Question

我写了一个Java代码来连接到main方法中的mysql数据库，并且我成功并获得了结果。但是当我在分离的类中分离数据库代码时，我遇到了与数据库连接的问题，但我什么也没做

这个代码：

package database;

import java.sql.ResultSet;
import java.sql.SQLException;

public class DataBase {
    public static void main(String[] args) throws ClassNotFoundException, SQLException {
        //Connection connect = DriverManager.getConnection("jdbc:mysql://localhost/javadb", "root", "123");
        System.out.println("sadsa");
        ConnectToDatabase db = new ConnectToDatabase("javadb", "root", "123");
        System.out.println("sadsa");

        String sqlStatement =    "SELECT  *\n" +
                                    "FROM `javadb`.`user`\n" +
                                    " LIMIT 1000;";


        ResultSet result = db.makeQuery(sqlStatement);

        while (result.next()) {
            System.out.println(result.getString("ID")
                    + " " + result.getString("UserName")
                    + " " + result.getString("Password")
                    );
        }

        db.closeConnection();

    }

}

分离的班级：

package database;

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


public class ConnectToDatabase {

    // Database Variables
    private final String databaseName;// = "jdbc:mysql://localhost/javadb";  //URL
    private final String databaseUserName;// = "root";
    private final String databasePassword;// = "123";
    private Connection connect;
    private Statement sqlStatement;

    // Connect to Database
    public ConnectToDatabase( String givenDatabaseName,String givenDatabaseUserName, String givenDatabasePassword) throws SQLException, ClassNotFoundException {
        Class.forName("com.mysql.jdbc.Driver");
        this.databaseName = givenDatabaseName;
        this.databaseUserName = givenDatabaseUserName;
        this.databasePassword = givenDatabasePassword;

        this.connect = DriverManager.getConnection("jdbc:mysql://localhost/"+givenDatabaseName, givenDatabaseName, givenDatabasePassword);
        this.sqlStatement = this.connect.createStatement();
    }

    public ResultSet makeQuery(String givenStatement) throws SQLException{
        setSqlStatement(givenStatement);
        return sqlStatement.executeQuery(givenStatement);
    }



    public String getDatabaseUserName() {
        return databaseUserName;
    }
    public String getDatabasePassword() {
        return databasePassword;
    }
    public String getDatabaseName() {
        return databaseName;
    }    
    public void setSqlStatement(Statement sqlStatement) {
        this.sqlStatement = sqlStatement;
    }
    public void closeConnection() throws SQLException{
        connect.close();
    }

    private void setSqlStatement(String givenStatement) {
        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }

}

注意：在主要方法中，如果我写相同的信息直接连接，这将正常工作：

Connection connect = DriverManager.getConnection("jdbc:mysql://localhost/javadb", "root", "123");

这是错误消息：

Exception in thread "main" java.sql.SQLException: Access denied for user 'javadb'@'localhost' (using password: YES)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1074)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4120)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4052)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:925)
    at com.mysql.jdbc.MysqlIO.secureAuth411(MysqlIO.java:4615)
    at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1302)
    at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2465)
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2498)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2283)
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:822)
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:404)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:317)
    at java.sql.DriverManager.getConnection(Unknown Source)
    at java.sql.DriverManager.getConnection(Unknown Source)
    at database.ConnectToDatabase.<init>(ConnectToDatabase.java:27)
    at database.DataBase.main(DataBase.java:15)
Java Result: 1

非常感谢

Answer 1

创建ConnectToDatabase实例时，可能没有传递正确的参数值。你能展示一部分代码吗？

Answer 2

您需要指定端口号。像

jdbc:mysql://localhost:3306/javadb

Answer 3

您必须提前指定端口号，但缺少分隔的类端口号。

Answer 4

Pablo Santa Cruz：它：

呼叫：

ConnectToDatabase db = new ConnectToDatabase("javadb", "root", "123");

方法：

public ConnectToDatabase( String givenDatabaseName,String givenDatabaseUserName, String givenDatabasePassword) throws SQLException, ClassNotFoundException {
        Class.forName("com.mysql.jdbc.Driver");
        this.databaseName = givenDatabaseName;
        this.databaseUserName = givenDatabaseUserName;
        this.databasePassword = givenDatabasePassword;

        this.connect = DriverManager.getConnection("jdbc:mysql://localhost/"+givenDatabaseName, givenDatabaseName, givenDatabasePassword);
//        "jdbc:mysql://localhost/?user=root&password=rootpassword"
//        connect = DriverManager.getConnection("jdbc:mysql://localhost/?user=root&password=rootpassword"); 
        this.sqlStatement = this.connect.createStatement();
    }

Answer 5

在ConnectTo数据库类

中为DriverManager类提供用户名和密码时出错

this.connect = DriverManager.getConnection（＆＃34; jdbc：mysql：// localhost /＆＃34; + givenDatabaseName，givenDatabaseName，givenDatabasePassword）;

这里给出两次Database（givenDatabaseName）名称而不是Database user（givenDatabaseUserName）名称;

希望有所帮助

java中具有分隔类的数据库连接

5 个答案: