712 lines
23 KiB
Markdown
712 lines
23 KiB
Markdown
# 延迟加载从库解决方案
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## 需求概述
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### 业务场景
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```
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主库（固定）+ 从库（库名可变）
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├─ 主库：存储配置表（包含从库库名）
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├─ 从库：启动时不加载，运行时根据配置表动态加载
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└─ 操作：更新配置表 → 动态加载从库 → 切换写入数据
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```
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### 核心需求
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1. **延迟加载**：应用启动时只加载主库，从库按需加载
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2. **动态切换**：运行时可以随时切换从库库名
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3. **配置管理**：从库配置存储在主库，便于管理
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4. **无侵入性**：使用现有 `@DataSource` 注解，无需修改业务代码
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---
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## 架构设计
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### 核心组件
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| 组件 | 职责 | 文件位置 |
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|------|------|---------|
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| **sys_datasource_config** | 存储从库配置信息 | 主库表 |
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| **SysDatasourceConfig** | 配置实体类 | `datai-system/domain/` |
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| **SysDatasourceConfigMapper** | 配置数据访问层 | `datai-system/mapper/` |
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| **DataSourceManager** | 数据源管理器（扩展） | `datai-framework/manager/` |
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| **DynamicDataSourceService** | 动态数据源业务服务 | `datai-system/service/` |
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| **DynamicDataSource** | 动态数据源路由 | `datai-framework/datasource/` |
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| **DynamicDataSourceContextHolder** | 数据源上下文持有者 | `datai-framework/datasource/` |
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### 工作流程
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```
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1. 应用启动
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└─ 只加载 MASTER 数据源
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└─ SLAVE 数据源不加载
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2. 运行时加载从库
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└─ 读取 sys_datasource_config 表
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└─ 创建 SLAVE 数据源
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└─ 注册到 DynamicDataSource
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3. 切换从库库名
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└─ 更新 sys_datasource_config 表
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└─ 移除旧 SLAVE 数据源
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└─ 创建新 SLAVE 数据源
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└─ 注册到 DynamicDataSource
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4. 使用从库
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└─ @DataSource(DataSourceType.SLAVE)
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└─ AOP 切面切换数据源
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└─ DynamicDataSourceContextHolder 设置上下文
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└─ DynamicDataSource 路由到 SLAVE
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```
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---
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## 实现步骤
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### 步骤 1：创建数据源配置表
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**文件位置：** `datai-system/src/main/resources/sql/sys_datasource_config.sql`
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```sql
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-- 数据源配置表
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-- 用于存储从库的配置信息，支持动态切换从库库名
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CREATE TABLE `sys_datasource_config` (
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`id` BIGINT(20) NOT NULL AUTO_INCREMENT COMMENT '主键ID',
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`ds_name` VARCHAR(50) NOT NULL COMMENT '数据源名称（如：SLAVE）',
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`db_name` VARCHAR(100) NOT NULL COMMENT '数据库名称',
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`db_host` VARCHAR(200) NOT NULL COMMENT '数据库主机',
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`db_port` INT(11) DEFAULT '3306' COMMENT '数据库端口',
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`username` VARCHAR(100) NOT NULL COMMENT '用户名',
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`password` VARCHAR(200) NOT NULL COMMENT '密码',
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`db_type` VARCHAR(20) DEFAULT 'mysql' COMMENT '数据库类型（mysql/postgresql/oracle等）',
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`status` CHAR(1) DEFAULT '0' COMMENT '状态（0正常 1停用）',
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`remark` VARCHAR(500) DEFAULT NULL COMMENT '备注',
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`create_by` VARCHAR(64) DEFAULT '' COMMENT '创建者',
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`create_time` DATETIME DEFAULT CURRENT_TIMESTAMP COMMENT '创建时间',
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`update_by` VARCHAR(64) DEFAULT '' COMMENT '更新者',
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`update_time` DATETIME DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT '更新时间',
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PRIMARY KEY (`id`),
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UNIQUE KEY `uk_ds_name` (`ds_name`)
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) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='数据源配置表';
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-- 初始化从库配置
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INSERT INTO `sys_datasource_config` (`ds_name`, `db_name`, `db_host`, `db_port`, `username`, `password`, `db_type`, `status`, `remark`)
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VALUES ('SLAVE', 'datai_slave', '117.72.193.251', 3306, 'root', '2026.DataI', 'mysql', '0', '从库配置');
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```
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---
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### 步骤 2：修改配置文件
