Spring、OSGi整合Hibernate 一

最新推荐文章于 2024-01-02 14:16:48 发布

最新推荐文章于 2024-01-02 14:16:48 发布 · 183 阅读

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#OSGI #Hibernate #Spring #Bean #SQL

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本文介绍了一种在OSGi环境中整合Hibernate的方法，通过自定义的Bundle实现了实体类的动态注册与SessionFactory的灵活管理。

   查询了很多网上的帖子，主流的整合方式大体为4种。前两种不必说了，没什么扩展性，不予考虑。第三种采用Eclipse-RegisterBuddy方式(官方的整合方式)和第四种则采用Eclipse插件的扩展点，这样种都不能脱离Equinox实现，最后还是决定用自己的一套方式。
        先来说说整合Hibernate的关键之处。其实用OSGi整合Hibernate很简单，但要通过Bundle方式做到可以扩展新的持久化层面的东西（比如添加新的表和操作）就比较费事了。因为Hibernate在初始化时根据注册的实体类创建SessionFactory，这样当有新的实体类添加进来时就要创建新的SessionFactory，这样系统中出现两个甚至多个SessionFatory会导致一系列的问题。显然整合Hibernate关键就是解决实体类注册与SessionFactory创建的问题。
      我的具体思路如下。
        首先将Hibernate单独多为一个Bundle（wanged_commons_hibernate）以便提供其他Bundle所需类包。
        然后建立一个用于提供实体注册接口的Bundle（wanged_core_persistent_entity_register），代码如下：

java 代码

package wanged.core.persistent.entity;
@SuppressWarnings("unchecked")
public interface EntityRegister {
/**
* 注册Hibernate的实体Class
* @return
*/
Class[] register();
}

建一个用来初始化SessionFactory和事务管理的Bundle（wanged_core_persistent），由于使用Spring提供的LocalSessionFactoryBean会有问题，所以我单独写了两个类。
类LocalSessionFactoryBean的代码：

java 代码

package wanged.core.persistent;
import java.util.HashMap;
import java.util.Properties;
import javax.sql.DataSource;
import org.hibernate.ConnectionReleaseMode;
import org.hibernate.HibernateException;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.cfg.Environment;
import org.springframework.jdbc.datasource.TransactionAwareDataSourceProxy;
import org.springframework.orm.hibernate3.AbstractSessionFactoryBean;
import org.springframework.orm.hibernate3.SpringSessionContext;
import org.springframework.orm.hibernate3.TransactionAwareDataSourceConnectionProvider;
import wanged.core.persistent.entity.EntityRegister;
@SuppressWarnings("unchecked")
public class LocalSessionFactoryBean extends AbstractSessionFactoryBean {
private static final ThreadLocal configTimeDataSourceHolder = new ThreadLocal();
private Properties hibernateProperties;
private HashMapnew HashMap
private Configuration configuration;
public static DataSource getConfigTimeDataSource() {
return (DataSource) configTimeDataSourceHolder.get();
}
/**
* 注册Entity的Class数组
*
* @param er
*/
@SuppressWarnings("unchecked")
public void setEntityRegister(EntityRegister[] erArr) {
for (EntityRegister er : erArr) {
this.addEntityRegister(er);
}
}
@SuppressWarnings("unchecked")
public void setEntityRegister(EntityRegister er) {
this.addEntityRegister(er);
}
private void addEntityRegister(EntityRegister er){
// TODO:对registerClass()中取得的数组进行验证
this.entityClasses.put(er, er.register());
}
/**
* 卸载Entity的Class数组
*
* @param er
*/
public void unsetEntityRegister(EntityRegister er) {
this.entityClasses.remove(er);
// TODO:重新初始化SessionFactory
}
public void setHibernateProperties(Properties hibernateProperties) {
this.hibernateProperties = hibernateProperties;
}
public Properties getHibernateProperties() {
if (this.hibernateProperties == null) {
this.hibernateProperties = new Properties();
}
return this.hibernateProperties;
}
@SuppressWarnings("unchecked")
protected SessionFactory buildSessionFactory() {
Configuration config = new Configuration();
DataSource dataSource = getDataSource();
if (dataSource != null) {
configTimeDataSourceHolder.set(dataSource);
}
try {
config.setProperty(Environment.RELEASE_CONNECTIONS, ConnectionReleaseMode.ON_CLOSE.toString());
if (isExposeTransactionAwareSessionFactory()) {
config.setProperty(Environment.CURRENT_SESSION_CONTEXT_CLASS, SpringSessionContext.class.getName());
}
if (this.hibernateProperties != null) {
config.addProperties(this.hibernateProperties);
}
if (dataSource != null) {
boolean actuallyTransactionAware = (isUseTransactionAwareDataSource() || dataSource instanceof TransactionAwareDataSourceProxy);
config.setProperty(Environment.CONNECTION_PROVIDER, actuallyTransactionAware ? TransactionAwareDataSourceConnectionProvider.class
.getName() : LocalDataSourceConnectionProvider.class.getName());
}
// 添加Entity的类
for (Class[] cArr : this.entityClasses.values()) {
for (Class c : cArr) {
config.addClass(c);
}
}
this.configuration = config;
return config.buildSessionFactory();
} finally {
if (dataSource != null) {
configTimeDataSourceHolder.set(null);
}
}
}
/**
* Return the Configuration object used to build the SessionFactory. Allows
* access to configuration metadata stored there (rarely needed).
*
* @throws IllegalStateException
* if the Configuration object has not been initialized yet
*/
public final Configuration getConfiguration() {
if (this.configuration == null) {
throw new IllegalStateException("Configuration not initialized yet");
}
return this.configuration;
}
public void destroy() throws HibernateException {
DataSource dataSource = getDataSource();
if (dataSource != null) {
configTimeDataSourceHolder.set(dataSource);
}
try {
super.destroy();
} finally {
if (dataSource != null) {
configTimeDataSourceHolder.set(null);
}
}
}
}

