四、Spring Boot 多数据源 自动切换

实现案例场景：
某系统除了需要从自己的主要数据库上读取和管理数据外，还有一部分业务涉及到其他多个数据库，要求可以在任何方法上可以灵活指定具体要操作的数据库。
为了在开发中以最简单的方法使用，本文基于注解和AOP的方法实现，在spring boot框架的项目中，添加本文实现的代码类后，只需要配置好数据源就可以直接通过注解使用，简单方便。
一配置二使用
1. 启动类注册动态数据源
2. 配置文件中配置多个数据源
3. 在需要的方法上使用注解指定数据源
1、在启动类添加 @Import({DynamicDataSourceRegister.class, MProxyTransactionManagementConfiguration.class})
@SpringBootApplication
@Import({DynamicDataSourceRegister.class}) // 注册动态多数据源
public class SpringBootSampleApplication {

// 省略其他代码
}

2、配置文件配置内容为：
（不包括项目中的其他配置，这里只是数据源相关的）
# 主数据源，默认的
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/test
spring.datasource.username=root
spring.datasource.password=123456

# 更多数据源
custom.datasource.names=ds1,ds2
custom.datasource.ds1.driver-class-name=com.mysql.jdbc.Driver
custom.datasource.ds1.url=jdbc:mysql://localhost:3306/test1
custom.datasource.ds1.username=root
custom.datasource.ds1.password=123456

custom.datasource.ds2.driver-class-name=com.mysql.jdbc.Driver
custom.datasource.ds2.url=jdbc:mysql://localhost:3306/test2
custom.datasource.ds2.username=root
custom.datasource.ds2.password=123456

3、使用方法
package org.springboot.sample.service;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.List;

import org.springboot.sample.datasource.TargetDataSource;
import org.springboot.sample.entity.Student;
import org.springboot.sample.mapper.StudentMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.RowMapper;
import org.springframework.stereotype.Service;

/**
* Student Service
*
*/
@Service
public class StudentService {

@Autowired
private JdbcTemplate jdbcTemplate;

// MyBatis的Mapper方法定义接口
@Autowired
private StudentMapper studentMapper;

@TargetDataSource(name="ds2")
public List<Student> likeName(String name){
return studentMapper.likeName(name);
}

public List<Student> likeNameByDefaultDataSource(String name){
return studentMapper.likeName(name);
}

/**
* 不指定数据源使用默认数据源
*
*/
public List<Student> getList(){
String sql = "SELECT ID,NAME,SCORE_SUM,SCORE_AVG, AGE FROM STUDENT";
return (List<Student>) jdbcTemplate.query(sql, new RowMapper<Student>(){

@Override
public Student mapRow(ResultSet rs, int rowNum) throws SQLException {
Student stu = new Student();
stu.setId(rs.getInt("ID"));
stu.setAge(rs.getInt("AGE"));
stu.setName(rs.getString("NAME"));
stu.setSumScore(rs.getString("SCORE_SUM"));
stu.setAvgScore(rs.getString("SCORE_AVG"));
return stu;
}

});
}

/**
* 指定数据源
*
* @return
*/
@TargetDataSource(name="ds1")
public List<Student> getListByDs1(){
String sql = "SELECT ID,NAME,SCORE_SUM,SCORE_AVG, AGE FROM STUDENT";
return (List<Student>) jdbcTemplate.query(sql, new RowMapper<Student>(){

@Override
public Student mapRow(ResultSet rs, int rowNum) throws SQLException {
Student stu = new Student();
stu.setId(rs.getInt("ID"));
stu.setAge(rs.getInt("AGE"));
stu.setName(rs.getString("NAME"));
stu.setSumScore(rs.getString("SCORE_SUM"));
stu.setAvgScore(rs.getString("SCORE_AVG"));
return stu;
}

});
}

/**
* 指定数据源
*
*/
@TargetDataSource(name="ds2")
public List<Student> getListByDs2(){
String sql = "SELECT ID,NAME,SCORE_SUM,SCORE_AVG, AGE FROM STUDENT";
return (List<Student>) jdbcTemplate.query(sql, new RowMapper<Student>(){

@Override
public Student mapRow(ResultSet rs, int rowNum) throws SQLException {
Student stu = new Student();
stu.setId(rs.getInt("ID"));
stu.setAge(rs.getInt("AGE"));
stu.setName(rs.getString("NAME"));
stu.setSumScore(rs.getString("SCORE_SUM"));
stu.setAvgScore(rs.getString("SCORE_AVG"));
return stu;
}

});
}
}

要注意的是，在使用MyBatis时，注解@TargetDataSource 不能直接在接口类Mapper上使用。
按上面的代码中StudentMapper为接口，代码如下：
package org.springboot.sample.mapper;

import java.util.List;

import org.springboot.sample.entity.Student;

/**
* StudentMapper，映射SQL语句的接口，无逻辑实现
*
*/
public interface StudentMapper {

// 注解 @TargetDataSource 不可以在这里使用
List<Student> likeName(String name);

Student getById(int id);

