Shardbatis是在mybatis 2.3.5代码的基础上进行一些扩展实现数据水平切分功能。 数据的水平切分包括多数据库的切分和多表的数据切分。目前shardbatis已经实现了单数据库的数据多表水平切分
mybatis2.3.5的核心类图（包含了spring对ibatis的封装SqlMapClientTemplate）如下（其他版本的ibatis的类图有略微不同）
改造后的类图
从这两张图上可以看出shardbatis里新增了接口SqlMapShardingExt，SqlMapShardingExt中具体的方法如下
public interface SqlMapShardingExt extends SqlMapExecutor{
/**
* 带有sharding功能的insert
* @param id
* @param parameterObject
* @param groups
* @return
* @throws SQLException
*/
Object insertWithSharding(String id, Object parameterObject,
ShardingFactorGroup... groups) throws SQLException;
/**
* 带有sharding功能的insert
* @param id
* @param groups
* @return
* @throws SQLException
*/
Object insertWithSharding(String id, ShardingFactorGroup... groups) throws SQLException;
/**
* 带有sharding功能的update
* @param id
* @param parameterObject
* @param groups
* @return
* @throws SQLException
*/
int updateWithSharding(String id, Object parameterObject, ShardingFactorGroup... groups)
throws SQLException;
/**
* 带有sharding功能的update
* @param id
* @param groups
* @return
* @throws SQLException
*/
int updateWithSharding(String id, ShardingFactorGroup... groups) throws SQLException;
/**
* 带有sharding功能的delete
* @param id
* @param parameterObject
* @param groups
* @return
* @throws SQLException
*/
int deleteWithSharding(String id, Object parameterObject, ShardingFactorGroup... groups)
throws SQLException;
/**
* 带有sharding功能的delete
* @param id
* @param groups
* @return
* @throws SQLException
*/
int deleteWithSharding(String id, ShardingFactorGroup... groups) throws SQLException;
/**
* 带有sharding功能的单记录查询
* @param id
* @param parameterObject
* @param groups
* @return
* @throws SQLException
*/
Object queryForObjectWithSharding(String id, Object parameterObject,
ShardingFactorGroup... groups) throws SQLException;
/**
* 带有sharding功能的单记录查询
* @param id
* @param groups
* @return
* @throws SQLException
*/
Object queryForObjectWithSharding(String id, ShardingFactorGroup... groups)
throws SQLException;
/**
* 带有sharding功能的单记录查询
* @param id
* @param parameterObject
* @param resultObject
* @param groups
* @return
* @throws SQLException
*/
Object queryForObjectWithSharding(String id, Object parameterObject,
Object resultObject, ShardingFactorGroup... groups)
throws SQLException;
/**
* 带有sharding功能的查询
* @param id
* @param parameterObject
* @param groups
* @return
* @throws SQLException
*/
List queryForListWithSharding(String id, Object parameterObject,
ShardingFactorGroup... groups) throws SQLException;
/**
* 带有sharding功能的查询
* @param id
* @param groups
* @return
* @throws SQLException
*/
List queryForListWithSharding(String id, ShardingFactorGroup... groups)
throws SQLException;
/**
* 带有sharding功能的查询
* @param id
* @param parameterObject
* @param skip
* @param max
* @param groups
* @return
* @throws SQLException
*/
List queryForListWithSharding(String id, Object parameterObject, int skip, int max,
ShardingFactorGroup... groups) throws SQLException;
/**
* 带有sharding功能的查询
* @param id
* @param skip
* @param max
* @param groups
* @return
* @throws SQLException
*/
List queryForListWithSharding(String id, int skip, int max,
ShardingFactorGroup... groups) throws SQLException;
/**
*
* @param id
* @param parameterObject
* @param rowHandler
* @param groups
* @throws SQLException
*/
void queryWithRowHandlerWithSharding(String id, Object parameterObject,
RowHandler rowHandler, ShardingFactorGroup... groups)
throws SQLException;
/**
*
* @param id
* @param rowHandler
* @param groups
* @throws SQLException
*/
void queryWithRowHandlerWithSharding(String id, RowHandler rowHandler,
ShardingFactorGroup... groups) throws SQLException;
/**
*
* @param id
* @param parameterObject
* @param keyProp
* @param groups
* @return
* @throws SQLException
*/
Map queryForMapWithSharding(String id, Object parameterObject, String keyProp,
ShardingFactorGroup... groups) throws SQLException;
/**
*
* @param id
* @param parameterObject
* @param keyProp
* @param valueProp
* @param groups
