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package com.centit.support.database.utils;

import com.alibaba.fastjson.JSONArray;
import com.alibaba.fastjson.JSONObject;
import com.centit.support.algorithm.DatetimeOpt;
import com.centit.support.algorithm.NumberBaseOpt;
import org.apache.commons.codec.binary.Base64;
import org.apache.commons.lang3.ArrayUtils;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;
import java.io.StringWriter;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

@SuppressWarnings("unused")
public abstract class DatabaseAccess {

    private DatabaseAccess() {
        throw new IllegalAccessError("Utility class");
    }

    protected static final Logger logger = LoggerFactory.getLogger(DatabaseAccess.class);
    /**
     * 调用数据库函数
     * @param conn  数据库链接
     * @param procName procName
     * @param sqlType
     *            返回值类型
     * @param paramObjs paramObjs
     * @return  调用数据库函数
     * @throws SQLException SQLException
     */
    public static Object callFunction(Connection conn, String procName, int sqlType, Object... paramObjs)
            throws SQLException {
        int n = paramObjs.length;
        StringBuilder procDesc = new StringBuilder("{?=call ");
        procDesc.append(procName).append("(");
        for (int i = 0; i < n; i++) {
            if (i > 0)
                procDesc.append(",");
            procDesc.append("?");
        }
        procDesc.append(")}");
        try(CallableStatement stmt = conn.prepareCall(procDesc.toString())){
            stmt.registerOutParameter(1, sqlType);
            for (int i = 0; i < n; i++) {
                if (paramObjs[i] == null)
                    stmt.setNull(i + 2, Types.NULL);
                else if (paramObjs[i] instanceof java.sql.Date)
                    stmt.setObject(i + 2, paramObjs[i]);
                else if (paramObjs[i] instanceof java.util.Date)
                    stmt.setObject(i + 2, DatetimeOpt.convertToSqlTimestamp((java.util.Date) paramObjs[i]));
                else
                    stmt.setObject(i + 2, paramObjs[i]);
            }
            stmt.execute();
            return stmt.getObject(1);
        }catch (SQLException e) {
            throw new DatabaseAccessException(procDesc.toString(),e);
        }
    }

    /**
     * 执行一个存储过程
     * @param conn  数据库链接
     * @param procName procName
     * @param paramObjs procName
     * @return 返回是否成功
     * @throws SQLException SQLException
     */
    public static boolean callProcedure(Connection conn, String procName, Object... paramObjs)
            throws SQLException {
        int n = paramObjs.length;
        StringBuilder procDesc = new StringBuilder("{call ");
        procDesc.append(procName).append("(");
        for (int i = 0; i < n; i++) {
            if (i > 0)
                procDesc.append(",");
            procDesc.append("?");
        }
        procDesc.append(")}");
        try(CallableStatement stmt = conn.prepareCall(procDesc.toString())){
            DatabaseAccess.setQueryStmtParameters(stmt,paramObjs);
            return stmt.execute();
        }catch (SQLException e) {
            throw new DatabaseAccessException(procDesc.toString(),e);
        }
    }

    /**
     * 直接运行SQL,update delete insert
     * @param conn conn
     * @param sSql sSql
     * @throws SQLException SQLException
     * @return 返回是否成功
     */
    public static boolean doExecuteSql(Connection conn, String sSql) throws SQLException {
        try(PreparedStatement stmt = conn.prepareStatement(sSql)){
            QueryLogUtils.printSql(logger,sSql);
            return stmt.execute();
        }catch (SQLException e) {
            throw new DatabaseAccessException(sSql,e);
        }
    }


    public static void setQueryStmtParameters(PreparedStatement stmt,Object[] paramObjs) throws SQLException{
        //query.getParameterMetadata().isOrdinalParametersZeroBased()?0:1;
        if (paramObjs != null) {
            for (int i = 0; i < paramObjs.length; i++) {
                if (paramObjs[i] == null)
                    stmt.setNull(i + 1, Types.NULL);
                else if (paramObjs[i] instanceof java.sql.Date)
                    stmt.setObject(i + 1, paramObjs[i]);
                else if (paramObjs[i] instanceof java.util.Date)
                    stmt.setObject(i + 1, DatetimeOpt.convertToSqlTimestamp((java.util.Date) paramObjs[i]));
                else
                    stmt.setObject(i + 1, paramObjs[i]);
            }
        }
    }

    public static void setQueryStmtParameters(PreparedStatement stmt,List paramObjs) throws SQLException{
        if (paramObjs != null) {
            for (int i = 0; i < paramObjs.size(); i++) {
                if (paramObjs.get(i) == null)
                    stmt.setNull(i + 1, Types.NULL);
                else if (paramObjs.get(i) instanceof java.sql.Date)
                    stmt.setObject(i + 1, paramObjs.get(i));
                else if (paramObjs.get(i) instanceof java.util.Date)
                    stmt.setObject(i + 1, DatetimeOpt.convertToSqlTimestamp((java.util.Date) paramObjs.get(i)));
                else
                    stmt.setObject(i + 1, paramObjs.get(i));
            }
        }
    }
    /*
     * 直接运行行带参数的 SQL,update delete insert
     */
    public static int doExecuteSql(Connection conn, String sSql, Object[] values) throws SQLException {
        QueryLogUtils.printSql(logger,sSql ,values );
        try(PreparedStatement stmt = conn.prepareStatement(sSql)){
            setQueryStmtParameters(stmt,values);
            return stmt.executeUpdate();
        }catch (SQLException e) {
            throw new DatabaseAccessException(sSql,e);
        }
    }

    /*
     * 执行一个带命名参数的sql语句
     */
    public static int doExecuteNamedSql(Connection conn, String sSql, Map values)
            throws SQLException {
        QueryAndParams qap = QueryAndParams.createFromQueryAndNamedParams(new QueryAndNamedParams(sSql, values));
        return doExecuteSql(conn, qap.getQuery(), qap.getParams());
    }

    private static JSONObject innerFetchResultSetRowToJSONObject(ResultSet rs,int cc, String[] fieldNames)
            throws SQLException, IOException {
        JSONObject jo = new JSONObject();
        for (int i = 0; i < cc; i++) {
            Object obj = rs.getObject(i + 1);
            if(obj!=null){
                if (obj instanceof Clob) {
                    jo.put(fieldNames[i], fetchClobString((Clob) obj));
                } else if (obj instanceof Blob) {
                    jo.put(fieldNames[i], fetchBlobAsBase64((Blob) obj));
                } else {
                    jo.put(fieldNames[i], obj);
                }
            }
        }
        return jo;
    }

    public static JSONObject fetchResultSetRowToJSONObject(ResultSet rs, String[] fieldnames)
            throws SQLException, IOException {

        if (rs.next()) {
            int cc = rs.getMetaData().getColumnCount();
            String[] fieldNames = new String[cc];
            int asFn = 0;
            if (fieldnames != null) {
                asFn = fieldnames.length;
                System.arraycopy(fieldnames,0,fieldNames,0,asFn);
                /*for (int i = 0; i < asFn; i++) {
                    fieldNames[i] = fieldnames[i];
                }*/
            }

            for (int i = asFn; i < cc; i++) {
                fieldNames[i] = mapColumnNameToField(
                    rs.getMetaData().getColumnLabel(i + 1));
            }


            return innerFetchResultSetRowToJSONObject(rs,cc,fieldNames);
        }
        return null;
    }

    public static JSONArray fetchResultSetToJSONArray(ResultSet rs, String[] fieldnames)
            throws SQLException, IOException {

        JSONArray ja = new JSONArray();
        int cc = rs.getMetaData().getColumnCount();

