Spring Boot 项目问题：Web server failed to start. Port 5566 was already in use.

• 在启动一个 Spring Boot 项目时，遇到以下错误信息

***************************
APPLICATION FAILED TO START
***************************

Description:

Web server failed to start. Port 5566 was already in use.

Action:

Identify and stop the process that's listening on port 5566 or configure this application to listen on another port.

问题原因

• Spring Boot 项目使用的的端口 5566 已被占用，错误信息已明确指出

Web server failed to start. Port 5566 was already in use.

处理策略

1. 终止占用端口的进程

# 查找占用进程

netstat -ano | findstr 【端口】

# 查看进程 ID 对应的程序

tasklist | findstr 【进程 ID】

# 终止进程

taskkill /PID 【进程 ID】 /F

2. 或者，修改 Spring Boot 项目的端口

server:
  port: 6677 # 修改为其他未被占用的端口

连带问题

1. 如下，是 Spring Boot 项目在端口被占用后，引发了数据库连接池关闭的连带问题

2. 此问题在端口占用问题被处理后也会得到处理

org.mybatis.spring.MyBatisSystemException
	at org.mybatis.spring.MyBatisExceptionTranslator.translateExceptionIfPossible(MyBatisExceptionTranslator.java:97)
	at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:439)
	at jdk.proxy2/jdk.proxy2.$Proxy61.selectOne(Unknown Source)
	at org.mybatis.spring.SqlSessionTemplate.selectOne(SqlSessionTemplate.java:160)
    ...
### Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Failed to obtain JDBC Connection
	at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:153)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:145)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:140)
    ...
Caused by: org.springframework.jdbc.CannotGetJdbcConnectionException: Failed to obtain JDBC Connection
	at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:83)
	at org.mybatis.spring.transaction.SpringManagedTransaction.openConnection(SpringManagedTransaction.java:80)
	at org.mybatis.spring.transaction.SpringManagedTransaction.getConnection(SpringManagedTransaction.java:67)
	at org.apache.ibatis.executor.BaseExecutor.getConnection(BaseExecutor.java:337)
    ...
Caused by: java.sql.SQLException: HikariDataSource HikariDataSource (null) has been closed.
	at com.zaxxer.hikari.HikariDataSource.getConnection(HikariDataSource.java:96)
	at org.springframework.jdbc.datasource.DataSourceUtils.fetchConnection(DataSourceUtils.java:159)
	at org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(DataSourceUtils.java:117)
	at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:80)
	...