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一、前言

通过切面注解方式根据不同业务动态切换数据库

二、操作

1、引入依赖

<dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-jpa</artifactId></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-aop</artifactId></dependency><dependency><groupId>com.zaxxer</groupId><artifactId>HikariCP</artifactId></dependency>
</dependencies>

2、配置默认数据库 1

• 在 application.properties 或 application.yml 配置数据库 1 信息：

spring.datasource.url=jdbc:mysql://localhost:3306/db1
spring.datasource.username=root
spring.datasource.password=password
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

3、定义数据源实体和 Repository

• 数据源实体 DataSourceConfig.java：

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;@Entity
public class DataSourceEntity {@Id@GeneratedValue(strategy = GenerationType.IDENTITY)private Long id;private String url;private String username;private String password;private String driverClassName;private String dataSourceKey; // 新增字段// Getters 和 Setterspublic Long getId() {return id;}public void setId(Long id) {this.id = id;}public String getUrl() {return url;}public void setUrl(String url) {this.url = url;}public String getUsername() {return username;}public void setUsername(String username) {this.username = username;}public String getPassword() {return password;}public void setPassword(String password) {this.password = password;}public String getDriverClassName() {return driverClassName;}public void setDriverClassName(String driverClassName) {this.driverClassName = driverClassName;}public String getDataSourceKey() {return dataSourceKey;}public void setDataSourceKey(String dataSourceKey) {this.dataSourceKey = dataSourceKey;}
}

• Repository 接口 DataSourceConfigRepository.java：

import org.springframework.data.jpa.repository.JpaRepository;public interface DataSourceConfigRepository extends JpaRepository<DataSourceEntity, Long> {
}

4、定义动态数据源

• 动态数据源上下文持有者 DynamicDataSourceContextHolder.java：

public class DynamicDataSourceContextHolder {private static final ThreadLocal<String> contextHolder = new ThreadLocal<>();public static void setDataSourceKey(String key) {contextHolder.set(key);}public static String getDataSourceKey() {return contextHolder.get();}public static void clearDataSourceKey() {contextHolder.remove();}
}

• 动态数据源类 DynamicDataSource.java：

import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;public class DynamicDataSource extends AbstractRoutingDataSource {@Overrideprotected Object determineCurrentLookupKey() {return DynamicDataSourceContextHolder.getDataSourceKey();}
}

5、配置数据源

import com.zaxxer.hikari.HikariDataSource;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;import javax.sql.DataSource;
import java.util.HashMap;
import java.util.List;
import java.util.Map;@Configuration
public class DataSourceConfig {@Autowiredprivate DataSourceConfigRepository dataSourceConfigRepository;@Primary@Beanpublic DataSource dataSource() {DynamicDataSource dynamicDataSource = new DynamicDataSource();Map<Object, Object> targetDataSources = new HashMap<>();// 从数据库 1 的 datasource 表加载所有数据源List<DataSourceEntity> dataSourceConfigs = dataSourceConfigRepository.findAll();for (DataSourceEntity config : dataSourceConfigs) {HikariDataSource dataSource = new HikariDataSource();dataSource.setJdbcUrl(config.getUrl());dataSource.setUsername(config.getUsername());dataSource.setPassword(config.getPassword());dataSource.setDriverClassName(config.getDriverClassName());targetDataSources.put(config.getId().toString(), dataSource);if ("db1".equals(config.getDataSourceKey())) { // 假设表中有一个字段表示数据源的 keydynamicDataSource.setDefaultTargetDataSource(dataSource);}}dynamicDataSource.setTargetDataSources(targetDataSources);return dynamicDataSource;}
}

6、定义切换数据源注解

import java.lang.annotation.*;@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface DataSourceSwitch {String value() default "db1";
}

7、定义切面类

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.aspectj.lang.reflect.MethodSignature;
import org.springframework.stereotype.Component;import java.lang.reflect.Method;
import java.util.List;@Aspect
@Component
public class DataSourceSwitchAspect {@Autowiredprivate DataSourceConfigRepository dataSourceConfigRepository;@Before("@annotation(com.example.annotation.DataSourceSwitch)")public void before(JoinPoint point) {MethodSignature signature = (MethodSignature) point.getSignature();Method method = signature.getMethod();DataSourceSwitch dataSourceSwitch = method.getAnnotation(DataSourceSwitch.class);if (dataSourceSwitch != null) {String dataSourceKey = dataSourceSwitch.value();List<DataSourceEntity> dataSourceConfigs = dataSourceConfigRepository.findAll();for (DataSourceConfig config : dataSourceConfigs) {if (dataSourceKey.equals(config.getDataSourceKey())) {DynamicDataSourceContextHolder.setDataSourceKey(config.getId().toString());break;}}}}@After("@annotation(com.example.annotation.DataSourceSwitch)")public void after(JoinPoint point) {DynamicDataSourceContextHolder.clearDataSourceKey();}
}

8、使用注解切换数据源

import com.example.annotation.DataSourceSwitch;
import com.example.entity.User;
import com.example.repository.UserRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;import java.util.List;@Service
public class UserService {@Autowiredprivate UserRepository userRepository;@DataSourceSwitch("db1")public List<User> getUsersFromDb1() {return userRepository.findAll();}@DataSourceSwitch("db2") // 假设 db2 是从 datasource 表获取的数据源 keypublic List<User> getUsersFromDb2() {return userRepository.findAll();}
}