spring boot 整合多数据源

小趴菜不能喝2023-09-21 21:19

多数据源产生的场景

一般情况下，不会有多数据源这样的场景出现，但老项目或者特殊需求的项目，可能会有这样的场景

  • 同一个应用需要访问两个数据库
  • 不用数据库中间件的读写分离

注入数据源选择的时机

声明两个数据源实例，在getConnection的时候根据业务的不同，注入不同数据源的连接

环境准备

准备sql脚本，建立两个库，这里mysql为例

sql 复制代码 
create database stu;
create database tech;
use stu;
create table student
(
    id varchar(50) not null comment '主键',
    name varchar(50) null comment '姓名',
    stu_no varchar(50) null comment '学号',
    constraint student_pk primary key (id)
);

insert into student values ('1','张同学','111');
insert into student values ('2','李同学','222');
use tech;
create table teacher
(
    id varchar(50) not null comment '主键',
    name varchar(50) null comment '姓名',
    teach_no varchar(50) null comment '教师号',
    constraint teacher_pk primary key (id)
);

insert into teacher values ('1','王老师','111');
insert into teacher values ('2','高老师','222');

实现DataSource方式实现多数据源

配置多数据源

bash 复制代码 
server:
  port: 9000
spring:
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    datasource1:
      url: jdbc:mysql://shilei.tech:3306/stu?useSSL=true&serverTimezone=Asia/Shanghai
      username: root
      password: root123456
      driver-class-name: com.mysql.cj.jdbc.Driver

    datasource2:
      url: jdbc:mysql://shilei.tech:3306/tech?useSSL=true&serverTimezone=Asia/Shanghai
      username: root
      password: root123456
      driver-class-name: com.mysql.cj.jdbc.Driver
    druid:
      initial-size: 5
      min-idle: 1
      max-active: 20

mybatis-plus:
  mapper-locations: classpath:/mapper/*.xml
  type-aliases-package: com.datasource.dynamicdatasource.model

添加数据源配置

java 复制代码 
package com.datasource.dynamicdatasource.config;

import com.alibaba.druid.pool.DruidDataSource;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import javax.sql.DataSource;

/**
 * @author sl
 */
@Configuration
public class DataSourceConfig {

    @Bean("dataSource1")
    @ConfigurationProperties(prefix = "spring.datasource.datasource1")
    public DataSource dataSource1(){
        DruidDataSource druidDataSource = new DruidDataSource();
        return druidDataSource;
    }


    @Bean("dataSource2")
    @ConfigurationProperties(prefix = "spring.datasource.datasource2")
    public DataSource dataSource2(){
        DruidDataSource druidDataSource = new DruidDataSource();
        return druidDataSource;
    }
}

实现DataSource多数据源

java 复制代码 
package com.datasource.dynamicdatasource.config;

import org.springframework.beans.factory.InitializingBean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;

import javax.annotation.Resource;
import javax.sql.DataSource;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.SQLFeatureNotSupportedException;
import java.util.logging.Logger;

/**
 * @author sl
 * @Primary主要注入的bean
 */
@Configuration
@Primary
public class DynamicDataSource implements DataSource {


    public static ThreadLocal<String> nameFlag = new ThreadLocal<>();

    @Resource
    private DataSource dataSource1;

    @Resource
    private DataSource dataSource2;

    @Override
    public Connection getConnection() throws SQLException {
        if("student".equals(nameFlag.get())){
            return dataSource1.getConnection();
        }
        return dataSource2.getConnection();
    }

    @Override
    public Connection getConnection(String username, String password) throws SQLException {
        return null;
    }

    @Override
    public <T> T unwrap(Class<T> iface) throws SQLException {
        return null;
    }

    @Override
    public boolean isWrapperFor(Class<?> iface) throws SQLException {
        return false;
    }

    @Override
    public PrintWriter getLogWriter() throws SQLException {
        return null;
    }

    @Override
    public void setLogWriter(PrintWriter out) throws SQLException {

    }

    @Override
    public void setLoginTimeout(int seconds) throws SQLException {

    }

    @Override
    public int getLoginTimeout() throws SQLException {
        return 0;
    }

    @Override
    public Logger getParentLogger() throws SQLFeatureNotSupportedException {
        return null;
    }
}

测试多数据源

java 复制代码 
package com.datasource.dynamicdatasource.controller;


import com.datasource.dynamicdatasource.config.DynamicDataSource;
import com.datasource.dynamicdatasource.model.Student;
import com.datasource.dynamicdatasource.model.Teacher;
import com.datasource.dynamicdatasource.service.StudentService;
import com.datasource.dynamicdatasource.service.TeacherService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

