如何處理在JDBC重複值，同時加入多個表

Question

以下是我的JDBC代碼，以從多個表

public Set<Bill> fetch(long billNo) { 

     System.out.println(" BillProductDetailsBusiness fetch()"); 
     status = "success"; 

     Set st = new HashSet(); 
     con = ConnectionFactory.getConnection(); 

     try { 

      String query = "select distinct bpd.product_id,bpd.bill_no," 
        + "bpd.qty, bpd.unit_price as up,bpd.selling_price sp," 
        + "bpd.discount_percent as dp, " 
        + "bd.*,cu.*,pr_dl.*, " 
        + " colors.color,pmodeld.model_no, ptype.product_type, " 
        + "sizes.size, pbrand.brand,suppd.name " 
        + "from bill_product_details as bpd " 
        + "left join bill_details as bd " 
        + "on bd.bill_no=bpd.bill_no " 
        + "left join product_details as pr_dl " 
        + "on bpd.product_id=pr_dl.barcode " 
        + "left join " 
        + "colors " 
        + "on pr_dl.color_id=colors.color_id " 
        + "left join " 
        + "product_model_details as pmodeld " 
        + "on pr_dl.model_id=pmodeld.model_no_id " 
        + "left join " 
        + " product_brand as pbrand " 
        + "on pr_dl.brand_id=pbrand.id " 
        + "left join " 
        + "product_types as ptype " 
        + "on pr_dl.product_type_id=ptype.product_type_id " 
        + "left join " 
        + "sizes " 
        + "on pr_dl.size_id=sizes.size_id " 
        + "left join " 
        + "supplier_details as suppd " 
        + " on pr_dl.supplier_id=suppd.id " 
        + "left join customer_details as cu " 
        + "on bd.customer_id=cu.id " 
        + "where bpd.bill_no=? "; 

      ps = con.prepareStatement(query); 
      ps.setLong(1, billNo); 

      System.out.println("Before execution"); 
      res = ps.executeQuery(); 
      Bill b; 
      ProductDetailsAction pb = null; 
      while (res.next()) { 
       b = new Bill(); 
       long product_id = res.getLong("product_id"); 
       int qty = res.getInt("qty"); 
       float unit_price_s = res.getFloat("up"); 
       float sell_price_s = res.getFloat("sp"); 
       int dis_per_s = res.getInt("dp"); 

       long bill_no = res.getLong("bill_no"); 
       long customer_id = res.getLong("customer_id"); 
       float sub_total = res.getFloat("sub_total"); 
       float vat = res.getFloat("vat"); 
       float total = res.getFloat("total"); 
       String payment_type = res.getString("payment_type"); 
       Timestamp add_date = res.getTimestamp("add_date"); 

       long bar_code = res.getLong("barcode"); 
       String color = res.getString("color"); 
       String model_no = res.getString("model_no"); 
       String brand = res.getString("brand"); 
       String product_type = res.getString("product_type"); 
       String size = res.getString("size"); 
       String supplier_name = res.getString("name"); 
       long quntity = res.getLong("quntity"); 
       float unit_price = res.getLong("unit_price"); 
       float selling_price = res.getLong("selling_price"); 
       int discount_percent = res.getInt("discount_percent"); 

       long id = res.getLong("id"); 
       String name = res.getString("name"); 
       String address = res.getString("address"); 
       String mobno = res.getString("mobno"); 
       Date dob = res.getDate("dob"); 
       Date anniversery = res.getDate("anniversery"); 
       Timestamp adddate = res.getTimestamp("add_date"); 
       //setting bill bean 
       System.out.println(bill_no + " " + sub_total); 
       b.getBillDetails().setBillNo(bill_no); 
       b.getBillDetails().setSubTotal(sub_total); 
       b.getBillDetails().setVat(vat); 
       b.getBillDetails().setTotal(total); 
       b.getBillDetails().setPaymentType(payment_type); 

       SimpleDateFormat DATE_FORMAT = new SimpleDateFormat("dd-MMM-yy hh:mm aaa"); 
       String pur_date = DATE_FORMAT.format(add_date); 
       b.getBillDetails().setDispDate(pur_date); 

       b.getCustomerDetails().setCustomerName(name); 
       b.getCustomerDetails().setAddress(address); 
       b.getCustomerDetails().setMobno(mobno); 
       pb = new ProductDetailsAction(); 
       pb.setBarCode(bar_code); 
       pb.setProductType(product_type); 
       pb.setProductSize(size); 
       pb.setQuantity(qty); 
       pb.setUnitPrice(unit_price_s); 
       pb.setSellingPrice(sell_price_s); 
       pb.setTotalSellingPrice(sell_price_s * qty); 
       pb.setDiscountPercentage(dis_per_s); 
       b.getProductDetails().add(pb); 
       st.add(b); 

      } 

      con.close(); 
     } catch (SQLException s) { 
      status = "failure"; 
      System.out.println("SQL code does not execute." + s); 
     } finally { 
      try { 
       if (con != null) { 
        con.close(); 
       } 
      } catch (SQLException sqe) { 
       status = "failure"; 
       System.out.println("SQLException " + sqe); 
      } 
     } 
     System.out.println("Returning from BillProductDetailsBusiness fetch() "); 

     return st; 
    } 

獲取數據Bill.java

public class Bill { 

     private CustomerAction customerDetails = new CustomerAction(); 
     private Set<ProductDetailsAction> productDetails = new   HashSet<ProductDetailsAction>(0); 
     private BillAction billDetails = new BillAction(); 
//getter and setter 
} 

我從多個表中獲取數據在jsp頁面中顯示。 這段代碼獲取正確的數據。 問題是，如果productDetails多於一個，那麼它重複customerDetails和billDetails多達productDetails。

我想一個customerDetails一個billDetails和一個或多個productDetails數據庫

可用如何解決這個問題。

Answer 1

我相信這個問題是要加入的表格，讓您的數據從SQL，這意味着數據庫重新將返回多行：

customer1 bill1 product1 
customer1 bill1 product2 
etc 

有解決這幾個方面。最簡單的，取決於是否有足夠的內存將數據保存在內存中，是將您的Bill存儲在散列表中，並且在遍歷行時，檢查Bill是否已經在散列表中。如果是，請將產品添加到帳單中的產品列表中，否則，創建一個新的Bill對象並添加到地圖中。

然後，當你在頁面上顯示它，你會顯示：

Bill1 
    - product1 
    - product2 

等等希望有所幫助。