 生成实体对象相关
commons-logging.jar _ 日志相关
dom4j.jar _ 解析xml
commons-collections.jar _ 集合框架
jta.jar _ 事务相关
antlr.jar
JPA标准中，面向对象的语法检查、识别。语法分析生成器，转换hql语法。如果没有此包 hql会出错。比如from com.person --> select * from PERSON;
如果没有这个jar包，会报错：
Exception in thread "main" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ java.lang.NoClassDefFoundError: antlr/ANTLRException at org.hibernate.hql.ast.ASTQueryTranslatorFactory.createQueryTranslator(ASTQueryTranslatorFactory.java:35) at org.hibernate.engine.query.HQLQueryPlan.<init>(HQLQueryPlan.java:74) at org.hibernate.engine.query.HQLQueryPlan.<init>(HQLQueryPlan.java:56) at org.hibernate.engine.query.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:72) at org.hibernate.impl.AbstractSessionImpl.getHQLQueryPlan(AbstractSessionImpl.java:133) at org.hibernate.impl.AbstractSessionImpl.createQuery(AbstractSessionImpl.java:112) at org.hibernate.impl.SessionImpl.createQuery(SessionImpl.java:1623) at com.test.orm.Service.findAll(Service.java:37) at com.test.orm.Service.main(Service.java:23) Caused by: java.lang.ClassNotFoundException: antlr.ANTLRException at java.net.URLClassLoader$1.run(URLClassLoader.java:202) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:190) at java.lang.ClassLoader.loadClass(ClassLoader.java:306) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) at java.lang.ClassLoader.loadClass(ClassLoader.java:247) ... 9 more
asm.jar
与字节码操作有关
如果没有这个jar包会报错
java.lang.NoClassDefFoundError: org/objectweb/asm/Type at net.sf.cglib.core.TypeUtils.parseType(TypeUtils.java:180) at net.sf.cglib.core.KeyFactory.<clinit>(KeyFactory.java:66) at net.sf.cglib.proxy.Enhancer.<clinit>(Enhancer.java:69) at org.hibernate.proxy.pojo.cglib.CGLIBLazyInitializer.getProxyFactory(CGLIBLazyInitializer.java:117) at org.hibernate.proxy.pojo.cglib.CGLIBProxyFactory.postInstantiate(CGLIBProxyFactory.java:43) at org.hibernate.tuple.entity.PojoEntityTuplizer.buildProxyFactory(PojoEntityTuplizer.java:162) at org.hibernate.tuple.entity.AbstractEntityTuplizer.<init>(AbstractEntityTuplizer.java:135) at org.hibernate.tuple.entity.PojoEntityTuplizer.<init>(PojoEntityTuplizer.java:55) at org.hibernate.tuple.entity.EntityEntityModeToTuplizerMapping.<init>(EntityEntityModeToTuplizerMapping.java:56) at org.hibernate.tuple.entity.EntityMetamodel.<init>(EntityMetamodel.java:295) at org.hibernate.persister.entity.AbstractEntityPersister.<init>(AbstractEntityPersister.java:434) at org.hibernate.persister.entity.SingleTableEntityPersister.<init>(SingleTableEntityPersister.java:109) at org.hibernate.persister.PersisterFactory.createClassPersister(PersisterFactory.java:55) at org.hibernate.impl.SessionFactoryImpl.<init>(SessionFactoryImpl.java:226) at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1294) at com.test.orm.Service.<clinit>(Service.java:16) Caused by: java.lang.ClassNotFoundException: org.objectweb.asm.Type at java.net.URLClassLoader$1.run(URLClassLoader.java:202) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:190) at java.lang.ClassLoader.loadClass(ClassLoader.java:306) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) at java.lang.ClassLoader.loadClass(ClassLoader.java:247) ... 16 more Exception in thread "main"
cglib.jar
实现持久化对象的字节码生成，用于生成code的类库
如果没有这个jar包，会报错
java.lang.NoClassDefFoundError: net/sf/cglib/proxy/CallbackFilter at org.hibernate.bytecode.cglib.BytecodeProviderImpl.getProxyFactoryFactory(BytecodeProviderImpl.java:33) at org.hibernate.tuple.entity.PojoEntityTuplizer.buildProxyFactoryInternal(PojoEntityTuplizer.java:182) at org.hibernate.tuple.entity.PojoEntityTuplizer.buildProxyFactory(PojoEntityTuplizer.java:160) at org.hibernate.tuple.entity.AbstractEntityTuplizer.<init>(AbstractEntityTuplizer.java:135) at org.hibernate.tuple.entity.PojoEntityTuplizer.<init>(PojoEntityTuplizer.java:55) at org.hibernate.tuple.entity.EntityEntityModeToTuplizerMapping.<init>(EntityEntityModeToTuplizerMapping.java:56) at org.hibernate.tuple.entity.EntityMetamodel.<init>(EntityMetamodel.java:295) at org.hibernate.persister.entity.AbstractEntityPersister.<init>(AbstractEntityPersister.java:434) at org.hibernate.persister.entity.SingleTableEntityPersister.