springboot结合mysql主从来实现读写分离的方法示例

1.实现的功能

    基于springboot框架，application.yml配置多个数据源，使用aop以及abstractrootingdatasource、threadlocal来实现多数据源切换，以实现读写分离。mysql的主从数据库需要进行设置数据之间的同步。

2.代码实现

    application.properties中的配置

spring.datasource.druid.master.driver-class-name=com.mysql.jdbc.driver
spring.datasource.druid.master.url=jdbc:mysql://127.0.0.1:3306/node2?useunicode=true&characterencoding=utf-8&allowmultiqueries=true&autoreconnect=true&usessl=false
spring.datasource.druid.master.username=root
spring.datasource.druid.master.password=123456
 
 
spring.datasource.druid.slave.driver-class-name=com.mysql.jdbc.driver
spring.datasource.druid.slave.url=jdbc:mysql://127.0.0.1:3306/node1?useunicode=true&characterencoding=utf-8&allowmultiqueries=true&autoreconnect=true&usessl=false
spring.datasource.druid.slave.username=root
spring.datasource.druid.slave.password=123456

写一个datasourceconfig.java来注入两个bean

 @bean
    @configurationproperties("spring.datasource.druid.master")
    public datasource masterdatasource() {
        logger.info("select master data source");
        return druiddatasourcebuilder.create().build();
    }
 
    @bean
    @configurationproperties("spring.datasource.druid.slave")
    public datasource slavedatasource() {
        logger.info("select slave data source");
        return druiddatasourcebuilder.create().build();
    }

写一个enum来标识有哪些数据源

public enum dbtypeenum {
    master, slave;
}

然后写一个threadlocal本地线程的管理类,用于设置当前线程是那一个数据源

private static final threadlocal<dbtypeenum> contextholder = new threadlocal<>();
 
    private static final threadlocal<dbtypeenum> contextholder2 = threadlocal.withinitial(() -> dbtypeenum.master);
 
    public static void set(dbtypeenum dbtype) {
        contextholder.set(dbtype);
    }
 
    public static dbtypeenum get() {
        return contextholder.get();
    }
 
    public static void master() {
        set(dbtypeenum.master);
        logger.info("切换到master数据源");
    }
 
    public static void slave() {
        set(dbtypeenum.slave);
        logger.info("切换到slave数据源");
    }
 
    public static void cleanall() {
        contextholder.remove();
    }

然后写一个dynamicdatasource继承abstractrootingdatasource,重写它的determinecurrentlookupkey方法。

public class dynamicdatasource extends abstractroutingdatasource {
    private logger logger = logmanager.getlogger(dynamicdatasource.class);
 
    @override
    protected object determinecurrentlookupkey() {
        logger.info("此时数据源为{}", dbcontextholder.get());
        return dbcontextholder.get();
    }
}

最后写一个aop来实现数据源切换

@aspect
@order(1)
@component
public class datasourceaop {
 
    private logger logger = logmanager.getlogger(datasourceaop.class);
 
    @pointcut("(execution(* com.springboot.demo.service..*.select*(..)) " +
            "|| execution(* com.springboot.demo.service..*.find*(..)) " +
            "|| execution(* com.springboot.demo.service..*.get*(..)))")
    public void readpointcut() {
        logger.info("read only operate ,into slave db");
    }
 
    @pointcut("execution(* com.springboot.demo.service..*.insert*(..)) " +
            "|| execution(* com.springboot.demo.service..*.update*(..)) " +
            "|| execution(* com.springboot.demo.service..*.delete*(..)) ")
    public void writepointcut() {
        logger.info("read or write operate ,into master db");
    }
 
    @before("readpointcut()")
    public void read() {
        logger.info("read operate");
        dbcontextholder.slave();
    }
 
    @before("writepointcut()")
    public void write() {
        logger.info("write operate");
        dbcontextholder.master();
    }
 
    @after("writepointcut(),readpointcut()")
    public void clean() {
        logger.info("datasource cleanall");
        dbcontextholder.cleanall();
    }
}

注意：这里只是使用了偷懒的方法，对于service里面的select、get、find前缀的方法都使用从库，对于insert、update和delete方法都使用主库。

可以使用注解如下来进行优化:

@retention(retentionpolicy.runtime)
@target(elementtype.method)
public @interface datasource {
 
    @aliasfor("datasource")
    dbtypeenum value() default dbtypeenum.master;
 
    dbtypeenum datasource() default dbtypeenum.master;

}

使用此注解来放入到service方法上，

@datasource(dbtypeenum.slave)

然后aop方法修改为：

private static final string point = "execution (* com.springboot.demo.service.*.*(..))";
 
 
 @around(point)
    public object datasourcearound(proceedingjoinpoint joinpoint) throws throwable {
        object[] args = joinpoint.getargs();
        object obj;
        object target = joinpoint.gettarget();
        string methodname = joinpoint.getsignature().getname();
        class clazz = target.getclass();
        class<?>[] parametertypes = ((methodsignature) joinpoint.getsignature()).getmethod().getparametertypes();
        boolean isdynamicdatasourcemethod = false;
        try {
            method method = clazz.getmethod(methodname, parametertypes);
            datasources currentdatasource = null;
            if (method != null && method.isannotationpresent(datasource.class)) {
                isdynamicdatasourcemethod = true;
                currentdatasource = method.getannotation(datasource.class).value();
                datasourcetypemanager.set(currentdatasource);
                log.info("datasourceinterceptor switch datasource to {}",currentdatasource);
            }
            obj = joinpoint.proceed(args);
            if (isdynamicdatasourcemethod) {
                log.info("datasourceinterceptor datasource {} proceed",currentdatasource);
            }
        } finally {
            if (isdynamicdatasourcemethod) {
                datasourcetypemanager.reset();
                log.info("datasourceinterceptor reset datasource to {}",datasourcetypemanager.get());
            }
        }
        return obj;
    }

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