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在使用JDBC的DAO类中,这两种方法中,哪一种是处理关闭ResultSet、PreparedStatement和Connection的try捕捉的最佳方法?

dao exception-handling jdbc java

TheItalianJobless · 技术社区 · 7 年前

我正在创建一个使用JDBC和MySQL的DAO类。我没有收到任何关于如何关闭标题中所列项目的指示,但我了解到这样做是一种良好的做法。现在我认为这应该在每个CRUD方法中完成,但处理异常似乎有点人为,我还不确定如何实现它。

第一个示例:

public boolean update2(Dto dto) {
    assert dto != null;
    if (readById(dto.getId()).getId() == 0) {
        throw new RuntimeException("Row with this id doesn't exist");
    }
    boolean flag = false;
    try {
        Connection connection = DAOFactory.createConnection();
        String sql = "SQL statement"; 
        try {
            PreparedStatement ps = connection.prepareStatement(sql);
            try {
                // Some stuff with preparedstatement
                ps.executeUpdate();
                flag = true;
            } finally {
                if (ps != null) ps.close();
            }
        } finally {
            if (connection != null) connection.close();
        }
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    } catch (SQLException e) {
        e.printStackTrace();
    }

    return flag;
}

第二个例子:

public boolean update(Dto dto) {
    assert dto != null;
    if (readById(dto.getId()).getId() == 0) {
        throw new RuntimeException("Row with this id doesn't exist");
    }
    boolean flag = false;
    PreparedStatement ps = null;
    Connection connection = null;
    try {
        connection = DAOFactory.createConnection();
        String sql = "SQL statement"; 
        ps = connection.prepareStatement(sql);
        // Some stuff with preparedstatement
        ps.executeUpdate();
        flag = true;
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        if (ps != null) {
            try {
                ps.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (connection != null) {
            try {
                connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

    return flag;
}

设计中是否有不只是主观的约定?

1 回复 | 直到 7 年前

ujulu 7 年前

假设您使用的是Java 1.7及以上版本,您可以使用 try with resources 简化资源关闭的声明。前提是资源实现 AutoClosable Connection 和 PreparedStatement

public boolean update2(String dto) {
    assert dto != null;

    if (readById(dto.getId()).getId() == 0) {
        throw new RuntimeException("Row with this id doesn't exist");
    }

    boolean flag = false;
    String sql = "SQL statement";
    try (Connection connection = DAOFactory.createConnection();
         PreparedStatement ps = connection.prepareStatement(sql)) {
        ps.executeUpdate();
        flag = true;
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    } catch (SQLException e) {
        e.printStackTrace();
    }

    return flag;
}