springboot配置多数据源后mybatis拦截器失效的解决

时间：2022-07-01 09:56:31

配置文件是通过springcloudconfig远程分布式配置。采用阿里Druid数据源。并支持一主多从的读写分离。分页组件通过拦截器拦截带有page后缀的方法名，动态的设置total总数。

1. 解析配置文件初始化数据源

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@Configuration
public class DataSourceConfiguration {
    /**
     * 数据源类型
     */
    @Value("${spring.datasource.type}")
    private Class<? extends DataSource> dataSourceType;
    /**
     * 主数据源配置
     *
     * @return
     */
    @Bean(name = "masterDataSource", destroyMethod = "close")
    @Primary
    @ConfigurationProperties(prefix = "spring.datasource")
    public DataSource masterDataSource() {
        DataSource source = DataSourceBuilder.create().type(dataSourceType).build();
        return source;
    }
    /**
     * 从数据源配置
     *
     * @return
     */
    @Bean(name = "slaveDataSource0")
    @ConfigurationProperties(prefix = "spring.slave0")
    public DataSource slaveDataSource0() {
        DataSource source = DataSourceBuilder.create().type(dataSourceType).build();
        return source;
    }
    /**
     * 从数据源集合
     *
     * @return
     */
    @Bean(name = "slaveDataSources")
    public List<DataSource> slaveDataSources() {
        List<DataSource> slaveDataSources = new ArrayList();
        slaveDataSources.add(slaveDataSource0());
        return slaveDataSources;
    }
}

2. 定义数据源枚举类型

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public enum DataSourceType {
    master("master", "master"), slave("slave", "slave");
    private String type;
    private String name;
    DataSourceType(String type, String name) {
        this.type = type;
        this.name = name;
    }
    public String getType() {
        return type;
    }
    public void setType(String type) {
        this.type = type;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
}

3. TheadLocal保存数据源类型

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public class DataSourceContextHolder {
    private static final ThreadLocal<String> local = new ThreadLocal<String>();
    public static ThreadLocal<String> getLocal() {
        return local;
    }
    public static void slave() {
        local.set(DataSourceType.slave.getType());
    }
    public static void master() {
        local.set(DataSourceType.master.getType());
    }
    public static String getJdbcType() {
        return local.get();
    }
    public static void clearDataSource(){
        local.remove();
    }
}

4. 自定义sqlSessionProxy

并将数据源填充到DataSourceRoute

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@Configuration
@ConditionalOnClass({EnableTransactionManagement.class})
@Import({DataSourceConfiguration.class})
public class DataSourceSqlSessionFactory {
    private Logger logger = Logger.getLogger(DataSourceSqlSessionFactory.class);
    @Value("${spring.datasource.type}")
    private Class<? extends DataSource> dataSourceType;
    @Value("${mybatis.mapper-locations}")
    private String mapperLocations;
    @Value("${mybatis.type-aliases-package}")
    private String aliasesPackage;
    @Value("${slave.datasource.number}")
    private int dataSourceNumber;
    @Resource(name = "masterDataSource")
    private DataSource masterDataSource;
    @Resource(name = "slaveDataSources")
    private List<DataSource> slaveDataSources;
    @Bean
    @ConditionalOnMissingBean
    public SqlSessionFactory sqlSessionFactory() throws Exception {
        logger.info("======================= init sqlSessionFactory");
        SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
        sqlSessionFactoryBean.setDataSource(roundRobinDataSourceProxy());
        PathMatchingResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
        sqlSessionFactoryBean.setMapperLocations(resolver.getResources(mapperLocations));
        sqlSessionFactoryBean.setTypeAliasesPackage(aliasesPackage);
        sqlSessionFactoryBean.getObject().getConfiguration().setMapUnderscoreToCamelCase(true);
        return sqlSessionFactoryBean.getObject();
    }
    @Bean(name = "roundRobinDataSourceProxy")
    public AbstractRoutingDataSource roundRobinDataSourceProxy() {
        logger.info("======================= init robinDataSourceProxy");
        DataSourceRoute proxy = new DataSourceRoute(dataSourceNumber);
        Map<Object, Object> targetDataSources = new HashMap();
        targetDataSources.put(DataSourceType.master.getType(), masterDataSource);
        if(null != slaveDataSources) {
            for(int i=0; i<slaveDataSources.size(); i++){
                targetDataSources.put(i, slaveDataSources.get(i));
            }
        }
        proxy.setDefaultTargetDataSource(masterDataSource);
        proxy.setTargetDataSources(targetDataSources);
        return proxy;
    }
}

5. 自定义路由

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public class DataSourceRoute extends AbstractRoutingDataSource {
    private Logger logger = Logger.getLogger(DataSourceRoute.class);
    private final int dataSourceNumber;
    
    public DataSourceRoute(int dataSourceNumber) {
        this.dataSourceNumber = dataSourceNumber;
    }
    @Override
    protected Object determineCurrentLookupKey() {
        String typeKey = DataSourceContextHolder.getJdbcType();
        logger.info("==================== swtich dataSource:" + typeKey);
        if (typeKey.equals(DataSourceType.master.getType())) {
            return DataSourceType.master.getType();
        }else{
            //从数据源随机分配
            Random random = new Random();
            int slaveDsIndex = random.nextInt(dataSourceNumber);
            return slaveDsIndex;
        }
    }
}

6. 定义切面，dao层定义切面

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@Aspect
@Component
public class DataSourceAop {
    private Logger logger = Logger.getLogger(DataSourceAop.class);
    @Before("execution(* com.dbq.iot.mapper..*.get*(..)) || execution(* com.dbq.iot.mapper..*.isExist*(..)) " +
            "|| execution(* com.dbq.iot.mapper..*.select*(..)) || execution(* com.dbq.iot.mapper..*.count*(..)) " +
            "|| execution(* com.dbq.iot.mapper..*.list*(..)) || execution(* com.dbq.iot.mapper..*.query*(..))" +
            "|| execution(* com.dbq.iot.mapper..*.find*(..))|| execution(* com.dbq.iot.mapper..*.search*(..))")
    public void setSlaveDataSourceType(JoinPoint joinPoint) {
        DataSourceContextHolder.slave();
        logger.info("=========slave, method:" + joinPoint.getSignature().getName());
    }
    @Before("execution(* com.dbq.iot.mapper..*.add*(..)) || execution(* com.dbq.iot.mapper..*.del*(..))" +
            "||execution(* com.dbq.iot.mapper..*.upDate*(..)) || execution(* com.dbq.iot.mapper..*.insert*(..))" +
            "||execution(* com.dbq.iot.mapper..*.create*(..)) || execution(* com.dbq.iot.mapper..*.update*(..))" +
            "||execution(* com.dbq.iot.mapper..*.delete*(..)) || execution(* com.dbq.iot.mapper..*.remove*(..))" +
            "||execution(* com.dbq.iot.mapper..*.save*(..)) || execution(* com.dbq.iot.mapper..*.relieve*(..))" +
            "|| execution(* com.dbq.iot.mapper..*.edit*(..))")
    public void setMasterDataSourceType(JoinPoint joinPoint) {
        DataSourceContextHolder.master();
        logger.info("=========master, method:" + joinPoint.getSignature().getName());
    }
}

7. 最后在写库增加事务管理

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@Configuration
@Import({DataSourceConfiguration.class})
public class DataSouceTranscation extends DataSourceTransactionManagerAutoConfiguration {
    private Logger logger = Logger.getLogger(DataSouceTranscation.class);
    @Resource(name = "masterDataSource")
    private DataSource masterDataSource;
    /**
     * 配置事务管理器
     *
     * @return
     */
    @Bean(name = "transactionManager")
    public DataSourceTransactionManager transactionManagers() {
        logger.info("===================== init transactionManager");
        return new DataSourceTransactionManager(masterDataSource);
    }
}

8. 在配置文件中增加数据源配置

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spring.datasource.name=writedb
spring.datasource.url=jdbc:mysql://192.168.0.1/master?useUnicode=true&amp;characterEncoding=utf8&amp;autoReconnect=true&amp;failOverReadOnly=false
spring.datasource.username=root
spring.datasource.password=1234
spring.datasource.type=com.alibaba.druid.pool.DruidDataSource
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.filters=stat
spring.datasource.initialSize=20
spring.datasource.minIdle=20
spring.datasource.maxActive=200
spring.datasource.maxWait=60000
#从库的数量
slave.datasource.number=1
spring.slave0.name=readdb
spring.slave0.url=jdbc:mysql://192.168.0.2/slave?useUnicode=true&amp;characterEncoding=utf8&amp;autoReconnect=true&amp;failOverReadOnly=false
spring.slave0.username=root
spring.slave0.password=1234
spring.slave0.type=com.alibaba.druid.pool.DruidDataSource
spring.slave0.driver-class-name=com.mysql.jdbc.Driver
spring.slave0.filters=stat
spring.slave0.initialSize=20
spring.slave0.minIdle=20
spring.slave0.maxActive=200
spring.slave0.maxWait=60000

