向架构的阶梯攀爬: ibatis 多数据源(一)

在程序中需要连接多个数据源

解决方案有几个

使用ibatis自带的Dao Framework来构件

一个dao.xml对应多个sql-map-config.xml,但是对应一个数据源

sql-map-config1.xml:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE sqlMapConfig PUBLIC "-//ibatis.//DTD SQL Map Config 2.0//EN"
    "http://ibatis./dtd/sql-map-config-2.dtd">
<sqlMapConfig>
 <properties resource="properties/database.properties" />
 <transactionManager type="JDBC">
  <dataSource type="SIMPLE">
   <property value="${driver1}" name="JDBC.Driver" />
   <property value="${url1}" name="JDBC.ConnectionURL" />
   <property value="${username1}" name="JDBC.Username" />
   <property value="${password1}" name="JDBC.Password" />
  </dataSource>
 </transactionManager> 
 <sqlMap resource="com/ibatis/nicholas/persistence/sqlmap/User.xml" />
</sqlMapConfig>

sql-map-config2.xml:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE sqlMapConfig PUBLIC "-//ibatis.//DTD SQL Map Config 2.0//EN"
    "http://ibatis./dtd/sql-map-config-2.dtd">
<sqlMapConfig>
 <properties resource="properties/database.properties" />
 <transactionManager type="JDBC">
  <dataSource type="SIMPLE">
   <property value="${driver2}" name="JDBC.Driver" />
   <property value="${url2}" name="JDBC.ConnectionURL" />
   <property value="${username2}" name="JDBC.Username" />
   <property value="${password2}" name="JDBC.Password" />
  </dataSource>
 </transactionManager>
 <sqlMap resource="com/ibatis/nicholas/persistence/sqlmap/User.xml" />
</sqlMapConfig>

dao1.xml:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE daoConfig
    PUBLIC "-//ibatis.//DTD DAO Configuration 2.0//EN"
    "http://ibatis./dtd/dao-2.dtd">
<daoConfig>
 <context>
  <transactionManager type="SQLMAP">
   <property name="SqlMapConfigResource"
    value="com/ibatis/nicholas/persistence/sqlmap/sql-map-config1.xml" />
  </transactionManager>
  <dao interface="com.ibatis.nicholas.persistence.dao.UserDao"
   implementation="com.ibatis.nicholas.persistence.daoimpl.UserDaoImpl" />
 </context>
</daoConfig>

dao2.xml:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE daoConfig
    PUBLIC "-//ibatis.//DTD DAO Configuration 2.0//EN"
    "http://ibatis./dtd/dao-2.dtd">
<daoConfig>
 <context>
  <transactionManager type="SQLMAP">
   <property name="SqlMapConfigResource"
    value="com/ibatis/nicholas/persistence/sqlmap/sql-map-config2.xml" />
  </transactionManager>
  <dao interface="com.ibatis.nicholas.persistence.dao.UserDao"
   implementation="com.ibatis.nicholas.persistence.daoimpl.UserDaoImpl" />
 </context>
</daoConfig>

DaoConfig.java:

import com.ibatis.common.resources.Resources;
import com.ibatis.dao.client.DaoManager;
import com.ibatis.dao.client.DaoManagerBuilder;
import java.io.Reader;
import java.util.Properties;
public class DaoConfig {
 private static final String resource1 = "com/ibatis/nicholas/persistence/dao1.xml";
 private static final String resource2 = "com/ibatis/nicholas/persistence/dao1.xml";
 private static final DaoManager daoManager1;
 private static final DaoManager daoManager2;
 static {
  try {
   daoManager1 = newDaoManager1(null);
   daoManager2 = newDaoManager2(null);
   Properties props = Resources
     .getResourceAsProperties("properties/database.properties");
  } catch (Exception e) {
   throw new RuntimeException("Description.  Cause: " + e, e);
  }
 }
 public static DaoManager getDaoManager1() {
  return daoManager1;
 }
 public static DaoManager getDaoManager2() {
  return daoManager2;
 }
 public static DaoManager newDaoManager1(Properties props) {
  try {
   Reader reader = Resources.getResourceAsReader(resource1);
   return DaoManagerBuilder.buildDaoManager(reader, props);
  } catch (Exception e) {
   throw new RuntimeException(
     "Could not initialize DaoConfig.  Cause: " + e, e);
  }
 }
 public static DaoManager newDaoManager2(Properties props) {
  try {
   Reader reader = Resources.getResourceAsReader(resource2);
   return DaoManagerBuilder.buildDaoManager(reader, props);
  } catch (Exception e) {
   throw new RuntimeException(
     "Could not initialize DaoConfig.  Cause: " + e, e);
  }
 }
}

然后在你的service中通过DaoConfig.java来取到相对应的daoManager...
实现多数据源

不过ibatis已经停止对DaoFramework的更新，并且建议我们使用spring的daoframework，所以下一篇将是将ibatis和spring的结合。