Question

我不了解 DatabaseAccess 类的目的。我很好奇对象名称＆＃34; conDA＆＃34; 如何包含数据库连接，即使不使用我创建的 getConnection（）方法也是如此。示例＆＃34; con2 = new Connection2（conDA）;＆＃34; 如何＆＃34; conDA＆＃34;对象名称可以理解为数据库的连接？以下是代码：

import java.sql.*;
public class Connection1 
{
    static Connection connection;
    static ConnectionDA conDA;
    static Connection2 con2;

    public static void main(String args[]) throws ClassNotFoundException, SQLException
    {
        conDA = new ConnectionDA(getConnection());
        System.out.println("Con1 Connected!!");
        con2 = new Connection2(conDA);  
    }

    public static Connection getConnection() throws ClassNotFoundException, SQLException
    {
        Class.forName("com.ibm.db2.jcc.DB2Driver");
        connection =  DriverManager.getConnection("jdbc:db2://localhost:50000/Sample", "ZeroCool","siliconvalley"); 

        return connection;
    }
}

第二课

import java.sql.*;
public class Connection2
{
    ConnectionDA conDA;
    Connection3 con3;

    public Connection2(ConnectionDA conDA) throws ClassNotFoundException
    {
        this.conDA = new ConnectionDA(conDA.getConnection());
        this.conDA = conDA;
        System.out.println("Con2 Connected!!");
        con3 = new Connection3(conDA);
    }
}

第3课

import java.sql.*;
public class Connection3 
{
    ConnectionDA conDA;

    public Connection3(ConnectionDA conDA) throws ClassNotFoundException
    {
        this.conDA = new ConnectionDA(conDA.getConnection());
        this.conDA = conDA;
        System.out.println("Con3 Connected!!");
    }
}

数据库访问类

import java.sql.*;
public class ConnectionDA 
{
    Connection connection;

    public ConnectionDA(Connection connection) throws ClassNotFoundException
    {
        this.connection = connection;
        System.out.println("ConDA Established!!!");
    }

    public Connection getConnection() 
    {
        return connection;
    }
}

Answer 1

如何将“conDA”对象名称理解为连接数据库？

因为ConnectionDA类具有getConnection实现方法，它返回类型为connection的对象。

public Connection3(ConnectionDA conDA) throws ClassNotFoundException
{
    this.conDA = new ConnectionDA(conDA.getConnection());
}

这里是getConnection（）方法的实现。

public class ConnectionDA 
{
    public Connection getConnection() 
    {
        return connection;
    }
}

我很好奇对象名称“conDA”是如何包含的数据库连接即使不使用getConnection（）方法我创建

这是因为，类在构造函数

上接收连接

public class ConnectionDA 
{
    Connection connection;

    public ConnectionDA(Connection connection) throws ClassNotFoundException
    {
        this.connection = connection;
    }

}

Java，将数据库连接传递到不同的类。

1 个答案: