[Java] 详解Spring Boot + Mybatis 实现动态数据源

create table `example` (
 `pk` bigint(20) unsigned not null auto_increment comment '主键',
 `message` varchar(100) not null,
 `create_time` datetime not null comment '创建时间',
 `modify_time` datetime default null comment '生效时间',
 primary key (`pk`)
) engine=innodb auto_increment=2 default charset=utf8 row_format=compact comment='测试用例表'

<dependency>
   <groupid>org.springframework.boot</groupid>
   <artifactid>spring-boot-starter-web</artifactid>
  </dependency>
  <dependency>
   <groupid>org.springframework.boot</groupid>
   <artifactid>spring-boot-starter-test</artifactid>
   <scope>test</scope>
  </dependency>
  <dependency>
   <groupid>org.mybatis.spring.boot</groupid>
   <artifactid>mybatis-spring-boot-starter</artifactid>
   <version>1.3.1</version>
  </dependency>
  <!-- spring aop -->
  <dependency>
   <groupid>org.springframework.boot</groupid>
   <artifactid>spring-boot-starter-aop</artifactid>
  </dependency>
  <dependency>
   <groupid>mysql</groupid>
   <artifactid>mysql-connector-java</artifactid>
   <version>5.1.8</version>
  </dependency>

#数据库设置
spring.datasource.example.jdbc-url=jdbc:mysql://localhost:3306/example?characterencoding=utf-8
spring.datasource.example.username=root
spring.datasource.example.password=123456
spring.datasource.example.driver-class-name=com.mysql.jdbc.driver

package com.main.example.dynamic.datasource;
 
import org.springframework.boot.springapplication;
import org.springframework.boot.autoconfigure.springbootapplication;
import org.springframework.boot.autoconfigure.jdbc.datasourceautoconfiguration;
 
@springbootapplication(exclude = {
  datasourceautoconfiguration.class
})
public class dynamicdatasourceapplication {
 
 public static void main(string[] args) {
  springapplication.run(dynamicdatasourceapplication.class, args);
 }
 
}

package com.main.example.config.dao;
 
import com.main.example.common.dataenum;
import com.main.example.common.dynamicdatasource;
import org.mybatis.spring.sqlsessionfactorybean;
import org.springframework.boot.context.properties.configurationproperties;
import org.springframework.boot.jdbc.datasourcebuilder;
import org.springframework.context.annotation.bean;
import org.springframework.context.annotation.configuration;
import org.springframework.context.annotation.propertysource;
import org.springframework.core.io.support.pathmatchingresourcepatternresolver;
import org.springframework.jdbc.datasource.datasourcetransactionmanager;
import org.springframework.transaction.platformtransactionmanager;
 
import javax.sql.datasource;
import java.util.hashmap;
import java.util.map;
 
//数据库配置统一在config/mysql/db.properties中
@configuration
@propertysource(value = "classpath:config/mysql/db.properties")
public class dbsourceconfig {
  private string typealiasespackage = "com.main.example.bean.**.*";
 
  @bean(name = "exampledatasource")
  @configurationproperties(prefix = "spring.datasource.example")
  public datasource exampledatasource() {
  return datasourcebuilder.create().build();
  }
 
  /*
   * 动态数据源
   * dbmap中存放数据源名称与数据源实例，数据源名称存于dataenum.dbsource中
   * setdefaulttargetdatasource方法设置默认数据源
   */
  @bean(name = "dynamicdatasource")
  public datasource dynamicdatasource() {
  dynamicdatasource dynamicdatasource = new dynamicdatasource();
  //配置多数据源
  map<object, object> dbmap = new hashmap();
  dbmap.put(dataenum.dbsource.example.getname(), exampledatasource());
  dynamicdatasource.settargetdatasources(dbmap);
 
  // 设置默认数据源
  dynamicdatasource.setdefaulttargetdatasource(exampledatasource());
 
  return dynamicdatasource;
  }
 
  /*
   * 数据库连接会话工厂
   * 将动态数据源赋给工厂
   * mapper存于resources/mapper目录下
   * 默认bean存于com.main.example.bean包或子包下，也可直接在mapper中指定
   */
  @bean(name = "sqlsessionfactory")
  public sqlsessionfactorybean sqlsessionfactory() throws exception {
  sqlsessionfactorybean sqlsessionfactory = new sqlsessionfactorybean();
  sqlsessionfactory.setdatasource(dynamicdatasource());
  sqlsessionfactory.settypealiasespackage(typealiasespackage); //扫描bean
  pathmatchingresourcepatternresolver resolver = new pathmatchingresourcepatternresolver();
  sqlsessionfactory.setmapperlocations(resolver.getresources("classpath*:mapper/*.xml"));  // 扫描映射文件
 
  return sqlsessionfactory;
  }
 
  @bean
  public platformtransactionmanager transactionmanager() {
  // 配置事务管理, 使用事务时在方法头部添加@transactional注解即可
  return new datasourcetransactionmanager(dynamicdatasource());
  }
}

package com.main.example.common;
 
import org.springframework.jdbc.datasource.lookup.abstractroutingdatasource;
 
public class dynamicdatasource extends abstractroutingdatasource {
 
  @override
  protected object determinecurrentlookupkey() {
  return dbsourcecontext.getdbsource();
  }
 
