9月份参加软件架构师大会,京东老师提到了他们解决数据库水平切分用的mybatis拦截器来实现,目前所做的项目用的是mybatis,而恰好也需要这个功能,研究了下基本实现了拦截器根据配置自动切分数据表来进行访问。新老代码的改造很简单,加几个配置即可。
一、具体使用配置
1.1、拦截器配置
<plugins>
<plugin interceptor="com.wagcy.plugin.mybatis.TableSegInterceptor"></plugin>
</plugins>
如果是与spring集成,则配置如下 <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="dataSource" ref="dataSource" />
<property name="plugins">
<array>
<bean id="tableSegInterceptor" class="com.vrv.im.plugin.mybatis.TableSegInterceptor"/>
</array>
</property>
</bean>
1.2、切分配置
@TableSeg(tableName="Blog",shardType="%5",shardBy="id")
public interface BlogMapper {
Blog selectBlog(int id);
Blog selectBlogByObj(Blog blog);
Blog selectBlogByMap(Map map);
}
tableName分表表名 ;shardType切分类型,如%5:取模,表示取5余数;shardType:切分字段。这里只是做了项目中用到最多的切分方式-取模,可以根据需要扩展。二、实现代码
2.1、拦截器实现
@Intercepts({ @Signature(type = StatementHandler.class, method = "prepare", args = { Connection.class }) })
public class TableSegInterceptor implements Interceptor {
private static final String tag = TableSegInterceptor.class.getName();
private static final ObjectFactory DEFAULT_OBJECT_FACTORY = new DefaultObjectFactory();
private static final ObjectWrapperFactory DEFAULT_OBJECT_WRAPPER_FACTORY = new DefaultObjectWrapperFactory();
@Override
public Object intercept(Invocation invocation) throws Throwable {
StatementHandler statementHandler = (StatementHandler) invocation
.getTarget();
MetaObject metaStatementHandler = MetaObject.forObject(
statementHandler, DEFAULT_OBJECT_FACTORY,
DEFAULT_OBJECT_WRAPPER_FACTORY);
String originalSql = (String) metaStatementHandler
.getValue("delegate.boundSql.sql");
BoundSql boundSql = (BoundSql) metaStatementHandler
.getValue("delegate.boundSql");
//Configuration configuration = (Configuration) metaStatementHandler
//.getValue("delegate.configuration");
Object parameterObject = metaStatementHandler
.getValue("delegate.boundSql.parameterObject");
if (originalSql!=null&&!originalSql.equals("")) {
MappedStatement mappedStatement = (MappedStatement) metaStatementHandler
.getValue("delegate.mappedStatement");
String id = mappedStatement.getId();
String className = id.substring(0, id.lastIndexOf("."));
Class<?> classObj = Class.forName(className);
//根据配置自动生成分表SQL
TableSeg tableSeg = classObj.getAnnotation(TableSeg.class);
if(tableSeg!=null){
AnalyzeActualSql as = new AnalyzeActualSqlImpl(mappedStatement, parameterObject, boundSql);
String newSql=as.getActualSql(originalSql, tableSeg);
if(newSql!=null){
LogUtil.d(tag,"分表后SQL =====>"+ newSql);
metaStatementHandler.setValue("delegate.boundSql.sql", newSql);
}
}
}
// 传递给下一个拦截器处理
return invocation.proceed();
}
@Override
public Object plugin(Object target) {
// 当目标类是StatementHandler类型时,才包装目标类,否者直接返回目标本身,减少目标被代理的
// 次数
if (target instanceof StatementHandler) {
return Plugin.wrap(target, this);
} else {
return target;
}
}
@Override
public void setProperties(Properties properties) {
// TODO Auto-generated method stub
}
2.2、切分策略解析
读取切分配置,可以根据自己的需要,扩展实现不同的切分策略。主要逻辑就是读取切分字段值,然后根据切分策略,得出切分后表的扩展名。2.3、切分字段值获取
/**
* 获取字段值
*
* @param propertyName
* @param isMutiPara
* @return
*/
public Object getFieldValue(String propertyName,boolean isMutiPara) {
MetaObject metaObject = parameterObject == null ? null : configuration
.newMetaObject(parameterObject);
Object value;
if (boundSql.hasAdditionalParameter(propertyName)) { // issue #448 ask first for additional params
value = boundSql.getAdditionalParameter(propertyName);
} else if (parameterObject == null) {
value = null;
} else if (typeHandlerRegistry.hasTypeHandler(parameterObject
.getClass())) {
if(isMutiPara)//多个参数,这情况就不应该匹配了
return null;
value = parameterObject;
} else {
value = metaObject == null ? null : metaObject
.getValue(propertyName);
}
return value;
}
2.4、切分配置
@Target({ ElementType.TYPE })
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @interface TableSeg {
/**
* 表名
* @return
*/
public String tableName();
/**
* 分表方式,取模,如%5:表示取5余数,
* 如果不设置,直接根据shardBy值分表
* @return
*/
public String shardType();
/**
* 根据什么字段分表
* 多个字段用数学表达表示,如a+b a-b
* @return
*/
public String shardBy();
}