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**文件位置：** `datai-admin/src/main/resources/application-druid.yml`
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```yaml
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spring:
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datasource:
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type: com.alibaba.druid.pool.DruidDataSource
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driverClassName: com.mysql.cj.jdbc.Driver
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dynamic:
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primary: MASTER
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xa: false # 暂不启用分布式事务
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datasource:
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MASTER: # 只配置主库
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url: jdbc:mysql://117.72.193.251/datai?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull&useSSL=true&serverTimezone=GMT%2B8&nullCatalogMeansCurrent=true
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username: root
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password: 2026.DataI
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# SLAVE: # 移除从库配置，运行时动态加载
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druid:
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initialSize: 5
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minIdle: 10
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maxActive: 20
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maxWait: 60000
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connectTimeout: 30000
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socketTimeout: 60000
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timeBetweenEvictionRunsMillis: 60000
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minEvictableIdleTimeMillis: 300000
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maxEvictableIdleTimeMillis: 900000
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validationQuery: SELECT 1
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testWhileIdle: true
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testOnBorrow: false
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testOnReturn: false
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filters: stat,wall,slf4j,log4j2
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connectionProperties: druid.stat.mergeSql=true;druid.stat.slowSqlMillis=5000
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```
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---
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### 步骤 3：创建实体类
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**文件位置：** `datai-system/src/main/java/com/datai/system/domain/SysDatasourceConfig.java`
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```java
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package com.datai.system.domain;
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import com.datai.common.core.domain.BaseEntity;
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public class SysDatasourceConfig extends BaseEntity {
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private static final long serialVersionUID = 1L;
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private Long id;
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private String dsName;
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private String dbName;
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private String dbHost;
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private Integer dbPort;
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private String username;
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private String password;
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private String dbType;
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private String status;
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public Long getId() {
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return id;
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}
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public void setId(Long id) {
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this.id = id;
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}
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public String getDsName() {
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return dsName;
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}
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public void setDsName(String dsName) {
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this.dsName = dsName;
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}
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public String getDbName() {
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return dbName;
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}
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public void setDbName(String dbName) {
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this.dbName = dbName;
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}
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public String getDbHost() {
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return dbHost;
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}
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public void setDbHost(String dbHost) {
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this.dbHost = dbHost;
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}
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public Integer getDbPort() {
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return dbPort;
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}
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public void setDbPort(Integer dbPort) {
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this.dbPort = dbPort;
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}
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public String getUsername() {
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return username;
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}
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public void setUsername(String username) {
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this.username = username;
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}
