我们是否需要在throw声明中在方法签名中已经提到的catch块中引发相同的异常

Question

I have a method in my Java App which throws SQLException . Is it necessary to throw the SQLException in the catch block so that the exception is thrown to the calling method where the exception is handled?

public void insert(Connection conn) throws SQLException
{
    try {
        // my code
    } catch (SQLException s) {
        throw s;
    }
}

Answer 1

If you want to handle the exception yourself and then pass it to the calling method, then yes, you will need to re-throw it:

public void insert(Connection conn) throws SQLException {
    try {
        // Your code.
    } catch (SQLException s) {
        // Handle s.
        throw s;
    }
}

If you don't need to do anything with the exception and just want to pass it to the calling method then you can just omit the try - catch and if an exception is thrown the calling method will receive it:

public void insert(Connection conn) throws SQLException {
    // Your code.
}

Answer 2

The error occur because you place your code inside a 'try-catch' block, if any exception will happen the catch block handle with it. not send to the calling method.

You can use the below function to thrown the exception to the calling method

public void insert(Connection conn) throws SQLException {
    //code.
}

Answer 3

If you declare exception in throws clause of the method, then you can:
1) throw exception of declared type.
2) throw exception of subtype of declared type.
3) swallow the exception. (Not recommended as you have declared it in signature)
4) throw any other runtime exception.

Now coming to your example, It would be good to re-throw the exception so that the caller method knows that something wrong happened and take appropriate action (eg if a transaction is running on the Connection object then roll-back the transaction).