Spring:一主多从DataSource的读写分离实现 博客分类： spring AbstractRoutingDataSourceSpring

对于一主多从的数据库配置, Spring的经典做法是继承AbstractRoutingDataSource. 不过个人觉得AbstractRoutingDataSource还是复杂了些, 于是自己实现了一个DynamicDataSource.

 

import org.springframework.jdbc.datasource.AbstractDataSource;

import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

/**
 * For read-write separation.
 *
 * @author [e-mail]
 */
class DynamicDataSource extends AbstractDataSource {
    private static final ThreadLocal<Boolean> readSeparable = ThreadLocal.withInitial(() -> Boolean.FALSE);
    //master datasource
    private DataSource master;
    //all-in-one slave datasources
    private SlaveDataSource slave;

    public static void setReadSeparable() {
        readSeparable.set(Boolean.TRUE);
    }

    private boolean isReadSeparable() {
        return readSeparable.get();
    }

    public DynamicDataSource setMaster(DataSource dataSource) {
        this.master = dataSource;
        return this;
    }

    public DynamicDataSource addSlave(DataSource dataSource) {
        if (slave == null) {
            slave = new SlaveDataSource();
        }
        slave.add(dataSource);
        return this;
    }

    @Override
    public Connection getConnection() throws SQLException {
        return getTargetDataSource().getConnection();
    }

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

    private DataSource getTargetDataSource() {
        return isReadSeparable() && slave != null ? slave : master;
    }

    /**
     * The all-in-one slave datasources.
     */
    static class SlaveDataSource extends AbstractDataSource {
        private List<DataSource> peers = new ArrayList<>();

        public SlaveDataSource add(DataSource dataSource) {
            peers.add(dataSource);
            return this;
        }

        @Override
        public Connection getConnection() throws SQLException {
            return getTargetSlaveDataSource().getConnection();
        }

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

        private DataSource getTargetSlaveDataSource() {
            return peers.get((int) (Math.random() * peers.size()));
        }
    }
}

 

 

初始化DataSource:

    @Bean
    @Primary
    public DataSource dataSource(){
        DynamicDataSource dynamicDataSource = new DynamicDataSource();
        //dynamicDataSource.setMaster(....);
        //dynamicDataSource.addSlave(...);
        //dynamicDataSource.addSlave(...);
        return dynamicDataSource;
    }

 

 

添加AOP:

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.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.core.Ordered;

import java.lang.reflect.Method;

/**
 * For read-write separation.
 *
 * @author [e-mail]
 */
@Aspect
public class DynamicDataSourceAspect implements Ordered {
    private static final Logger LOG = LoggerFactory.getLogger(DynamicDataSourceAspect.class);

    @Pointcut("@annotation(com.myCompany.annotation.ReadSeparable)")
    public void readSeparable() {
    }

    @Before("readSeparable()")
    public void selectDataSourceOnFly(JoinPoint joinPoint) {
        if (!MethodSignature.class.isInstance(joinPoint.getSignature())) {
            return;
        }
        Method targetMethod = ((MethodSignature) joinPoint.getSignature()).getMethod();
        DynamicDataSource.setReadSeparable();
        LOG.info(String.format("ReadSeparable advised on thread: {%s}, method:{%s}", Thread.currentThread().getName(), targetMethod.toString()));
    }

    @Override
    public int getOrder() {
        return -999;
    }

 

 

ReadSeparable注解:

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

/**
 * For read-write separation.
 *
 * @author [e-mail]
 */
@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface ReadSeparable {
    /**
     * Alias for {@link #threshold}.
     */
    int value() default 30;

    /**
     * Define how much latency in seconds is tolerable.
     */
    int threshold() default 30;
}

 

 

在需要读写分离的方法上添加ReadSeparable注解即可. DynamicDataSourceAspect捕获到ReadSeparable的方法, 并设置DynamicDataSource的readSeparable为true.  DynamicDataSource根据readSeparable的值来决定是从master还是从slave来取得connection. 如果是从SlaveDataSource中取的话, 则从多个slave中随机取一个, 此处为负载均衡的扩展点.