java - 从 Java 应用程序创建到 2 个数据库的连接

Question

我有 Connection 类的代码，它只从一个数据库获取连接。看下面的DBConnection.java

package eksim.db.sql;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;


public class DBConnection {

    public Connection conn=null;
    private static DBConnection dbConn=null;
    static final String DB_URL=
            "jdbc:sqlserver://10.0.0.47\\test;databaseName=a;";
    static final String DB_USER="sa";
    static final String DB_PASS="123";




    public DBConnection(){
         if(conn==null){
             try{
                 Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver").newInstance();
                 conn=DriverManager.getConnection(DB_URL, DB_USER, DB_PASS);
             }
             catch(Exception ex){
                 ex.printStackTrace();
             }
         }
    }





    public static  DBConnection getInstance(){
        DBConnection conn=null;
        if(dbConn==null){
            System.out.println("New");
            dbConn=new DBConnection();
            conn=dbConn;
        } else{
            conn=dbConn;
        }
        return conn;
    }
    public Connection getCon() throws SQLException{
        return this.conn;
    }
}

现在，我想创建另一个到不同数据库的连接。谁能给我建议修改这段代码，以便将 Connection 的结果放入 2 个数据库中？感谢您的回复

Answer 1

您需要提供一些方法来识别不同的连接，还需要配置这些连接。

您可以提供一个 newInstance 方法，并向其传递一个名称，该名称用于标识连接和创建该连接所需的连接属性。

然后，当您想获得对连接的引用时，您可以简单地使用 getInstance(name)

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.HashMap;
import java.util.Map;

public class DBConnection {

    public Connection conn = null;

    private static Map<String, DBConnection> mapInstances = new HashMap<String, DBConnection>(25);

    private String dbURL;
    private String dbUser;
    private String dbPassword;

    private DBConnection(String dbURL, String dbUser, String dbPassword) {
        this.dbPassword = dbPassword;
        this.dbURL = dbURL;
        this.dbUser = dbUser;
    }

    public synchronized static DBConnection newInstance(String name, String dbURL, String dbUser, String dbPassword) {
        DBConnection con = new DBConnection(dbURL, dbUser, dbPassword);
        mapInstances.put(name, con);
        return con;
    }

    public synchronized static DBConnection getInstance(String name) {
        return mapInstances.get(name);
    }

    public synchronized Connection getCon() throws SQLException {
        if (conn == null) {
            try {
                Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver").newInstance();
                conn = DriverManager.getConnection(dbURL, dbUser, dbPassword);
            } catch (Exception ex) {
                ex.printStackTrace();
            }
        }
        return this.conn;
    }

}

例如……

DBConnection db1 = DBConnection.newInstance("db1", ....);
DBConnection db2 = DBConnection.newInstance("db2", ....);

当你想再次访问连接时......

DBConnection db1 = DBConnection.getInstance("db1");
DBConnection db2 = DBConnection.getInstance("db2");