        String[] fieldNames = new String[cc];
        int asFn = 0;
        if (fieldnames != null) {
            asFn = fieldnames.length;
            for (int i = 0; i < asFn; i++) {
                fieldNames[i] = StringUtils.isBlank(fieldnames[i])?
                                mapColumnNameToField(rs.getMetaData().getColumnLabel(i + 1)):
                                fieldnames[i];
            }
        }

        for (int i = asFn; i < cc; i++) {
            fieldNames[i] = mapColumnNameToField(
                    rs.getMetaData().getColumnLabel(i + 1));
        }

        while (rs.next()) {
            ja.add(innerFetchResultSetRowToJSONObject(rs,cc,fieldNames));
        }
        return ja;
    }

    public static String mapColumnNameToField(String colName){
        if(StringUtils.isBlank(colName)){
            return colName;
        }

        if(colName.indexOf('_')>=0){
            int nl = colName.length();
            char [] ch = colName.toCharArray();
            int i=0 , j=0;
            while(i='A' && colName.charAt(0)<='Z'){
            return colName.toLowerCase();
        }else {
            return colName;
        }
    }

    public static String[] mapColumnsNameToFields(List colNames){
        if(colNames==null || colNames.size()==0)
            return null;
        String[] fns = new String[colNames.size()];
        for(int i=0;i fields = QueryUtils.getSqlFiledNames(sSql);
                    fns = mapColumnsNameToFields(fields);
                }
                return fetchResultSetToJSONArray(rs, fns);
                //rs.close();
                //stmt.close();
                //return ja;
            }
        }catch (SQLException e) {
            throw new DatabaseAccessException(sSql,e);
        }
    }


    public static JSONObject getObjectAsJSON(Connection conn, String sSql, Object[] values, String[] fieldnames)
            throws SQLException, IOException {
        QueryLogUtils.printSql( logger, sSql ,values );
        try(PreparedStatement stmt = conn.prepareStatement(sSql)){
            setQueryStmtParameters(stmt,values);

            try(ResultSet rs = stmt.executeQuery()) {
                if (rs == null)
                    return null;

                String[] fns = fieldnames;
                if (ArrayUtils.isEmpty(fns)) {
                    List fields = QueryUtils.getSqlFiledNames(sSql);
                    fns = mapColumnsNameToFields(fields);
                }
                return fetchResultSetRowToJSONObject(rs, fns);
                //rs.close();
                //stmt.close();
                //return ja;
            }
        }catch (SQLException e) {
            throw new DatabaseAccessException(sSql,e);
        }
    }

    public static JSONObject getObjectAsJSON(Connection conn, String sSql, Object[] values)
            throws SQLException, IOException {
        return getObjectAsJSON(conn,sSql,values,null);
    }

    public static JSONObject getObjectAsJSON(Connection conn, String sSql)
            throws SQLException, IOException {
        return getObjectAsJSON(conn,sSql,(Object[]) null,null);
    }

    public static JSONObject getObjectAsJSON(Connection conn, String sSql, Map values, String[] fieldnames)
            throws SQLException, IOException {
        QueryAndParams qap = QueryAndParams.createFromQueryAndNamedParams(new QueryAndNamedParams(sSql, values));
        return getObjectAsJSON(conn,qap.getQuery(),qap.getParams(),fieldnames);
    }

    public static JSONObject getObjectAsJSON(Connection conn, String sSql, Map values)
            throws SQLException, IOException {
        QueryAndParams qap = QueryAndParams.createFromQueryAndNamedParams(new QueryAndNamedParams(sSql, values));
        return getObjectAsJSON(conn,qap.getQuery(),qap.getParams(),null);
    }

    public static JSONArray findObjectsAsJSON(Connection conn, String sSql, Object[] values)
            throws SQLException, IOException {
        return findObjectsAsJSON(conn, sSql, values, null);
    }

    public static JSONArray findObjectsAsJSON(Connection conn, String sSql) throws SQLException, IOException {
        return findObjectsAsJSON(conn, sSql, null, null);
    }

    public static JSONArray findObjectsAsJSON(Connection conn, String sSql, Object value)
            throws SQLException, IOException {
        return findObjectsAsJSON(conn, sSql, new Object[] { value }, null);
    }


    public static JSONArray findObjectsAsJSON(Connection conn, String sSql, Object value, String[] fieldnames)
            throws SQLException, IOException {
        return findObjectsAsJSON(conn, sSql, new Object[] { value }, fieldnames);
    }

