配置流程

（一）配置文件配置

#多源數(shù)據(jù)庫(kù)配置
#第一數(shù)據(jù)庫(kù)
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(shù)據(jù)庫(kù)
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(gè)DataSourceConfig配置類(lèi)，代碼如下：

/**
 * 多數(shù)據(jù)源配置
 */
@Configuration
public class DataSourceConfig {
    /**
     * 第一數(shù)據(jù)源
     * @return
     */
    @Bean(name = "primaryDataSource")
    @Qualifier("primaryDataSource")
    @ConfigurationProperties(prefix="spring.datasource.primary")
    public DataSource primaryDataSource() {
        return DataSourceBuilder.create().build();
    }

    /**
     * 第二數(shù)據(jù)源
     * @return
     */
    @Primary  //默認(rèn)選擇這個(gè)數(shù)據(jù)源進(jìn)行執(zhí)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(lái)進(jìn)行測(cè)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(cè)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(shù)據(jù)庫(kù)添加數(shù)據(jù)
        jdbcTemplate1.update("insert into user_test(name,age) values(?, ?)","多源數(shù)據(jù)庫(kù)",150);
        //往第二數(shù)據(jù)庫(kù)添加數(shù)據(jù)
        JdbcTemplate2.update("insert into user_test_1(name,age) values(?, ?)","多源數(shù)據(jù)庫(kù)",150);
    }

（四）報(bào)錯(cuò)

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(bào)錯(cuò)信息有幾個(gè)，之前沒(méi)有添加多源數(shù)據(jù)的時(shí)候正常，主要是后面這個(gè)報(bào)錯(cuò)：

SpringBoot配置多數(shù)據(jù)源Consider marking one of the beans as @Primary

主要問(wèn)題報(bào)錯(cuò)位置

（五）報(bào)錯(cuò)分析

從字面意思可以知道，本來(lái)只需要一個(gè)bean，但是找到了兩個(gè)bean，系統(tǒng)不知道需要用到哪一個(gè)bean，所以報(bào)錯(cuò)，而系統(tǒng)所找到的就是我們之前配置的兩個(gè)多源數(shù)據(jù)寫(xiě)的bean。

回到剛才的配置類(lèi)，我們發(fā)現(xiàn)，我們已經(jīng)在第二數(shù)據(jù)源上面加上了@Primary，按道理來(lái)說(shuō)，系統(tǒng)應(yīng)該默認(rèn)執(zhí)行該方法，不至于說(shuō)找不到需要選擇執(zhí)行哪個(gè)bean
等等.....
剛才我們添加的@Primary的方法只是用來(lái)讀取配置文件該選擇哪個(gè)數(shù)據(jù)庫(kù)而已，但是對(duì)JdbcTemplate支持的方法并沒(méi)有告訴系統(tǒng)該執(zhí)行哪一個(gè)！！！！！
那么問(wèn)題就很好解決了
真相只有一個(gè)......
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(yùn)行測(cè)試單元