MySQL主從複製的原理圖解及Java語言範例使用

package com.xinxin.order.context.config;
import com.alibaba.druid.pool.DruidDataSourceFactory;
import lombok.Data;
import lombok.SneakyThrows;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.*;
import org.springframework.jdbc.datasource.DataSourceTransactionManager;
import org.springframework.util.CollectionUtils;
import javax.sql.DataSource;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
@Slf4j
@Data
@Configuration
@PropertySource("classpath:config/datasource.properties")
@ConfigurationProperties(prefix = "spring.datasource")
public class DataSourceConfig {
    /**
     * 主庫資料來源資訊
     */
    private Map<String, String> masters;
    /**
     * 從庫資料來源資訊
     */
    private List<Map<String, String>> slaves;
    @SneakyThrows
    @Bean
    public DataSource masterDataSource() {
        log.info("masters:{}", masters);
        if (CollectionUtils.isEmpty(masters)) {
            throw new Exception("主庫資料來源不能為空");
        }
        return DruidDataSourceFactory.createDataSource(masters);
    }
    @SneakyThrows
    @Bean
    public List<DataSource> slaveDataSources() {
        if (CollectionUtils.isEmpty(slaves)) {
            throw new Exception("從庫資料來源不能為空");
        }
        final ArrayList<DataSource> dataSources = new ArrayList<>();
        for (Map<String, String> slaveProperties : slaves) {
            log.info("slave:{}", slaveProperties);
            dataSources.add(DruidDataSourceFactory.createDataSource(slaveProperties));
        }
        return dataSources;
    }
    @Bean
    @Primary
    @DependsOn({"masterDataSource", "slaveDataSources"})
    public DataSource routingDataSource(@Qualifier("masterDataSource") DataSource masterDataSource,
                                        @Qualifier("slaveDataSources") List<DataSource> slaveDataSources) {
        final Map<Object, Object> targetDataSources = new HashMap<>();
        targetDataSources.put(DataSourceContextHolder.MASTER, masterDataSource);
        for (int i = 0; i < slaveDataSources.size(); i++) {
            targetDataSources.put(DataSourceContextHolder.SLAVE + i, slaveDataSources.get(i));
        }
        final DataSourceRouter dataSourceRouter = new DataSourceRouter();
        dataSourceRouter.setTargetDataSources(targetDataSources);
        dataSourceRouter.setDefaultTargetDataSource(masterDataSource);
        return dataSourceRouter;
    }
    @Bean
    public DataSourceTransactionManager dataSourceTransactionManager(
            @Qualifier("routingDataSource") DataSource routingDataSource) {
        return new DataSourceTransactionManager(routingDataSource);
    }
}

package com.xinxin.order.context.config;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.StringUtils;
@Slf4j
public class DataSourceContextHolder {
    public static final String MASTER = "master";
    public static final String SLAVE = "slave";
    private static ThreadLocal<String> CONTEXT_HOLDER = new ThreadLocal<>();
    public static void setDatasourceType(String dataSourceType) {
        if (StringUtils.isBlank(dataSourceType)) {
            log.error("dataSourceType為空");
        }
        log.info("設定dataSource: {}", dataSourceType);
        CONTEXT_HOLDER.set(dataSourceType);
    }
    public static String getDataSourceType() {
        return CONTEXT_HOLDER.get() == null ? MASTER : CONTEXT_HOLDER.get();
    }
    public static void remove() {
        CONTEXT_HOLDER.remove();
    }
}

package com.xinxin.order.context.config;
import lombok.extern.slf4j.Slf4j;
import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;
@Slf4j
public class DataSourceRouter extends AbstractRoutingDataSource {
    @Override
    protected Object determineCurrentLookupKey() {
        log.info("當前資料來源為: {}", DataSourceContextHolder.getDataSourceType());
        return DataSourceContextHolder.getDataSourceType();
    }
}

@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface ReadOnly {
    String value() default DataSourceContextHolder.MASTER;
}

package com.xinxin.order.aspect;
import com.xinxin.order.annotation.ReadOnly;
import com.xinxin.order.context.config.DataSourceContextHolder;
import lombok.extern.slf4j.Slf4j;
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.Ordered;
import org.springframework.stereotype.Component;
@Slf4j
@Aspect
@Component
public class DynamicDataSourceAspect implements Ordered {
    @Before(value = "execution(* *(..))&& @annotation(readOnly)")
    public void before(JoinPoint joinPoint, ReadOnly readOnly) {
        log.info(joinPoint.getSignature().getName() + "走從庫");
        DataSourceContextHolder.setDatasourceType(DataSourceContextHolder.SLAVE);
    }
    @After(value = "execution(* *(..))&& @annotation(readOnly)")
    public void after(JoinPoint joinPoint, ReadOnly readOnly) {
        log.info(joinPoint.getSignature().getName() + "清除資料來源");
        DataSourceContextHolder.remove();
    }
    @Override
    public int getOrder() {
        return 0;
    }
}