nested exception is org.apache.http.conn.HttpHostConnectException

这个异常通常是由于网络连接问题引起的。具体来说，它表示你的程序无法连接到指定的主机。可能的原因包括主机名错误、端口号错误、网络故障、防火墙屏蔽等等。

为了解决这个问题，你可以尝试以下几个步骤：

1. 检查主机名和端口号是否正确，确保它们与你的目标服务一致。

2. 确认你的网络连接正常。可以使用 ping 命令或者 tracert 命令来测试连接。

3. 检查你的防火墙设置，确保它们不会屏蔽对目标主机的连接。

4. 如果你使用的是代理服务器，检查代理服务器的设置是否正确。

5. 尝试使用其他网络环境或者其他计算机重新运行程序，以确定问题是否与你的本地环境有关。

如果以上步骤都不能解决问题，你可能需要更详细的信息来诊断问题。可以查看系统日志或者网络日志，以了解更多关于连接失败的信息。

相关问题

Connection refused(Connection refused);nested exception is org.apache.http.conn.HttpHostConnectException: Connect to localhost: 8003

Connection refused错误是指连接被拒绝的错误。在给出的引用中，有两个相关的错误：
- org.apache.http.conn.HttpHostConnectException: Connect to localhost:80 [localhost/127.0.0.1, localhost/0:0:0:0:0:0:0:1] failed: Connection refused: connect
- Connection refused: connect; nested exception is java.net.ConnectException: Connection refused: connect

这些错误通常是由于无法建立与目标主机的连接而引起的。出现这个错误的原因可能有很多，但常见的原因包括以下几点：
1. 目标主机没有在指定的端口上监听连接请求。
2. 防火墙或网络设置阻止了连接请求。
3. 目标主机不可达或不可用。

要解决这个问题，可以考虑以下几个步骤：
1. 确保目标主机正在运行，并且相应的服务正在监听指定的端口。
2. 检查防火墙或网络设置，确保允许连接请求通过指定的端口。
3. 检查网络连接是否正常，确保目标主机可达和可用。

如果以上步骤都没有解决问题，可以尝试参考提供的引用和[4]中的解决办法，这些解决办法可能会提供更具体的信息和思路来解决问题。<span class="em">1</span><span class="em">2</span><span class="em">3</span><span class="em">4</span>

nested exception is org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.

nested exception is org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.PersistenceException:
Error querying database. Cause: org.apache.ibatis.executor.ExecutorException: A query was run and no Result Maps were found for the Mapped Statement 'com.example.mapper.UserMapper.getUserById'. It's likely that neither a Result Type nor a Result Map was specified.
Cause: org.apache.ibatis.executor.ExecutorException: A query was run and no Result Maps were found for the Mapped Statement 'com.example.mapper.UserMapper.getUserById'. It's likely that neither a Result Type nor a Result Map was specified.

This exception is thrown when there is an issue with executing a query using MyBatis framework. In this case, the nested exception is org.apache.ibatis.exceptions.PersistenceException, which indicates that there was an error querying the database.

The specific error message states that no Result Maps were found for the Mapped Statement 'com.example.mapper.UserMapper.getUserById'. This means that either a Result Type or a Result Map was not specified for the query.

To resolve this issue, you need to make sure that the appropriate Result Type or Result Map is specified for the query in the MyBatis mapping file (XML) or in the annotation-based configuration.