在Spring项目中使用 Mybatis 如何实现动态切换数据源

发布时间：2020-11-17 16:20:11

来源：亿速云

阅读：108

作者：Leah

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实现思路是：

第一步，实现动态切换数据源：配置两个DataSource，配置两个SqlSessionFactory指向两个不同的DataSource，两个SqlSessionFactory都用一个SqlSessionTemplate，同时重写Mybatis提供的SqlSessionTemplate类，最后配置Mybatis自动扫描。

第二步，利用aop切面，拦截dao层所有方法，因为dao层方法命名的特点，比如所有查询sql都是select开头，或者get开头等等，拦截这些方法，并把当前数据源切换至从库。

spring中配置如下：

主库数据源配置：

2

从库数据源配置：

主库SqlSessionFactory配置：

从库SqlSessionFactory配置：

两个SqlSessionFactory使用同一个SqlSessionTemplate配置：

配置Mybatis自动扫描dao

自己重写了SqlSessionTemplate代码如下：

package com.sincetimes.slg.framework.core;

import static java.lang.reflect.Proxy.newProxyInstance;

import static org.apache.ibatis.reflection.ExceptionUtil.unwrapThrowable;

import static org.mybatis.spring.SqlSessionUtils.closeSqlSession;

import static org.mybatis.spring.SqlSessionUtils.getSqlSession;

import static org.mybatis.spring.SqlSessionUtils.isSqlSessionTransactional;

import java.lang.reflect.InvocationHandler;

import java.lang.reflect.Method;

import java.sql.Connection;

import java.util.List;

import java.util.Map;

import org.apache.ibatis.exceptions.PersistenceException;

import org.apache.ibatis.executor.BatchResult;

import org.apache.ibatis.session.Configuration;

import org.apache.ibatis.session.ExecutorType;

import org.apache.ibatis.session.ResultHandler;

import org.apache.ibatis.session.RowBounds;

import org.apache.ibatis.session.SqlSession;

import org.apache.ibatis.session.SqlSessionFactory;

import org.mybatis.spring.MyBatisExceptionTranslator;

import org.mybatis.spring.SqlSessionTemplate;

import org.springframework.dao.support.PersistenceExceptionTranslator;

import org.springframework.util.Assert;

import com.sincetimes.slg.framework.util.SqlSessionContentHolder;

/**

*

* TODO 重写SqlSessionTemplate

* @author ccg

* @version 1.0

* Created 2017年4月21日 下午3:15:15

*/

public class DynamicSqlSessionTemplate extends SqlSessionTemplate {

private final SqlSessionFactory sqlSessionFactory;

private final ExecutorType executorType;

private final SqlSession sqlSessionProxy;

private final PersistenceExceptionTranslator exceptionTranslator;

private Map targetSqlSessionFactorys;

private SqlSessionFactory defaultTargetSqlSessionFactory;

public void setTargetSqlSessionFactorys(Map targetSqlSessionFactorys) {

this.targetSqlSessionFactorys = targetSqlSessionFactorys;

}

public Map getTargetSqlSessionFactorys(){

return targetSqlSessionFactorys;

}

public void setDefaultTargetSqlSessionFactory(SqlSessionFactory defaultTargetSqlSessionFactory) {

this.defaultTargetSqlSessionFactory = defaultTargetSqlSessionFactory;

}

public DynamicSqlSessionTemplate(SqlSessionFactory sqlSessionFactory) {

this(sqlSessionFactory, sqlSessionFactory.getConfiguration().getDefaultExecutorType());

}

public DynamicSqlSessionTemplate(SqlSessionFactory sqlSessionFactory, ExecutorType executorType) {

this(sqlSessionFactory, executorType, new MyBatisExceptionTranslator(sqlSessionFactory.getConfiguration()

.getEnvironment().getDataSource(), true));

}

public DynamicSqlSessionTemplate(SqlSessionFactory sqlSessionFactory, ExecutorType executorType,

PersistenceExceptionTranslator exceptionTranslator) {

super(sqlSessionFactory, executorType, exceptionTranslator);

this.sqlSessionFactory = sqlSessionFactory;

this.executorType = executorType;

this.exceptionTranslator = exceptionTranslator;

this.sqlSessionProxy = (SqlSession) newProxyInstance(

SqlSessionFactory.class.getClassLoader(),

new Class[] { SqlSession.class },

new SqlSessionInterceptor());

this.defaultTargetSqlSessionFactory = sqlSessionFactory;

