14.玩转Spring Boot 多数据源

玩转Spring Boot 多数据源

      在项目中有的时候需要用到多个数据源，有个问题就是单数据源的事务是没有问题的，多数据源是会存在事务问题的。这里不做事务讲解，事务可以用JTA分布式事务，也可以用MQ。具体不做叙述，接下来说如何实现多数据源并且使用AOP来切换。

本例代码使用Mybatis具体请看：10.玩转Spring
Boot 集成Mybatis，11.玩转Spring
Boot 集成Druid

1.在pom中加入以下依赖：

<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-configuration-processor</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-aop</artifactId>
</dependency>

2.application.properties内容如下：

spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/springboot?useUnicode=true&characterEncoding=utf8
spring.datasource.username=root
spring.datasource.password=root

spring.datasource.driver-class-name1=com.mysql.jdbc.Driver
spring.datasource.url1=jdbc:mysql://localhost:3306/springboot2?useUnicode=true&characterEncoding=utf8
spring.datasource.username1=root
spring.datasource.password1=root

#最小连接数量
spring.datasource.minIdle=2
#最大连接数量
spring.datasource.maxActive=5
#获取连接等待超时的时间
spring.datasource.maxWait=60000
#间隔多久才进行一次检测，检测需要关闭的空闲连接，单位是毫秒
spring.datasource.timeBetweenEvictionRunsMillis=60000
#连接在池中最小生存的时间，单位是毫秒
spring.datasource.minEvictableIdleTimeMillis=300000
#验证SQL
spring.datasource.validationQuery=SELECT 'x' FROM DUAL
spring.datasource.testWhileIdle=true
spring.datasource.testOnBorrow=false
spring.datasource.testOnReturn=false
#打开PSCache，并且指定每个连接上PSCache的大小如果用Oracle，
#则把poolPreparedStatements配置为true，mysql可以配置为false。分库分表较多的数据库，建议配置为false。
spring.datasource.poolPreparedStatements=true
spring.datasource.maxPoolPreparedStatementPerConnectionSize=20
#配置监控统计拦截的filters
spring.datasource.filters=stat

3.MybatisConfig代码如下：

package com.chengli.springboot.dynamicds.config;

import java.sql.SQLException;
import java.util.HashMap;
import java.util.Map;

import javax.sql.DataSource;

import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.jdbc.datasource.DataSourceTransactionManager;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.annotation.EnableTransactionManagement;

import com.alibaba.druid.pool.DruidDataSource;
import com.chengli.springboot.dynamicds.dynmic.DynmicDataSource;

@Configuration
@MapperScan(basePackages = { "com.chengli.springboot.dynamicds" }, annotationClass = Mapper.class) // 定义扫描的ROOT包，以及注解
@EnableTransactionManagement // 开启注解事务
public class MybatisConfig {
@Autowired
private DruidConfigProperties druidConfigProperties;

@Primary//设置为主要的，当同一个类型存在多个Bean的时候，spring 会默认注入以@Primary注解的bean
@Bean(initMethod = "init", destroyMethod = "close")
public DataSource springbootDataSource() throws SQLException {
DruidDataSource druidDataSource = new DruidDataSource();
druidDataSource.setDriverClassName(druidConfigProperties.getDriverClassName());
druidDataSource.setUrl(druidConfigProperties.getUrl());
druidDataSource.setUsername(druidConfigProperties.getUsername());
druidDataSource.setPassword(druidConfigProperties.getPassword());
druidDataSource.setInitialSize(druidConfigProperties.getMinIdle());
druidDataSource.setMinIdle(druidConfigProperties.getMinIdle());
druidDataSource.setMaxActive(druidConfigProperties.getMaxActive());
druidDataSource.setMaxWait(druidConfigProperties.getMaxWait());
druidDataSource.setTimeBetweenEvictionRunsMillis(druidConfigProperties.getTimeBetweenEvictionRunsMillis());
druidDataSource.setMinEvictableIdleTimeMillis(druidConfigProperties.getMinEvictableIdleTimeMillis());
druidDataSource.setValidationQuery(druidConfigProperties.getValidationQuery());
druidDataSource.setTestWhileIdle(druidConfigProperties.getTestWhileIdle());
druidDataSource.setTestOnBorrow(druidConfigProperties.getTestOnBorrow());
druidDataSource.setTestOnReturn(druidConfigProperties.getTestOnReturn());
druidDataSource.setPoolPreparedStatements(druidConfigProperties.getPoolPreparedStatements());
druidDataSource.setMaxPoolPreparedStatementPerConnectionSize(druidConfigProperties.getMaxPoolPreparedStatementPerConnectionSize());
druidDataSource.setFilters(druidConfigProperties.getFilters());
return druidDataSource;
}

