java - 仅当不在主方法中时才出错 : oracle. jdbc.driver.OracleDriver ClassNotFoundException

Question

我有两个完全相同的方法，唯一的区别是其中一个是在应用程序运行时调用的，另一个是 main(String[] args) 方法。

主要方法有效，尽管它只发布控制台信息。

然而，另一种方法应该返回连接对象。相反，我得到了一个 ClassNotFoundException。

工作代码:

public static void main(String[] args) throws ClassNotFoundException, SQLException {

    System.out.println("-------- Oracle JDBC Connection Testing ------");

    try {

        Class.forName("oracle.jdbc.driver.OracleDriver");

    } catch (ClassNotFoundException e) {

        System.out.println("Where is your Oracle JDBC Driver?");
        e.printStackTrace();

        throw e;
    }

    System.out.println("Oracle JDBC Driver Registered!");

    try {

        connection = DriverManager.getConnection(
            "jdbc:oracle:thin:@localhost:1521:xe", "randy",
            "test");

    } catch (SQLException e) {

        System.out.println("Connection Failed! Check output console");
        e.printStackTrace();
        throw e;

    }

    if (connection != null) {
        System.out.println("Happy");
    } else {
        throw new SQLException("Failed to setup the connection");
    }
}

结果:

-------- Oracle JDBC Connection Testing ------
Oracle JDBC Driver Registered!
Happy

---

但是，如果我将其作为常规方法而不是在我的 main 方法中调用，则会出现错误。这是代码:

错误代码:

public static Connection connect() throws SQLException, ClassNotFoundException {

    if(connection != null){
        return connection;
    }

    System.out.println("-------- Oracle JDBC Connection Testing ------");

    try {

        Class.forName("oracle.jdbc.driver.OracleDriver");

    } catch (ClassNotFoundException e) {

        System.out.println("Where is your Oracle JDBC Driver?");
        e.printStackTrace();
        throw e;
    }

    System.out.println("Oracle JDBC Driver Registered!");

    try {

        connection = DriverManager.getConnection(
            "jdbc:oracle:thin:@localhost:1521:xe", "randy",
            "test");

    } catch (SQLException e) {

        System.out.println("Connection Failed! Check output console");
        e.printStackTrace();
        throw e;

    }

    if (connection != null) {
        return connection;
    } else {
        throw new SQLException("Failed to setup the connection");
    }
}

结果:

-------- Oracle JDBC Connection Testing ------
Where is your Oracle JDBC Driver?
java.lang.ClassNotFoundException: oracle.jdbc.driver.OracleDriver

---

为什么会出现该错误以及如何解决该问题？

Answer 1

如果常规方法 connect() 是从 Java EE web 应用程序中调用的，请确保您的 oracle 驱动程序 jar 位于 web-inf/lib 目录中