如何从Excel读取SQL查询并传递给JDBC代码

Question

Can someone suggest/help on the below query.

I have the below code which retrieve the data from database, the SQL query i am hard coding want to pass in excel and read the SQL query from excel and store the SQL query output in the result column.

package com.DBUtility;

import java.io.*;  
import java.sql.*;  


public class DataRetrieveMainClass {  
    public static void main(String args[]) throws Exception {

    PrintColumnAndData PrintCl=new PrintColumnAndData();

        try {
            Class.forName("oracle.jdbc.driver.OracleDriver");
            Connection con = DriverManager.getConnection("jdbc:oracle:thin:@123.32.23.123:8080/orcl", "Test1", "******");

            PreparedStatement ps = con.prepareStatement("select * from MSG where MID='1234'");
            ResultSet rs = ps.executeQuery();

            try {

                PrintCl.printResultColumns(rs);
            } catch (SQLException e) {
                System.err.println(e.getMessage());
            }

            con.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}


** - Excel File:**

SQL QUERY                                    RESULT
______________________________________________________
select * from MSG where MID='1234'

Answer 1

public static void main(String args[]){
    writeExcel(getSQLObjects());
}

private static ArrayList<MyObject> getSQLObjects(){
    PrintColumnAndData PrintCl=new PrintColumnAndData();
    ArrayList<MyObject> objList = new ArrayList<MyObject>();
    try {
        Class.forName("oracle.jdbc.driver.OracleDriver");
        try (Connection con = DriverManager.getConnection("jdbc:oracle:thin:@123.32.23.123:8080/orcl", "Test1", "******")){
            PreparedStatement ps = con.prepareStatement("select * from MSG where MID='1234'");
            ResultSet rs = ps.executeQuery();
            while(rs.next()) {
                MyObject object = new MyObject();
                //set object values for each column using rs.getString() etc.
            objList.add(object);
            }
        }
    }catch(SQLException e) {
        e.printStackTrace();
    }catch(ClassNotFoundException e) {
        e.printStackTrace();
    }catch (Exception e) {
        e.printStackTrace();
    }
    return objList;
}

private static void writeExcel(ArrayList<MyObject> objList) {
    Workbook book = null;
    try {
        try {
            book = new WorkbookFactory.create(new File("myFile"));
            Sheet sheet = book.getSheet("mySheet");
            int startRow = 1;
            for(MyObject obj : objList) {
                Row row = sheet.createRow(startRow);
                row.getCell(0).setCellValue(obj.value);
                row.getCell(1).setCellValue(obj.otherValue);
                //etc.
                startRow++;
            }
            book.write(new FileOutputStream(new File("myFile")));
        }finally {
            book.close();
        }
    }catch(IOException e) {
        e.printStackTrace();
    }catch(Exception e) {
        e.printStackTrace();
    }
}

That should be a huge help for you (might need to be modified slightly to fit your needs, but should give you a 'map' to your solution nonetheless). Your code seems a bit clumsy at the moment and very disorganized. You should separate your SQL database call and the excel writing into separate methods (if not classes) to handle these; I personally even create a class for the connection itself. You should also consider creating a class to represent an object to pass between the two (data transfer object).

Some things that I assumed: you are using Apache POI for excel, your excel file and the sheet for it already exist (you are just populating it), and you have headers in the first row of the sheet (hence startRow = 1).