Spring + Mybatis 项目实现动态切换数据源-白红宇

Spring + Mybatis 项目实现动态切换数据源

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发布时间：2019-06-26

本文共 13583 字，大约阅读时间需要 45 分钟。

项目背景：项目开发中数据库使用了读写分离，所有查询语句走从库，除此之外走主库。

最简单的办法其实就是建两个包，把之前数据源那一套配置copy一份，指向另外的包，但是这样扩展很有限，所有采用下面的办法。

参考了两篇文章如下：

这两篇文章都对原理进行了分析，下面只写自己的实现过程其他不再叙述。

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：

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：

1 
     
      2     
      3     
      
       4         
         5             
          6             
          7           8     
      9

配置Mybatis自动扫描dao

自己重写了SqlSessionTemplate代码如下：

1 package com.sincetimes.slg.framework.core;  2   3 import static java.lang.reflect.Proxy.newProxyInstance;  4 import static org.apache.ibatis.reflection.ExceptionUtil.unwrapThrowable;  5 import static org.mybatis.spring.SqlSessionUtils.closeSqlSession;  6 import static org.mybatis.spring.SqlSessionUtils.getSqlSession;  7 import static org.mybatis.spring.SqlSessionUtils.isSqlSessionTransactional;  8    9 import java.lang.reflect.InvocationHandler; 10 import java.lang.reflect.Method; 11 import java.sql.Connection; 12 import java.util.List; 13 import java.util.Map; 14  15 import org.apache.ibatis.exceptions.PersistenceException; 16 import org.apache.ibatis.executor.BatchResult; 17 import org.apache.ibatis.session.Configuration; 18 import org.apache.ibatis.session.ExecutorType; 19 import org.apache.ibatis.session.ResultHandler; 20 import org.apache.ibatis.session.RowBounds; 21 import org.apache.ibatis.session.SqlSession; 22 import org.apache.ibatis.session.SqlSessionFactory; 23 import org.mybatis.spring.MyBatisExceptionTranslator; 24 import org.mybatis.spring.SqlSessionTemplate; 25 import org.springframework.dao.support.PersistenceExceptionTranslator; 26 import org.springframework.util.Assert; 27  28 import com.sincetimes.slg.framework.util.SqlSessionContentHolder; 29  30  31 /** 32  *  33  * TODO         重写SqlSessionTemplate 34  * @author      ccg 35  * @version        1.0 36  * Created        2017年4月21日 下午3:15:15 37  */ 38 public class DynamicSqlSessionTemplate extends SqlSessionTemplate { 39   40     private final SqlSessionFactory sqlSessionFactory; 41     private final ExecutorType executorType; 42     private final SqlSession sqlSessionProxy; 43     private final PersistenceExceptionTranslator exceptionTranslator; 44   45     private Map
     
       targetSqlSessionFactorys; 46     private SqlSessionFactory defaultTargetSqlSessionFactory; 47   48     public void setTargetSqlSessionFactorys(Map
      
        targetSqlSessionFactorys) { 49         this.targetSqlSessionFactorys = targetSqlSessionFactorys; 50     } 51      52     public Map
       
         getTargetSqlSessionFactorys(){ 53         return targetSqlSessionFactorys; 54     } 55   56     public void setDefaultTargetSqlSessionFactory(SqlSessionFactory defaultTargetSqlSessionFactory) { 57         this.defaultTargetSqlSessionFactory = defaultTargetSqlSessionFactory; 58     } 59   60     public DynamicSqlSessionTemplate(SqlSessionFactory sqlSessionFactory) { 61         this(sqlSessionFactory, sqlSessionFactory.getConfiguration().getDefaultExecutorType()); 62     } 63   64     public DynamicSqlSessionTemplate(SqlSessionFactory sqlSessionFactory, ExecutorType executorType) { 65         this(sqlSessionFactory, executorType, new MyBatisExceptionTranslator(sqlSessionFactory.getConfiguration() 66                 .getEnvironment().getDataSource(), true)); 67     } 68   69     public DynamicSqlSessionTemplate(SqlSessionFactory sqlSessionFactory, ExecutorType executorType, 70             PersistenceExceptionTranslator exceptionTranslator) { 71   72         super(sqlSessionFactory, executorType, exceptionTranslator); 73   74         this.sqlSessionFactory = sqlSessionFactory; 75         this.executorType = executorType; 76         this.exceptionTranslator = exceptionTranslator; 77          78         this.sqlSessionProxy = (SqlSession) newProxyInstance( 79                 SqlSessionFactory.class.getClassLoader(), 80                 new Class[] { SqlSession.class },  81                 new SqlSessionInterceptor()); 82   83         this.defaultTargetSqlSessionFactory = sqlSessionFactory; 84     } 85   86     @Override 87     public SqlSessionFactory getSqlSessionFactory() { 88   89         SqlSessionFactory targetSqlSessionFactory = targetSqlSessionFactorys.get(SqlSessionContentHolder.getContextType()); 90         if (targetSqlSessionFactory != null) { 91             return targetSqlSessionFactory; 92         } else if (defaultTargetSqlSessionFactory != null) { 93             return defaultTargetSqlSessionFactory; 94         } else { 95             Assert.notNull(targetSqlSessionFactorys, "Property 'targetSqlSessionFactorys' or 'defaultTargetSqlSessionFactory' are required"); 96             Assert.notNull(defaultTargetSqlSessionFactory, "Property 'defaultTargetSqlSessionFactory' or 'targetSqlSessionFactorys' are required"); 97         } 98         return this.sqlSessionFactory; 99     }100  101     @Override102     public Configuration getConfiguration() {103         return this.getSqlSessionFactory().getConfiguration();104     }105  106     public ExecutorType getExecutorType() {107         return this.executorType;108     }109  110     public PersistenceExceptionTranslator getPersistenceExceptionTranslator() {111         return this.exceptionTranslator;112     }113  114     /**115      * {
    @inheritDoc}116      */117     public 
        
