SpringBoot集成Hint语法组件的代码详解

public class HintContext {

    private static final ThreadLocal<String> hint = ThreadLocal.withInitial(() -> null);

    public static void markHint(String s) {
        hint.set(s);
    }

    public static boolean isHint() {
        return StringUtils.isNotBlank(hint.get());
    }

    public static String getHint() {
        return hint.get();
    }

    public static void clear() {
        hint.remove();
    }

}

     private void changeSQL(BoundSql boundSql, String hint) {
                String originalSql = boundSql.getSql();
                String newSql = originalSql.replaceFirst("(?i)SELECT\s+", "SELECT "+ hint +" ");
                // 使用MetaObject对象将新的SQL语句设置到BoundSql对象中
                MetaObject metaObject = SystemMetaObject.forObject(boundSql);
                metaObject.setValue("sql", newSql);
        }

<dependency>
  <groupId>com.github.hint</groupId>
  <artifactId>mybatis-hint-spring-boot-starter</artifactId>
</dependency>

hint:
  enable: true

//采用MysqlEnum的hint语句
public UserInfoVO getInfoById(Long id) {

        // 强制路由到主库查询
        HintContext.markHint(MysqlEnum.TO_MASTER.getHint());
        // 执行数据库查询
        User pojo = this.getById(id);
        if (pojo == null) {
            return null;
        }
        UserInfoVO userInfoVO = new UserInfoVO();
        userInfoVO.setCode(pojo.getCode());
        userInfoVO.setName(pojo.getUsername());
        return userInfoVO;
    }

//自定义的hint语句
public UserInfoVO getInfoById(Long id) {

        // 强制路由到指定的实例
        HintContext.markHint("/* to server test_ro_1 */");
        // 执行数据库查询
        User pojo = this.getById(id);
        if (pojo == null) {
            return null;
        }
        UserInfoVO userInfoVO = new UserInfoVO();
        userInfoVO.setCode(pojo.getCode());
        userInfoVO.setName(pojo.getUsername());
        return userInfoVO;
    }