配置流程
（一）配置文件配置
#多源數據庫配置
#第一數據庫
spring.datasource.primary.url=jdbc:MySQL://localhost:3306/spring?useUnicode=true&characterEncoding=utf-8&useSSL=false
spring.datasource.primary.username=root
spring.datasource.primary.password=123456
spring.datasource.primary.driver-class-name=com.mysql.jdbc.Driver
#第二數據庫
spring.datasource.secondary.url=jdbc:mysql://localhost:3306/spring1?useUnicode=true&characterEncoding=utf-8&useSSL=false
spring.datasource.secondary.username=root
spring.datasource.secondary.password=123456
spring.datasource.secondary.driver-class-name=com.mysql.jdbc.Driver
（二）新建一個DataSourceConfig配置類，代碼如下：
/**
* 多數據源配置
*/
@Configuration
public class DataSourceConfig {
/**
* 第一數據源
* @return
*/
@Bean(name = "primaryDataSource")
@Qualifier("primaryDataSource")
@ConfigurationProperties(prefix="spring.datasource.primary")
public DataSource primaryDataSource() {
return DataSourceBuilder.create().build();
}
/**
* 第二數據源
* @return
*/
@Primary //默認選擇這個數據源進行執行
@Bean(name = "secondaryDataSource")
@Qualifier("secondaryDataSource")
@ConfigurationProperties(prefix="spring.datasource.secondary")
public DataSource secondaryDataSource() {
return DataSourceBuilder.create().build();
}
/**
* 本例使用的是jdbcTemplate來進行測試，所以添加jdbcTemplate的支持如下
* @param dataSource
* @return
*/
@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);
}
}
（三）新建測試用例
@Autowired
@Qualifier("primaryJdbcTemplate")
protected JdbcTemplate jdbcTemplate1;
@Autowired
@Qualifier("secondaryJdbcTemplate")
protected JdbcTemplate JdbcTemplate2;
@Test
public void test() throws Exception {
//往第一數據庫添加數據
jdbcTemplate1.update("insert into user_test(name,age) values(?, ?)","多源數據庫",150);
//往第二數據庫添加數據
JdbcTemplate2.update("insert into user_test_1(name,age) values(?, ?)","多源數據庫",150);
}
（四）報錯
JAVA.lang.IllegalStateException: Failed to load ApplicationContext
at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:124)
at org.springframework.test.context.support.DefaultTestContext.getApplicationContext(DefaultTestContext.java:83)
at org.springframework.test.context.web.ServletTestExecutionListener.setUpRequestContextIfNecessary(ServletTestExecutionListener.java:189)
at org.springframework.test.context.web.ServletTestExecutionListener.prepareTestInstance(ServletTestExecutionListener.java:131)
at org.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:230)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.createTest(SpringJUnit4ClassRunner.java:228)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner$1.runReflectiveCall(SpringJUnit4ClassRunner.java:287)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.methodBlock(SpringJUnit4ClassRunner.java:289)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:247)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:94)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:191)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'learnController': Unsatisfied dependency expressed through field 'learnService'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'learnServiceImpl': Unsatisfied dependency expressed through field 'learnDao'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'learnDaoImpl': Unsatisfied dependency expressed through field 'jdbcTemplate'; nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type 'org.springframework.jdbc.core.JdbcTemplate' available: expected single matching bean but found 2: primaryJdbcTemplate,secondaryJdbcTemplate
報錯信息有幾個，之前沒有添加多源數據的時候正常，主要是后面這個報錯：
主要問題報錯位置
（五）報錯分析
從字面意思可以知道，本來只需要一個bean，但是找到了兩個bean，系統不知道需要用到哪一個bean，所以報錯，而系統所找到的就是我們之前配置的兩個多源數據寫的bean。
回到剛才的配置類，我們發現，我們已經在第二數據源上面加上了@Primary，按道理來說，系統應該默認執行該方法，不至于說找不到需要選擇執行哪個bean
等等.....
剛才我們添加的@Primary的方法只是用來讀取配置文件該選擇哪個數據庫而已，但是對JdbcTemplate支持的方法并沒有告訴系統該執行哪一個！！！！！
那么問題就很好解決了
真相只有一個......
在secondaryJdbcTemplate方法上添加@Primary注解，如下：
@Primary
@Bean(name = "secondaryJdbcTemplate")
public JdbcTemplate secondaryJdbcTemplate(
@Qualifier("secondaryDataSource") DataSource dataSource) {
return new JdbcTemplate(dataSource);
}
ok ，重新運行測試單元
久違的綠色又出來了
綠了綠了，哈哈哈，看一下數據庫是否添加成功
看一下兩個庫的數據是否添加成功
數據添加成功，兩個庫中都有數據
原文來源鏈接：
https://www.jianshu.com/p/c2ec8a283a80