String getNameById(int id);

}
请将下面几个类放到Spring Boot项目中。
DynamicDataSource.Java
DynamicDataSourceAspect.java
DynamicDataSourceContextHolder.java
DynamicDataSourceRegister.java
TargetDataSource.java
package org.springboot.sample.datasource;

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

/**
* 动态数据源
*
*/
public class DynamicDataSource extends AbstractRoutingDataSource {

@Override
protected Object determineCurrentLookupKey() {
return DynamicDataSourceContextHolder.getDataSourceType();
}

}

package org.springboot.sample.datasource;

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;

/**
* 切换数据源Advice
*
*/
@Aspect
@Order(-1)// 保证该AOP在@Transactional之前执行
@Component
public class DynamicDataSourceAspect {

private static final Logger logger = LoggerFactory.getLogger(DynamicDataSourceAspect.class);

@Before("@annotation(ds)")
public void changeDataSource(JoinPoint point, TargetDataSource ds) throws Throwable {
String dsId = ds.name();
if (!DynamicDataSourceContextHolder.containsDataSource(dsId)) {
logger.error("数据源[{}]不存在，使用默认数据源 > {}", ds.name(), point.getSignature());
} else {
logger.debug("Use DataSource : {} > {}", ds.name(), point.getSignature());
DynamicDataSourceContextHolder.setDataSourceType(ds.name());
}
}

@After("@annotation(ds)")
public void restoreDataSource(JoinPoint point, TargetDataSource ds) {
logger.debug("Revert DataSource : {} > {}", ds.name(), point.getSignature());
DynamicDataSourceContextHolder.clearDataSourceType();
}

}
package org.springboot.sample.datasource;

import java.util.ArrayList;
import java.util.List;

public class DynamicDataSourceContextHolder {

private static final ThreadLocal<String> contextHolder = new ThreadLocal<String>();
public static List<String> dataSourceIds = new ArrayList<>();

public static void setDataSourceType(String dataSourceType) {
contextHolder.set(dataSourceType);
}

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

public static void clearDataSourceType() {
contextHolder.remove();
}

/**
* 判断指定DataSrouce当前是否存在
*
* @param dataSourceId
* @return
* @author SHANHY
* @create 2016年1月24日
*/
public static boolean containsDataSource(String dataSourceId){
return dataSourceIds.contains(dataSourceId);
}
}
package org.springboot.sample.datasource;

import java.util.HashMap;
import java.util.Map;

import javax.sql.DataSource;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.MutablePropertyValues;
import org.springframework.beans.PropertyValues;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.GenericBeanDefinition;
import org.springframework.boot.autoconfigure.jdbc.DataSourceBuilder;
import org.springframework.boot.bind.RelaxedDataBinder;
import org.springframework.boot.bind.RelaxedPropertyResolver;
import org.springframework.context.EnvironmentAware;
import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
import org.springframework.core.convert.ConversionService;
import org.springframework.core.convert.support.DefaultConversionService;
import org.springframework.core.env.Environment;
import org.springframework.core.type.AnnotationMetadata;

/**
* 动态数据源注册<br/>
* 启动动态数据源请在启动类中（如SpringBootSampleApplication）
* 添加 @Import(DynamicDataSourceRegister.class)
*
*/
public class DynamicDataSourceRegister
implements ImportBeanDefinitionRegistrar, EnvironmentAware {

private static final Logger logger = LoggerFactory.getLogger(DynamicDataSourceRegister.class);

private ConversionService conversionService = new DefaultConversionService();
private PropertyValues dataSourcePropertyValues;

// 如配置文件中未指定数据源类型，使用该默认值
private static final Object DATASOURCE_TYPE_DEFAULT = "org.apache.tomcat.jdbc.pool.DataSource";
// private static final Object DATASOURCE_TYPE_DEFAULT =
// "com.zaxxer.hikari.HikariDataSource";

// 数据源
private DataSource defaultDataSource;
private Map<String, DataSource> customDataSources = new HashMap<>();

@Override
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
Map<Object, Object> targetDataSources = new HashMap<Object, Object>();
// 将主数据源添加到更多数据源中
targetDataSources.put("dataSource", defaultDataSource);
DynamicDataSourceContextHolder.dataSourceIds.add("dataSource");
// 添加更多数据源
targetDataSources.putAll(customDataSources);
for (String key : customDataSources.keySet()) {
DynamicDataSourceContextHolder.dataSourceIds.add(key);
}

// 创建DynamicDataSource
GenericBeanDefinition beanDefinition = new GenericBeanDefinition();
beanDefinition.setBeanClass(DynamicDataSource.class);
beanDefinition.setSynthetic(true);
MutablePropertyValues mpv = beanDefinition.getPropertyValues();
mpv.addPropertyValue("defaultTargetDataSource", defaultDataSource);
mpv.addPropertyValue("targetDataSources", targetDataSources);
registry.registerBeanDefinition("dataSource", beanDefinition);

logger.info("Dynamic DataSource Registry");
}

/**
* 创建DataSource
*
* @param type
* @param driverClassName
* @param url
* @param username
* @param password
* @return
*/
@SuppressWarnings("unchecked")
public DataSource buildDataSource(Map<String, Object> dsMap) {
try {
Object type = dsMap.get("type");
if (type == null)
type = DATASOURCE_TYPE_DEFAULT;// 默认DataSource