    /**
     * 执行一个带命名参数的查询并返回JSONArray
     *
     * @param conn conn
     * @param sSql sSql
     * @param values values
     * @param fieldnames
     *            对字段重命名
     * @return  执行一个带命名参数的查询并返回JSONArray
     * @throws SQLException SQLException
     * @throws IOException IOException
     */
    public static JSONArray findObjectsByNamedSqlAsJSON(Connection conn, String sSql, Map values,
            String[] fieldnames) throws SQLException, IOException {

        QueryAndParams qap = QueryAndParams.createFromQueryAndNamedParams(new QueryAndNamedParams(sSql, values));

        return findObjectsAsJSON(conn, qap.getQuery(), qap.getParams(), fieldnames);
    }

    /*
     * 执行一个带命名参数的查询并返回JSONArray
     */
    public static JSONArray findObjectsByNamedSqlAsJSON(Connection conn, String sSql, Map values)
            throws SQLException, IOException {

        QueryAndParams qap = QueryAndParams.createFromQueryAndNamedParams(new QueryAndNamedParams(sSql, values));

        return findObjectsAsJSON(conn, qap.getQuery(), qap.getParams(), null);
    }

    public static String fetchClobString(Clob clob) throws IOException {
        try (Reader reader = clob.getCharacterStream()){
            StringWriter writer = new StringWriter();
            char[] buf = new char[1024];
            int len;
            while ((len = reader.read(buf)) != -1) {
                writer.write(buf, 0, len);
            }
            //reader.close();
            return writer.toString();
        } catch (SQLException e) {
            logger.error(e.getMessage(),e);//e.printStackTrace();
            throw new IOException("write clob error", e);
        }
    }

    public static byte[] fetchBlobBytes(Blob blob) throws IOException {
        try (InputStream is = blob.getBinaryStream()){
            byte[] readBytes = new byte[is.available()];
            int nl = is.read(readBytes);
            if(nl>0)
                return readBytes;
            return null;
            // out.writeString(new String(Base64.encodeBase64(readBytes)));
        } catch (SQLException e) {
            logger.error(e.getMessage(),e);//e.printStackTrace();
            throw new IOException("write clob error", e);
        }
    }

    public static String fetchBlobAsBase64(Blob blob) throws IOException {
        try (InputStream is = blob.getBinaryStream()){
            byte[] readBytes = new byte[is.available()];
            int nl = is.read(readBytes);
            if(nl>0)
                return new String(Base64.encodeBase64(readBytes));
            return null;

        } catch (SQLException e) {
            logger.error(e.getMessage(),e);//e.printStackTrace();
            throw new IOException("write clob error", e);
        }
    }

    public static Object fetchLobField(Object fieldData, boolean blobAsBase64String) {
        if(fieldData==null)
            return null;
        try {
            if (fieldData instanceof Clob) {
                return DatabaseAccess.fetchClobString((Clob) fieldData);
            }

            if (fieldData instanceof Blob) {
                if (blobAsBase64String)
                    return DatabaseAccess.fetchBlobAsBase64((Blob) fieldData);
                else
                    return DatabaseAccess.fetchBlobBytes((Blob) fieldData);
            }

            return fieldData;
        } catch (IOException e) {
            logger.error(e.getMessage(),e);//e.printStackTrace();
        }
        return null;
    }

    public static List fetchResultSetToObjectsList(ResultSet rs) throws SQLException, IOException {

