SpringBoot+Mybatis-Plus实现mysql读写分离方案的示例代码

POOPE

1. 引入mybatis-plus相关包，pom.xml文件

2. 配置文件application.property增加多库配置
mysql 数据源配置

spring.datasource.primary.jdbc-url=jdbc:mysql://xx.xx.xx.xx:3306/portal?useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC&characterEncoding=utf8&serverTimezone=GMT%2B8
spring.datasource.primary.username=root
spring.datasource.primary.password=root
spring.datasource.primary.driver-class-name=com.mysql.cj.jdbc.Driver
#mysql slave 数据源配置
 
spring.datasource.slave.jdbc-url=jdbc:mysql://xx.xx.xx.xx:3306/portal?useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC&characterEncoding=utf8&serverTimezone=GMT%2B8
spring.datasource.slave.username=root
spring.datasource.slave.password=root
spring.datasource.slave.driver-class-name=com.mysql.cj.jdbc.Driver

3. 配置数据源及注解
数据源配置 MultiDataSourceConfig.Java

/**
* 配置多数据源
*/
@Profile("dev")//开发模式配置文件
@Configuration
@MapperScan(basePackages = "com.csc.portal.mapper")//扫描包
public class MultiDataSourceConfig {
 
/**
* 主数据源
* @return
*/
@Bean
@ConfigurationProperties(prefix = "spring.datasource.primary")
public DataSource masterDataSource() {
return DataSourceBuilder.create().build();
}
 
/**
* 从数据源
* @return
*/
@Bean
@ConfigurationProperties(prefix = "spring.datasource.slave")
public DataSource slaveDataSource() {
return DataSourceBuilder.create().build();
}
 
/**
* 路由数据源，前面两个数据源是为了创建此数据源
* @param masterDataSource 主数据源
* @param slaveDataSource 从数据源
* @return
*/
@Bean
public DataSource myRoutingDataSource(@Qualifier("masterDataSource") DataSource masterDataSource,
@Qualifier("slaveDataSource") DataSource slaveDataSource) {
Map<Object, Object> targetDataSources = new HashMap<>();
targetDataSources.put(DBTypeEnum.MASTER, masterDataSource);
targetDataSources.put(DBTypeEnum.SLAVE, slaveDataSource);
MyRoutingDataSource myRoutingDataSource = new MyRoutingDataSource();
myRoutingDataSource.setDefaultTargetDataSource(slaveDataSource);//设置默认数据源
myRoutingDataSource.setTargetDataSources(targetDataSources);//设置路由表，使用map的key，value方式得到对应数据源
return myRoutingDataSource;
}

数据库枚举类

public enum DBTypeEnum {
MASTER, SLAVE;
}

注解

@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface Master {
}

@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface Slave {
}

4. Mybatis-plus配置

@EnableTransactionManagement
@Configuration
@MapperScan(basePackages = "com.csc.portal.mapper")
public class MybatisPlusConfig {
/**
* 分页插件
*/
@Bean
public PaginationInterceptor paginationInterceptor() {
return new PaginationInterceptor();
}
 
@Resource(name = "myRoutingDataSource")
private DataSource myRoutingDataSource;
/**
* 使用MyBatis Plus的sqlSessionFactory代替，
* 此处注意mybatis与mybatisPlus的配置不同，不然扫描不到对数据操作的方法。会报未绑定错误
* @return sqlSessionFactory
* @throws Exception
*/
@Bean
public SqlSessionFactory sqlSessionFactory() throws Exception {
MybatisSqlSessionFactoryBean sqlSessionFactoryBean = new MybatisSqlSessionFactoryBean();
sqlSessionFactoryBean.setDataSource(myRoutingDataSource);
sqlSessionFactoryBean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath:mapper/*.xml"));
MybatisConfiguration mybatisConfiguration = new MybatisConfiguration();
sqlSessionFactoryBean.setConfiguration(mybatisConfiguration);
return sqlSessionFactoryBean.getObject();
}
 
/**
* 此处为使用mybatis时的sqlsessionFactory配置
* @return
* @throws Exception
*/
/*
@Bean
public SqlSessionFactory sqlSessionFactory() throws Exception {
SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
sqlSessionFactoryBean.setDataSource(myRoutingDataSource);
sqlSessionFactoryBean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath:mapper/*.xml"));
return sqlSessionFactoryBean.getObject();
}
*/
 