}

@Override

public SqlSessionFactory getSqlSessionFactory() {

SqlSessionFactory targetSqlSessionFactory = targetSqlSessionFactorys.get(SqlSessionContentHolder.getContextType());

if (targetSqlSessionFactory != null) {

return targetSqlSessionFactory;

} else if (defaultTargetSqlSessionFactory != null) {

return defaultTargetSqlSessionFactory;

} else {

Assert.notNull(targetSqlSessionFactorys, "Property 'targetSqlSessionFactorys' or 'defaultTargetSqlSessionFactory' are required");

Assert.notNull(defaultTargetSqlSessionFactory, "Property 'defaultTargetSqlSessionFactory' or 'targetSqlSessionFactorys' are required");

}

return this.sqlSessionFactory;

}

@Override

public Configuration getConfiguration() {

return this.getSqlSessionFactory().getConfiguration();

}

public ExecutorType getExecutorType() {

return this.executorType;

}

public PersistenceExceptionTranslator getPersistenceExceptionTranslator() {

return this.exceptionTranslator;

}

/**

* {@inheritDoc}

*/

public T selectOne(String statement) {

return this.sqlSessionProxy. selectOne(statement);

}

/**

* {@inheritDoc}

*/

public T selectOne(String statement, Object parameter) {

return this.sqlSessionProxy. selectOne(statement, parameter);

}

/**

* {@inheritDoc}

*/

public Map selectMap(String statement, String mapKey) {

return this.sqlSessionProxy. selectMap(statement, mapKey);

}

/**

* {@inheritDoc}

*/

public Map selectMap(String statement, Object parameter, String mapKey) {

return this.sqlSessionProxy. selectMap(statement, parameter, mapKey);

}

/**

* {@inheritDoc}

*/

public Map selectMap(String statement, Object parameter, String mapKey, RowBounds rowBounds) {

return this.sqlSessionProxy. selectMap(statement, parameter, mapKey, rowBounds);

}

/**

* {@inheritDoc}

*/

public List selectList(String statement) {

return this.sqlSessionProxy. selectList(statement);

}

/**

* {@inheritDoc}

*/

public List selectList(String statement, Object parameter) {

return this.sqlSessionProxy. selectList(statement, parameter);

}

/**

* {@inheritDoc}

*/

public List selectList(String statement, Object parameter, RowBounds rowBounds) {

return this.sqlSessionProxy. selectList(statement, parameter, rowBounds);

}

/**

* {@inheritDoc}

*/

public void select(String statement, ResultHandler handler) {

this.sqlSessionProxy.select(statement, handler);

}

/**

* {@inheritDoc}

*/

public void select(String statement, Object parameter, ResultHandler handler) {

this.sqlSessionProxy.select(statement, parameter, handler);

}

/**

* {@inheritDoc}

*/

public void select(String statement, Object parameter, RowBounds rowBounds, ResultHandler handler) {

this.sqlSessionProxy.select(statement, parameter, rowBounds, handler);

}

/**

* {@inheritDoc}

*/

public int insert(String statement) {

return this.sqlSessionProxy.insert(statement);

}

/**

* {@inheritDoc}

*/

public int insert(String statement, Object parameter) {

return this.sqlSessionProxy.insert(statement, parameter);

}

/**

* {@inheritDoc}

*/

public int update(String statement) {

return this.sqlSessionProxy.update(statement);

}

/**

* {@inheritDoc}

*/

public int update(String statement, Object parameter) {

return this.sqlSessionProxy.update(statement, parameter);

}

/**

* {@inheritDoc}

*/

public int delete(String statement) {

return this.sqlSessionProxy.delete(statement);

}

/**

* {@inheritDoc}

*/

public int delete(String statement, Object parameter) {

return this.sqlSessionProxy.delete(statement, parameter);

}

/**

* {@inheritDoc}

*/

public T getMapper(Class type) {

return getConfiguration().getMapper(type, this);

}

/**

* {@inheritDoc}

*/

public void commit() {

throw new UnsupportedOperationException("Manual commit is not allowed over a Spring managed SqlSession");