/**
 * @author sl
 */
@RestController
public class TestDataSourceController {

    @Autowired
    private StudentService studentService;

    @Autowired
    private TeacherService teacherService;

    @GetMapping("/stu")
    public String getStu(){
        DynamicDataSource.nameFlag.set("student");
        List<Student> allStudent = studentService.findAllStudent();
        return allStudent.toString();
    }

    @GetMapping("/tech")
    public String getTech(){
        DynamicDataSource.nameFlag.set("teacher");
        List<Teacher> allTeacher = teacherService.findAllTeacher();
        return allTeacher.toString();
    }
}

效果如下所示

此实现方式的弊端

实现DataSource接口我们本质上只使用了一个方法，就是getConnection()这个无参的方法，其他方法，当内部调用时可能会导致错误，我们不可能实现所有的方法，所以我们继承AbstractRoutingDataSource抽象类

继承AbstractRoutingDataSource实现多数据源

AbstractRoutingDataSource的结构

可以看到AbstractRoutingDataSource继承自DataSource，提供了一些实现方法

AbstractRoutingDataSource的重要属性

targetDataSources 所有数据源 (需指定)

defaultTargetDataSource 默认数据源(需指定)

resolvedDataSources= targetDataSources 负责最终切换的数据源map 等于 tagetDataSources

继承AbstractRoutingDataSource实现多数据源

java 复制代码 
package com.datasource.dynamicdatasource.config;

import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;

import javax.annotation.Resource;
import javax.sql.DataSource;
import java.util.HashMap;
import java.util.Map;


/**
 * @author sl
 * @Primary主要注入的bean
 */
@Configuration
@Primary
public class DynamicDataSource extends AbstractRoutingDataSource {


    public static ThreadLocal<String> nameFlag = new ThreadLocal<>();

    @Resource
    private DataSource dataSource1;

    @Resource
    private DataSource dataSource2;


    @Override
    protected Object determineCurrentLookupKey() {
        // 返回当前数据源的标识
        return nameFlag.get();
    }

    @Override
    public void afterPropertiesSet() {

        // 为targetDataSources 初始化所有数据源
        Map<Object,Object> targetDataSources=new HashMap<>();

        targetDataSources.put("student",dataSource1);
        targetDataSources.put("teacher",dataSource2);

        super.setTargetDataSources(targetDataSources);
        // 设置默认数据源
        super.setDefaultTargetDataSource(dataSource1);

        // 循环给resolvedDataSources，也就是最终数据源map
        super.afterPropertiesSet();

    }
}

determineCurrentLookupKey的作用

看一段源码，就是通过determineCurrentLookupKey获取数据源的key，然后去resolvedDataSources中取数据源，resolvedDataSources数据源其实就是targetDataSources

java 复制代码 
	protected DataSource determineTargetDataSource() {
		Assert.notNull(this.resolvedDataSources, "DataSource router not initialized");
		Object lookupKey = determineCurrentLookupKey();
		DataSource dataSource = this.resolvedDataSources.get(lookupKey);
		if (dataSource == null && (this.lenientFallback || lookupKey == null)) {
			dataSource = this.resolvedDefaultDataSource;
		}
		if (dataSource == null) {
			throw new IllegalStateException("Cannot determine target DataSource for lookup key [" + lookupKey + "]");
		}
		return dataSource;
	}

测试多数据源

java 复制代码 
package com.datasource.dynamicdatasource.controller;


import com.datasource.dynamicdatasource.config.DynamicDataSource;
import com.datasource.dynamicdatasource.model.Student;
import com.datasource.dynamicdatasource.model.Teacher;
import com.datasource.dynamicdatasource.service.StudentService;
import com.datasource.dynamicdatasource.service.TeacherService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

/**
 * @author sl
 */
@RestController
public class TestDataSourceController {

    @Autowired
    private StudentService studentService;

    @Autowired
    private TeacherService teacherService;

    @GetMapping("/stu")
    public String getStu(){
        // 默认数据源就是student
        List<Student> allStudent = studentService.findAllStudent();
        return allStudent.toString();
    }

    @GetMapping("/tech")
    public String getTech(){
        DynamicDataSource.nameFlag.set("teacher");
        List<Teacher> allTeacher = teacherService.findAllTeacher();
        return allTeacher.toString();
    }
}

