测试springboot多个数据源配置时，需要安装多个mysql容器，由于资源限制，当前只有一台虚拟机，如果在一台机器上安装多个mysql实例，是可以的，但步骤比较繁琐，使用docker来安装MySQL容器，非常简单，只需要简单几步，对于测试非常方便
dcker部署多个mysql容器
1、下载mysql镜像，这里下载5.7.23版本
docker pull mysql:5.7.23
2、启动一个mysql容器
docker run --name db001 -p 3306:3306 -e MYSQL_ROOT_PASSWORD=12345 -d mysql:5.7.23
3、启动第二个mysql容器
docker run --name db002 -p 3307:3306 -e MYSQL_ROOT_PASSWORD=12345 -d mysql:5.7.23
有时，启动的时候可能会出现以下提示,且容器未正常启动，此时可以重启下docker，然后在启动mysql容器来尝试解决该问题
[root@localhost ~]# docker run --name db002 -p 3307:3306 -e MYSQL_ROOT_PASSWORD=12345 -d mysql
4e9380ef9bb8d81ac686116ad266377eb0e97ab80ceb6b653cf4c8214f3c9718
/usr/bin/docker-current: Error response from daemon: driver failed programming external connectivity on endpoint mysql_test2 (00ccfe607d64b17f0ee91b426cbe5b814fea70bf110960e8621959d35a9cfc62): (iptables failed: iptables --wait -t nat -A DOCKER -p tcp -d 0/0 --dport 3307 -j DNAT --to-destination 172.17.0.3:3306 ! -i docker0: iptables: No chain/target/match by that name.
4、查看mysql容器启动情况
上述映射到mysql容器的端口均为3306，每个容器都有一个小型的linux系统
使用java连接mysql容器
java连接mysql容器与不使用docker容器相比，没有什么不同。只是如果没有使用ssl，则在java连接mysql容器时，需要添加参数useSSL=false，或者配置ssl
spring.datasource.url=jdbc:mysql://192.168.101.116:3307/myapp002?useSSL=false
否则会出现以下异常
com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server. at com.mysql.cj.jdbc.exceptions.SQLError.createCommunicationsException(SQLError.java:174) ~[mysql-connector-java-8.0.17.jar:8.0.17] at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:64) ~[mysql-connector-java-8.0.17.jar:8.0.17] at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:827) ~[mysql-connector-java-8.0.17.jar:8.0.17] at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:447) ~[mysql-connector-java-8.0.17.jar:8.0.17] at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:237) ~[mysql-connector-java-8.0.17.jar:8.0.17] at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:199) ~[mysql-connector-java-8.0.17.jar:8.0.17] at com.zaxxer.hikari.util.DriverDataSource.getConnection(DriverDataSource.java:136) ~[HikariCP-3.2.0.jar:na] at com.zaxxer.hikari.pool.PoolBase.newConnection(PoolBase.java:369) ~[HikariCP-3.2.0.jar:na] at com.zaxxer.hikari.pool.PoolBase.newPoolEntry(PoolBase.java:198) ~[HikariCP-3.2.0.jar:na] at com.zaxxer.hikari.pool.HikariPool.createPoolEntry(HikariPool.java:467) [HikariCP-3.2.0.jar:na] at com.zaxxer.hikari.pool.HikariPool.checkFailFast(HikariPool.java:541) [HikariCP-3.2.0.jar:na] at com.zaxxer.hikari.pool.HikariPool.<init>(HikariPool.java:115) [HikariCP-3.2.0.jar:na] at com.zaxxer.hikari.HikariDataSource.getConnection(HikariDataSource.java:112) [HikariCP-3.2.0.jar:na] at org.springframework.jdbc.datasource.DataSourceUtils.fetchConnection(DataSourceUtils.java:157) [spring-jdbc-5.1.9.RELEASE.jar:5.1.9.RELEASE] at org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(DataSourceUtils.java:115) [spring-jdbc-5.1.9.RELEASE.jar:5.1.9.RELEASE] at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:78) [spring-jdbc-5.1.9.RELEASE.jar:5.1.9.RELEASE] at org.springframework.jdbc.core.JdbcTemplate.execute(JdbcTemplate.java:370) [spring-jdbc-5.1.9.RELEASE.jar:5.1.9.RELEASE] at org.springframework.jdbc.core.JdbcTemplate.query(JdbcTemplate.java:451) [spring-jdbc-5.1.9.RELEASE.jar:5.1.9.RELEASE] at org.springframework.jdbc.core.JdbcTemplate.query(JdbcTemplate.java:461) [spring-jdbc-5.1.9.RELEASE.jar:5.1.9.RELEASE] at org.springframework.jdbc.core.JdbcTemplate.queryForList(JdbcTemplate.java:489) [spring-jdbc-5.1.9.RELEASE.jar:5.1.9.RELEASE] at com.demo.bootdemo.MainBusi.run(MainBusi.java:25) [classes/:na] at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:780) [spring-boot-2.1.7.RELEASE.jar:2.1.7.RELEASE] at org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:764) [spring-boot-2.1.7.RELEASE.jar:2.1.7.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:319) [spring-boot-2.1.7.RELEASE.jar:2.1.7.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:1214) [spring-boot-2.1.7.RELEASE.jar:2.1.7.