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public String getPassword() {
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return password;
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}
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public void setPassword(String password) {
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this.password = password;
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}
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public String getDbType() {
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return dbType;
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}
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public void setDbType(String dbType) {
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this.dbType = dbType;
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}
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public String getStatus() {
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return status;
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}
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public void setStatus(String status) {
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this.status = status;
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}
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}
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```
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---
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### 步骤 4：创建 Mapper
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**文件位置：** `datai-system/src/main/java/com/datai/system/mapper/SysDatasourceConfigMapper.java`
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```java
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package com.datai.system.mapper;
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import com.datai.system.domain.SysDatasourceConfig;
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import org.apache.ibatis.annotations.Mapper;
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@Mapper
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public interface SysDatasourceConfigMapper {
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SysDatasourceConfig selectByDsName(String dsName);
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int updateByDsName(SysDatasourceConfig config);
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int insert(SysDatasourceConfig config);
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}
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```
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**文件位置：** `datai-system/src/main/resources/mapper/system/SysDatasourceConfigMapper.xml`
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```xml
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<?xml version="1.0" encoding="UTF-8" ?>
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<!DOCTYPE mapper
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PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
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"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
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<mapper namespace="com.datai.system.mapper.SysDatasourceConfigMapper">
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<resultMap type="SysDatasourceConfig" id="SysDatasourceConfigResult">
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<id property="id" column="id" />
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<result property="dsName" column="ds_name" />
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<result property="dbName" column="db_name" />
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<result property="dbHost" column="db_host" />
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<result property="dbPort" column="db_port" />
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<result property="username" column="username" />
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<result property="password" column="password" />
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<result property="dbType" column="db_type" />
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<result property="status" column="status" />
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<result property="remark" column="remark" />
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<result property="createBy" column="create_by" />
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<result property="createTime" column="create_time" />
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<result property="updateBy" column="update_by" />
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<result property="updateTime" column="update_time" />
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</resultMap>
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<select id="selectByDsName" parameterType="String" resultMap="SysDatasourceConfigResult">
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SELECT * FROM sys_datasource_config WHERE ds_name = #{dsName}
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</select>
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<update id="updateByDsName" parameterType="SysDatasourceConfig">
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UPDATE sys_datasource_config
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<set>
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<if test="dbName != null and dbName != ''">db_name = #{dbName},</if>
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<if test="dbHost != null and dbHost != ''">db_host = #{dbHost},</if>
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<if test="dbPort != null">db_port = #{dbPort},</if>
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<if test="username != null and username != ''">username = #{username},</if>
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<if test="password != null and password != ''">password = #{password},</if>
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<if test="dbType != null and dbType != ''">db_type = #{dbType},</if>
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<if test="status != null and status != ''">status = #{status},</if>
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<if test="remark != null">remark = #{remark},</if>
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update_by = #{updateBy},
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update_time = sysdate()
