SpringBoot使用 druid 连接池来优化分页语句

// 记录统计的 sql
String countSql = "select count(0) from (" + sql+ ") tmp_count";
PreparedStatement countStmt = connection.prepareStatement(countSql);
BoundSql countBS = new BoundSql(mappedStatement.getConfiguration(), countSql, boundSql.getParameterMappings(), parameterObject);
setParameters(countStmt, mappedStatement, countBS,parameterObject);

SELECT g.*
  , ROUND(6378.138 * 2 * ASIN(SQRT(POW(SIN((? * PI() / 180 - t.latitude * PI() / 180) / 2), 2) + COS(? * PI() / 180) * COS(t.latitude * PI() / 180) * POW(SIN((? * PI() / 180 - t.longitude * PI() / 180) / 2), 2))), 2) AS distancecd
  , t.agentname, t.agentlogo, t.compaddress
FROM t_bas_integral_goods g
  LEFT JOIN t_bas_agent t ON g.agentid = t.AGENTID
WHERE t.AGENTTYPE = '2'
  AND t.pass = '0'
  AND t.dl_type = '4'
  AND g.type = 0
ORDER BY distancecd ASC

String countSql = PagerUtils.count(sql, DbType.mysql);
System.out.println(countSql);

SELECT COUNT(*)
FROM t_bas_integral_goods g
 LEFT JOIN t_bas_agent t ON g.agentid = t.AGENTID
WHERE t.AGENTTYPE = '2'
 AND t.pass = '0'
 AND t.dl_type = '4'
 AND g.type = 0

String countSql = PagerUtils.count(sql, dbType);
PreparedStatement countStmt = connection.prepareStatement(countSql);
BoundSql countBS = new BoundSql(mappedStatement.getConfiguration(), countSql, boundSql.getParameterMappings(), parameterObject);
setParameters(countStmt, mappedStatement, countBS,parameterObject);

select * from xxx where type = #{type} order by xx

SELECT COUNT(*)
FROM xxx
WHERE type = #{type}

@Select("select * from xxx where type = #{type} order by xx")
Object test(@Param("type") String type);

/**
 * 原始 sql，用于方便 druid 工具进行分页
 *
 * @author L.cm
 */
public class MicaRawSqlSource implements SqlSource {
  private final String rawSql;
  private final SqlSource sqlSource;
  public MicaRawSqlSource(Configuration configuration, SqlNode rootSqlNode, Class<?> parameterType) {
    this(configuration, getSql(configuration, rootSqlNode), parameterType);
  }
  public MicaRawSqlSource(Configuration configuration, String sql, Class<?> parameterType) {
    SqlSourceBuilder sqlSourceParser = new SqlSourceBuilder(configuration);
    Class<?> clazz = parameterType == null ? Object.class : parameterType;
    this.rawSql = sql;
    this.sqlSource = sqlSourceParser.parse(sql, clazz, new HashMap<>());
  }
  // ... ...
}

// 进行分页
Configuration configuration = mappedStatement.getConfiguration();
SqlSourceBuilder sqlSourceParser = new SqlSourceBuilder(configuration);
Class<?> parameterType = parameterObject.getClass();
Connection connection = (Connection) invocation.getArgs()[0];
// 1. 对 sql 进行判断，如果没有 ? 号，则直接处理
String boundRawSql = boundSql.getSql();
if (boundRawSql.indexOf(CharPool.QUESTION_MARK) == -1) {
  // 不包含 ？ 号
  String countSql = PagerUtils.count(boundRawSql, dbType);
  SqlSource newSqlSource = sqlSourceParser.parse(countSql, parameterType, new HashMap<>());
  BoundSql newBoundSql = newSqlSource.getBoundSql(parameterObject);
  int count = getCount(connection, mappedStatement, parameterObject, newBoundSql);
  StringBuilder sqlBuilder = new StringBuilder(boundRawSql);
  Page page = getPageParam(parameterObject, sqlBuilder, count);
  String pageSql = generatePageSql(sqlBuilder.toString(), dbType, page);
  // 将分页sql语句反射回BoundSql.
  setField(boundSql, "sql", pageSql);
  return invocation.proceed();
}
// 2. 按 SqlSource 进行解析
SqlSource sqlSource = mappedStatement.getSqlSource();
// xml 中的动态 sql
int count;
if (sqlSource instanceof DynamicSqlSource) {
  SqlNode rootSqlNode = PagePlugin.getField(sqlSource, "rootSqlNode");
  DynamicContext context = new DynamicContext(configuration, parameterObject);
  rootSqlNode.apply(context);
  // 生成 count sql，带 #{xxx} 变量的 sql
  String countSql = PagerUtils.count(context.getSql(), dbType);
  SqlSource newSqlSource = sqlSourceParser.parse(countSql, parameterType, context.getBindings());
  BoundSql newBoundSql = newSqlSource.getBoundSql(parameterObject);
  count = getCount(connection, mappedStatement, parameterObject, newBoundSql);
} else if (sqlSource instanceof MicaRawSqlSource) {
  String rawSql = ((MicaRawSqlSource) sqlSource).getRawSql();
  DynamicContext context = new DynamicContext(configuration, parameterObject);
  // 生成 count sql，带 #{xxx} 变量的 sql
  String countSql = PagerUtils.count(rawSql, dbType);
  SqlSource newSqlSource = sqlSourceParser.parse(countSql, parameterType, context.getBindings());
  BoundSql newBoundSql = newSqlSource.getBoundSql(parameterObject);
  count = getCount(connection, mappedStatement, parameterObject, newBoundSql);
} else {
  throw new IllegalArgumentException("不支持的 sql 分页形式，请使用 xml 或者注解");
}