Question

如何完美地抛出DAO异常......有人可以帮助我。

catch块应该给出什么异常。有人可以告诉我如何完美地完成这项工作。

  public static List<Product> loadProductsAvailable() throws **//throws which exception for dao**

    SQLException {
            List<Product> productList = new ArrayList<>();
            Connection connection = null;
            ResultSet resultSet = null;
            Statement statement = null;
            try {
                connection = ConnectionFactory.getConnection();
                statement = connection.createStatement();
                resultSet = statement.executeQuery(GET_ALL_PRODUCTS_SQL);
                while (resultSet.next()) {
                    productList.add(getProductFromResultSet(resultSet));
                }
            } finally {
                try {
                    if (connection != null) {
                        statement.close();
                        resultSet.close();
                        connection.close();
                    }
                } catch (  **//what exception should be given here to throw dao exception**    ) {
                    **//how to code for dao exception**
                }
            }
            return productList;

        }

Answer 1

在catch中抛出异常如下：

 try { 

 }  catch(DAOException e) {     
     throw new DAOException(DAOException.TYPE.SQLE, e); 
 }

Answer 2

//在例外情况下在dao包中创建以下自定义异常类公共类DataAccessException扩展Exception {

private String exceptionMsg;

public DataAccessException(String exceptionMsg){
    this.exceptionMsg = exceptionMsg;
}


public String getExceptionMsg() {
    return exceptionMsg;
}


public void setExceptionMsg(String exceptionMsg) {
    this.exceptionMsg = exceptionMsg;
}

}

    public static List<Product> loadProductsAvailable() throws **//throws which DataAccessException {
        List<Product> productList = new ArrayList<>();
        Connection connection = null;
        ResultSet resultSet = null;
        Statement statement = null;
        try {
            connection = ConnectionFactory.getConnection();
            statement = connection.createStatement();
            resultSet = statement.executeQuery(GET_ALL_PRODUCTS_SQL);
            while (resultSet.next()) {
                productList.add(getProductFromResultSet(resultSet));
            }
        } finally {
            try {
                if (connection != null) {
                    statement.close();
                    resultSet.close();
                    connection.close();
                }
            } catch (DataAccessException dataAccessException    ) {
               throw new DataAccessException("Data base Access Exception"+dataAccessException.getMessage());
            }
        }
        return productList;

    }

Answer 3

您可以为dao图层定义自定义例外，并使用它从那里投掷。您可以在该异常类中定义errorCode和errorMessage，如此

public class DaoLayerException extends RuntimeException {

    private String errorMessage;

    private int errorCode;

    public DaoLayerException() {

    }

    public DaoLayerException(int code, String message) {

        this.errorMessage = message;
        this.errorCode = code;
    }

}

然后在你的代码中使用

try {

       //your code

        } catch (Exception e) {

            throw new DaoLayerException("yourerrorcode", e.getMessage());

        }

如何抛出并捕获DAOException

3 个答案: