连接到用户输入数据库

Question

我有Connect（）方法，它有一个字符串参数，这个参数是用户的输入。我创建了2个数据库：test和test2，但我只能从用户输入连接到test db。我是否应该对承载2个dbs的服务器进行更改，以便能够连接到用户编写的任何数据库？？？

  public void Connect(String DataBase) {
            try{
                Class.forName("com.mysql.jdbc.Driver");
                con = DriverManager.getConnection("jdbc:mysql://localhost:3306/" + DataBase);
                st = con.createStatement();
                System.out.println("Connected to " + DataBase + " !!!");
                con.close();
            }catch(SQLException se){
                System.out.println("Cannot connect to database " + DataBase);
            }
            catch(Exception ex){
                System.out.println("Error: " + ex);
            }  
        }

主要方法

   // DB1Connect connect = new DBConnect("test");
    //connect.getData();

    Scanner scanner = new Scanner(System.in);
    System.out.println("Choose from these choices");
    System.out.println("-------------------------\n");
    System.out.println("1 - Connect to a specific DB schema");
    System.out.println("2 - List DB schema structure: tables, fields, types");
    System.out.println("3 - List table structure: fields, types");
    System.out.println("4 - Quit");
    int choice = scanner.nextInt();
     switch(choice) {
         case 1:
             System.out.println("Enter the Db's name:");
             String dbName = scanner.next();
             DBConnect connect = new DBConnect();
             connect.Connect(dbName);
             break;
         case 2:

             break;
         default:
             System.out.println("Incorrect option");
     }
}

堆栈跟踪：

Enter the Db's name:
test2
com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Access denied for user ''@'localhost' to database 'test2'
Cannot connect to database test2
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
    at com.mysql.jdbc.Util.getInstance(Util.java:381)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1030)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3491)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3423)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:910)
    at com.mysql.jdbc.MysqlIO.secureAuth411(MysqlIO.java:3923)
    at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1273)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2031)
    at com.mysql.jdbc.ConnectionImpl.(ConnectionImpl.java:718)
    at com.mysql.jdbc.JDBC4Connection.(JDBC4Connection.java:46)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:302)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:282)
    at java.sql.DriverManager.getConnection(DriverManager.java:664)
    at java.sql.DriverManager.getConnection(DriverManager.java:270)
    at medapp.DBConnect.Connect(DBConnect.java:19)
    at medapp.MedApp.main(MedApp.java:29)

Answer 1

与服务器建立连接后，尝试连接到数据库。

  public void Connect(String DataBase) {
            try{
                Class.forName("com.mysql.jdbc.Driver");
                con = DriverManager.getConnection("jdbc:mysql://localhost:3306/");
                st = con.createStatement();
                st.execute("USE " + "[" + DataBase + "]");
                System.out.println("Connected to " + DataBase + " !!!");
                con.close();
            }catch(SQLException se){
                System.out.println("Cannot connect to database " + DataBase);
            }
            catch(Exception ex){
                System.out.println("Error: " + ex);
            }  
        }

数据库是否需要验证？如果是，请尝试以下操作：

Properties connProperties;
connProperties = new Properties();
connProperties.setProperty("user", getUsername());
connProperties.setProperty("password",getPassword());

con = DriverManager.getConnection("jdbc:mysql://localhost:3306/" + DataBase, connProperties);

此外，检查数据库是否存在也是一个好主意

stat.executeQuery("SELECT * FROM sys.sysdatabases");