如何将 ArrayList 数据插入数据库

Question

我尝试使用 ArrayList 将数据插入数据库。有一个错误消息。 那是我的 Custmer.class 方法。这就是我将 ArrayList 传递给另一个类时得到的结果。

incompatible types: ArrayList<String> cannot be converted to ArrayList<Inquiries>

我想知道如何使用正确的使用 OOP 概念来做到这一点

   public void passingMsg(ArrayList<Inquiries> arrlist){
        try {
            System.out.println("Method "+arrlist);
            String sq = "INSERT INTO Inquiries (name,mail,tp,msg)VALUES(?,?,?)";
            PreparedStatement pr = con.prepareStatement(sq);
            for(int i=0;i<arrlist.size();i++){
                pr.setString(1,arrlist.get(i).getName());
                pr.setString(2,arrlist.get(i).getMail());
                pr.setString(3,arrlist.get(i).getTp());
                pr.setString(4,arrlist.get(i).getMsg());


            }
            pr.executeQuery();//executeBatch();
        } catch (SQLException ex) {
        }

    }

这就是我从用户那里获取价值的方式

 String name = txtName.getText();
        String mail = txtEmail.getText();
        String tp = txtTp.getText();
        String msg = txtMsg.getText();

        ArrayList<String> arrInq = new ArrayList<String>();
        arrInq.add(name);
        arrInq.add(mail);
        arrInq.add(tp);
        arrInq.add(msg);


        Custmer c =new Custmer();
        if( c.passingMsg(arrInq)){
            try {
                JOptionPane.showMessageDialog(this, "Successs!!");
            } catch (Exception e) {
                 JOptionPane.showMessageDialog(this, "Unsuccesss!!");
                e.printStackTrace();
            }
        }

这是我的 Inquiries.class ：

public class Inquiries {
    private String name;
    private String mail;
    private String tp;
    private String msg;


     public Inquiries(String name,String mail,String tp,String msg){
        this.name = name;
        this.mail = mail;
        this.tp = tp;
        this.msg = msg;
    }
//     
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getMail() {
        return mail;
    }
    public void setMail(String mail) {
        this.mail = mail;
    }
    public String getTp() {
        return tp;
    }
    public void setTp(String tp) {
        this.tp = tp;
    }
    public String getMsg() {
        return msg;
    }
    public void setMsg(String msg) {
        this.msg = msg;
    }

}

有人可以解释一下这有什么问题吗？请问？

Answer 1

您为ArrayList 使用了错误的类型参数。你需要ArrayList<Inquiries> 而不是ArrayList<String>。要解决此问题，您应该删除此代码...

    ArrayList<String> arrInq = new ArrayList<String>();
    arrInq.add(name);
    arrInq.add(mail);
    arrInq.add(tp);
    arrInq.add(msg);

...并将其替换为以下代码：

    ArrayList<Inquiries> arrInq = new ArrayList<Inquiries>();
    arrInq.add(new Inquiries(name, mail, tp, msg));

Answer 2

让我们以 O-O-P 的方式交谈。 这里 Inquiries 是你的模型，模型只不过是一个简单的类，它有实例成员和公共方法来获取和设置模型的实例变量的值。

一般我们将所有与数据库相关的操作代码放在各自的模型中。 例如我有模型“Model”，它通常映射到数据库表，说它是“TableModel”，我会做这样的事情：

public class Model{
    private int id;
    private String attr;
    //other properties of the model

    public int getId(){
      return id;
    }
    public void setId(int id){
      this.id=id;
    }
    //other getters and setters

    //here we write methods to performs database operations 
    public void save(){
        //use "this" to get properties of object
        //logic to save to this object in database table TableModel as record
    }
    public void delete(int id){
        //logic to delete this object i.e. from database table TableModel 
    }
    public Model get(int id){
       //retrieve record   from table TableModel with this id
    }
   //other methods to get data from database.
}

现在的问题是我如何在其他课程中使用它。假设我有模型对象的列表，我希望将它们插入数据库。我会这样做：

public class AnotherClass{
    public void someMethod(){
        //create list of models objects e.g. get them from user interface
       ArrayList<Model> models=new ArrayList<>();
       for(int i=0;i<3;i++){
            Model model=new Model();
            model.setId(i);
            model.setAttr("attr"+i);
            models.add(model);
       }
       SomeOtherClass obj=new SomeOtherClass();
       obj.insert(models);
    }
}

public class SomeOtherClass{
   //other code above.....

   //my method that inserts each Model object in database
   //Note: this is sample method , you should do it in optimized way
   // e.g. batch insert
    public void insert(ArrayList<Model> models){

      for(Model myModel:models){
          myModel.save();
      }

   }
   //other code below.....
}