        List datas ;
        int col = rs.getMetaData().getColumnCount();
        if(rs.next()){
            datas = new ArrayList<>();
            datas.add(innerFetchResultSetRowToObjects(rs,col));
        } else {
            return null;
        }
        while (rs.next()) {
            datas.add(innerFetchResultSetRowToObjects(rs,col));
        }
        return datas;
    }


    private static Object[] innerFetchResultSetRowToObjects(ResultSet rs,int col) throws SQLException, IOException {
        Object[] objs = new Object[col];
        for (int i = 1; i <= col; i++) {
            Object obj = rs.getObject(i);
            if (obj instanceof Clob) {
                objs[i - 1] = fetchClobString((Clob) obj);
            } else if (obj instanceof Blob) {
                objs[i - 1] = fetchBlobAsBase64((Blob) obj);
            } else {
                objs[i - 1] = obj;
            }
        }
        return objs;

    }

    public static Object[] fetchResultSetRowToObjects(ResultSet rs) throws SQLException, IOException {
        if(rs.next()) {
            int col = rs.getMetaData().getColumnCount();
            return innerFetchResultSetRowToObjects(rs,col);
        }
        return null;
    }

    /*
     * 执行一个带参数的查询
     */
    public static List findObjectsBySql(Connection conn, String sSql, Object[] values)
            throws SQLException, IOException {
        QueryLogUtils.printSql(logger, sSql, values);
        try(PreparedStatement stmt = conn.prepareStatement(sSql)){
            setQueryStmtParameters(stmt,values);
            // stmt.setMaxRows(max);
            try(ResultSet rs = stmt.executeQuery()) {
                // rs.absolute(row)
                return fetchResultSetToObjectsList(rs);
            }
        }catch (SQLException e) {
            throw new DatabaseAccessException(sSql,e);
        }
    }

    /*
     * 执行一个带参数的查询
     *
     */
    public static List findObjectsBySql(Connection conn, String sSql, List values)
            throws SQLException, IOException {
        QueryLogUtils.printSql(logger, sSql, values);
        try(PreparedStatement stmt = conn.prepareStatement(sSql)){
            setQueryStmtParameters(stmt,values);
            try(ResultSet rs = stmt.executeQuery()) {
                return fetchResultSetToObjectsList(rs);
            }
        }catch (SQLException e) {
            throw new DatabaseAccessException(sSql,e);
        }
    }

    /*
     * 执行只带一个参数的查询
     *
     */
    public static List findObjectsBySql(Connection conn, String sSql, Object value)
            throws SQLException, IOException {
        QueryLogUtils.printSql(logger, sSql, value );
        try(PreparedStatement stmt = conn.prepareStatement(sSql)){
            setQueryStmtParameters(stmt,new Object[]{value});

            try(ResultSet rs = stmt.executeQuery()) {
                return fetchResultSetToObjectsList(rs);
            }
            //rs.close();
            //stmt.close();
            //return datas;
        }catch (SQLException e) {
            throw new DatabaseAccessException(sSql,e);
        }
    }

    /*
     * 执行只带一个参数的查询
     *
     */
    public static List findObjectsBySql(Connection conn, String sSql) throws SQLException, IOException {
        QueryLogUtils.printSql(logger, sSql);
        try(PreparedStatement stmt = conn.prepareStatement(sSql);
            ResultSet rs = stmt.executeQuery()){
            return fetchResultSetToObjectsList(rs);
            //rs.close();
            //stmt.close();
            //return datas;
        }catch (SQLException e) {
            throw new DatabaseAccessException(sSql,e);
        }
    }

    /*
     * 执行一个带命名参数的查询
     *
     */
    public static List findObjectsByNamedSql(Connection conn,
            String sSql, Map values)
            throws SQLException, IOException {
        QueryAndParams qap = QueryAndParams.
                createFromQueryAndNamedParams(new QueryAndNamedParams(sSql, values));
        return findObjectsBySql(conn, qap.getQuery(), qap.getParams());
    }



    /*
     * *执行一个标量查询
     */
    public static Object[] getSingleRow(Connection conn, String sSql, Map values)
            throws SQLException, IOException {

