解决 jdbcUrl is required with driverClassName

终于解决了。
jdbcUrl is required with driverClassName

我在写瓦力老师的寻屋项目，前两节就搞的我好痛苦。由于瓦力老师用的spring-boot依赖是1.xx多。我用的是2.2.5.RELEASE

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.5.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

所以很多东西都变了。
这个错误主要是多数据源引用不明确引起的。
后面配置多数据源时，即 JPA 和H2。在测试H2测试的时候一直报错。
即使我加了这句

#一般情况下走dev（开发）配置，所以我们可以把一些公共配置放到dev配置下，一些个性配置可以分开放
spring.profiles.active=dev

也没有用。
后面在spring网站配置多数据源的时候看到了解决方案。
下面是spring提供的一些信息：
9.9.2. Configure Two DataSources
If you need to configure multiple data sources, you can apply the same tricks that are described in the previous section. You must, however, mark one of the DataSource instances as @Primary, because various auto-configurations down the road expect to be able to get one by type.

If you create your own DataSource, the auto-configuration backs off. In the following example, we provide the exact same feature set as the auto-configuration provides on the primary data source:

@Bean
@Primary
@ConfigurationProperties("app.datasource.first")
public DataSourceProperties firstDataSourceProperties() {
    return new DataSourceProperties();
}

@Bean
@Primary
@ConfigurationProperties("app.datasource.first.configuration")
public HikariDataSource firstDataSource() {
    return firstDataSourceProperties().initializeDataSourceBuilder().type(HikariDataSource.class).build();
}

@Bean
@ConfigurationProperties("app.datasource.second")
public BasicDataSource secondDataSource() {
    return DataSourceBuilder.create().type(BasicDataSource.class).build();
}

firstDataSourceProperties has to be flagged as @Primary so that the database initializer feature uses your copy (if you use the initializer).

Both data sources are also bound for advanced customizations. For instance, you could configure them as follows:

app.datasource.first.url=jdbc:mysql://localhost/first
app.datasource.first.username=dbuser
app.datasource.first.password=dbpass
app.datasource.first.configuration.maximum-pool-size=30

app.datasource.second.url=jdbc:mysql://localhost/second
app.datasource.second.username=dbuser
app.datasource.second.password=dbpass
app.datasource.second.max-total=30

You can apply the same concept to the secondary DataSource as well, as shown in the following example:

@Bean
@Primary
@ConfigurationProperties("app.datasource.first")
public DataSourceProperties firstDataSourceProperties() {
    return new DataSourceProperties();
}

@Bean
@Primary
@ConfigurationProperties("app.datasource.first.configuration")
public HikariDataSource firstDataSource() {
    return firstDataSourceProperties().initializeDataSource