spring-boot学习：八、数据库连接之自定义配置

尽管spring boot为我们封装了大量的配置，开箱即用；但是每个项目背景不一样，最归会有一些个性化的需求，比如连接多个数据库，数据库配置需要独立开。以下介绍如何自定义数据库配置。

因为个人习惯，做项目时习惯将数据库配置独立配置到一个单独的文件database.properties中，如：

1. 将配置在application.properties中的数据库配置移入到database.properties（参照上图）

2. 在pom.xml中加入database.properties作为资源文件

<build>
    <finalName>${name}-${profiles.activation}</finalName>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
    <resources>
        <resource>
            <directory>src/main/resources</directory>
            <excludes>
                <exclude>config/</exclude>
            </excludes>
        </resource>
        <resource>
            <directory>src/main/resources/config/${profiles.activation}</directory>
            <filtering>true</filtering>
            <includes>
                <include>application.properties</include>
                <include>database.properties</include>
            </includes>
        </resource>
    </resources>
</build>

3. 指定配置文件路径

package com.kevin.springbootstudy;

import org.springframework.boot.Banner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.boot.web.servlet.support.SpringBootServletInitializer;
import org.springframework.context.annotation.PropertySource;

@SpringBootApplication
@PropertySource(value={"classpath:database.properties"})
public class SpringBootStudyApplication{

    public static void main(String[] args) {
        SpringApplication app = new SpringApplication(SpringBootStudyApplication.class);
        app.setBannerMode(Banner.Mode.OFF);
        app.run(args);
    }
}

4. 运行测试 访问http://127.0.0.1:8081/dbtime返回数据库时间

5. 如果想自定义配置的前缀，比如将spring.datasource.改为app.datasource.

1) database.properties

# mysql
app.datasource.url=jdbc:mysql://localhost:3306/springboot2?characterEncoding=utf8&serverTimezone=Asia/Shanghai
app.datasource.username=kevin
app.datasource.password=123

2) 在Application中定义DataSource

@Bean
@ConfigurationProperties(prefix = "app.datasource")
public DataSource dataSource(){
    return DataSourceBuilder.create().type(HikariDataSource.class).build();
}

3）运行后测试报异常：dataSource or dataSourceClassName or jdbcUrl is required. 意思是需要配置jdbcUrl。将datasource.url改为datasource.jdbc-url，重新测试即可

4）如果使用springboot的默认配置，但是将datasource.url改为datasource.jdbc-url会出现什么？

Description:

Failed to configure a DataSource: url attribute is not specified and no embedded datasource could be configured.

Reason: Failed to determine a suitable driver class


Action:

Consider the following:
	If you want an embedded database (H2, HSQL or Derby), please put it on the classpath.
	If you have database settings to be loaded from a particular profile you may need to activate it (no profiles are currently active).

启动报错，意思就是如果使用默认配置，需要配置datasource.url

总结: 如果使用springboot内置的数据库配置datasource，则需要配置spring.datasource.url，否则需要配置jdbc-url

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