我们在做一些兼容非MySQL数据库时，经常遇到一些关键字，或者语法差异问题。 这里举个极端例子，有个字段为desc，因为与数据库关键字冲突，在mysql中需要使用`desc`，而guassdb中需要使用"desc"

针对有语法差异的，利用mybatis的@Intercepts注解插件拦截，在拦截器中，处理与mysql的兼容性问题，通过类型判断，写不同逻辑

import org.apache.ibatis.executor.statement.StatementHandler;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.plugin.Interceptor;
import org.apache.ibatis.plugin.Intercepts;
import org.apache.ibatis.plugin.Invocation;
import org.apache.ibatis.plugin.Signature;import java.lang.reflect.Field;
import java.sql.Connection;
import java.util.Properties;@Intercepts(@Signature(type = StatementHandler.class, method = "prepare", args = {Connection.class, Integer.class}))
public class SqlDialectInterceptor implements Interceptor {private String databaseType;public SqlDialectInterceptor(String databaseType) {this.databaseType = databaseType;}@Overridepublic Object intercept(Invocation invocation) throws Throwable {StatementHandler statementHandler = (StatementHandler) invocation.getTarget();BoundSql boundSql = statementHandler.getBoundSql();String sql = boundSql.getSql();String adjustedSql = adjustedSql(sql);Field sqlField = boundSql.getClass().getDeclaredField("sql");sqlField.setAccessible(true);sqlField.set(boundSql, adjustedSql);return invocation.proceed();}private String adjustedSql(String sql) {if (databaseType.toLowerCase().contains("mysql")) {sql = sql.replace("\"desc\"", "`desc`");} else {sql = sql.replace("`desc`", "\"desc\"");}return sql;}@Overridepublic void setProperties(Properties properties) {Interceptor.super.setProperties(properties);}
}

import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.annotation.MapperScan;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.DatabaseMetaData;@Configuration
@MapperScan(basePackages = "com.db.mapper")
public class SqlSessionFactoryConfig {private static final Logger loggder = LoggerFactory.getLogger(SqlSessionFactoryConfig.class);private final DataSource dataSource;public SqlSessionFactoryConfig(DataSource dataSource) {this.dataSource = dataSource;}@Beanpublic SqlSessionFactoryBean createSqlSessionFactory() {try {SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();PathMatchingResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();String packageXmlConfigPath = PathMatchingResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX + "mybatis/mapper/**/*.xml";// 设置 mapper 配置文件路径sqlSessionFactoryBean.setMapperLocations(resolver.getResources(packageXmlConfigPath));// 设置数据源sqlSessionFactoryBean.setDataSource(dataSource);// 设置 mybatis 配置文件路径sqlSessionFactoryBean.setConfigLocation(new ClassPathResource("mybatis/mybatis-config.xml"));sqlSessionFactoryBean.setPlugins(new SqlDialectInterceptor(getDatabaseType(dataSource)));return sqlSessionFactoryBean;} catch (Exception ex) {throw new RuntimeException(ex.getMessage(), ex);}}private String getDatabaseType(DataSource dataSource) {try (Connection connection = dataSource.getConnection()) {DatabaseMetaData metaData = connection.getMetaData();String databaseProductName = metaData.getDatabaseProductName();loggder.info("init getDatabaseType: {}", databaseProductName);return databaseProductName;} catch (Exception ex) {loggder.info("init getDatabaseType error {}", ex.getMessage(), ex);return "mysql";}}
}