SpringBoot 集成 MyBatis
Java 框架 SpringBoot Spring MyBatis Java
本文介绍 SpringBoot 集成 MyBatis 的基本配置、通过 AOP 和注解动态实现切换数据源的方法，以及利用 MyBatis 拦截器打印完整可执行 SQL 的方法

# SpringBoot 集成 MyBatis

# 简介

  1. MyBatis 基于 Apache 的开源项目 iBatis，是一款优秀的持久层框架

  2. mybatis-spring-boot-starter 提供了 MyBatis 和 SpringBoot 无缝集成的方式

  3. maven 引入 mybatis-spring-boot-starter

    <dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>2.1.1</version>
</dependency>

    SpringBoot 2.x 需要 mybatis-spring-boot-starter 2.1 及以上版本

  4. mybatis-spring-boot-starter 提供的基本功能

    • 自动发现存在的 DataSource
    • 利用 SqlSessionFactoryBean 创建 SqlSessionFactory
    • 创建并注册 SqlSessionTemplate
    • 自动扫描 mappers，注册到 Spring 上下文中方便注入

# 基础配置

  1. 配置数据源连接

    spring:
  datasource:
    url: jdbc:mysql://localhost:3306/demo?useSSL=true&useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai
    driver-class-name: com.mysql.cj.jdbc.Driver
    username: root
    password: root

  2. 配置连接池和数据源初始化

    spring:
  datasource:
    # ...（数据源连接配置）
    # 指定连接池
    type: com.zaxxer.hikari.HikariDataSource
    initialization-mode: always
    continue-on-error: true
    # 指定初始化使用的 SQL 脚本
    schema:
      - "classpath:db/schema.sql"
    data:
      - "classpath:db/
    # 配置 hikari 连接词
    hikari:
      minimum-idle: 5
      connection-test-query: SELECT 1 FROM DUAL
      maximum-pool-size: 20
      auto-commit: true
      idle-timeout: 30000
      pool-name: DemoHikariCP
      max-lifetime: 60000
      connection-timeout: 30000

    常用的连接池有 DBCP，tomcat-jdbc，CP30，Druid 等，SpringBoot 默认使用 hikari

  3. 配置 mapper 文件路径

    mybatis:
  mapper-locations: classpath:mybatis/mappers/*.xml
  type-aliases-package: com.example.demo.model

  4. 启动类或其他配置类上配置扫描 mapper 接口文件的包名

    @Configuration
@MapperScan(value = {"com.example.demo.mapper"})
public class DataSourceConfig {

}

  5. 使用 Java 类代替 yaml 文件进行配置

    配置数据源 DataSource

    @Configuration
@MapperScan(value = {"com.example.demo.mapper"})
public class DataSourceConfig {

    @Bean
    public DataSource dataSource() {
        HikariDataSource dataSource = new HikariDataSource();
        // 配置连接属性
        dataSource.setJdbcUrl("jdbc:mysql://localhost:3306/demo?useSSL=true&useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai");
        dataSource.setDriverClassName("com.mysql.cj.jdbc.Driver");
        dataSource.setUsername("root");
        dataSource.setPassword("root");
		// 配置连接池参数
        dataSource.setMinimumIdle(5);
        dataSource.setConnectionTestQuery("SELECT 1 FROM DUAL");
        dataSource.setMaximumPoolSize(20);
        dataSource.setAutoCommit(true);
        dataSource.setIdleTimeout(30000);
        dataSource.setPoolName("Config-HikariCP");
        dataSource.setMaxLifetime(60000);
        dataSource.setConnectionTimeout(30000);

        return dataSource;
    }
}

    配置数据源初始化 dataSourceInitializer

    @Bean
public DataSourceInitializer dataSourceInitializer() {
    // 指定数据源初始化设置
    ResourceDatabasePopulator resourceDatabasePopulator = new ResourceDatabasePopulator();
    resourceDatabasePopulator.addScript(new ClassPathResource("/db/schema.sql"));
    resourceDatabasePopulator.addScript(new ClassPathResource("/db/data.sql"));
    resourceDatabasePopulator.setContinueOnError(true);
    DataSourceInitializer dataSourceInitializer = new DataSourceInitializer();
    dataSourceInitializer.setDatabasePopulator(resourceDatabasePopulator);
    dataSourceInitializer.setDataSource(dataSource());
    return dataSourceInitializer;
}

