MySQL、oracle分页原生查询

//根据表名 关键字 进行分页查询
@Override
public JSONArray doGet(String tableName, String keyWord,int pageNum,int pageSize) {
ResultSet result = null;
PreparedStatement pre = null;
try {
//根据数据库类型查询表的所有列名
String dataType = con.getMetaData().getDatabaseProductName();
String columnSql = "";
switch (dataType) {
case "MySQL":
columnSql = "select COLUMN_NAME from information_schema.COLUMNS where table_name ='"+tableName+"'";
break;

case "Oracle":
columnSql = "select COLUMN_NAME from all_tab_columns where table_name ='"+tableName+"'";
default:
break;
}
pre = con.prepareStatement(columnSql);
result = pre.executeQuery();
//拼接sql
StringBuilder sql = new StringBuilder("select * from "+tableName+" t where ");
ResultSetMetaData md = result.getMetaData();// 得到结果集(rs)的结构信息，比如字段数、字段名等
int columnCount = md.getColumnCount(); // 返回此 ResultSet 对象中的列数
while (result.next()) {
for(int i=1;i<=columnCount;i++){
sql.append(sql.append("t."+result.getObject(i))+" like '%"+keyWord+"%' or ");
}
}
sql = sql.delete(sql.length()-3, sql.length());//去掉sql末尾的or
if("MySQL".equals(dataType)){//MySQL分页语句拼接
sql = sql.append("LIMIT "+pageNum+","+pageSize+"");
}
if("Oracle".equals(dataType)){//Oracle分页语句拼接
String sqlStr = "SELECT * FROM (SELECT a.*, ROWNUM rn FROM ("+sql+") a WHERE ROWNUM <="+pageNum*pageSize+" ) WHERE rn >="+(pageNum-1)*pageSize+"";
sql = sql.replace(0,sql.length(), sqlStr);
}
pre = con.prepareStatement(sql.toString());
result = pre.executeQuery();
} catch (Exception e) {
e.printStackTrace();
}
return resultSetToList(pre, result);
}

/**
* 将Res
4000
ultSet结果集转成JSONArray
*
* @param pre
* @param rs
* @return
* @author
*/
public JSONArray resultSetToList(PreparedStatement pre, ResultSet result) {

if (result == null)
return null;

JSONArray array = new JSONArray();
try {
ResultSetMetaData md = result.getMetaData();// 得到结果集(rs)的结构信息，比如字段数、字段名等

int columnCount = md.getColumnCount(); // 返回此 ResultSet 对象中的列数

JSONObject json = null;
while (result.next()) {
json = new JSONObject();
for (int i = 1; i <= columnCount; i++) {
if(!"".equals(result.getObject(i))){
if(result.getObject(i) instanceof Date){
json.put(md.getColumnName(i), sdf.format(result.getObject(i)));
}else{
json.put(md.getColumnName(i), result.getObject(i));
}
}else{
json.put(md.getColumnName(i), "");
}

}
array.put(json);
}
} catch (SQLException | JSONException e) {
e.printStackTrace();
} finally {
close(result);
close(pre);
close(con);
}

//"返回json数据：" + array);
return array;
}