// 典型錯(cuò)誤配置方式
@Bean
public DataSource dataSource1() { /* 配置1 */ }
 
@Bean
public DataSource dataSource2() { /* 配置2 */ }
 
// 啟動(dòng)時(shí)報(bào)錯(cuò)：
// No qualifying bean of type 'javax.sql.DataSource' available: 
// expected single matching bean but found 2

@Configuration
@ConditionalOnClass({ DataSource.class, EmbeddedDatabaseType.class })
@ConditionalOnMissingBean(DataSource.class) // 關(guān)鍵點(diǎn)！
@EnableConfigurationProperties(DataSourceProperties.class)
public class DataSourceAutoConfiguration { ... }

@Bean
@Primary // 必須明確指定主事務(wù)管理器
public PlatformTransactionManager txManager1(DataSource dataSource1) {
    return new DataSourceTransactionManager(dataSource1);
}

@SpringBootApplication(exclude = {
    DataSourceAutoConfiguration.class,
    DataSourceTransactionManagerAutoConfiguration.class,
    JdbcTemplateAutoConfiguration.class
})
public class MultiDataSourceApp { ... }

# application.yml
primary:
  datasource:
    url: jdbc:mysql://primary/db
    username: admin
    password: pwd123
secondary:
  datasource:
    url: jdbc:mysql://secondary/db
    username: reader
    password: read123
@Configuration
public class DataSourceConfig {
 
    // 主數(shù)據(jù)源（必須標(biāo)記@Primary）
    @Bean(name = "primaryDataSource")
    @Primary
    @ConfigurationProperties(prefix = "primary.datasource")
    public DataSource primaryDataSource() {
        return DataSourceBuilder.create().build();
    }
 
    // 從數(shù)據(jù)源
    @Bean(name = "secondaryDataSource")
    @ConfigurationProperties(prefix = "secondary.datasource")
    public DataSource secondaryDataSource() {
        return DataSourceBuilder.create().build();
    }
}

@Configuration
public class TransactionManagerConfig {
 
    @Bean(name = "primaryTransactionManager")
    @Primary
    public PlatformTransactionManager primaryTxManager(
            @Qualifier("primaryDataSource") DataSource dataSource) {
        return new DataSourceTransactionManager(dataSource);
    }
 
    @Bean(name = "secondaryTransactionManager")
    public PlatformTransactionManager secondaryTxManager(
            @Qualifier("secondaryDataSource") DataSource dataSource) {
        return new DataSourceTransactionManager(dataSource);
    }
}

@Bean(name = "primaryJdbcTemplate")
public JdbcTemplate primaryJdbcTemplate(
        @Qualifier("primaryDataSource") DataSource dataSource) {
    return new JdbcTemplate(dataSource);
}
 
@Bean(name = "secondaryJdbcTemplate")
public JdbcTemplate secondaryJdbcTemplate(
        @Qualifier("secondaryDataSource") DataSource dataSource) {
    return new JdbcTemplate(dataSource);
}

// 明確指定使用哪個(gè)事務(wù)管理器
@Transactional(value = "secondaryTransactionManager", 
               propagation = Propagation.REQUIRES_NEW)
public void batchInsert() {
    // 使用secondary數(shù)據(jù)源執(zhí)行操作
}

@Bean(name = "primaryDataSource")
@ConfigurationProperties(prefix = "primary.datasource.hikari")
public DataSource primaryDataSource() {
    return DataSourceBuilder.create()
           .type(HikariDataSource.class).build();
}
 
// application.yml
primary:
  datasource:
    hikari:
      maximum-pool-size: 20
      connection-timeout: 3000

@Bean
public DataSourcePoolMetrics primaryDataSourceMetrics(
        @Qualifier("primaryDataSource") DataSource dataSource) {
    return new DataSourcePoolMetrics(dataSource, 
           "primary", Tags.empty());
}