java - ResultSet 为包含另一个 POJO 的数组列表的 POJO

Question

希望有人能帮助我。我有一个具有以下结构的 POJO:

public class Invoice{

private String docNum;
private String customer;
private ArrayList<InvoiceDetails> invoiceDetails;

/* Getters and setters*/
}

另一个 POJO 具有以下内容

public class InvoiceDetails{

private String taxRate;
private Double taxAmount;
private Double amount;

/* Getters and setters*/
}

我想知道的是从这样的结果集中填写 Pojo Invoice 的最佳方式:

String sql= "SELECT  InvoiceNumber, Customer, TaxRate, TaxAmount,Amount FROM TAX_VIEW WHERE Date=?"
PreparedStatement pst = cn.prepareStatement(Config.SQL_FACTURAS, ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);
     pst.setDate(1, date);
     ResultSet rs = pst.executeQuery();

假设ResultSet可以为同一张发票返回多条记录，是否可以一劳永逸，而不需要第二次迭代？非常感谢

Answer 1

在你看来，我猜已经存在一个连接。我想 Invoice.docNum 与 SELECT 中的 InvoiceNumber 相同。 (为什么有不同的名字？)因此，您应该将“ORDER BY InvoiceNumber”添加到您的选择中，并在处理循环中验证它的更改。代码是伪代码，未经测试:

ResultSet rs = pst.executeQuery();
Invoice invoice=new Invoice();
while(rs.next()){
    if (invoice.getDocNum().compareTo(rs.getString(1))!=0) {
         // This is a new Invoice, so process previous if not the first one
         // and create a new instance
         invoice=new Invoice();
         invoice.setDocNum(rs.getString(1));
         invoice.setCustomer(rs.getString(2));
         invoice.setInvoiceDetails(new ArrayList<InvoiceDetails>());
    }
    InvoiceDetails invoiceDetails = new InvoiceDetails();
    invoiceDetails.setTaxRate(rs.getString(3));
    // ... further member settings, and finally add to list:
    invoice.getInvoiceDetails.add(invoiceDetails);
}
// finally process the last Invoice if it is not empty