application.yml文件中配置多个数据源报错找不到数据源

出现这种情况一般是因为在多数据源配置时，没有正确指定默认数据源。可以尝试在application.yml中添加以下代码：

spring:
  datasource:
    type: com.zaxxer.hikari.HikariDataSource
    driver-class-name: com.mysql.jdbc.Driver
    url: jdbc:mysql://localhost:3306/defaultdb?useSSL=false
    username: root
    password: root
    hikari:
      minimum-idle: 10
      maximum-pool-size: 100
      auto-commit: true
      connection-timeout: 30000
      idle-timeout: 600000
      max-lifetime: 1800000
      connection-test-query: SELECT 1 FROM DUAL
    testWhileIdle: true
    testOnBorrow: false
    testOnReturn: false
    filters: stat,wall,log4j
    default:
      type: com.zaxxer.hikari.HikariDataSource
      driver-class-name: com.mysql.jdbc.Driver
      url: jdbc:mysql://localhost:3306/my_db1?useSSL=false
      username: root
      password: root
      hikari:
        minimum-idle: 10
        maximum-pool-size: 100
        auto-commit: true
        connection-timeout: 30000
        idle-timeout: 600000
        max-lifetime: 1800000
        connection-test-query: SELECT 1 FROM DUAL
      testWhileIdle: true
      testOnBorrow: false
      testOnReturn: false
      filters: stat,wall,log4j
    db2:
      type: com.zaxxer.hikari.HikariDataSource
      driver-class-name: com.mysql.jdbc.Driver
      url: jdbc:mysql://localhost:3306/my_db2?useSSL=false
      username: root
      password: root
      hikari:
        minimum-idle: 10
        maximum-pool-size: 100
        auto-commit: true
        connection-timeout: 30000
        idle-timeout: 600000
        max-lifetime: 1800000
        connection-test-query: SELECT 1 FROM DUAL
      testWhileIdle: true
      testOnBorrow: false
      testOnReturn: false
      filters: stat,wall,log4j

其中，`default`表示默认数据源，`db2`为第二个数据源。需要注意的是，多数据源配置时，需要在使用的地方指定具体的数据源。例如，在DAO层中，可以使用`@Qualifier`注解指定使用的数据源名称，如：

@Repository
@Qualifier("db2")
public class UserDaoImpl implements UserDao {
    @Autowired
    @Qualifier("db2")
    private JdbcTemplate jdbcTemplate;
    //...
}