java - 用通用功能包装代码，同时传递参数

Question

我有以下代码:

public void createProject() throws ServiceException {
    Project project = new ProjectMapper().map(pipeline);

    // repeating code
    Connection conn;
    try {
        conn = JDBCConnectionManager.getConnection(POOL_NAME, DB_CONNECTION_TIMEOUT);
    } catch (SQLException e1) {
        e1.printStackTrace();
        throw new ServiceException(e1);
    }
    try {
    // end repeating code

        ProjectAccess.writeProject(conn, project);

    // repeating code
    } catch (SQLException | JsonProcessingException e) {
        e.printStackTrace();
        throw new ServiceException(e);
    } finally {
        try {
            releaseConnection(conn);
        } catch (Exception e) {
            e.printStackTrace();
            throw new ServiceException(e);
        }
    }
    // end repeating code
}

基本上我想摆脱两个 try/catch block 并将它们放入包装器中，因为它们始终相同。 我考虑过使用函数式接口(interface)，它几乎可以工作，只是我必须将 conn 变量传递到我的代码中，这不适用于我的解决方案:

@FunctionalInterface
interface DatabaseLogic {        
    public void execute() throws SQLException, JsonProcessingException;        
}

public void executeSql(DatabaseLogic dl) throws ServiceException {
    Connection conn;
    try {
        conn = JDBCConnectionManager.getConnection(POOL_NAME, DB_CONNECTION_TIMEOUT);
    } catch (SQLException e1) {
        e1.printStackTrace();
        throw new ServiceException(e1);
    }
    try {
        dl.execute(conn);
    } catch (SQLException | JsonProcessingException e) {
        e.printStackTrace();
        throw new ServiceException(e);
    } finally {
        try {
            releaseConnection(conn);
        } catch (Exception e) {
            e.printStackTrace();
            throw new ServiceException(e);
        }
    }
}


    new DatabaseRunner().executeSql(() -> {
        IDataCursor pipelineCursor = pipeline.getCursor();
        String projectName = IDataUtil.getString(pipelineCursor, "projectName");
        // how can I access the conn object here?
        ProjectAccess.deleteProject(conn, projectName);
    });

那么，正如我在评论中所写，有没有办法使用函数式接口(interface)并从封闭方法访问变量？

Answer 1

哼，当然几分钟后我就明白了。我只需要将 Connection 参数添加到接口(interface)即可:

public void execute(Connection conn) throws SQLException, JsonProcessingException;

new DatabaseRunner().executeSql((conn) -> {
    IDataCursor pipelineCursor = pipeline.getCursor();
    String projectName = IDataUtil.getString(pipelineCursor, "projectName");
    ProjectAccess.deleteProject(conn, projectName);
});