Spring boot实现数据库读写分离的方法

Spring boot实现数据库读写分离的方法

背景

数据库配置主从之后，如何在代码层面实现读写分离？

用户自定义设置数据库路由

Spring boot提供了AbstractRoutingDataSource根据用户定义的规则选择当前的数据库，这样我们可以在执行查询之前，设置读取从库，在执行完成后，恢复到主库。

实现可动态路由的数据源，在每次数据库查询操作前执行

ReadWriteSplitRoutingDataSource.java

import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;

/**

* @author songrgg

* @since 1.0

*/

public class ReadWriteSplitRoutingDataSource extends AbstractRoutingDataSource {

@Override

protected Object determineCurrentLookupKey() {

return DbContextHolder.getDbType();

}

}

线程私有路由配置，用于ReadWriteSplitRoutingDataSource动态读取配置

DbContextHolder.java

/**

* @author songrgg

* @since 1.0

*/

public class DbContextHolder {

public enum DbType {

MASTER,

SLAVE

}

private static final ThreadLocal contextHolder = new ThreadLocal<>();

public static void setDbType(DbType dbType) {

if(dbType == null){

throw new NullPointerException();

}

contextHolder.set(dbType);

}

public static DbType getDbType() {

return contextHolder.get() == null ? DbType.MASTER : contextHolder.get();

}

public static void clearDbType() {

contextHolder.remove();

}

}

AOP优化代码

利用AOP将设置数据库的操作从代码中抽离，这里的粒度控制在方法级别，所以利用注解的形式标注这个方法涉及的数据库事务只读，走从库。

只读注解，用于标注方法的数据库操作只走从库。

ReadOnlyConnection.java

package com.wallstreetcn.hatano.config;

import java.lang.annotation.ElementType;

import java.lang.annotation.Retention;

import java.lang.annotation.RetentionPolicy;

import java.lang.annotation.Target;

/**

* Indicates the database operations is bound to the slave database.

* AOP interceptor will set the database to the slave with this interface.

* @author songrgg

* @since 1.0

*/

@Target({ElementType.METHOD, ElementType.TYPE})

@Retention(RetentionPolicy.RUNTIME)

public @interface ReadOnlyConnection {

}

ReadOnlyConnectionInterceptor.java

import org.aspectj.lang.ProceedingJoinPoint;

import org.aspectj.lang.annotation.Around;

import org.aspectj.lang.annotation.Aspect;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

import org.springframework.core.Ordered;

import org.springframework.stereotype.Component;

/**

* Intercept the database operations, bind database to read-only database as this annotation

* is applied.

* @author songrgg

* @since 1.0

*/

@Aspect

@Component

public class ReadOnlyConnectionInterceptor implements Ordered {

private static final Logger logger = LoggerFactory.getLogger(ReadOnlyConnectionInterceptor.class);

@Around("@annotation(readOnlyConnection)")

public Object proceed(ProceedingJoinPoint proceedingJoinPoint, ReadOnlyConnection readOnlyConnection) throws Throwable {

try {

logger.info("set database connection to read only");

DbContextHolder.setDbType(DbContextHolder.DbType.SLAVE);

Object result = proceedingJoinPoint.proceed();

return result;

} finally {

DbContextHolder.clearDbType();

logger.info("restore database connection");

}

}

@Override

public int getOrder() {

return 0;

}

}

UserService.java

@ReadOnlyConnection

public List getUsers(Integer page, Integer limit) {

return repository.findAll(new PageRequest(page, limit));

}

配置Druid数据库连接池

build.gradle

compile("com.alibaba:druid:1.0.18")

groovy依赖注入

配置dataSource为可路由数据源

context.groovy

import com.alibaba.druid.pool.DruidDataSource

import DbContextHolder

import ReadWriteSplitRoutingDataSource

** SOME INITIALIZED CODE LOAD PROPERTIES **

def dataSourceMaster = new DruidDataSource()

dataSourceMaster.url = properties.get('datasource.master.url')

println("master set to " + dataSourceMaster.url)

dataSourceMaster.username = properties.get('datasource.master.username')

dataSourceMaster.password = properties.get('datasource.master.password')

def dataSourceSlave = new DruidDataSource()

dataSourceSlave.url = properties.get('datasource.slave.url')

println("slave set to " + dataSourceSlave.url)

dataSourceSlave.username = properties.get('datasource.slave.username')

dataSourceSlave.password = properties.get('datasource.slave.password')

beans {

dataSource(ReadWriteSplitRoutingDataSource) { bean ->

targetDataSources = [

(DbContextHolder.DbType.MASTER): dataSourceMaster,

(DbContextHolder.DbType.SLAVE): dataSourceSlave

]

}

}

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