}

/**

* {@inheritDoc}

*/

public void commit(boolean force) {

throw new UnsupportedOperationException("Manual commit is not allowed over a Spring managed SqlSession");

}

/**

* {@inheritDoc}

*/

public void rollback() {

throw new UnsupportedOperationException("Manual rollback is not allowed over a Spring managed SqlSession");

}

/**

* {@inheritDoc}

*/

public void rollback(boolean force) {

throw new UnsupportedOperationException("Manual rollback is not allowed over a Spring managed SqlSession");

}

/**

* {@inheritDoc}

*/

public void close() {

throw new UnsupportedOperationException("Manual close is not allowed over a Spring managed SqlSession");

}

/**

* {@inheritDoc}

*/

public void clearCache() {

this.sqlSessionProxy.clearCache();

}

/**

* {@inheritDoc}

*/

public Connection getConnection() {

return this.sqlSessionProxy.getConnection();

}

/**

* {@inheritDoc}

* @since 1.0.2

*/

public List flushStatements() {

return this.sqlSessionProxy.flushStatements();

}

/**

* Proxy needed to route MyBatis method calls to the proper SqlSession got from Spring's Transaction Manager It also

* unwraps exceptions thrown by {@code Method#invoke(Object, Object...)} to pass a {@code PersistenceException} to

* the {@code PersistenceExceptionTranslator}.

*/

private class SqlSessionInterceptor implements InvocationHandler {

public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {

final SqlSession sqlSession = getSqlSession(

DynamicSqlSessionTemplate.this.getSqlSessionFactory(),

DynamicSqlSessionTemplate.this.executorType,

DynamicSqlSessionTemplate.this.exceptionTranslator);

try {

Object result = method.invoke(sqlSession, args);

if (!isSqlSessionTransactional(sqlSession, DynamicSqlSessionTemplate.this.getSqlSessionFactory())) {

// force commit even on non-dirty sessions because some databases require

// a commit/rollback before calling close()

sqlSession.commit(true);

}

return result;

} catch (Throwable t) {

Throwable unwrapped = unwrapThrowable(t);

if (DynamicSqlSessionTemplate.this.exceptionTranslator != null && unwrapped instanceof PersistenceException) {

Throwable translated = DynamicSqlSessionTemplate.this.exceptionTranslator

.translateExceptionIfPossible((PersistenceException) unwrapped);

if (translated != null) {

unwrapped = translated;

}

}

throw unwrapped;

} finally {

closeSqlSession(sqlSession, DynamicSqlSessionTemplate.this.getSqlSessionFactory());

}

}

}

}

SqlSessionContentHolder类代码如下：

package com.sincetimes.slg.framework.util;

public abstract class SqlSessionContentHolder {

public final static String SESSION_FACTORY_MASTER = "master";

public final static String SESSION_FACTORY_SLAVE = "slave";

private static final ThreadLocal contextHolder = new ThreadLocal();

public static void setContextType(String contextType) {

contextHolder.set(contextType);

}

public static String getContextType() {

return contextHolder.get();

}

public static void clearContextType() {

contextHolder.remove();

}

}

最后就是写切面去对dao所有方法进行处理了，代码很简单如下：

package com.sincetimes.slg.framework.core;

import org.aspectj.lang.JoinPoint;

import org.aspectj.lang.annotation.Aspect;

import org.aspectj.lang.annotation.Before;

import org.aspectj.lang.annotation.Pointcut;

import com.sincetimes.slg.framework.util.SqlSessionContentHolder;

@Aspect

public class DynamicDataSourceAspect {

@Pointcut("execution( * com.sincetimes.slg.dao.*.*(..))")

public void pointCut(){

}

@Before("pointCut()")

public void before(JoinPoint jp){

String methodName = jp.getSignature().getName();

//dao方法查询走从库

if(methodName.startsWith("query") || methodName.startsWith("get") || methodName.startsWith("count") || methodName.startsWith("list")){

SqlSessionContentHolder.setContextType(SqlSessionContentHolder.SESSION_FACTORY_SLAVE);

}else{

SqlSessionContentHolder.setContextType(SqlSessionContentHolder.SESSION_FACTORY_MASTER);

}

}

}

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