Error only if not in main method: oracle.jdbc.driver.OracleDriver ClassNotFoundException

Question

I have two methods that are exactly the same, the only difference is that one of them is called while the app is running, and the other is a main(String[] args) method.

The main method works, although that only posts console information.

The other method, however, is supposed to return the connection object. Instead, I get a ClassNotFoundException .

Working code:

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");
    }
}

result:

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

---

However if I call it as a regular method instead of in my main method, I get the error. This is the code:

Error code:

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");
    }
}

result:

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

---

Why do I get that error and how do I solve this problem?

Answer 1

如果从 Java EE Web 应用程序内部调用常规方法connect() ，请确保您的 oracle 驱动程序 jar 位于 web-inf/lib 目录中