    配置 MyBatis 映射文件位置和 typeAlias

    @Bean
public SqlSessionFactory sqlSessionFactory() throws Exception {
    SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
    sqlSessionFactoryBean.setDataSource(dataSource());
    sqlSessionFactoryBean.setMapperLocations(
        new PathMatchingResourcePatternResolver().getResources("classpath*:mybatis/mappers/*.xml")
    );
    sqlSessionFactoryBean.setTypeAliasesPackage("com.example.demo.entity");

    return sqlSessionFactoryBean.getObject();
}

# 多数据源

  1. 基本配置实现

    原理：使用 @MapperScan 注解对不同包的 mapper 类绑定不同的 sqlSessionFactory，即映射文件

    数据源和 mybatis 配置部分也可以使用 YAML 配置

    使用 Java 配置类配置如下

    @Configuration
// 配置 mapper 扫描，不同包下使用不同的 sqlSessionFactory
@MapperScan(value = {"com.example.demo.mapper"}, sqlSessionFactoryRef = "sqlSessionFactory")
@MapperScan(value = {"com.example.demo.mapper2"}, sqlSessionFactoryRef = "sqlSessionFactory2")
public class DataSourceConfig {

    // 配置主数据源
    @Bean
    @Primary
    public DataSource dataSource() {
        HikariDataSource dataSource = new HikariDataSource();
        dataSource.setJdbcUrl("jdbc:mysql://localhost:3306/demo?useSSL=true&useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai");
        dataSource.setDriverClassName("com.mysql.cj.jdbc.Driver");
        dataSource.setUsername("root");
        dataSource.setPassword("root");

        dataSource.setMinimumIdle(5);
        dataSource.setConnectionTestQuery("SELECT 1 FROM DUAL");
        dataSource.setMaximumPoolSize(20);
        dataSource.setAutoCommit(true);
        dataSource.setIdleTimeout(30000);
        dataSource.setPoolName("Config-HikariCP");
        dataSource.setMaxLifetime(60000);
        dataSource.setConnectionTimeout(30000);

        return dataSource;
    }

    // 配置数据源 2
    @Bean
    public DataSource dataSource2() {
        // 同上数据源配置代码，指定的另外数据库
    }


    // 配置 mybatis sqlSessionFactory
    @Bean("sqlSessionFactory")
    @Primary
    public SqlSessionFactory sqlSessionFactory() throws Exception {
        SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
        sqlSessionFactoryBean.setDataSource(dataSource());
        sqlSessionFactoryBean.setMapperLocations(
                new PathMatchingResourcePatternResolver().getResources("classpath*:mybatis/mappers/*.xml")
        );
        sqlSessionFactoryBean.setTypeAliasesPackage("com.example.demo.entity");

        return sqlSessionFactoryBean.getObject();
    }

    // 配置 mybatis sqlSessionFactory2
    @Bean("sqlSessionFactory2")
    public SqlSessionFactory sqlSessionFactory2() throws Exception {
        SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
        sqlSessionFactoryBean.setDataSource(dataSource2());
        sqlSessionFactoryBean.setMapperLocations(
                new PathMatchingResourcePatternResolver().getResources("classpath*:mybatis/mappers2/*.xml")
        );
        sqlSessionFactoryBean.setTypeAliasesPackage("com.example.demo.entity");

        return sqlSessionFactoryBean.getObject();
    }
}

    如上配置后进行测试，mapper 包下 mapper 类将使用主数据源，mapper2 包下 mapper 类将使用数据源 2

  2. AOP 实现动态切换

    原理：继承 AbstractRoutingDataSource，重写 determineCurrentLookupKey 方法

    动态数据源类：

    public class DynamicDataSource extends AbstractRoutingDataSource {

    @Override
    protected DataSource determineTargetDataSource() {
        return super.determineTargetDataSource();
    }

    /**
     * 通过设置数据源 Key 值来切换数据
     */
    @Override
    protected Object determineCurrentLookupKey() {
        return DynamicDataSourceContextHolder.getDataSourceKey();
    }

    /**
     * 设置默认数据源
     *
     * @param defaultDataSource
     */
    public void setDefaultDataSource(Object defaultDataSource) {
        super.setDefaultTargetDataSource(defaultDataSource);
    }

    /**
     * 设置数据源
     *
     * @param dataSources
     */
    public void setDataSources(Map<Object, Object> dataSources) {
        super.setTargetDataSources(dataSources);
        // 将数据源的 key 放到数据源上下文的 key 集合中，用于切换时判断数据源是否有效
        DynamicDataSourceContextHolder.addDataSourceKeys(dataSources.keySet());
    }
}

    DynamicDataSourceContextHolder，用于保存和获取数据源 key

    public class DynamicDataSourceContextHolder {

    private static final ThreadLocal<String> contextHolder = new ThreadLocal<>();


    /**
     * 数据源的 key 集合，用于切换时判断数据源是否存在
     */
    public static List<Object> dataSourceKeys = new ArrayList<>();