          T selectOne(String statement) {118         return this.sqlSessionProxy.
         
           selectOne(statement);119     }120  121     /**122      * {
    @inheritDoc}123      */124     public 
          
            T selectOne(String statement, Object parameter) {125 return this.sqlSessionProxy.
           
             selectOne(statement, parameter);126 }127 128 /**129 * { @inheritDoc}130 */131 public 
            
              Map
             
               selectMap(String statement, String mapKey) {132 return this.sqlSessionProxy.
              
                selectMap(statement, mapKey);133 }134 135 /**136 * { @inheritDoc}137 */138 public 
               
                 Map
                
                  selectMap(String statement, Object parameter, String mapKey) {139 return this.sqlSessionProxy.
                 
                   selectMap(statement, parameter, mapKey);140 }141 142 /**143 * { @inheritDoc}144 */145 public 
                  
                    Map
                   
                     selectMap(String statement, Object parameter, String mapKey, RowBounds rowBounds) {146 return this.sqlSessionProxy.
                    
                      selectMap(statement, parameter, mapKey, rowBounds);147 }148 149 /**150 * { @inheritDoc}151 */152 public 
                     
                       List
                      
                        selectList(String statement) {153 return this.sqlSessionProxy.
                       
                         selectList(statement);154 }155 156 /**157 * { @inheritDoc}158 */159 public 
                        
                          List
                         
                           selectList(String statement, Object parameter) {160 return this.sqlSessionProxy.
                          
                            selectList(statement, parameter);161 }162 163 /**164 * { @inheritDoc}165 */166 public 
                           
                             List
                            
                              selectList(String statement, Object parameter, RowBounds rowBounds) {167 return this.sqlSessionProxy.
                             
                               selectList(statement, parameter, rowBounds);168 }169 170 /**171 * { @inheritDoc}172 */173 public void select(String statement, ResultHandler handler) {174 this.sqlSessionProxy.select(statement, handler);175 }176 177 /**178 * { @inheritDoc}179 */180 public void select(String statement, Object parameter, ResultHandler handler) {181 this.sqlSessionProxy.select(statement, parameter, handler);182 }183 184 /**185 * { @inheritDoc}186 */187 public void select(String statement, Object parameter, RowBounds rowBounds, ResultHandler handler) {188 this.sqlSessionProxy.select(statement, parameter, rowBounds, handler);189 }190 191 /**192 * { @inheritDoc}193 */194 public int insert(String statement) {195 return this.sqlSessionProxy.insert(statement);196 }197 198 /**199 * { @inheritDoc}200 */201 public int insert(String statement, Object parameter) {202 return this.sqlSessionProxy.insert(statement, parameter);203 }204 205 /**206 * { @inheritDoc}207 */208 public int update(String statement) {209 return this.sqlSessionProxy.update(statement);210 }211 212 /**213 * { @inheritDoc}214 */215 public int update(String statement, Object parameter) {216 return this.sqlSessionProxy.update(statement, parameter);217 }218 219 /**220 * { @inheritDoc}221 */222 public int delete(String statement) {223 return this.sqlSessionProxy.delete(statement);224 }225 226 /**227 * { @inheritDoc}228 */229 public int delete(String statement, Object parameter) {230 return this.sqlSessionProxy.delete(statement, parameter);231 }232 233 /**234 * { @inheritDoc}235 */236 public 
                              
