@Component
@Slf4j
@Intercepts({
        @Signature(type = StatementHandler.class, method = "prepare", args = {Connection.class, Integer.class})
})
public class DynamicSqlInterceptor implements Interceptor {
 ...
}

# 動(dòng)態(tài)sql配置
dynamicSql:
  placeholder: "@dynamicSql"
  date: "2023-07-10 20:10:30"

public interface DynamicSqlMapper {
    @DynamicSql
    Long count();
}

<mapper namespace="ltd.newbee.mall.core.dao.DynamicSqlMapper">
    <select id="count" resultType="java.lang.Long">
        select count(1) from member
        where create_time > @dynamicSql
    </select>
</mapper>

@Component
@Slf4j
@Intercepts({
        @Signature(type = StatementHandler.class, 
                method = "prepare", args = {Connection.class, Integer.class})
})
public class DynamicSqlInterceptor implements Interceptor {
    @Value("${dynamicSql.placeholder}")
    private String placeholder;
    @Value("${dynamicSql.date}")
    private  String dynamicDate;
    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        // 1. 獲取 StatementHandler 對(duì)象也就是執(zhí)行語(yǔ)句
        StatementHandler statementHandler = (StatementHandler) invocation.getTarget();
        // 2. MetaObject 是 MyBatis 提供的一個(gè)反射幫助類，可以優(yōu)雅訪問對(duì)象的屬性，這里是對(duì) statementHandler 對(duì)象進(jìn)行反射處理，
        MetaObject metaObject = MetaObject.forObject(statementHandler, SystemMetaObject.DEFAULT_OBJECT_FACTORY,
                SystemMetaObject.DEFAULT_OBJECT_WRAPPER_FACTORY,
                        new DefaultReflectorFactory());
        // 3. 通過 metaObject 反射獲取 statementHandler 對(duì)象的成員變量 mappedStatement
        MappedStatement mappedStatement = (MappedStatement) metaObject.getValue("delegate.mappedStatement");
        // mappedStatement 對(duì)象的 id 方法返回執(zhí)行的 mapper 方法的全路徑名，如ltd.newbee.mall.core.dao.UserMapper.insertUser
        String id = mappedStatement.getId();
        // 4. 通過 id 獲取到 Dao 層類的全限定名稱，然后反射獲取 Class 對(duì)象
        Class<?> classType = Class.forName(id.substring(0, id.lastIndexOf(".")));
        // 5. 獲取包含原始 sql 語(yǔ)句的 BoundSql 對(duì)象
        BoundSql boundSql = statementHandler.getBoundSql();
        String sql = boundSql.getSql();
        log.info("替換前---sql：{}", sql);
        // 攔截方法
        String mSql = null;
        // 6. 遍歷 Dao 層類的方法
        for (Method method : classType.getMethods()) {
            // 7. 判斷方法上是否有 DynamicSql 注解，有的話，就認(rèn)為需要進(jìn)行 sql 替換
            if (method.isAnnotationPresent(DynamicSql.class)) {
                mSql = sql.replaceAll(placeholder, String.format("'%s'", dynamicDate));
                break;
            }
        }
        if (StringUtils.isNotBlank(mSql)) {
            log.info("替換后---mSql：{}", mSql);
            // 8. 對(duì) BoundSql 對(duì)象通過反射修改 SQL 語(yǔ)句。
            Field field = boundSql.getClass().getDeclaredField("sql");
            field.setAccessible(true);
            field.set(boundSql, mSql);
        }
        // 9. 執(zhí)行修改后的 SQL 語(yǔ)句。
        return invocation.proceed();
    }
    @Override
    public Object plugin(Object target) {
        // 使用 Plugin.wrap 方法生成代理對(duì)象
        return Plugin.wrap(target, this);
    }
    @Override
    public void setProperties(Properties properties) {
        // 獲取配置文件中的屬性值
    }
}

// 測(cè)試類
@SpringBootTest
@RunWith(SpringRunner.class)
public class DynamicTest {
    @Autowired
    private DynamicSqlMapper dynamicSqlMapper;
    @Test
    public void test() {
        Long count = dynamicSqlMapper.count();
        Assert.notNull(count, "count不能為null");
    }
}

2023-07-11 22:13:33.375 [main] INFO  l.n.m.config.DynamicSqlInterceptor - [intercept,52] - 替換前---sql：select count(1) from member
        where create_time > @dynamicSql
2023-07-11 22:13:33.376 [main] INFO  l.n.m.config.DynamicSqlInterceptor - [intercept,62] - 替換后---mSql：select count(1) from member
        where create_time > '2023-07-10 20:10:30'