Mybatis 在dao中获取分页的总记录数

/**
	 * get total count
	 * @param sqlSession
	 * @param statementName
	 * @param values
	 * @return
	 */
	private long getTotalCount(SqlSession sqlSession, String statementName,Object values ) {
		Map parameterMap=toParameterMap(values);
		long count=0l;
		try {
			MappedStatement mst = sqlSession.getConfiguration().getMappedStatement(statementName);
			BoundSql boundSql = mst.getBoundSql(parameterMap);
			String sql = " select count(*) total_count from (" + boundSql.getSql()+ ") ";
			PreparedStatement pstmt = sqlSession.getConnection().prepareStatement(sql);
//			BoundSql countBS = new BoundSql(mst.getConfiguration(),sql,boundSql.getParameterMappings(),parameterMap);  
			setParameters(pstmt,mst,boundSql,parameterMap);
			ResultSet rs=pstmt.executeQuery(); 
			if (rs.next()){ 
				count = rs.getLong("total_count");
			}
            rs.close();
            pstmt.close();
		} catch (Exception e) {
			count=0l;
			e.printStackTrace();
			throw new RuntimeException(e);
		}
		
		return count;
	}
	
    /** 
     * 对SQL参数(?)设值,参考org.apache.ibatis.executor.parameter.DefaultParameterHandler 
     * @param ps 
     * @param mappedStatement 
     * @param boundSql 
     * @param parameterObject 
     * @throws SQLException
     */  
    private void setParameters(PreparedStatement ps,MappedStatement mappedStatement,BoundSql boundSql,Object parameterObject) throws SQLException {  
        ErrorContext.instance().activity("setting parameters").object(mappedStatement.getParameterMap().getId());  
        List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();  
        if (parameterMappings != null) {
            Configuration configuration = mappedStatement.getConfiguration();  
            TypeHandlerRegistry typeHandlerRegistry = configuration.getTypeHandlerRegistry();  
            MetaObject metaObject = parameterObject == null ? null: configuration.newMetaObject(parameterObject);  
            for (int i = 0; i < parameterMappings.size(); i++) {  
                ParameterMapping parameterMapping = parameterMappings.get(i);  
                if (parameterMapping.getMode() != ParameterMode.OUT) {  
                    Object value;
                    String propertyName = parameterMapping.getProperty();  
                    PropertyTokenizer prop = new PropertyTokenizer(propertyName);
                    if (parameterObject == null) {  
                        value = null;  
                    } else if (typeHandlerRegistry.hasTypeHandler(parameterObject.getClass())) {  
                        value = parameterObject;  
                    } else if (boundSql.hasAdditionalParameter(propertyName)) {  
                        value = boundSql.getAdditionalParameter(propertyName);  
                    } else if (propertyName.startsWith(ForEachSqlNode.ITEM_PREFIX)&& boundSql.hasAdditionalParameter(prop.getName())) {  
                        value = boundSql.getAdditionalParameter(prop.getName());  
                        if (value != null) {  
                            value = configuration.newMetaObject(value).getValue(propertyName.substring(prop.getName().length()));  
                        }  
                    } else {  
                        value = metaObject == null ? null : metaObject.getValue(propertyName);  
                    }  
                    TypeHandler typeHandler = parameterMapping.getTypeHandler();  
                    if (typeHandler == null) {  
                        throw new ExecutorException("There was no TypeHandler found for parameter "+ propertyName + " of statement "+ mappedStatement.getId());  
                    }
                    typeHandler.setParameter(ps, i + 1, value, parameterMapping.getJdbcType());  
                }  
            }  
        }  
    }  
    
    protected Map toParameterMap(Object parameter) {
		if (parameter == null) {
			return new HashMap();
		}
		
		if (parameter instanceof Map) {
			return (Map<?,?>) parameter;
		} else {
			try {
				return PropertyUtils.describe(parameter);
			} catch (Exception e) {
				e.printStackTrace();
				return null;
			}
		}
	}