springboot配置多數據源（JdbcTemplate方式）

在實際開發中可能會遇到需要配置多個數據源的情況，比如：需要使用多個host、需要使用多種數據庫（MySql、Oracle、SqlServer...）

如果使用springboot開發，可做如下配置：

Config：

import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.jdbc.DataSourceBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.jdbc.core.JdbcTemplate;

import javax.sql.DataSource;

@Configuration
public class DataSourceConfig {

    @Bean(name = "testDataSource")
    @Primary
    @Qualifier("testDataSource")
    @ConfigurationProperties(prefix="spring.datasource.hikari.mysql")
    public DataSource testDataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean(name = "formalDataSource")
    @Qualifier("formalDataSource")
    @ConfigurationProperties(prefix = "spring.datasource.formal.mysql")
    public DataSource formalDataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean(name="testJdbcTemplate")
    public JdbcTemplate testJdbcTemplate (
            @Qualifier("testDataSource")  DataSource testDataSource ) {
        return new JdbcTemplate(testDataSource);
    }

    @Bean(name = "formalJdbcTemplate")
    public JdbcTemplate formalJdbcTemplate(
            @Qualifier("formalDataSource") DataSource formalDataSource){
        return new JdbcTemplate(formalDataSource);
    }
}

配置文件 application.properties

spring.datasource.hikari.mysql.jdbc-url =jdbc:mysql://mysql2.cdqdops.org:3306/standard?useUnicode=true&characterEncoding=utf-8&useSSL=false&allowMultiQueries=true
spring.datasource.hikari.mysql.username = root
spring.datasource.hikari.mysql.password = 123456
spring.datasource.hikari.mysql.driver-class-Name = com.mysql.jdbc.Driver

spring.datasource.formal.mysql.jdbc-url =jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf-8&useSSL=false&allowMultiQueries=true
spring.datasource.formal.mysql.username = root
spring.datasource.formal.mysql.password = 1314
spring.datasource.formal.mysql.driver-class-Name = com.mysql.jdbc.Driver

注意事項

使用多個數據源時，需要添加@Primary注解

@Primary：自動裝配時當出現多個Bean候選者時，被注解為@Primary的Bean將作為首選者

當然,primary意味着"主要的",類似與SQL語句中的"primary key",有且只能有一個

開發時,別人將注釋掉的代碼恢復,出現了多個"@Primary",就導致了如下錯誤:

[root@app4 logs]# tail stdout.log 
Caused by: org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type 'javax.sql.DataSource' available: more than one 'primary' bean found among candidates: [mysqlDataSource, formalDataSource, sqlServerDataSource]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.determinePrimaryCandidate(DefaultListableBeanFactory.java:1381)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.determineAutowireCandidate(DefaultListableBeanFactory.java:1341)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1110)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory$DependencyObjectProvider.getIfUnique(DefaultListableBeanFactory.java:1728)
	at org.springframework.boot.autoconfigure.jdbc.DataSourceInitializerInvoker.getDataSourceInitializer(DataSourceInitializerInvoker.java:100)
	at org.springframework.boot.autoconfigure.jdbc.DataSourceInitializerInvoker.afterPropertiesSet(DataSourceInitializerInvoker.java:62)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1758)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1695)
	... 32 common frames omitted