如何使用数组方法通过RMI 从数据库的table 中获取完整的数据？

Question

我想通过 RMI 从数据库 table 中获取完整的数据。我在 Java 接口中使用了数组方法，并且在实现 class 中实现了该方法。我的意图是通过实现获取数组中的数据，并在客户端通过 JTable 显示它。我在数据库中创建了一个单列 table。我必须从 table 获取全部数据到客户端。

我附上了我所做的编码。我已经评论了我得到的代码部分的错误。

界面

public interface Interface extends Remote {
     public static String[] getArray() throws Remote Exception; // Here it shows missing method 
                                                               //  body or declare abstract
}

实施

public class TheImplementation extends UnicastRemoteObject implements Interface{
    
    public TheImplementation()throws Remote Exception{
        super();
    }
    
    private static final long serialVersionUID = -3763231206310559L;
    
    Connection con;
    PreparedStatement pst;
    ResultSet rst;

    public static String[] getArray() throws RemoteException{
        String fruitdetails = null; 
        try {
            Connection connection=ConnectionProvider.getConnection();
            Statement st=connection.createStatement();
            ResultSet rs=st.executeQuery("select *from details");
            while(rs.next()) { 
                fruitdetails= rs.getString("fruit");
                String tbData[]={fruitdetails};
            }
        }
        catch (SQLException e) {
            JOptionPane.showMessageDialog(null, e);
        }
        return tbData;// Here it shows error. Cannot find symbol.
                           // I tried to declare array at top. But, It didn't work.
    }
}

Answer 1

remote interfaces中的抽象方法不能是静态的，所以需要将接口定义改成下面这样

public interface Interface extends java.rmi.Remote {
    public String[] getArray() throws RemoteException;
}

远程方法返回的值必须是serializable. Arrays in java are serializable, however arrays have a fixed size and since you are returning the result of a database query you cannot know the size. Hence I suggest that method getArray return an ArrayList or better yet, a CachedRowSet。

public interface Interface extends Remote {
    public CachedRowSet getArray() throws RemoteException;
}

由于 class TheImplementation 是您的 RMI 服务器 class，log exceptions rather than display a JOptionPane and you should always log the stack trace 可能更好。请注意，远程方法必须声明它们抛出 RemoteException 以通知 RMI 客户端远程方法失败。因此，除了记录异常之外，方法 getArray 还可以抛出 RemoteException.

以下代码演示。

import java.rmi.Remote;
import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import javax.sql.rowset.CachedRowSet;
import javax.sql.rowset.RowSetFactory;
import javax.sql.rowset.RowSetProvider;

public class TheImplementation extends UnicastRemoteObject implements Interface {

    public TheImplementation() throws RemoteException {
        super();
    }

    private static final long serialVersionUID = -3763231206310559L;

    public CachedRowSet getArray() throws RemoteException {
        try (Connection con = ConnectionProvider.getConnection();
             Statement st = con.createStatement();
             ResultSet rs = st.executeQuery("select * from details")) {
            RowSetFactory factory = RowSetProvider.newFactory();
            CachedRowSet fruitDetails = factory.createCachedRowSet();
            fruitDetails.populate(rs);
            return fruitDetails;
        }
        catch (SQLException e) {
            throw new RemoteException("Method 'getArray()' failed.", e);
        }
    }
}

注意上面的代码还用了try-with-resources保证ResultSet,Statement和Connection都关闭了

如何使用数组方法通过RMI 从数据库的table 中获取完整的数据？

How to fetch complete data from the database's table through RMI using the array method?

java

rmi