JBOSS动态创建数据源

前段时间让研究如何动态创建数据源，关于这个我们讨论出有两种方案，一种是将数据源放到persistence.xml文件中，然后在persistence.xml中动态添加节点，代码中根据不同的unitname创建不同的entitymanager。一种是数据源放到JBOSS里，通过JBOSS的api动态添加数据源节点，然后在persistence.xml中动态添加节点，代码中根据不同的unitname创建不同的entitymanager。

方案一：1.将在JBOSS里的数据源连接放到persistence.xml文件中

<persistence-unit name="itoo_xiaozuo3" transaction-type="RESOURCE_LOCAL">
    <provider>org.hibernate.ejb.HibernatePersistence</provider>  
    <properties>
      <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5Dialect"/>
      <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>
      <property name="hibernate.connection.username" value="root"/>
      <property name="hibernate.connection.password" value="123456"/>
      <property name="hibernate.connection.url" value="jdbc:mysql://192.168.**.**:3306/itoo_xiaozuo3?useUnicode=true&amp;characterEncoding=UTF-8"/>
      <property name="hibernate.max_fetch_depth" value="3"/>
      <property name="hibernate.show_sql" value="true"/>
      <property name="hibernate.hbm2ddl.auto" value="update"/>
    </properties>
  </persistence-unit>

2.通过dom4j在persistence.xml文件中在添加一套节点

/**
	 * 操作dom4j创建xml数据源
	 *
	 * @param name 持久化名称 数据库名称
	 * @throws DocumentException 异常
	 * @throws IOException 异常
	 */
	public boolean AddDataSourceXml(String name) throws DocumentException, IOException{
		boolean flag=false;
		
		try {
			String filepath = "D:/9gxpt/app/database.test/src/main/resources/META-INF/persistence.xml"; 
			Document doc=new SAXReader().read(new File(filepath));
			Element root=doc.getRootElement();
			System.out.println(root);

			Element clazz=root.addElement("persistence-unit");
			//实体单元名称
			clazz.addAttribute("name", name);
			clazz.addAttribute("transaction-type", "RESOURCE_LOCAL");

			Element provider=clazz.addElement("provider"); 
			provider.setText("org.hibernate.ejb.HibernatePersistence");

			Element properties = clazz.addElement("properties");
			Element property1=properties.addElement("property");
			property1.addAttribute("name", "hibernate.dialect"); 
			property1.addAttribute("value", "org.hibernate.dialect.MySQL5Dialect");

			Element property2=properties.addElement("property");
			property2.addAttribute("name", "hibernate.connection.driver_class"); 
			property2.addAttribute("value", "com.mysql.jdbc.Driver");

			Element property3=properties.addElement("property");
			property3.addAttribute("name", "hibernate.connection.username"); 
			property3.addAttribute("value", "root");

			Element property4=properties.addElement("property");
			property4.addAttribute("name", "hibernate.connection.password"); 
			property4.addAttribute("value", "123456");

			//数据库名称
			Element property5=properties.addElement("property");
			property5.addAttribute("name", "hibernate.connection.url"); 
			property5.addAttribute("value", "jdbc:mysql://192.168.24.46:3306/"+name+"?useUnicode=true&characterEncoding=UTF-8");

			Element property6=properties.addElement("property");
			property6.addAttribute("name", "hibernate.max_fetch_depth"); 
			property6.addAttribute("value", "3");

			Element property7=properties.addElement("property");
			property7.addAttribute("name", "hibernate.show_sql"); 
			property7.addAttribute("value", "true");

			Element property8=properties.addElement("property");
			property8.addAttribute("name", "hibernate.hbm2ddl.auto"); 
			property8.addAttribute("value", "update");

			XMLWriter writer = new XMLWriter(new FileWriter(filepath));
			writer.write(doc); 
			writer.close(); 
			
			flag=true;
		} catch (Exception e) {
			System.out.println(e);
		}
		return flag;

	}

3.将添加的节点格式化,为什么有这一步呢，是因为上面添加的xml节点，jboss不重启情况下不识别，但是不管对该xml文件做任何操作之后就可以读取出来了。

public boolean FormatXml() throws DocumentException, IOException {
		boolean flag = false;
		String filename = "D:/9gxpt/app/database.test/src/main/resources/META-INF/persistence.xml"; 

		try {
			SAXReader saxReader = new SAXReader();
			Document document = saxReader.read(new File(filename));
			XMLWriter writer = null;
			/** 格式化输出,类型IE浏览一样 */
			OutputFormat format = OutputFormat.createPrettyPrint();
			/** 指定XML编码 */
			format.setEncoding("UTF-8");
			writer = new XMLWriter(new FileWriter(new File(filename)), format);
			writer.write(document);
			writer.close();

			/** 执行成功,需返回true */

			flag = true;
		} catch (Exception ex) {
			ex.printStackTrace();

		}

		return flag;
	}

4.创建数据库，切换数据库。切换数据库就是从persistence.xml文件里读取刚添加的unit单元，create一个entitymanager就行。

/**
	 * 创建数据库
	 *
	 * @param name
	 * @return
	 */
	public boolean CreateDataBase(String name){
		boolean flag=false;
		
		try {
			EntityManagerFactory factory=Persistence.createEntityManagerFactory(a); 
			
			EntityManager em = factory.createEntityManager();
			String sql="create database if not exists `"+name+"` ";
			em.getTransaction().begin();
			 
			Query query=em.createNativeQuery(sql);
			query.executeUpdate();
			
			em.getTransaction().commit();
			em.close();
			System.out.println("数据库创建成功！");
			flag=true;
		} catch (Exception e) {
			e.printStackTrace();
		}
	
		return flag;
	
	}
/**
	 * 切换数据库
	 *
	 * @param name
	 * @return
	 */
	public boolean SwitchDataSource(String name){
		boolean flag=false;
		try {
			EntityManagerFactory factory1=Persistence.createEntityManagerFactory(name); 
			EntityManager em1 = factory1.createEntityManager();
			em1.getTransaction().begin();
			 String sql1="create table blog_user( user_name char(15) not null check(user_name !=''),user_password char(15) not null, user_emial varchar(20) not null unique, primary key(user_name) )";
			Query query1=em1.createNativeQuery(sql1);
			query1.executeUpdate();  
			
			em1.getTransaction().commit();
			em1.close();
			
			flag = true;  
		} catch (Exception e) {
			e.printStackTrace();
		}

		return flag;
	}

总结，方案一就是往persistence.xml文件里创建了一套数据库连接节点，然后用SQL语句创建数据库，接着创建一个entitymanager。虽然效果达到了，但是容器事务就不能保证了。