                                T getMapper(Class
                               
                                 type) {237 return getConfiguration().getMapper(type, this);238 }239 240 /**241 * { @inheritDoc}242 */243 public void commit() {244 throw new UnsupportedOperationException("Manual commit is not allowed over a Spring managed SqlSession");245 }246 247 /**248 * { @inheritDoc}249 */250 public void commit(boolean force) {251 throw new UnsupportedOperationException("Manual commit is not allowed over a Spring managed SqlSession");252 }253 254 /**255 * { @inheritDoc}256 */257 public void rollback() {258 throw new UnsupportedOperationException("Manual rollback is not allowed over a Spring managed SqlSession");259 }260 261 /**262 * { @inheritDoc}263 */264 public void rollback(boolean force) {265 throw new UnsupportedOperationException("Manual rollback is not allowed over a Spring managed SqlSession");266 }267 268 /**269 * { @inheritDoc}270 */271 public void close() {272 throw new UnsupportedOperationException("Manual close is not allowed over a Spring managed SqlSession");273 }274 275 /**276 * { @inheritDoc}277 */278 public void clearCache() {279 this.sqlSessionProxy.clearCache();280 }281 282 /**283 * { @inheritDoc}284 */285 public Connection getConnection() {286 return this.sqlSessionProxy.getConnection();287 }288 289 /**290 * { @inheritDoc}291 * @since 1.0.2292 */293 public List
                                
                                  flushStatements() {294 return this.sqlSessionProxy.flushStatements();295 }296 297 /**298 * Proxy needed to route MyBatis method calls to the proper SqlSession got from Spring's Transaction Manager It also299 * unwraps exceptions thrown by { @code Method#invoke(Object, Object...)} to pass a { @code PersistenceException} to300 * the { @code PersistenceExceptionTranslator}.301 */302 private class SqlSessionInterceptor implements InvocationHandler {303 public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {304 final SqlSession sqlSession = getSqlSession(305 DynamicSqlSessionTemplate.this.getSqlSessionFactory(),306 DynamicSqlSessionTemplate.this.executorType, 307 DynamicSqlSessionTemplate.this.exceptionTranslator);308 try {309 Object result = method.invoke(sqlSession, args);310 if (!isSqlSessionTransactional(sqlSession, DynamicSqlSessionTemplate.this.getSqlSessionFactory())) {311 // force commit even on non-dirty sessions because some databases require312 // a commit/rollback before calling close()313 sqlSession.commit(true);314 }315 return result;316 } catch (Throwable t) {317 Throwable unwrapped = unwrapThrowable(t);318 if (DynamicSqlSessionTemplate.this.exceptionTranslator != null && unwrapped instanceof PersistenceException) {319 Throwable translated = DynamicSqlSessionTemplate.this.exceptionTranslator320 .translateExceptionIfPossible((PersistenceException) unwrapped);321 if (translated != null) {322 unwrapped = translated;323 }324 }325 throw unwrapped;326 } finally {327 closeSqlSession(sqlSession, DynamicSqlSessionTemplate.this.getSqlSessionFactory());328 }329 }330 }331 332 }

SqlSessionContentHolder类代码如下：

1 package com.sincetimes.slg.framework.util; 2  3 public abstract class SqlSessionContentHolder { 4  5     public final static String SESSION_FACTORY_MASTER = "master"; 6     public final static String SESSION_FACTORY_SLAVE = "slave"; 7      8     private static final ThreadLocal
     
       contextHolder = new ThreadLocal
      
       ();   9     10     public static void setContextType(String contextType) {  11         contextHolder.set(contextType);  12     }  13       14     public static String getContextType() {  15         return contextHolder.get();  16     }  17       18     public static void clearContextType() {  19         contextHolder.remove();  20     } 21 }

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：

1 package com.sincetimes.slg.framework.core; 2  3 import org.aspectj.lang.JoinPoint; 4 import org.aspectj.lang.annotation.Aspect; 5 import org.aspectj.lang.annotation.Before; 6 import org.aspectj.lang.annotation.Pointcut; 7  8 import com.sincetimes.slg.framework.util.SqlSessionContentHolder; 9 10 @Aspect11 public class DynamicDataSourceAspect {12 13     @Pointcut("execution( * com.sincetimes.slg.dao.*.*(..))")14     public void pointCut(){15         16     }17     @Before("pointCut()")18     public void before(JoinPoint jp){19         String methodName = jp.getSignature().getName();  20         //dao方法查询走从库21         if(methodName.startsWith("query") || methodName.startsWith("get") || methodName.startsWith("count") || methodName.startsWith("list")){22             SqlSessionContentHolder.setContextType(SqlSessionContentHolder.SESSION_FACTORY_SLAVE);23         }else{24             SqlSessionContentHolder.setContextType(SqlSessionContentHolder.SESSION_FACTORY_MASTER);25         }26     }27     28 }

转载于:https://www.cnblogs.com/FlyHeLanMan/p/6744171.html

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