        List objList = DatabaseAccess.findObjectsByNamedSql(conn,sSql, values);
        if(objList!=null && objList.size()>0)
            return objList.get(0);
        return null;
    }
    /*
     * * 执行一个标量查询
     */
    public static Object[] getSingleRow(Connection conn, String sSql, Object[] values)
            throws SQLException, IOException {

        List objList = DatabaseAccess.findObjectsBySql(conn,sSql, values);
        if(objList!=null && objList.size()>0)
            return objList.get(0);
        return null;
    }


    /*
     * * 执行一个标量查询
     */
    public static Object[] getSingleRow(Connection conn, String sSql)
            throws SQLException, IOException {
        List objList = DatabaseAccess.findObjectsBySql(conn,sSql);
        if(objList!=null && objList.size()>0)
            return objList.get(0);
        return null;
    }

    /*
     * * 执行一个标量查询
     */
    public static Object[] getSingleRow(Connection conn, String sSql,Object value)
            throws SQLException, IOException {
        List objList = DatabaseAccess.findObjectsBySql(conn,sSql,value);
        if(objList!=null && objList.size()>0)
            return objList.get(0);
        return null;
    }


    /* 下面是分页查询相关的语句 */
    /*----------------------------------------------------------------------------- */
    public static Object fetchScalarObject(List rsDatas) throws IOException {
        if (rsDatas == null || rsDatas.size() == 0)
            return null;
        Object[] firstRow = rsDatas.get(0);
        if (firstRow == null || firstRow.length == 0)
            return null;
        return firstRow[0];
    }


    /**
     * 执行一个标量查询
     * @param conn 数据库链接
     * @param sSql sql 语句
     * @param values 参数
     * @return 返回值 object
     * @throws SQLException SQLException
     * @throws IOException SQLException
     */
    public static Object getScalarObjectQuery(Connection conn, String sSql, Map values)
            throws SQLException, IOException {

        List objList = DatabaseAccess.findObjectsByNamedSql(conn,sSql, values);

        return DatabaseAccess.fetchScalarObject(objList);
    }
    /*
     * * 执行一个标量查询
     */
    public static Object getScalarObjectQuery(Connection conn, String sSql, Object[] values)
            throws SQLException, IOException {

        List objList = DatabaseAccess.findObjectsBySql(conn,sSql, values);

        return DatabaseAccess.fetchScalarObject(objList);
    }


    /*
     * * 执行一个标量查询
     */
    public static Object getScalarObjectQuery(Connection conn, String sSql)
            throws SQLException, IOException {
        List objList = DatabaseAccess.findObjectsBySql(conn,sSql);
        return DatabaseAccess.fetchScalarObject(objList);
    }

    /*
     * * 执行一个标量查询
     */
    public static Object getScalarObjectQuery(Connection conn, String sSql,Object value)
            throws SQLException, IOException {
        List objList = DatabaseAccess.findObjectsBySql(conn,sSql,value);
        return DatabaseAccess.fetchScalarObject(objList);
    }

    /**
     * 将sql语句转换为查询总数的语句，
     * 输入的语句为不带分页查询的语句，对于oracle来说就是where中没有rowunm，Mysql语句中没有limitDB2中没有fetch等等
     *
     * @param conn conn
     * @param sSql sSql
     * @param values
     *            参数应该都在条件语句中，如果标量子查询中也有参数可能会有SQLException异常
     * @return Long
     * @throws SQLException
     *             如果标量子查询中也有参数可能会有SQLException异常
     * @throws IOException
     *             这个查询应该不会有这个异常
     */
    public static Long queryTotalRows(Connection conn, String sSql, Object[] values)
            throws SQLException, IOException {

        Object scalarObj = DatabaseAccess.getScalarObjectQuery(conn, QueryUtils.buildGetCountSQL(sSql), values);

        return NumberBaseOpt.castObjectToLong(scalarObj);
    }

    /**
     * 将sql语句转换为查询总数的语句，
     * 输入的语句为不带分页查询的语句，对于oracle来说就是where中没有rowunm，Mysql语句中没有limitDB2中没有fetch等等
     *
     * @param conn conn
     * @param sSql sSql
     * @param values 命名参数
     * @return Long
     * @throws SQLException
     *             这个查询应该不会有这个异常
     * @throws IOException
     *             这个查询应该不会有这个异常
     */
    public static Long queryTotalRows(Connection conn, String sSql, Map values)
            throws SQLException, IOException {