AOP自定义注解方式+AbstractRoutingDataSource实现多数据源

数据源的切换还是使用AbstractRoutingDataSource，只不过切换方式采用aop拦截自定义注解切换数据源，这种方式也是mybatis-plus多数据源插件所采用的方式

自定义注解

java 复制代码 
package com.datasource.dynamicdatasource.annotation;

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

/**
 * @author sl
 */
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface MyDataSource {

    String value() default "student";
}

配置切面

XML 复制代码 
<dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-aop</artifactId>
</dependency>
java 复制代码 
package com.datasource.dynamicdatasource.aspect;

import com.datasource.dynamicdatasource.annotation.MyDataSource;
import com.datasource.dynamicdatasource.config.DynamicDataSource;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.stereotype.Component;

import java.lang.reflect.Method;

/**
 * @author sl
 *@Aspect 标识是一个切面
 */
@Aspect
@Component
public class DatasourceAspect {

    /**
     * 切点规则
     */
    @Pointcut("@annotation(com.datasource.dynamicdatasource.annotation.MyDataSource)")
    public void pointcut() {
    }

    @Before("pointcut()")
    public void dataSourceAspect(JoinPoint joinPoint){
        // 获取方法
        Method method = ((MethodSignature) joinPoint.getSignature()).getMethod();

        // 判断方法中是否添加了注解
        if(method.isAnnotationPresent(MyDataSource.class)){
            // 获取方法上的注解
            MyDataSource annotation = method.getAnnotation(MyDataSource.class);

            String value = annotation.value();
            //  设置数据源
            DynamicDataSource.nameFlag.set(value);
        }
    }
}

测试自定义注解切换数据源

java 复制代码 
    @GetMapping("/tech")
    @MyDataSource("teacher")
    public String getTech(){
        List<Teacher> allTeacher = teacherService.findAllTeacher();
        return allTeacher.toString();
    }

dynamic-datasource多数据源组件实现多数据源

官方文档及搭建指南地址：多数据源 | MyBatis-Plus

引入依赖

XML 复制代码 
<dependency>
  <groupId>com.baomidou</groupId>
  <artifactId>dynamic-datasource-spring-boot-starter</artifactId>
  <version>3.6.1</version>
</dependency>

配置数据源

bash 复制代码 
server:
  port: 9000
spring:
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    dynamic:
      #设置默认的数据源或者数据源组,默认值即为master
      primary: master
      #严格匹配数据源,默认false. true未匹配到指定数据源时抛异常,false使用默认数据源
      strict: false
      datasource:
        master:
          url: jdbc:mysql://shilei.tech:3306/stu?useSSL=true&serverTimezone=Asia/Shanghai
          username: root
          password: root123456
          driver-class-name: com.mysql.cj.jdbc.Driver
        teacher:
          url: jdbc:mysql://shilei.tech:3306/tech?useSSL=true&serverTimezone=Asia/Shanghai
          username: root
          password: root123456
          driver-class-name: com.mysql.cj.jdbc.Driver
      druid:
        initial-size: 5
        min-idle: 1
        max-active: 20

mybatis-plus:
  mapper-locations: classpath:/mapper/*.xml
  type-aliases-package: com.datasource.dynamicdatasource.model

测试数据源切换

数据源切换使用@DS注解，不使用此注解，使用默认数据源，方法上使用>类上使用

java 复制代码 
package com.datasource.dynamicdatasource.controller;


import com.baomidou.dynamic.datasource.annotation.DS;
import com.datasource.dynamicdatasource.model.Student;
import com.datasource.dynamicdatasource.model.Teacher;
import com.datasource.dynamicdatasource.service.StudentService;
import com.datasource.dynamicdatasource.service.TeacherService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

/**
 * @author sl
 */
@RestController
public class TestDataSourceController {

    @Autowired
    private StudentService studentService;

    @Autowired
    private TeacherService teacherService;

    @GetMapping("/stu")
    public String getStu(){
        List<Student> allStudent = studentService.findAllStudent();
        return allStudent.toString();
    }

    @GetMapping("/tech")
    @DS("teacher")
    public String getTech(){
        List<Teacher> allTeacher = teacherService.findAllTeacher();
        return allTeacher.toString();
    }
}

项目启动日志中可以看到两个数据源的加载信息

访问tech以及stu都能正常访问，代表动态数据源添加成功

需要注意的问题

使用多数据源要注意事务的控制，提交和回滚策略，可以观看spring多数据源事务解决方案

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