Question

I have a jsp (itemSearch.jsp) to display all items based on user submission. Once the user submits i am calling java method to submit all parameters as shown below

submitItems = itemManager.getProcessedItems(1, itemID, startPage, endPage, fromDate, toDate);

here in getProcessedItems i am fetching data using JDBC connection

public ArrayList getProcessedItems(1, itemID, startPage, endPage, fromDate, toDate) {
ArrayList p_items=new ArrayList();
Connection connection = null;
String sqlStatement = null;

try {
            connection = DBManager.getConnection(DBManager.EPM_DATASOURCE_NAME);
            if(set==1) {

                sqlStatement =  "SELECT I.lineid, I.date,S.STATUS, S.DATETIME, ";
                sqlStatement += "S.TOTAL FROM ITEM I, LITEM LI, ITEM_STATUS S ";
                sqlStatement += "WHERE I.LINEID=LI.ID AND I.ITEMID=? ";

                if (fromDate !=null && toDate!=null){
                    SimpleDateFormat fd = new SimpleDateFormat("MM/dd/yyyy");
                    String fromdateString = fd.format(fromDate);
                    String todateString = fd.format(toDate);
                    sqlStatement += " AND I.PDATE BETWEEN RANGE_DATE('" + fd.format(fromDate) + "','MM/DD/YYYY') AND RANGE_DATE('" + fd.format(toDate) + "','MM/DD/YYYY')";

                }           
                sqlStatement += "ORDER BY I.PDATE DESC";
            } 

            PreparedStatement ps = connection.prepareStatement(paginationBegin+sqlStatement+paginationEnd);
            ps.setInt(1, ID);
            ResultSet rs = ps.executeQuery();
            while(rs.next()) {
                if(items.contains(new Integer(rs.getInt("itemid")))==false) {
                items.add(new Integer(rs.getInt("itemid")));
                ReportItem ri = new ReportItem();
                 ri.setLineItemID(rs.getInt("lineid"));
                 ri.setTransmitted(rs.getTimestamp("idate"));
                 ri.setStatus(rs.getString("status"));
                 ri.setStatusDateTime(rs.getTimestamp("s_datetime"));
                 p_items.add(ri);
                }
               }
            rs.close();
            ps.close();
        } catch (SQLException e) {
            log("ERROR");
        } catch (NamingException e) {
            log("ERROR");
        } finally {
            DBManager.closeConnection(connection);
        }

        return p_items;
}

This properly displays data in itemSearch.jsp but now i want to add CSV file (hyperlink in jsp) which contains displayed data in the file for downloading.

i.e

<div align="right" class="TableRows" style="padding-right:10px"><a href="" class="TableRowLinks">CSV File</a></div> 

Questions
1. How to generate CSV file from queried result ?
2. How to give link for the same in jsp file?

Answer 1

You can use SuperCSV

Why do you want to write in a JSP file?
Use servlet for it, just create a file with .csv extension and write your response in it.

Code Sample:

class Order {
    Integer orderNumber;
    Integer parentOrder;
    Integer productNumber;
    String  userComment;

    public Integer getOrderNumber() {
        return orderNumber;
    }
    public void setOrderNumber(int orderNumber) {
        this.orderNumber = orderNumber;
    }
    public Integer getParentOrder() {
        return parentOrder;
    }
    public void setParentOrder(int parentOrder) {
        this.parentOrder = parentOrder;
    }
    public Integer getProductNumber() {
        return productNumber;
    }
    public void setProductNumber(int productNumber) {
        this.productNumber = productNumber;
    }
    public String getUserComment() {
        return userComment;
    }
    public void setUserComment(String userComment) {
        this.userComment = userComment;
    }
}

Writing partial objects to a CSV file

public void should_partial_write() throws Exception {
    // The data to write
    Order mainOrder = new Order();
    mainOrder.setOrderNumber(1);
    mainOrder.setProductNumber(42);
    mainOrder.setUserComment("some comment");
    Order subOorder = new Order();
    subOorder.setOrderNumber(2);
    subOorder.setParentOrder(1);
    subOorder.setProductNumber(43);

    // for testing write to a string rather than a file
    StringWriter outFile = new StringWriter();

    // setup header for the file and processors. Notice the match between the header and the attributes of the
    // objects to write. The rules are that
    // - if optional "parent orders" are absent, write -1
    // - and optional user comments absent are written as ""
    String[] header = new String[] { "orderNumber", "parentOrder", "productNumber", "userComment" };
    CellProcessor[] Processing = new CellProcessor[] { null, new ConvertNullTo(-1), null, new ConvertNullTo("\"\"") };

    // write the partial data
    CsvBeanWriter writer = new CsvBeanWriter(outFile, CsvPreference.EXCEL_PREFERENCE);
    writer.writeHeader(header);
    writer.write(mainOrder, header, Processing);
    writer.write(subOorder, header, Processing);
    writer.close();

    // show output
    System.out.println(outFile.toString());
}