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</set>
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WHERE ds_name = #{dsName}
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</update>
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<insert id="insert" parameterType="SysDatasourceConfig" useGeneratedKeys="true" keyProperty="id">
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INSERT INTO sys_datasource_config (
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ds_name, db_name, db_host, db_port, username, password, db_type, status, remark, create_by, create_time
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) VALUES (
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#{dsName}, #{dbName}, #{dbHost}, #{dbPort}, #{username}, #{password}, #{dbType}, #{status}, #{remark}, #{createBy}, sysdate()
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)
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</insert>
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</mapper>
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```
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---
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### 步骤 5：扩展 DataSourceManager
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**文件位置：** `datai-framework/src/main/java/com/datai/framework/manager/DataSourceManager.java`
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在现有代码中添加以下方法：
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```java
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public class DataSourceManager implements InitializingBean {
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// ... 现有代码 ...
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public synchronized void addDynamicDataSource(String name, String url, String username, String password) {
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if (targetDataSources.containsKey(name)) {
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logger.warn("数据源 {} 已存在，先移除旧数据源", name);
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removeDataSource(name);
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}
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Properties prop = new Properties();
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prop.setProperty("druid.url", url);
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prop.setProperty("druid.username", username);
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prop.setProperty("druid.password", password);
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DruidProperties druidProperties = SpringUtils.getBean(DruidProperties.class);
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prop.setProperty("druid.initialSize", String.valueOf(druidProperties.getInitialSize()));
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prop.setProperty("druid.minIdle", String.valueOf(druidProperties.getMinIdle()));
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prop.setProperty("druid.maxActive", String.valueOf(druidProperties.getMaxActive()));
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prop.setProperty("druid.maxWait", String.valueOf(druidProperties.getMaxWait()));
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prop.setProperty("druid.validationQuery", druidProperties.getValidationQuery());
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prop.setProperty("druid.testWhileIdle", String.valueOf(druidProperties.isTestWhileIdle()));
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prop.setProperty("druid.testOnBorrow", String.valueOf(druidProperties.isTestOnBorrow()));
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prop.setProperty("druid.testOnReturn", String.valueOf(druidProperties.isTestOnReturn()));
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prop.setProperty("druid.filters", druidProperties.getFilters());
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prop.setProperty("druid.connectionProperties", druidProperties.getConnectionProperties());
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prop.setProperty("druid.timeBetweenEvictionRunsMillis",
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String.valueOf(druidProperties.getTimeBetweenEvictionRunsMillis()));
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prop.setProperty("druid.minEvictableIdleTimeMillis",
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String.valueOf(druidProperties.getMinEvictableIdleTimeMillis()));
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prop.setProperty("druid.maxEvictableIdleTimeMillis",
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String.valueOf(druidProperties.getMaxEvictableIdleTimeMillis()));
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DataSource dataSource = createDataSource(name, prop);
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putDataSource(name, dataSource);
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logger.info("动态数据源 {} 添加成功", name);
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}
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public synchronized void removeDataSource(String name) {
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DataSource dataSource = targetDataSources.remove(name);
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if (dataSource != null) {
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dataSourceKeyIndex.remove(dataSource);
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dsDatabaseId.remove(name);
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if (dataSource instanceof DruidDataSource) {
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try {
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((DruidDataSource) dataSource).close();
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} catch (Exception e) {
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logger.error("关闭数据源 {} 失败", name, e);
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}
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}
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logger.info("数据源 {} 已移除", name);
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}
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}
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public synchronized void updateDataSource(String name, String url, String username, String password) {
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removeDataSource(name);
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addDynamicDataSource(name, url, username, password);