    /**
     * 切换数据源
     *
     * @param key
     */
    public static void setDataSourceKey(String key) {
        contextHolder.set(key);
    }

    /**
     * 获取数据源
     *
     * @return
     */
    public static String getDataSourceKey() {
        return contextHolder.get();
    }

    /**
     * 重置数据源
     */
    public static void clearDataSourceKey() {
        contextHolder.remove();
    }

    /**
     * 判断是否包含数据源
     *
     * @param key 数据源 key
     * @return
     */
    public static boolean containDataSourceKey(String key) {
        return dataSourceKeys.contains(key);
    }

    /**
     * 添加数据源 keys
     *
     * @param keys
     * @return
     */
    public static boolean addDataSourceKeys(Collection<? extends Object> keys) {
        return dataSourceKeys.addAll(keys);
    }
}

    数据源配置类

    @Configuration
@MapperScan(value = {"com.example.demo.mapper"})
public class DataSourceConfig {

    // 配置主数据源
    @Bean
    public DataSource dataSource() {
        HikariDataSource dataSource = new HikariDataSource();
        dataSource.setJdbcUrl("jdbc:mysql://localhost:3306/demo?useSSL=true&useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai");
        dataSource.setDriverClassName("com.mysql.cj.jdbc.Driver");
        dataSource.setUsername("root");
        dataSource.setPassword("root");

        dataSource.setMinimumIdle(5);
        dataSource.setConnectionTestQuery("SELECT 1 FROM DUAL");
        dataSource.setMaximumPoolSize(20);
        dataSource.setAutoCommit(true);
        dataSource.setIdleTimeout(30000);
        dataSource.setPoolName("Config-HikariCP");
        dataSource.setMaxLifetime(60000);
        dataSource.setConnectionTimeout(30000);

        return dataSource;
    }

    // 配置数据源 2
    @Bean
    public DataSource dataSource2() {
        // ...数据源配置
    }


    // 配置动态数据源
    @Bean("dynamicDataSource")
    public DataSource dynamicDataSource() {
        DynamicDataSource dynamicDataSource = new DynamicDataSource();
        Map<Object, Object> dataSourceMap = new HashMap<>(2);
        // 注册数据源，此处可以定制为从配置文件读取
        dataSourceMap.put("master", dataSource());
        dataSourceMap.put("second", dataSource2());
        dynamicDataSource.setDefaultDataSource(dataSource());
        dynamicDataSource.setDataSources(dataSourceMap);
        return dynamicDataSource;
    }


    // 配置 mybatis sqlSessionFactory
    @Bean("sqlSessionFactory")
    @Primary
    public SqlSessionFactory sqlSessionFactory() throws Exception {
        SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
        sqlSessionFactoryBean.setDataSource(dynamicDataSource());
        sqlSessionFactoryBean.setMapperLocations(
                new PathMatchingResourcePatternResolver().getResources("classpath*:mybatis/mappers/*.xml")
        );
        sqlSessionFactoryBean.setTypeAliasesPackage("com.example.demo.entity");

        return sqlSessionFactoryBean.getObject();
    }

    // 配置事务管理器
    @Bean
    public PlatformTransactionManager transactionManager() {
        return new DataSourceTransactionManager(dynamicDataSource());
    }
}

    AOP 代理方法，执行前切换数据源，执行后恢复默认

    @Aspect
// 设置 Order 使切面在 @Transactional 之前执行
@Order(-1)
@Component
public class DynamicDataSourceAspect {

    private Logger logger = LoggerFactory.getLogger(this.getClass());

    /**
     * 切换数据源
     *
     * @param point
     * @param dataSource
     */
    @Before("@annotation(dataSource)")
    public void switchDataSource(JoinPoint point, DataSource dataSource) {
        String dataSourceKey = dataSource.value();
        if (!DynamicDataSourceContextHolder.containDataSourceKey(dataSourceKey)) {
            logger.info("DataSource [{}] doesn't exist, use default", dataSource.value());
        } else {
            // 切换数据源
            DynamicDataSourceContextHolder.setDataSourceKey(dataSource.value());
            logger.info("Switch DataSource to [{}] in Method [{}]", dataSourceKey, point.getSignature());
        }
    }

    /**
     * 重置数据源
     *
     * @param point
     * @param dataSource
     */
    @After("@annotation(dataSource))")
    public void resetDataSource(JoinPoint point, DataSource dataSource) {
        // 将数据源置为默认数据源
        DynamicDataSourceContextHolder.clearDataSourceKey();
        logger.info("Reset DataSource to default in Method [{}]", point.getSignature());
    }
}