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:1203) [spring-boot-2.1.7.RELEASE.jar:2.1.7.RELEASE] at com.demo.bootdemo.MultidatasourceApplication.main(MultidatasourceApplication.java:10) [classes/:na] Caused by: com.mysql.cj.exceptions.CJCommunicationsException: Communications link failure The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server. at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_172] at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source) ~[na:1.8.0_172] at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source) ~[na:1.8.0_172] at java.lang.reflect.Constructor.newInstance(Unknown Source) ~[na:1.8.0_172] at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:61) ~[mysql-connector-java-8.0.17.jar:8.0.17] at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:105) ~[mysql-connector-java-8.0.17.jar:8.0.17] at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:151) ~[mysql-connector-java-8.0.17.jar:8.0.17] at com.mysql.cj.exceptions.ExceptionFactory.createCommunicationsException(ExceptionFactory.java:167) ~[mysql-connector-java-8.0.17.jar:8.0.17] at com.mysql.cj.protocol.a.NativeProtocol.negotiateSSLConnection(NativeProtocol.java:340) ~[mysql-connector-java-8.0.17.jar:8.0.17] at com.mysql.cj.protocol.a.NativeAuthenticationProvider.negotiateSSLConnection(NativeAuthenticationProvider.java:777) ~[mysql-connector-java-8.0.17.jar:8.0.17] at com.mysql.cj.protocol.a.NativeAuthenticationProvider.proceedHandshakeWithPluggableAuthentication(NativeAuthenticationProvider.java:486) ~[mysql-connector-java-8.0.17.jar:8.0.17] at com.mysql.cj.protocol.a.NativeAuthenticationProvider.connect(NativeAuthenticationProvider.java:202) ~[mysql-connector-java-8.0.17.jar:8.0.17] at com.mysql.cj.protocol.a.NativeProtocol.connect(NativeProtocol.java:1348) ~[mysql-connector-java-8.0.17.jar:8.0.17] at com.mysql.cj.NativeSession.connect(NativeSession.java:163) ~[mysql-connector-java-8.0.17.jar:8.0.17] at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:947) ~[mysql-connector-java-8.0.17.jar:8.0.17] at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:817) ~[mysql-connector-java-8.0.17.jar:8.0.17] ... 24 common frames omitted Caused by: javax.net.ssl.SSLHandshakeException: java.security.cert.CertificateNotYetValidException: NotBefore: Mon Sep 16 23:20:24 CST 2019 at sun.security.ssl.Alerts.getSSLException(Unknown Source) ~[na:1.8.0_172] at sun.security.ssl.SSLSocketImpl.fatal(Unknown Source) ~[na:1.8.0_172] at sun.security.ssl.Handshaker.fatalSE(Unknown Source) ~[na:1.8.0_172] at sun.security.ssl.Handshaker.fatalSE(Unknown Source) ~[na:1.8.0_172] at sun.security.ssl.ClientHandshaker.serverCertificate(Unknown Source) ~[na:1.8.0_172] at sun.security.ssl.ClientHandshaker.processMessage(Unknown Source) ~[na:1.8.0_172] at sun.security.ssl.Handshaker.processLoop(Unknown Source) ~[na:1.8.0_172] at sun.security.ssl.Handshaker.process_record(Unknown Source) ~[na:1.8.0_172] at sun.security.ssl.SSLSocketImpl.readRecord(Unknown Source) ~[na:1.8.0_172] at sun.security.ssl.SSLSocketImpl.performInitialHandshake(Unknown Source) ~[na:1.8.0_172] at sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source) ~[na:1.8.0_172] at sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source) ~[na:1.8.0_172] at com.mysql.cj.protocol.ExportControlled.performTlsHandshake(ExportControlled.java:316) ~[mysql-connector-java-8.0.17.jar:8.0.17] at com.mysql.cj.protocol.StandardSocketFactory.performTlsHandshake(StandardSocketFactory.java:188) ~[mysql-connector-java-8.0.17.jar:8.0.17] at com.mysql.cj.protocol.a.NativeSocketConnection.performTlsHandshake(NativeSocketConnection.java:99) ~[mysql-connector-java-8.0.17.jar:8.0.17] at com.mysql.cj.protocol.a.NativeProtocol.negotiateSSLConnection(NativeProtocol.java:331) ~[mysql-connector-java-8.0.17.jar:8.0.17] ... 31 common frames omitted Caused by: java.security.cert.CertificateNotYetValidException: NotBefore: Mon Sep 16 23:20:24 CST 2019 at sun.security.x509.CertificateValidity.valid(Unknown Source) ~[na:1.8.0_172] at sun.security.x509.X509CertImpl.checkValidity(Unknown Source) ~[na:1.8.0_172] at sun.security.x509.X509CertImpl.checkValidity(Unknown Source) ~[na:1.8.0_172] at com.mysql.cj.protocol.ExportControlled$X509TrustManagerWrapper.checkServerTrusted(ExportControlled.java:363) ~[mysql-connector-java-8.0.17.jar:8.0.17] at sun.security.ssl.AbstractTrustManagerWrapper.checkServerTrusted(Unknown Source) ~[na:1.8.0_172] ... 43 common frames omitted
另外，docker容器启动一定要设置内存大小，根据-m参数指定，单位为b、k、m和g