@Bean(initMethod = "init", destroyMethod = "close")
public DataSource eziliaoDataSource() throws SQLException {
DruidDataSource druidDataSource = new DruidDataSource();
druidDataSource.setDriverClassName(druidConfigProperties.getDriverClassName1());
druidDataSource.setUrl(druidConfigProperties.getUrl1());
druidDataSource.setUsername(druidConfigProperties.getUsername1());
druidDataSource.setPassword(druidConfigProperties.getPassword1());
druidDataSource.setInitialSize(druidConfigProperties.getMinIdle());
druidDataSource.setMinIdle(druidConfigProperties.getMinIdle());
druidDataSource.setMaxActive(druidConfigProperties.getMaxActive());
druidDataSource.setMaxWait(druidConfigProperties.getMaxWait());
druidDataSource.setTimeBetweenEvictionRunsMillis(druidConfigProperties.getTimeBetweenEvictionRunsMillis());
druidDataSource.setMinEvictableIdleTimeMillis(druidConfigProperties.getMinEvictableIdleTimeMillis());
druidDataSource.setValidationQuery(druidConfigProperties.getValidationQuery());
druidDataSource.setTestWhileIdle(druidConfigProperties.getTestWhileIdle());
druidDataSource.setTestOnBorrow(druidConfigProperties.getTestOnBorrow());
druidDataSource.setTestOnReturn(druidConfigProperties.getTestOnReturn());
druidDataSource.setPoolPreparedStatements(druidConfigProperties.getPoolPreparedStatements());
druidDataSource.setMaxPoolPreparedStatementPerConnectionSize(druidConfigProperties.getMaxPoolPreparedStatementPerConnectionSize());
druidDataSource.setFilters(druidConfigProperties.getFilters());
return druidDataSource;
}

@Bean
public DataSource dynmicDataSource() throws SQLException {
DynmicDataSource dynmicDataSource = new DynmicDataSource();
Map<Object, Object> targetDataSources = new HashMap<>();
targetDataSources.put("springbootDataSource", springbootDataSource());
targetDataSources.put("eziliaoDataSource", eziliaoDataSource());
dynmicDataSource.setTargetDataSources(targetDataSources);

dynmicDataSource.setDefaultTargetDataSource(springbootDataSource());
return dynmicDataSource;
}

@Bean
public SqlSessionFactory sqlSessionFactory(@Qualifier("dynmicDataSource")DataSource dataSource) throws Exception {
SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
sqlSessionFactoryBean.setDataSource(dataSource);
sqlSessionFactoryBean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath:mapper/*.xml"));

// 添加Mybatis插件，例如分页，在之类创建你插件添加进去即可，这里我就不做叙述了。
// sqlSessionFactoryBean.setPlugins(new Interceptor[]{你的插件});

return sqlSessionFactoryBean.getObject();
}

@Bean
public PlatformTransactionManager transactionManager(@Qualifier("dynmicDataSource")DataSource dataSource) {
return new DataSourceTransactionManager(dataSource);
}

}

4.DruidConfigProperties代码修改，代码如下：

@Component
@ConfigurationProperties(prefix = "spring.datasource")
public class DruidConfigProperties {
private String driverClassName;
private String url;
private String username;
private String password;

private String driverClassName1;
private String url1;
private String username1;
private String password1;

private Integer minIdle;
private Integer maxActive;
private Integer maxWait;
private Long timeBetweenEvictionRunsMillis;
private Long minEvictableIdleTimeMillis;
private String validationQuery;
private Boolean testWhileIdle;
private Boolean testOnBorrow;
private Boolean testOnReturn;
private Boolean poolPreparedStatements;
private Integer maxPoolPreparedStatementPerConnectionSize;
private String filters;
.........get set 方法省略
}

5.定义类，实现AbstractRoutingDataSource，代码如下：

package com.chengli.springboot.dynamicds.dynmic;

import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;

public class DynmicDataSource extends AbstractRoutingDataSource {

/**
* 返回的内容是targetDataSources 的Key
*/
@Override
protected Object determineCurrentLookupKey() {
return DynmicDataSourceContextHolder.getDataSourceKey();
}

}

6.自定义注解UseDataSource

package com.chengli.springboot.dynamicds.dynmic;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target({ ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface UseDataSource {
String value();
}

7.创建DynmicDataSourceContextHolder，用于设置当前使用的数据源Key

package com.chengli.springboot.dynamicds.dynmic;

public class DynmicDataSourceContextHolder {
private static final ThreadLocal<String> contextHolder = new ThreadLocal<String>();

public static String getDataSourceKey() {
return contextHolder.get();
}

public static void setDataSourceKey(String dataSourcekey) {
contextHolder.set(dataSourcekey);
}
public static void clear() {
contextHolder.remove();
}
}

8.自定义AOP，设置数据源DynamicDataSourceAspect

package com.chengli.springboot.dynamicds.dynmic;

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

@Aspect
@Order(-1) //spring order排序后执行顺序是从小到大，目的是确保在事务管理器执行前先执行
@Component
public class DynamicDataSourceAspect {

@Before("@annotation(useDataSource)")//拦截注解 UseDataSource
public void setDataSourceType(JoinPoint point, UseDataSource useDataSource) throws Throwable {
DynmicDataSourceContextHolder.setDataSourceKey(useDataSource.value());
}
@After("@annotation(useDataSource)")
public void clearDataSourceType(JoinPoint point, UseDataSource useDataSource) {
DynmicDataSourceContextHolder.clear();
}
}

到这里就完成啦，主要代码就上面这些，测试以及完整示例代码在QQ交流群中：springboot-dynamic-ds.zip

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