最终尝试捕获，然后再次尝试捕获

Question

我经常遇到如下情况：

try{ 
     ...
     stmts
     ...
} 
catch(Exception ex) {
     ... 
     stmts
     ... 
} finally {
     connection.close // throws an exception
}

仍然需要尝试-最终在内部捕获块。

克服此问题的最佳实践是什么？

Answer 1

写一个SQLUtils类，其中包含static closeQuietly捕获和记录此类异常的方法，然后根据需要使用。

您最终会看到如下内容：

public class SQLUtils 
{
  private static Log log = LogFactory.getLog(SQLUtils.class);

  public static void closeQuietly(Connection connection)
  {
    try
    {
      if (connection != null)
      {
        connection.close();
      }
    }
    catch (SQLExcetpion e)
    {
      log.error("An error occurred closing connection.", e);
    }
  }

  public static void closeQuietly(Statement statement)
  {
    try
    {
      if (statement!= null)
      {
        statement.close();
      }
    }
    catch (SQLExcetpion e)
    {
      log.error("An error occurred closing statement.", e);
    }
  }

  public static void closeQuietly(ResultSet resultSet)
  {
    try
    {
      if (resultSet!= null)
      {
        resultSet.close();
      }
    }
    catch (SQLExcetpion e)
    {
      log.error("An error occurred closing result set.", e);
    }
  }
}

您的客户端代码将类似于：

Connection connection = null;
Statement statement = null;
ResultSet resultSet = null;
try 
{
  connection = getConnection();
  statement = connection.prepareStatement(...);
  resultSet = statement.executeQuery();

  ...
}
finally
{
  SQLUtils.closeQuietly(resultSet);
  SQLUtils.closeQuietly(statment);
  SQLUtils.closeQuietly(connection);
}

更新： 自Java
7开始，各种JDBC接口都得到了扩展java.lang.AutoCloseable，而以上代码回答了原始问题，如果您直接针对JDBC
API编写代码，则现在可以对其进行结构化：

try (
  Connection connection = getConnection();
  PreparedStatement statement = connection.prepareStatement(...);
  ResultSet resultSet = statement.executeQuery()
)
{
  ...
}