Java 无法连接到Apache Derby数据库

我尝试使用ApacheDerby10.15.2.0来编写一个表并从中读取。我在本地Windows计算机上运行数据库，安装了Java版本：

14.0.2

java-jar%DERBY\u HOME%\lib\derbyrun.jar ij

命令的输出：

ij版本10.15

我使用以下Java代码建立连接，然后创建数据库和表：

Connection connect = null;
PreparedStatement statement = null;
ResultSet resultSet = null;

try {
    Class.forName("org.apache.derby.jdbc.ClientDriver");
    connect = DriverManager
            .getConnection("jdbc:derby://localhost:1527/testdb;create=true");
    PreparedStatement createTable = connect.prepareStatement("CREATE TABLE Student (\n" +
            "   Id INT NOT NULL GENERATED ALWAYS AS IDENTITY,\n" +
            "   Age INT NOT NULL,\n" +
            "   First_Name VARCHAR(255),\n" +
            "   last_name VARCHAR(255),\n" +
            "   PRIMARY KEY (Id)\n" +
            ");");

    statement = connect.prepareStatement("SELECT * from Student");

    resultSet = statement.executeQuery();
    while (resultSet.next()) {
        String user = resultSet.getString("First_Name");
        String number = resultSet.getString("Id");
        System.out.println("User: " + user);
        System.out.println("ID: " + number);
    }
} catch (Exception e) {
    throw e;
}

执行期间的错误消息：

线程“main”java.sql.SQLNonTransientConnectionException连接被拒绝时出现异常：connect

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你启动了derby吗？你必须启动derby网络服务器。有关更多背景信息，请参见此答案：