这样就实现了在springcloud框架下的读写分离，并且支持多个从库的负载均衡（简单的通过随机分配，也有网友通过算法实现平均分配，具体做法是通过一个线程安全的自增长Integer类型，取余实现。个人觉得没大必要。如果有大神有更好的方法可以一起探讨。）

Mabatis分页配置可通过dao层的拦截器对特定方法进行拦截，拦截后添加自己的逻辑代码，比如计算total等，具体代码如下（参考了网友的代码，主要是通过@Intercepts注解）：

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@Intercepts({@Signature(type = StatementHandler.class, method = "prepare", args = {Connection.class, Integer.class})})
public class PageInterceptor implements Interceptor {
    private static final Log logger = LogFactory.getLog(PageInterceptor.class);
    private static final ObjectFactory DEFAULT_OBJECT_FACTORY = new DefaultObjectFactory();
    private static final ObjectWrapperFactory DEFAULT_OBJECT_WRAPPER_FACTORY = new DefaultObjectWrapperFactory();
    private static final ReflectorFactory DEFAULT_REFLECTOR_FACTORY = new DefaultReflectorFactory();
    private static String defaultDialect = "mysql"; // 数据库类型(默认为mysql)
    private static String defaultPageSqlId = ".*Page$"; // 需要拦截的ID(正则匹配)
    private String dialect = ""; // 数据库类型(默认为mysql)
    private String pageSqlId = ""; // 需要拦截的ID(正则匹配)
    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        StatementHandler statementHandler = (StatementHandler) invocation.getTarget();
        MetaObject metaStatementHandler = MetaObject.forObject(statementHandler, DEFAULT_OBJECT_FACTORY,
                DEFAULT_OBJECT_WRAPPER_FACTORY,DEFAULT_REFLECTOR_FACTORY);
        // 分离代理对象链(由于目标类可能被多个拦截器拦截，从而形成多次代理，通过下面的两次循环可以分离出最原始的的目标类)
        while (metaStatementHandler.hasGetter("h")) {
            Object object = metaStatementHandler.getValue("h");
            metaStatementHandler = MetaObject.forObject(object, DEFAULT_OBJECT_FACTORY, DEFAULT_OBJECT_WRAPPER_FACTORY,DEFAULT_REFLECTOR_FACTORY);
        }
        // 分离最后一个代理对象的目标类
        while (metaStatementHandler.hasGetter("target")) {
            Object object = metaStatementHandler.getValue("target");
            metaStatementHandler = MetaObject.forObject(object, DEFAULT_OBJECT_FACTORY, DEFAULT_OBJECT_WRAPPER_FACTORY,DEFAULT_REFLECTOR_FACTORY);
        }
        Configuration configuration = (Configuration) metaStatementHandler.getValue("delegate.configuration");
        if (null == dialect || "".equals(dialect)) {
            logger.warn("Property dialect is not setted,use default 'mysql' ");
            dialect = defaultDialect;
        }
        if (null == pageSqlId || "".equals(pageSqlId)) {
            logger.warn("Property pageSqlId is not setted,use default '.*Page$' ");
            pageSqlId = defaultPageSqlId;
        }
        MappedStatement mappedStatement = (MappedStatement) metaStatementHandler.getValue("delegate.mappedStatement");
        // 只重写需要分页的sql语句。通过MappedStatement的ID匹配，默认重写以Page结尾的MappedStatement的sql
        if (mappedStatement.getId().matches(pageSqlId)) {
            BoundSql boundSql = (BoundSql) metaStatementHandler.getValue("delegate.boundSql");
            Object parameterObject = boundSql.getParameterObject();
            if (parameterObject == null) {
                throw new NullPointerException("parameterObject is null!");
            } else {
                PageParameter page = (PageParameter) metaStatementHandler
                        .getValue("delegate.boundSql.parameterObject.page");
                String sql = boundSql.getSql();
                // 重写sql
                String pageSql = buildPageSql(sql, page);
                metaStatementHandler.setValue("delegate.boundSql.sql", pageSql);
                metaStatementHandler.setValue("delegate.rowBounds.offset", RowBounds.NO_ROW_OFFSET);
                metaStatementHandler.setValue("delegate.rowBounds.limit", RowBounds.NO_ROW_LIMIT);
                Connection connection = (Connection) invocation.getArgs()[0];
                // 重设分页参数里的总页数等
                setPageParameter(sql, connection, mappedStatement, boundSql, page);
            }
        }
        // 将执行权交给下一个拦截器
        return invocation.proceed();
    }
    /**
     * @param sql
     * @param connection
     * @param mappedStatement
     * @param boundSql
     * @param page
     */
    private void setPageParameter(String sql, Connection connection, MappedStatement mappedStatement,
                                  BoundSql boundSql, PageParameter page) {
        // 记录总记录数
        String countSql = "select count(0) from (" + sql + ") as total";
        PreparedStatement countStmt = null;
        ResultSet rs = null;
        try {
            countStmt = connection.prepareStatement(countSql);
            BoundSql countBS = new BoundSql(mappedStatement.getConfiguration(), countSql,
                    boundSql.getParameterMappings(), boundSql.getParameterObject());
            Field metaParamsField = ReflectUtil.getFieldByFieldName(boundSql, "metaParameters");
            if (metaParamsField != null) {
                try {
                    MetaObject mo = (MetaObject) ReflectUtil.getValueByFieldName(boundSql, "metaParameters");
                    ReflectUtil.setValueByFieldName(countBS, "metaParameters", mo);
                } catch (SecurityException | NoSuchFieldException | IllegalArgumentException
                        | IllegalAccessException e) {
                    // TODO Auto-generated catch block
                     logger.error("Ignore this exception", e);
                }
            }
            Field additionalField = ReflectUtil.getFieldByFieldName(boundSql, "additionalParameters");
            if (additionalField != null) {
                try {
                    Map<String, Object> map = (Map<String, Object>) ReflectUtil.getValueByFieldName(boundSql, "additionalParameters");
                    ReflectUtil.setValueByFieldName(countBS, "additionalParameters", map);
                } catch (SecurityException | NoSuchFieldException | IllegalArgumentException
                        | IllegalAccessException e) {
                    // TODO Auto-generated catch block
                    logger.error("Ignore this exception", e);
                }
            }
            setParameters(countStmt, mappedStatement, countBS, boundSql.getParameterObject());
            rs = countStmt.executeQuery();
            int totalCount = 0;
            if (rs.next()) {
                totalCount = rs.getInt(1);
            }
            page.setTotalCount(totalCount);
            int totalPage = totalCount / page.getPageSize() + ((totalCount % page.getPageSize() == 0) ? 0 : 1);
            page.setTotalPage(totalPage);
        } catch (SQLException e) {
            logger.error("Ignore this exception", e);
        } finally {
            try {
                if (rs != null){
                    rs.close();
                }
            } catch (SQLException e) {
                logger.error("Ignore this exception", e);
            }
            try {
                if (countStmt != null){
                    countStmt.close();
                }
            } catch (SQLException e) {
                logger.error("Ignore this exception", e);
            }
        }
    }
    /**
     * 对SQL参数(?)设值
     *
     * @param ps
     * @param mappedStatement
     * @param boundSql
     * @param parameterObject
     * @throws SQLException
     */
    private void setParameters(PreparedStatement ps, MappedStatement mappedStatement, BoundSql boundSql,
                               Object parameterObject) throws SQLException {
        ParameterHandler parameterHandler = new DefaultParameterHandler(mappedStatement, parameterObject, boundSql);
        parameterHandler.setParameters(ps);
    }
    /**
     * 根据数据库类型，生成特定的分页sql
     *
     * @param sql
     * @param page
     * @return
     */
    private String buildPageSql(String sql, PageParameter page) {
        if (page != null) {
            StringBuilder pageSql = new StringBuilder();
            pageSql = buildPageSqlForMysql(sql,page);
            return pageSql.toString();
        } else {
            return sql;
        }
    }
    /**
     * mysql的分页语句
     *
     * @param sql
     * @param page
     * @return String
     */
    public StringBuilder buildPageSqlForMysql(String sql, PageParameter page) {
        StringBuilder pageSql = new StringBuilder(100);
        String beginrow = String.valueOf((page.getCurrentPage() - 1) * page.getPageSize());
        pageSql.append(sql);
        pageSql.append(" limit " + beginrow + "," + page.getPageSize());
        return pageSql;
    }
    @Override
    public Object plugin(Object target) {
        if (target instanceof StatementHandler) {
            return Plugin.wrap(target, this);
        } else {
            return target;
        }
    }
    @Override
    public void setProperties(Properties properties) {
    }
}

这里碰到一个比较有趣的问题，就是sql如果是foreach参数，在拦截后无法注入。需要加入以下代码才可以（有得资料上只提到重置metaParameters）。

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Field metaParamsField = ReflectUtil.getFieldByFieldName(boundSql, "metaParameters");
if (metaParamsField != null) {
    try {
        MetaObject mo = (MetaObject) ReflectUtil.getValueByFieldName(boundSql, "metaParameters");
        ReflectUtil.setValueByFieldName(countBS, "metaParameters", mo);
    } catch (SecurityException | NoSuchFieldException | IllegalArgumentException
            | IllegalAccessException e) {
        // TODO Auto-generated catch block
         logger.error("Ignore this exception", e);
    }
}
Field additionalField = ReflectUtil.getFieldByFieldName(boundSql, "additionalParameters");
if (additionalField != null) {
    try {
        Map<String, Object> map = (Map<String, Object>) ReflectUtil.getValueByFieldName(boundSql, "additionalParameters");
        ReflectUtil.setValueByFieldName(countBS, "additionalParameters", map);
    } catch (SecurityException | NoSuchFieldException | IllegalArgumentException
            | IllegalAccessException e) {
        // TODO Auto-generated catch block
        logger.error("Ignore this exception", e);
    }
}

读写分离倒是写好了，但是发现增加了mysql一主多从的读写分离后，此分页拦截器直接失效。

最后分析原因是因为，我们在做主从分离时，自定义了SqlSessionFactory，导致此拦截器没有注入。

在上面第4步中，DataSourceSqlSessionFactory中注入拦截器即可，具体代码如下

通过注解引入拦截器类：

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@Import({DataSourceConfiguration.class,PageInterceptor.class})

注入拦截器

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@Autowired
    private PageInterceptor pageInterceptor;

SqlSessionFactoryBean中设置拦截器

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sqlSessionFactoryBean.setPlugins(newInterceptor[]{pageInterceptor});

这里碰到一个坑，就是设置plugins时必须在sqlSessionFactoryBean.getObject()之前。

SqlSessionFactory在生成的时候就会获取plugins，并设置到Configuration中，如果在之后设置则不会注入。

可跟踪源码看到：

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sqlSessionFactoryBean.getObject()
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public SqlSessionFactory getObject() throws Exception {
    if (this.sqlSessionFactory == null) {
      afterPropertiesSet();
    }
    return this.sqlSessionFactory;
}
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public void afterPropertiesSet() throws Exception {
    notNull(dataSource, "Property 'dataSource' is required");
    notNull(sqlSessionFactoryBuilder, "Property 'sqlSessionFactoryBuilder' is required");
    state((configuration == null && configLocation == null) || !(configuration != null && configLocation != null),
              "Property 'configuration' and 'configLocation' can not specified with together");
    this.sqlSessionFactory = buildSqlSessionFactory();
  }

buildSqlSessionFactory()

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if (!isEmpty(this.plugins)) {
      for (Interceptor plugin : this.plugins) {
        configuration.addInterceptor(plugin);
        if (LOGGER.isDebugEnabled()) {
          LOGGER.debug("Registered plugin: '" + plugin + "'");
        }
      }
    }

最后贴上正确的配置代码(DataSourceSqlSessionFactory代码片段)

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@Bean
@ConditionalOnMissingBean
public SqlSessionFactory sqlSessionFactory() throws Exception {
        logger.info("======================= init sqlSessionFactory");
        SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
        sqlSessionFactoryBean.setPlugins(new Interceptor[]{pageInterceptor});
        sqlSessionFactoryBean.setDataSource(roundRobinDataSourceProxy());
        PathMatchingResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
        sqlSessionFactoryBean.setMapperLocations(resolver.getResources(mapperLocations));
        sqlSessionFactoryBean.setTypeAliasesPackage(aliasesPackage);
        SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBean.getObject();
        sqlSessionFactory.getConfiguration().setMapUnderscoreToCamelCase(true);
        return sqlSessionFactory;
}

以上为个人经验，希望能给大家一个参考，也希望大家多多支持服务器之家。

原文链接：https://www.jianshu.com/p/36fb90db79ce

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