类LocalDataSourceConnectionProvider的代码：

java 代码

package wanged.core.persistent;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;
import javax.sql.DataSource;
import org.hibernate.HibernateException;
import org.hibernate.connection.ConnectionProvider;
import org.hibernate.util.JDBCExceptionReporter;
public class LocalDataSourceConnectionProvider implements ConnectionProvider {
private DataSource dataSource;
private DataSource dataSourceToUse;
public void configure(Properties props) throws HibernateException {
this.dataSource = LocalSessionFactoryBean.getConfigTimeDataSource();
if (this.dataSource == null) {
throw new HibernateException("No local DataSource found for configuration - " +
"dataSource property must be set on LocalSessionFactoryBean");
}
this.dataSourceToUse = getDataSourceToUse(this.dataSource);
}
protected DataSource getDataSourceToUse(DataSource originalDataSource) {
return originalDataSource;
}
public DataSource getDataSource() {
return dataSource;
}
public Connection getConnection() throws SQLException {
try {
return this.dataSourceToUse.getConnection();
}
catch (SQLException ex) {
JDBCExceptionReporter.logExceptions(ex);
throw ex;
}
}
public void closeConnection(Connection con) throws SQLException {
try {
con.close();
}
catch (SQLException ex) {
JDBCExceptionReporter.logExceptions(ex);
throw ex;
}
}
public void close() {
}
public boolean supportsAggressiveRelease() {
return false;
}
}

如果你对比其与Spring提供的同名类中的代码，相差不大。
下面来看看配置文件，我把Bean的初始化放在bean.xml中：

xml 代码

<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="org.gjt.mm.mysql.Driver" />
<property name="url" value="jdbc:mysql://localhost:3306/cms" />
<property name="username" value="root" />
<property name="password" value="root" />
<property name="connectionProperties">
<props>
<prop key="useUnicode">true</prop>
<prop key="characterEncoding">GBK</prop>
</props>
</property>
</bean>
<bean id="sessionFactory" class="wanged.core.persistent.LocalSessionFactoryBean">
<property name="hibernateProperties">
<props>
<prop key="hibernate.dialect">org.hibernate.dialect.MySQLDialect</prop>
<prop key="hibernate.show_sql">false</prop>
<prop key="hibernate.cache.use_query_cache">true</prop>
<prop key="hibernate.jdbc.batch_size">20</prop>
</props>
</property>
<property name="dataSource" ref="dataSource" />
<property name="entityRegister" ref="entityRegister" />
</bean>
<bean id="txManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager">
<property name="sessionFactory" ref="sessionFactory" />
</bean>

而服务与引用的声明放在osgi-service.xml中：

xml 代码

<osgi:reference id="entityRegister" interface="wanged.core.persistent.entity.EntityRegister" cardinality="1..n"/>
<osgi:service interface="org.hibernate.SessionFactory" ref="sessionFactory" />
<osgi:service interface="org.springframework.transaction.PlatformTransactionManager" ref="txManager" />