springboot实现动态数据库切换

随着项目中的开发，有的时候我们项目需要可以从多个数据库查询结果。比如：user表从datasource来查询，user1从datasource1查询。具体的业务的话具体实现。

那如果我们从springboot角度开发，怎么办?

aop注解方式

准备工作

二个数据库和二张表建好了，其中testdatasource1为芳年25岁的张三， testdatasource2为芳年30岁的李四。

新建springboot项目，添加依赖

<dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>


        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-aop</artifactId>
            <version>5.1.5.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
        </dependency>
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjweaver</artifactId>
            <version>1.9.2</version>
        </dependency>

配置二个数据源

#配置主数据库
spring.datasource.primary.jdbc-url=jdbc:mysql://localhost:3306/testdatasource1?useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC&useSSL=false
spring.datasource.primary.username=root
spring.datasource.primary.password=root
spring.datasource.primary.driver-class-name=com.mysql.cj.jdbc.Driver

##配置次数据库
spring.datasource.secondary.jdbc-url=jdbc:mysql://localhost:3306/testdatasource2?useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC&useSSL=false
spring.datasource.secondary.username=root
spring.datasource.secondary.password=root
spring.datasource.secondary.driver-class-name=com.mysql.cj.jdbc.Driver


spring.http.encoding.charset=UTF-8
spring.http.encoding.enabled=true
spring.http.encoding.force=true

注意

Springboot2.0 在配置数据库连接的时候需要使用jdbc-url，如果只使用url的话会报jdbcUrl is required with driverClassName.错误。

新建一个配置类

@Configuration
@MapperScan(basePackages = "com.mzd.multipledatasources.mapper", sqlSessionFactoryRef = "SqlSessionFactory") //basePackages 我们接口文件的地址
public class DynamicDataSourceConfig {

    // 将这个对象放入Spring容器中
    @Bean(name = "PrimaryDataSource")
    // 表示这个数据源是默认数据源
    @Primary
    // 读取application.properties中的配置参数映射成为一个对象
    // prefix表示参数的前缀
    @ConfigurationProperties(prefix = "spring.datasource.primary")
    public DataSource getDateSource1() {
        return DataSourceBuilder.create().build();
    }


    @Bean(name = "SecondaryDataSource")
    @ConfigurationProperties(prefix = "spring.datasource.secondary")
    public DataSource getDateSource2() {
        return DataSourceBuilder.create().build();
    }


    @Bean(name = "dynamicDataSource")
    public DynamicDataSource DataSource(@Qualifier("PrimaryDataSource") DataSource primaryDataSource,
                                        @Qualifier("SecondaryDataSource") DataSource secondaryDataSource) {

        //这个地方是比较核心的targetDataSource 集合是我们数据库和名字之间的映射
        Map<Object, Object> targetDataSource = new HashMap<>();
        targetDataSource.put(DataSourceType.DataBaseType.Primary, primaryDataSource);
        targetDataSource.put(DataSourceType.DataBaseType.Secondary, secondaryDataSource);
        DynamicDataSource dataSource = new DynamicDataSource(); 
        dataSource.setTargetDataSources(targetDataSource);
        dataSource.setDefaultTargetDataSource(primaryDataSource);//设置默认对象
        return dataSource;
    }


    @Bean(name = "SqlSessionFactory")
    public SqlSessionFactory SqlSessionFactory(@Qualifier("dynamicDataSource") DataSource dynamicDataSource)
            throws Exception {
        SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
        bean.setDataSource(dynamicDataSource);
        bean.setMapperLocations(
                new PathMatchingResourcePatternResolver().getResources("classpath*:mapping/*/*.xml"));//设置我们的xml文件路径
        return bean.getObject();
    }
}

public class DynamicDataSource extends AbstractRoutingDataSource {

    @Override
    protected Object determineCurrentLookupKey() {
        DataSourceType.DataBaseType dataBaseType = DataSourceType.getDataBaseType();
        return dataBaseType;
    }

}

public class DataSourceType {

    //内部枚举类，用于选择特定的数据类型
    public enum DataBaseType {
        Primary, Secondary
    }

    // 使用ThreadLocal保证线程安全
    private static final ThreadLocal<DataBaseType> TYPE = new ThreadLocal<DataBaseType>();

    // 往当前线程里设置数据源类型
    public static void setDataBaseType(DataBaseType dataBaseType) {
        if (dataBaseType == null) {
            throw new NullPointerException();
        }
        TYPE.set(dataBaseType);
    }

    // 获取数据源类型
    public static DataBaseType getDataBaseType() {
        DataBaseType dataBaseType = TYPE.get() == null ? DataBaseType.Primary : TYPE.get();
        return dataBaseType;
    }

    // 清空数据类型
    public static void clearDataBaseType() {
        TYPE.remove();
    }

}

@Component
@Mapper
public interface PrimaryUserMapper {

    List<User> findAll();
}


@Component
@Mapper
public interface SecondaryUserMapper {

    List<User> findAll();
}

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.jdkcb.mybatisstuday.mapper.one.PrimaryUserMapper">

    <select id="findAll" resultType="com.jdkcb.mybatisstuday.pojo.User">
                select * from sys_user;
    </select>

</mapper>


<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.jdkcb.mybatisstuday.mapper.two.SecondaryUserMapper">

    <select id="findAll" resultType="com.jdkcb.mybatisstuday.pojo.User">
                select * from sys_user2;
    </select>


</mapper>

接下来配合我们的自定义注解来实现动态切换

/**
 * 切换数据注解 可以用于类或者方法级别 方法级别优先级 > 类级别
 */
@Target({ElementType.METHOD, ElementType.TYPE, ElementType.PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface DataSource {
    String value() default "primary"; //该值即key值，默认使用默认数据库
}

@Aspect
@Component
public class DynamicDataSourceAspect {
    private static final Logger logger = LoggerFactory.getLogger(DynamicDataSourceAspect.class);

    @Before("@annotation(dataSource)")//拦截我们的注解
    public void changeDataSource(JoinPoint point, DataSource dataSource) throws Throwable {
        String value = dataSource.value();
        if (value.equals("primary")){
            DataSourceType.setDataBaseType(DataSourceType.DataBaseType.Primary);
        }else if (value.equals("secondary")){
            DataSourceType.setDataBaseType(DataSourceType.DataBaseType.Secondary);
        }else {
            DataSourceType.setDataBaseType(DataSourceType.DataBaseType.Primary);//默认使用主数据库
        }

    }

    @After("@annotation(dataSource)") //清除数据源的配置
    public void restoreDataSource(JoinPoint point, DataSource dataSource) {
        DataSourceType.clearDataBaseType();


    }
}

具体使用方法：

@Component
@Mapper
public interface PrimaryUserMapper {

    @DataSource
    List<User> findAll();
}

@Component
@Mapper
public interface SecondaryUserMapper {

    @DataSource("secondary")//指定数据源为:secondary
    List<User> findAll();
}

接下来，大家测试一下效果就好了。欢迎大家关注我