        Object scalarObj = DatabaseAccess.getScalarObjectQuery(conn, QueryUtils.buildGetCountSQL(sSql), values);

        return NumberBaseOpt.castObjectToLong(scalarObj);
    }

    private static String makePageQuerySql(Connection conn, String sSql,  int pageNo,
                                           int pageSize ){
        int offset = (pageNo > 1 && pageSize > 0)?(pageNo - 1) * pageSize:0;
        String query;
        switch(DBType.mapDBType(conn)){
            case Oracle:
                query = QueryUtils.buildOracleLimitQuerySQL(sSql, offset, pageSize, false);
                break;
            case DB2:
                query = QueryUtils.buildDB2LimitQuerySQL(sSql, offset, pageSize);
                break;
            case SqlServer:
                query = QueryUtils.buildSqlServerLimitQuerySQL(sSql, offset, pageSize);
                break;
            case MySql:
                query = QueryUtils.buildMySqlLimitQuerySQL(sSql, offset, pageSize, false);
                break;
            default:
                query = sSql;
                break;
        }
        return query;
    }

    /* 下面是根据不同数据库生成不同的查询语句进行分页查询相关的语句 */
    /*----------------------------------------------------------------------------- */

    /**
     * 执行一个带参数的分页查询，这个是完全基于jdbc实现的，对不同的数据库来说效率差别可能很大
     *
     * @param conn
     *            数据库连接
     * @param sSql
     *            sql语句，这个语句必须用命名参数
     * @param values
     *            命名参数对应的变量
     * @param pageNo 第几页
     * @param pageSize 每页大小 ，小于1 为不分页
     * @return JSONArray
     * @throws SQLException SQLException
     * @throws IOException IOException
     */
    public static List findObjectsBySql(Connection conn, String sSql, Object[] values, int pageNo,
                                                        int pageSize) throws SQLException, IOException {
        String query = makePageQuerySql(conn, sSql, pageNo, pageSize );
        if(query.equals(sSql)){
            try(PreparedStatement stmt = conn.prepareStatement(sSql)){
                setQueryStmtParameters(stmt,values);

                if (pageNo > 0 && pageSize > 0)
                    stmt.setMaxRows(pageNo * pageSize);

                try(ResultSet rs = stmt.executeQuery()) {

                    if (pageNo > 1 && pageSize > 0)
                        rs.absolute((pageNo - 1) * pageSize);

                    return DatabaseAccess.fetchResultSetToObjectsList(rs);
                    //rs.close();
                    //stmt.close();
                    //return datas;
                }
            }catch (SQLException e) {
                throw new DatabaseAccessException(sSql, e);
            }
        }else
            return findObjectsBySql(conn, query, values);
    }



    /**
     *
     * @param conn
     *            数据库连接
     * @param sSql
     *            sql语句，这个语句必须用命名参数
     * @param values
     *            命名参数对应的变量
     * @param fieldnames 对字段重命名
     * @param pageNo 第几页
     * @param pageSize 每页大小 ，小于1 为不分页
     *            字段名称作为json中Map的key，没有这个参数的函数会自动从sql语句中解析字段名作为json中map的
     * @return JSONArray实现了List JSONObject 接口，JSONObject实现了Map String,
     *         Object 接口。所以可以直接转换为List Map String,Object
     * @throws SQLException SQLException
     * @throws IOException IOException
     */
    public static JSONArray findObjectsAsJSON(Connection conn, String sSql, Object[] values, String[] fieldnames,
            int pageNo, int pageSize) throws SQLException, IOException {