* @return
* @throws SQLException
*/
Map queryForMapWithSharding(String id, Object parameterObject, String keyProp,
String valueProp, ShardingFactorGroup... groups)
throws SQLException;
通过SqlMapClientImpl和SqlMapSessionImpl对SqlMapShardingExt的实现是的ibatis具有了DB sharding的功能，iBATIS会自动根据配置的或者是编码的sharding策略将原始的sql语句转变为对应目标表名的sql。
下面看一下如何在iBATIS中配置和使用sharding功能
1.配置sharding策略。在sql-map-config.xml中添加如下配置
<shardingConfig>
<!-- 对于app_test使用默认的切分策略,默认的切分策略只是简单按数值取模生成新的表名,如何实现切分策略后面再介绍 -->
<sharding tableName="app_test" strategyClass="com.ibatis.sqlmap.engine.sharding.impl.DefaultShardingStrategy"/>
<!-- 没有配置切分策略等于使用默认的切分策略 -->
<sharding tableName="app_2test" />
</shardingConfig>
这里再通过实例简单介绍一下使用DefaultShardingStrategy时对sql的convert结果
比如sqlmap中定义的原始sql为：
SELECT EMPLOYEEIDNO FROM mytable WHERE SALARY >= 50000
那经过convert后的结果将可能是
SELECT EMPLOYEEIDNO FROM mytable_1 WHERE SALARY >= 50000
又例如原始sql为
SELECT a.* FROM ANTIQUES a,ANTIQUEOWNERS b, mytable c where a.id=b.id and b.id=c.id
convert的结果可能为
SELECT a.* FROM ANTIQUES_0 AS a, ANTIQUEOWNERS_1 AS b, mytable_1 AS c WHERE a.id = b.id AND b.id = c.id
开始使用sharding api
public class SqlMapClientTest {
SqlMapClient sqlMapper;
@Before
public void init() {
Reader reader;
try {
reader = Resources.getResourceAsReader('sql-map-config.xml');
sqlMapper = SqlMapClientBuilder.buildSqlMapClient(reader);
reader.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
@Test
public void testSharding() throws Exception {
Map param = new HashMap();
param.put('cnt', 'ttt');
ShardingFactorGroup g = new ShardingFactorGroup();//ShardingFactorGroup为切分策略提供必要参数
g.setTableName('App_Test');//设置为哪张表配置切分策略
g.setParam(new Integer(123));//设置为切分策略提供参数
//这里还可以通过g.setShardingStrategy(...)来设置切分策略
//通过API配置的切分策略可以覆盖xml里配置的App_Test表的切分策略
Integer count = (Integer) sqlMapper.queryForObjectWithSharding(
'AppTest.select_paging_count_by_map', param, g);
Assert.assertEquals(count.toString(), '0');
}
@Test
public void testUpdate() throws SQLException {
ShardingFactorGroup g = new ShardingFactorGroup();
g.setTableName('App_Test');
g.setParam(new Integer(123));
String cnt = 'testUpdate' + System.currentTimeMillis();
AppTest at1 = new AppTest();
at1.setCnt(cnt);
Integer id = (Integer) sqlMapper.insertWithSharding(
'AppTest.insert_h2', at1, g);
AppTest parameterObject = new AppTest();
parameterObject.setCnt(cnt);
AppTest ret = (AppTest) sqlMapper.queryForObjectWithSharding(
'AppTest.select_by_condition', parameterObject, g);
Assert.assertEquals(ret.getId().toString(), id.toString());
ret.setCnt('NEW_CONTENT');
Integer count = sqlMapper.updateWithSharding('AppTest.update', ret, g);
Assert.assertEquals(count.toString(), '1');
count = (Integer) sqlMapper.queryForObjectWithSharding(
'AppTest.select_paging_count', ret, g);
Assert.assertEquals(count.toString(), '1');
}
@Test
public void testDelete() throws SQLException {
ShardingFactorGroup g = new ShardingFactorGroup();
g.setTableName('App_Test');
g.setParam(new Integer(123));
String cnt = 'testDelete' + System.currentTimeMillis();
AppTest at1 = new AppTest();
at1.setCnt(cnt);
Integer id = (Integer) sqlMapper.insertWithSharding(
'AppTest.insert_h2', at1, g);
AppTest parameterObject = new AppTest();
parameterObject.setCnt(cnt);
AppTest ret = (AppTest) sqlMapper.queryForObjectWithSharding(
'AppTest.select_by_condition', parameterObject, g);
Assert.assertEquals(ret.getId().toString(), id.toString());
Integer row = sqlMapper.deleteWithSharding('AppTest.delete', ret, g);
Assert.assertEquals(row.toString(), '1');
}
}
实现自己的sharding策略,只要实现一个简单的接口即可
public interface ShardingStrategy {
/**
* 计算得到新的表名
* @param baseTableName 逻辑表名
* @param params 为sharding逻辑提供必要参数
* @return
*/
public String getTargetTableName(String baseTableName,Object params);
}
关于shardbatis在spring中的使用方法，以及一些使用注意事项和性能测试结果请大家移步到项目主页http://code.google.com/p/shardbatis/上查看
作者: SeanHe
声明: 本文系JavaEye网站发布的原创文章，未经作者书面许可，严禁任何网站转载本文，否则必将追究法律责任！
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