Spring、OSGi整合Hibernate 一

         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

<!-- 本地调试使用连接池-->
  <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>

  <!-- 服务实现类定义 -->
  <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" />

这里的 引用 "实体注册" 服务需要在我们的实体Bundle中实现，现在已经搭好了架子，下一步就需要创建自己的实体Bundle和数据库操作的Bundle。由于这个Blog保存时经常保存不住，需要重写，所以我尽可能的将其划分开来写。