}

package com.main.example.common;
 
import org.apache.log4j.logger;
 
public class dbsourcecontext {
  private static logger logger = logger.getlogger(dbsourcecontext.class);
 
  private static final threadlocal<string> dbcontext = new threadlocal<string>();
 
  public static void setdbsource(string source) {
  logger.debug("set source ====>" + source);
  dbcontext.set(source);
  }
 
  public static string getdbsource() {
  logger.debug("get source ====>" + dbcontext.get());
  return dbcontext.get();
  }
 
  public static void cleardbsource() {
  dbcontext.remove();
  }
}

package com.main.example.config.dao;
 
import java.lang.annotation.*;
 
/**
 * 动态数据源注解
 * @author
 * @date april 12, 2019
 */
@target({elementtype.method, elementtype.type})
@retention(retentionpolicy.runtime)
@documented
public @interface dbsource {
  /**
   * 数据源key值
   * @return
   */
  string value();
}

package com.main.example.config.dao;
 
import com.main.example.common.dbsourcecontext;
import org.apache.log4j.logger;
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.springframework.core.annotation.order;
import org.springframework.stereotype.component;
 
/**
 * 动态数据源切换处理器
 * @author linzhibao
 * @date april 12, 2019
 */
@aspect
@order(-1) // 该切面应当先于 @transactional 执行
@component
public class dynamicdatasourceaspect {
  private static logger logger = logger.getlogger(dynamicdatasourceaspect.class);
  /**
   * 切换数据源
   * @param point
   * @param dbsource
   */
  //@before("@annotation(dbsource)") 注解在对应方法，拦截有@dbsource的方法
  //注解在类对象，拦截有@dbsource类下所有的方法
  @before("@within(dbsource)")
  public void switchdatasource(joinpoint point, dbsource dbsource) {
    // 切换数据源
    dbsourcecontext.setdbsource(dbsource.value());
  }
 
  /**
   * 重置数据源
   * @param point
   * @param dbsource
   */
  //注解在类对象，拦截有@dbsource类下所有的方法
  @after("@within(dbsource)")
  public void restoredatasource(joinpoint point, dbsource dbsource) {
  // 将数据源置为默认数据源
  dbsourcecontext.cleardbsource();
  }
}

package com.main.example.dao;
 
import com.main.example.common.dataenum;
import com.main.example.config.dao.dbsource;
import org.springframework.context.annotation.bean;
import org.springframework.stereotype.component;
 
import javax.annotation.resource;
import java.util.list;
 
@component("exampledao")
//切换数据源注解，以dataenum.dbsource中的值为准
@dbsource("example")
public class exampledao extends daobase {
  private static final string mapper_name_space = "com.main.example.dao.examplemapper";
 
  public list<string> selectallmessages() {
  return selectlist(mapper_name_space, "selectallmessages");
  }
}

package com.main.example.dao;
 
import org.springframework.beans.factory.annotation.autowired;
import org.springframework.web.bind.annotation.requestmapping;
import org.springframework.web.bind.annotation.restcontroller;
 
import java.util.arraylist;
import java.util.list;
 
@restcontroller
public class testexampledao {
  @autowired
  exampledao exampledao;
 
  @requestmapping(value = "/test/example")
  public list<string> selectallmessages() {
  try {
    list<string> ldata = exampledao.selectallmessages();
    if(ldata == null){system.out.println("*********it is null.***********");return null;}
    for(string d : ldata) {
    system.out.println(d);
    }
    return ldata;
  }catch(exception e) {
    e.printstacktrace();
  }
 
  return new arraylist<>();
  }
}

<?xml version="1.0" encoding="utf-8" ?>
<!doctype mapper
  public "-//mybatis.org//dtd mapper 3.0//en"
  "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.main.example.dao.examplemapper">
  <select id="selectallmessages" resulttype="java.lang.string">
  select
  message
  from example
  </select>
 
</mapper>

@propertysource(value = "classpath:config/mysql/db.properties")

@configurationproperties(prefix = "spring.datasource.example")

@springbootapplication(exclude = {
  datasourceautoconfiguration.class
})