<init>(SingleTableEntityPersister.java:109) at org.hibernate.persister.PersisterFactory.createClassPersister(PersisterFactory.java:55) at org.hibernate.impl.SessionFactoryImpl.<init>(SessionFactoryImpl.java:226) at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1294) at com.test.orm.Service.<clinit>(Service.java:16) Caused by: java.lang.ClassNotFoundException: net.sf.cglib.proxy.CallbackFilter at java.net.URLClassLoader$1.run(URLClassLoader.java:202) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:190) at java.lang.ClassLoader.loadClass(ClassLoader.java:306) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) at java.lang.ClassLoader.loadClass(ClassLoader.java:247) ... 13 more Exception in thread "main"
commons-logging.jar
Apache标准日志接口
如果没有这个jar包，会报错
java.lang.NoClassDefFoundError: org/apache/commons/logging/LogFactory at org.hibernate.cfg.Configuration.<clinit>(Configuration.java:120) at com.test.orm.Service.<clinit>(Service.java:14) Caused by: java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory at java.net.URLClassLoader$1.run(URLClassLoader.java:202) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:190) at java.lang.ClassLoader.loadClass(ClassLoader.java:306) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) at java.lang.ClassLoader.loadClass(ClassLoader.java:247) ... 2 more Exception in thread "main"
dom4j.jar
解析读取xml
如果没有这个jar包，会报错
java.lang.NoClassDefFoundError: org/dom4j/DocumentException at com.test.orm.Service.<clinit>(Service.java:14) Caused by: java.lang.ClassNotFoundException: org.dom4j.DocumentException at java.net.URLClassLoader$1.run(URLClassLoader.java:202) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:190) at java.lang.ClassLoader.loadClass(ClassLoader.java:306) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) at java.lang.ClassLoader.loadClass(ClassLoader.java:247) ... 1 more Exception in thread "main"
commons-collections.jar
集合与数据结构的增强包。Apache的集合框架，比jdk的功能完善。
如果没有这个jar包，会报错
java.lang.NoClassDefFoundError: org/apache/commons/collections/SequencedHashMap at org.hibernate.mapping.Table.<init>(Table.java:33) at org.hibernate.cfg.Mappings.addTable(Mappings.java:165) at org.hibernate.cfg.HbmBinder.bindRootPersistentClassCommonValues(HbmBinder.java:290) at org.hibernate.cfg.HbmBinder.bindRootClass(HbmBinder.java:273) at org.hibernate.cfg.HbmBinder.bindRoot(HbmBinder.java:144) at org.hibernate.cfg.Configuration.add(Configuration.java:669) at org.hibernate.cfg.Configuration.addInputStream(Configuration.java:504) at org.hibernate.cfg.Configuration.addResource(Configuration.java:536) at org.hibernate.cfg.Configuration.addClass(Configuration.java:586) at com.test.orm.Service.<clinit>(Service.java:15) Caused by: java.lang.ClassNotFoundException: org.apache.commons.collections.SequencedHashMap at java.net.URLClassLoader$1.run(URLClassLoader.java:202) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:190) at java.lang.ClassLoader.loadClass(ClassLoader.java:306) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) at java.lang.ClassLoader.loadClass(ClassLoader.java:247) ... 10 more Exception in thread "main"
jta.jar
事务处理
如果没有这个jar包，会报错
log4j:WARN No appenders could be found for logger (org.hibernate.cfg.Environment). log4j:WARN Please initialize the log4j system properly. Exception in thread "main" java.lang.NoClassDefFoundError: javax/transaction/Synchronization at org.hibernate.impl.SessionImpl.<init>(SessionImpl.java:213) at org.hibernate.impl.SessionFactoryImpl.openSession(SessionFactoryImpl.java:473) at org.hibernate.impl.SessionFactoryImpl.openSession(SessionFactoryImpl.java:497) at org.hibernate.impl.SessionFactoryImpl.openSession(SessionFactoryImpl.java:505) at com.test.orm.Service.findAll(Service.java:34) at com.test.orm.Service.main(Service.java:26) Caused by: java.lang.ClassNotFoundException: javax.transaction.Synchronization at java.net.URLClassLoader$1.run(URLClassLoader.java:202) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:190) at java.lang.ClassLoader.loadClass(ClassLoader.java:306) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) at java.lang.ClassLoader.loadClass(ClassLoader.java:247) ... 6 more