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}
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}
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```
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---
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### 步骤 6：创建动态数据源服务
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**文件位置：** `datai-system/src/main/java/com/datai/system/service/DynamicDataSourceService.java`
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```java
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package com.datai.system.service;
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import com.datai.common.annotation.DataSource;
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import com.datai.common.enums.DataSourceType;
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import com.datai.framework.manager.DataSourceManager;
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import com.datai.system.domain.SysDatasourceConfig;
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import com.datai.system.mapper.SysDatasourceConfigMapper;
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import org.springframework.beans.factory.annotation.Autowired;
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import org.springframework.stereotype.Service;
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@Service
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public class DynamicDataSourceService {
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@Autowired
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private DataSourceManager dataSourceManager;
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@Autowired
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private SysDatasourceConfigMapper configMapper;
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@DataSource(DataSourceType.MASTER)
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public void loadSlaveDataSource() {
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SysDatasourceConfig config = configMapper.selectByDsName("SLAVE");
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if (config == null) {
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throw new RuntimeException("从库配置不存在");
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}
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if (!"0".equals(config.getStatus())) {
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throw new RuntimeException("从库配置已停用");
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}
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String url = buildJdbcUrl(config);
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dataSourceManager.addDynamicDataSource(
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config.getDsName(),
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url,
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config.getUsername(),
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config.getPassword()
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);
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}
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@DataSource(DataSourceType.MASTER)
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public void updateSlaveConfig(String newDbName) {
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SysDatasourceConfig config = configMapper.selectByDsName("SLAVE");
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if (config == null) {
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throw new RuntimeException("从库配置不存在");
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}
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config.setDbName(newDbName);
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configMapper.updateByDsName(config);
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String url = buildJdbcUrl(config);
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dataSourceManager.updateDataSource(
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config.getDsName(),
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url,
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config.getUsername(),
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config.getPassword()
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);
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}
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@DataSource(DataSourceType.MASTER)
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public SysDatasourceConfig getSlaveConfig() {
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return configMapper.selectByDsName("SLAVE");
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}
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private String buildJdbcUrl(SysDatasourceConfig config) {
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String urlPattern;
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switch (config.getDbType().toLowerCase()) {
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case "mysql":
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urlPattern = "jdbc:mysql://%s:%d/%s?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull&useSSL=true&serverTimezone=GMT%%2B8";
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break;
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case "postgresql":
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urlPattern = "jdbc:postgresql://%s:%d/%s";
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break;
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case "oracle":
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urlPattern = "jdbc:oracle:thin:@%s:%d:%s";
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break;
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default:
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throw new RuntimeException("不支持的数据库类型：" + config.getDbType());
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}
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return String.format(urlPattern, config.getDbHost(), config.getDbPort(), config.getDbName());
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}
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}
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```
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---
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### 步骤 7：创建控制器（可选）
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**文件位置：** `datai-admin/src/main/java/com/datai/web/controller/system/DatasourceController.java`