# 打印日志

  1. 打印 Mybatis 日志

    以 logback 为例，配置 logback.xml

    <!--定义 logger
        name 指定要输出日志的包
        level 指定等级
        additivity 指定是否将 root 的 appender 加入到 logger 中
    -->
<logger name="com.example.dao" level="${level}" additivity="true">
	<!-- 配置 appender -->
    <appender-ref ref="errorAppender" />
    <appender-ref ref="debugAppender" />
    <appender-ref ref="infoAppender" />
</logger>

<!-- mybatis 日志 -->
<!-- mybatis 打印 sql
     SpringBoot 项目只要配置 dao 或 mapper 包
     普通 SSM 项目可能还需要以下配置
 -->
<logger name="org.apache.ibatis" level="DEBUG" />
<logger name="java.sql" level="DEBUG" />

  2. 打印完整 SQL

    上面通过 logback 配置文件进行的配置只能打印预处理的 SQL 语句，不便于直接执行调试

    借助 MyBatis 的拦截器，可以获取 MyBatis 封装的 SQL 语句对象，可进一步获得参数，拼接 SQL 并打印

    @Intercepts({
        @Signature(type = Executor.class, method = "update", args = {MappedStatement.class, Object.class}),
        @Signature(type = Executor.class, method = "query",
                args = {MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class})})
public class SqlPrintingInterceptor implements Interceptor {

    private static final Logger logger = LoggerFactory.getLogger(SqlPrintingInterceptor.class);

    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        // 获取 SQL 描述语句对象
        MappedStatement mappedStatement = (MappedStatement) invocation.getArgs()[0];
        // 获取参数
        Object parameter = null;
        if (invocation.getArgs().length > 1) {
            parameter = invocation.getArgs()[1];
        }
        // 获取 SQL Id
        String sqlId = mappedStatement.getId();
        // 获取 BoundSql 即 mybatis 封装的 SQL 对象
        BoundSql boundSql = mappedStatement.getBoundSql(parameter);
        // 获取配置
        Configuration configuration = mappedStatement.getConfiguration();
        // 计时，执行
        long start = System.currentTimeMillis();
        Object returnValue = invocation.proceed();
        long time = System.currentTimeMillis() - start;
        // 打印 SQL
        showSql(configuration, boundSql, time, sqlId);
        return returnValue;
    }
    
    /**
     * 处理 sql 中的字符
     
     * @param configuration
     * @param boundSql
     * @param time
     * @param sqlId
     */
    private static void showSql(Configuration configuration, BoundSql boundSql, long time, String sqlId) {
        Object parameterObject = boundSql.getParameterObject();
        List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
        // 替换空格、换行、tab缩进等
        String sql = boundSql.getSql().replaceAll("[\\s]+", " ");
        if (parameterMappings.size() > 0 && parameterObject != null) {
            TypeHandlerRegistry typeHandlerRegistry = configuration.getTypeHandlerRegistry();
            if (typeHandlerRegistry.hasTypeHandler(parameterObject.getClass())) {
                sql = sql.replaceFirst("\\?", getParameterValue(parameterObject));
            } else {
                MetaObject metaObject = configuration.newMetaObject(parameterObject);
                for (ParameterMapping parameterMapping : parameterMappings) {
                    String propertyName = parameterMapping.getProperty();
                    if (metaObject.hasGetter(propertyName)) {
                        Object obj = metaObject.getValue(propertyName);
                        sql = sql.replaceFirst("\\?", getParameterValue(obj));
                    } else if (boundSql.hasAdditionalParameter(propertyName)) {
                        Object obj = boundSql.getAdditionalParameter(propertyName);
                        sql = sql.replaceFirst("\\?", getParameterValue(obj));
                    }
                }
            }
        }
        logs(time, sql, sqlId);
    }

    /**
     * 对不同类型参数进行处理
     *
     * @param obj
     * @return
     */
    private static String getParameterValue(Object obj) {
        String value;
        if (obj instanceof String) {
            value = "'" + obj + "'";
        } else if (obj instanceof Date) {
            DateFormat formatter = DateFormat.getDateTimeInstance(DateFormat.DEFAULT, DateFormat.DEFAULT, Locale.CHINA);
            value = "'" + formatter.format(new Date()) + "'";
        } else {
            if (obj != null) {
                value = obj.toString();
            } else {
                value = "";
            }
        }
        return value.replace("$", "\\$");
    }

    /**
     * 打印 log
     
     * @param time
     * @param sql
     * @param sqlId
     */
    private static void logs(long time, String sql, String sqlId) {
        String sb = "==> Executed [" + sqlId + "] in " + time + " ms with sql：" + sql;
        logger.info(sb);
    }

    @Override
    public Object plugin(Object target) {
        return Plugin.wrap(target, this);
    }

    @Override
    public void setProperties(Properties properties0) {
    }
}
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