Class<? extends DataSource> dataSourceType;
dataSourceType = (Class<? extends DataSource>) Class.forName((String) type);

String driverClassName = dsMap.get("driver-class-name").toString();
String url = dsMap.get("url").toString();
String username = dsMap.get("username").toString();
String password = dsMap.get("password").toString();

DataSourceBuilder factory = DataSourceBuilder.create().driverClassName(driverClassName).url(url)
.username(username).password(password).type(dataSourceType);
return factory.build();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
return null;
}

/**
* 加载多数据源配置
*/
@Override
public void setEnvironment(Environment env) {
initDefaultDataSource(env);
initCustomDataSources(env);
}

/**
* 初始化主数据源
*
*/
private void initDefaultDataSource(Environment env) {
// 读取主数据源
RelaxedPropertyResolver propertyResolver = new RelaxedPropertyResolver(env, "spring.datasource.");
Map<String, Object> dsMap = new HashMap<>();
dsMap.put("type", propertyResolver.getProperty("type"));
dsMap.put("driver-class-name", propertyResolver.getProperty("driver-class-name"));
dsMap.put("url", propertyResolver.getProperty("url"));
dsMap.put("username", propertyResolver.getProperty("username"));
dsMap.put("password", propertyResolver.getProperty("password"));

defaultDataSource = buildDataSource(dsMap);

dataBinder(defaultDataSource, env);
}

/**
* 为DataSource绑定更多数据
*
* @param dataSource
* @param env
*/
private void dataBinder(DataSource dataSource, Environment env){
RelaxedDataBinder dataBinder = new RelaxedDataBinder(dataSource);
//dataBinder.setValidator(new LocalValidatorFactory().run(this.applicationContext));
dataBinder.setConversionService(conversionService);
dataBinder.setIgnoreNestedProperties(false);//false
dataBinder.setIgnoreInvalidFields(false);//false
dataBinder.setIgnoreUnknownFields(true);//true
if(dataSourcePropertyValues == null){
Map<String, Object> rpr = new RelaxedPropertyResolver(env, "spring.datasource").getSubProperties(".");
Map<String, Object> values = new HashMap<>(rpr);
// 排除已经设置的属性
values.remove("type");
values.remove("driver-class-name");
values.remove("url");
values.remove("username");
values.remove("password");
dataSourcePropertyValues = new MutablePropertyValues(values);
}
dataBinder.bind(dataSourcePropertyValues);
}

/**
* 初始化更多数据源
*
*/
private void initCustomDataSources(Environment env) {
// 读取配置文件获取更多数据源，也可以通过defaultDataSource读取数据库获取更多数据源
RelaxedPropertyResolver propertyResolver = new RelaxedPropertyResolver(env, "custom.datasource.");
String dsPrefixs = propertyResolver.getProperty("names");
for (String dsPrefix : dsPrefixs.split(",")) {// 多个数据源
Map<String, Object> dsMap = propertyResolver.getSubProperties(dsPrefix + ".");
DataSource ds = buildDataSource(dsMap);
customDataSources.put(dsPrefix, ds);
dataBinder(ds, env);
}
}

}
package org.springboot.sample.datasource;

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;

/**
* 在方法上使用，用于指定使用哪个数据源
*
*/
@Target({ ElementType.METHOD, ElementType.TYPE })
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface TargetDataSource {
String name();
}
本文代码博主是经过测试后没有问题才发出来共享给大家的。对于连接池参数配置会应用到所有数据源上。
比如配置一个：
spring.datasource.maximum-pool-size=80
1

1
那么我们所有的数据源都会自动应用上。
补充：
如果你使用的是SpringMVC，并集成了Shiro，一般按网上的配置你可能是：
<bean class="org.springframework.aop.framework.autoproxy.DefaultAdvisorAutoProxyCreator" depends-on="lifecycleBeanPostProcessor">
<property name="proxyTargetClass" value="true" />
</bean>

<bean class="org.apache.shiro.spring.security.interceptor.AuthorizationAttributeSourceAdvisor">
<property name="securityManager" ref="securityManager"/>
</bean>

那么你请不要这样做，请按下面方法配置：
<!-- AOP式方法级权限检查 -->
<!-- 不要使用 DefaultAdvisorAutoProxyCreator 会出现二次代理的问题，这里不详述。 mark by shanhy 2016-05-15 -->
<aop:config proxy-target-class="true"/>
<!-- 或者你使用了 <aop:aspectj-autoproxy proxy-target-class="true" /> 也可以。 -->

<bean class="org.apache.shiro.spring.security.interceptor.AuthorizationAttributeSourceAdvisor">
<property name="securityManager" ref="securityManager"/>
</bean>