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```java
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package com.datai.web.controller.system;
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import com.datai.common.annotation.DataSource;
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import com.datai.common.core.controller.BaseController;
|
||
import com.datai.common.core.domain.AjaxResult;
|
||
import com.datai.common.enums.DataSourceType;
|
||
import com.datai.system.domain.SysDatasourceConfig;
|
||
import com.datai.system.service.DynamicDataSourceService;
|
||
import org.springframework.beans.factory.annotation.Autowired;
|
||
import org.springframework.web.bind.annotation.*;
|
||
|
||
@RestController
|
||
@RequestMapping("/system/datasource")
|
||
public class DatasourceController extends BaseController {
|
||
|
||
@Autowired
|
||
private DynamicDataSourceService dynamicDataSourceService;
|
||
|
||
@PostMapping("/loadSlave")
|
||
public AjaxResult loadSlave() {
|
||
dynamicDataSourceService.loadSlaveDataSource();
|
||
return AjaxResult.success("从库加载成功");
|
||
}
|
||
|
||
@PostMapping("/switchSlave/{dbName}")
|
||
public AjaxResult switchSlave(@PathVariable String dbName) {
|
||
dynamicDataSourceService.updateSlaveConfig(dbName);
|
||
return AjaxResult.success("从库切换成功");
|
||
}
|
||
|
||
@GetMapping("/getSlaveConfig")
|
||
@DataSource(DataSourceType.MASTER)
|
||
public AjaxResult getSlaveConfig() {
|
||
SysDatasourceConfig config = dynamicDataSourceService.getSlaveConfig();
|
||
return AjaxResult.success(config);
|
||
}
|
||
}
|
||
```
|
||
|
||
---
|
||
|
||
## 使用示例
|
||
|
||
### 示例 1：启动时加载从库
|
||
|
||
```java
|
||
@Component
|
||
public class DataSourceInitializer implements ApplicationRunner {
|
||
|
||
@Autowired
|
||
private DynamicDataSourceService dynamicDataSourceService;
|
||
|
||
@Override
|
||
public void run(ApplicationArguments args) throws Exception {
|
||
try {
|
||
dynamicDataSourceService.loadSlaveDataSource();
|
||
logger.info("从库数据源加载成功");
|
||
} catch (Exception e) {
|
||
logger.warn("从库数据源加载失败，将延迟加载", e);
|
||
}
|
||
}
|
||
}
|
||
```
|
||
|
||
### 示例 2：切换从库库名
|
||
|
||
```java
|
||
@Service
|
||
public class OrderService {
|
||
|
||
@Autowired
|
||
private DynamicDataSourceService dynamicDataSourceService;
|
||
|
||
@Autowired
|
||
private OrderMapper orderMapper;
|
||
|
||
@DataSource(DataSourceType.MASTER)
|
||
public void processOrderToSlave(Long orderId, String slaveDbName) {
|
||
Order order = orderMapper.selectById(orderId);
|
||
|
||
dynamicDataSourceService.updateSlaveConfig(slaveDbName);
|
||
|
||
writeToSlave(order);
|
||
}
|
||
|
||
@DataSource(DataSourceType.SLAVE)
|
||
private void writeToSlave(Order order) {
|
||
orderMapper.insert(order);
|
||
}
|
||
}
|
||
```
|
||
|
||
### 示例 3：使用从库写入数据
|
||
|
||
```java
|
||
@Service
|
||
public class DataService {
|
||
|
||
@Autowired
|
||
private DataMapper dataMapper;
|
||
|
||
@DataSource(DataSourceType.SLAVE)
|
||
public void writeToSlave(Data data) {
|
||
dataMapper.insert(data);
|
||
}
|
||
|
||
@DataSource(DataSourceType.MASTER)
|
||
public void writeToMaster(Data data) {
|
||
dataMapper.insert(data);
|
||
}
|
||
}
|
||
```
|
||
|
||
---
|
||
|
||
## 注意事项
|
||
|
||
### ⚠️ 事务问题
|
||
|
||
**错误做法：**
|
||
|
||
```java
|
||
@Transactional // ❌ 不要在事务中切换数据源
|
||
public void switchAndWrite() {
|
||
dynamicDataSourceService.updateSlaveConfig("new_db");
|
||
writeToSlave(data);
|
||
}
|
||
```
|
||
|
||
**正确做法：**
|
||
|
||
```java
|
||
public void switchAndWrite() {
|
||
dynamicDataSourceService.updateSlaveConfig("new_db");
|
||
writeToSlave(data); // 另一个方法，独立事务
|
||
}
|
||
```
|
||
|
||
### ⚠️ 连接池管理
|
||
|
||
- 切换数据源时会关闭旧连接池
|
||
- 可能有短暂的服务不可用（毫秒级）
|
||
- 建议在低峰期切换
|
||
|
||
### ⚠️ 并发问题
|
||
|
||
已通过 `synchronized` 关键字保证线程安全：
|
||
|
||
```java
|
||
public synchronized void updateDataSource(String name, String url, String username, String password) {
|
||
removeDataSource(name);
|
||
addDynamicDataSource(name, url, username, password);
|
||
}
|
||
```
|
||
|
||
### ⚠️ 数据库类型支持
|
||
|
||
当前支持：
|
||
- MySQL
|
||
- PostgreSQL
|
||
- Oracle
|
||
|
||
如需支持其他数据库，在 `buildJdbcUrl()` 方法中添加对应的 URL 模板。
|
||
|
||
---
|
||
|
||
## 方案优势
|
||
|
||
| 特性 | 说明 |
|
||
|------|------|
|
||
| ✅ 延迟加载 | 启动时只加载主库，从库按需加载 |
|
||
| ✅ 动态切换 | 运行时可以随时切换从库库名 |
|
||
| ✅ 配置管理 | 从库配置存储在主库，便于管理 |
|
||
| ✅ 线程安全 | 使用 synchronized 和 ThreadLocal 保证线程隔离 |
|
||
| ✅ 无侵入 | 使用现有 `@DataSource` 注解，无需修改业务代码 |
|
||
| ✅ 易扩展 | 支持多种数据库类型 |
|
||
|
||
---
|
||
|
||
## 测试验证
|
||
|
||
### 测试步骤
|
||
|
||
1. **执行 SQL 脚本**：创建 `sys_datasource_config` 表
|
||
2. **修改配置文件**：移除 SLAVE 配置
|
||
3. **启动应用**：验证只加载 MASTER 数据源
|
||
4. **调用加载接口**：`POST /system/datasource/loadSlave`
|
||
5. **验证从库可用**：使用 `@DataSource(DataSourceType.SLAVE)` 写入数据
|
||
6. **切换从库库名**：`POST /system/datasource/switchSlave/new_db_name`
|
||
7. **验证新从库**：确认数据写入到新数据库
|
||
|
||
### 验证命令
|
||
|
||
```bash
|
||
# 1. 加载从库
|
||
curl -X POST http://localhost:8080/system/datasource/loadSlave
|
||
|
||
# 2. 查看从库配置
|
||
curl http://localhost:8080/system/datasource/getSlaveConfig
|
||
|
||
# 3. 切换从库
|
||
curl -X POST http://localhost:8080/system/datasource/switchSlave/datai_slave_new
|
||
```
|
||
|
||
---
|
||
|
||
## 相关文件
|
||
|
||
| 文件 | 路径 |
|
||
|------|------|
|
||
| 配置文件 | [application-druid.yml](file:///d:/idea_demo/datai/datai-admin/src/main/resources/application-druid.yml) |
|
||
| 数据源管理器 | [DataSourceManager.java](file:///d:/idea_demo/datai/datai-framework/src/main/java/com/datai/framework/manager/DataSourceManager.java) |
|
||
| 动态数据源 | [DynamicDataSource.java](file:///d:/idea_demo/datai/datai-framework/src/main/java/com/datai/framework/datasource/DynamicDataSource.java) |
|
||
| 上下文持有者 | [DynamicDataSourceContextHolder.java](file:///d:/idea_demo/datai/datai-framework/src/main/java/com/datai/framework/datasource/DynamicDataSourceContextHolder.java) |
|
||
| 数据源注解 | [DataSource.java](file:///d:/idea_demo/datai/datai-common/src/main/java/com/datai/common/annotation/DataSource.java) |
|
||
| 数据源类型 | [DataSourceType.java](file:///d:/idea_demo/datai/datai-common/src/main/java/com/datai/common/enums/DataSourceType.java) |
|
||
| AOP 切面 | [DataSourceAspect.java](file:///d:/idea_demo/datai/datai-framework/src/main/java/com/datai/framework/aspectj/DataSourceAspect.java) |
|
||
|
||
---
|
||
|
||
## 总结
|
||
|
||
本方案实现了延迟加载从库的功能，通过在主库存储从库配置，运行时动态创建和切换数据源，满足了业务需求。方案具有以下特点：
|
||
|
||
1. **灵活性高**：支持运行时动态切换从库库名
|
||
2. **侵入性低**：使用现有注解机制，无需修改业务代码
|
||
3. **可维护性强**：配置集中管理，便于运维
|
||
4. **线程安全**：通过同步机制保证并发安全
|
||
|
||
该方案适用于需要动态切换数据源的业务场景，如多租户数据隔离、数据归档、报表库切换等。
|