        String query = makePageQuerySql(conn, sSql, pageNo, pageSize );

        if(query.equals(sSql)) {
            try (PreparedStatement stmt = conn.prepareStatement(sSql)){
                setQueryStmtParameters(stmt, values);

                if (pageNo > 0 && pageSize > 0)
                    stmt.setMaxRows(pageNo * pageSize);

                try(ResultSet rs = stmt.executeQuery()) {

                    if (rs == null)
                        return new JSONArray();

                    if (pageNo > 1 && pageSize > 0)
                        rs.absolute((pageNo - 1) * pageSize);

                    String[] fns = fieldnames;
                    if (ArrayUtils.isEmpty(fns)) {
                        List fields = QueryUtils.getSqlFiledNames(sSql);
                        fns = mapColumnsNameToFields(fields);
                    }
                    return fetchResultSetToJSONArray(rs, fns);
                    //rs.close();
                    //stmt.close();
                    //return ja;
                }
            } catch (SQLException e) {
                throw new DatabaseAccessException(sSql, e);
            }
        }else {
            String[] fns = fieldnames;
            if (ArrayUtils.isEmpty(fns)) {
                List fields = QueryUtils.getSqlFiledNames(sSql);
                fns = mapColumnsNameToFields(fields);
            }
            return findObjectsAsJSON(conn, query, values, fns);
        }
    }

    /**
     *
     * @param conn
     *            数据库连接
     * @param sSql
     *            sql语句，这个语句必须用命名参数
     * @param values
     *            命名参数对应的变量
     * @param pageNo 第几页
     * @param pageSize 每页大小 ，小于1 为不分页
     *            字段名称作为json中Map的key，没有这个参数的函数会自动从sql语句中解析字段名作为json中map的
     * @return JSONArray实现了List JSONObject 接口，JSONObject实现了Map String,
     *         Object 接口。所以可以直接转换为List Map String,Object
     * @throws SQLException SQLException
     * @throws IOException IOException
     * */
    public static JSONArray findObjectsAsJSON(Connection conn, String sSql, Object[] values,
            int pageNo, int pageSize) throws SQLException, IOException {
        return findObjectsAsJSON(conn,sSql,values,null,pageNo,pageSize);
    }

    /**
     * 执行分页一个带命名参数的查询
     *
     * @param conn
     *            数据库连接
     * @param sSql
     *            sql语句，这个语句必须用命名参数
     * @param values
     *            命名参数对应的变量
     * @param pageNo 第几页
     * @param pageSize 每页大小 ，小于1 为不分页
     * @return JSONArray
     * @throws SQLException SQLException
     * @throws IOException IOException
     */
    public static List findObjectsByNamedSql(
            Connection conn, String sSql, Map values,
            int pageNo, int pageSize)
            throws SQLException, IOException {

        QueryAndParams qap = QueryAndParams.createFromQueryAndNamedParams(new QueryAndNamedParams(sSql, values));

        return findObjectsBySql(conn, qap.getQuery(), qap.getParams(),pageNo,pageSize);
    }



    /**
     * 执行一个带命名参数的查询并返回JSONArray
     *
     * @param conn
     *            数据库连接
     * @param sSql
     *            sql语句，这个语句必须用命名参数
     * @param values
     *            命名参数对应的变量
     * @param fieldnames 对字段重命名
     *            对字段重命名
     * @param pageNo 第几页
     * @param pageSize 每页大小 ，小于1 为不分页
     * @return JSONArray
     * @throws SQLException SQLException
     * @throws IOException IOException
     */
    public static JSONArray findObjectsByNamedSqlAsJSON(
            Connection conn, String sSql, Map values,
            String[] fieldnames,int pageNo, int pageSize)throws SQLException, IOException {

        QueryAndParams qap = QueryAndParams.createFromQueryAndNamedParams(new QueryAndNamedParams(sSql, values));

        return findObjectsAsJSON(conn, qap.getQuery(), qap.getParams(), fieldnames,pageNo,pageSize);
    }

}
    

    

    

            

    

            



    
    






    
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