/**
* 事务配置
* @return 事务管理器
*/
@Bean
public DataSourceTransactionManager transactionManager() {
DataSourceTransactionManager tx = new DataSourceTransactionManager();
tx.setDataSource(myRoutingDataSource);
return tx;
}

5. 增加数据源管理类
DBContextHolder.java

public class DBContextHolder {
 
/**
* 外部一个请求将会产生一个线程与之对应，每个线程的变量可用ThreadLocal进行存储
*/
private static final ThreadLocal<DBTypeEnum> contextHolder = new ThreadLocal<>();
 
public static void set(DBTypeEnum dbType) {
contextHolder.set(dbType);
}
 
public static DBTypeEnum get() {
return contextHolder.get();
}
 
public static void master() {
set(DBTypeEnum.MASTER);
System.out.println("切换到master");
}
 
public static void slave() {
set(DBTypeEnum.SLAVE);
System.out.println("切换到slave");
}
 
}

指定选择数据源
MyRoutingDataSource.java 方法determineCurrentLookupKey决定最终使用哪个数据源进行操作，若为空则使用默认数据源。

public class MyRoutingDataSource extends AbstractRoutingDataSource {
@Nullable
@Override
protected Object determineCurrentLookupKey() {
System.out.println("线程名："+Thread.currentThread().getName()+":"+DBContextHolder.get());
return DBContextHolder.get();
/* if (DBContextHolder.get() != null) {
System.out.println("线程名："+Thread.currentThread().getName()+":"+DBContextHolder.get());
return DBContextHolder.get();
} else {
System.out.println("未匹配到指定数据库,默认切换到Master");
return DBTypeEnum.MASTER;
}*/
//return DBContextHolder.get();
}
 
}

6. 增加aop切面

@Aspect
@Component
@Order(0)//配置注解优先级，优于事物注解@Transactional先进行数据源切换，
//不然在事物中进行数据源切换无效
public class DataSourceAop {
 
@Pointcut(/*"!@annotation(com.csc.portal.annotation.Master) " +
"&& (execution(* com.csc.portal.service..*.select*(..)) " +
"|| execution(* com.csc.portal.service..*.get*(..))"+*/
" @annotation(com.csc.portal.annotation.Slave)")
public void readPointcut() {
 
}
 
@Pointcut("@annotation(com.csc.portal.annotation.Master) " //+
/* "|| execution(* com.csc.portal.service..*.insert*(..)) " +
"|| execution(* com.csc.portal.service..*.add*(..)) " +
"|| execution(* com.csc.portal.service..*.update*(..)) " +
"|| execution(* com.csc.portal.service..*.edit*(..)) " +
"|| execution(* com.csc.portal.service..*.delete*(..)) " +
"|| execution(* com.csc.portal.service..*.remove*(..))"*/)
public void writePointcut() {
 
}
 
@Before("readPointcut()")
public void read() {
//获取拦截类
DBContextHolder.slave();
System.out.println(Thread.currentThread().getName()+DBContextHolder.get());
}
 
@Before("writePointcut()")
public void write() {
//获取拦截类
/* String className = pjp.getTarget().getClass().getName();
System.out.println("当前线程"+Thread.currentThread().getName()+" 拦截类为：" + className);
 
//获取拦截的方法名
MethodSignature msig = (MethodSignature) pjp.getSignature();
Method currentMethod = null;
try {
currentMethod = pjp.getTarget().getClass().getMethod(msig.getName(), msig.getParameterTypes());
} catch (NoSuchMethodException e) {
e.printStackTrace();
}
String methodName = currentMethod.getName();
System.out.println("拦截方法名为：" + methodName);*/
DBContextHolder.master();
System.out.println(Thread.currentThread().getName()+DBContextHolder.get());
}
}

6. 实际应用

• 在service层方法前增加注解@Master表示使用主库，进行增删改的操作使用主库。
  
• 在service层方法前增加注解@Slave表示使用从库，进行查的操作使用从库，默认使用从库，可不配置。
  
• @ Transactional注解加到service层，增加了@Transactional注解后，启用事务后，一个事务内部的connection是复用的，所以就算AOP切了数据源字符串，但是数据源并不会被真正修改。所以@Transactional注解不要写在controller层，不然在service层也切换不了数据源。
  
• @Transactional与@Master可同时使用，已经配置@Master注解的优先级较高，先切换数据源后执行事务。
  

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原文链接：https://blog.csdn.net/AAAAABBBBBYYYYY/article/details/110875245