Spring+MyBatis读写分离 Spring+MyBatis实现数据读写分离的实例代码

时间:2021-03-24 三无程序员人气:0

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本文介绍了Spring Boot + MyBatis读写分离，有需要了解Spring+MyBatis读写分离的朋友可参考。希望此文章对各位有所帮助。

其最终实现功能：

默认更新操作都使用写数据源
读操作都使用slave数据源
特殊设置：可以指定要使用的数据源类型及名称（如果有名称，则会根据名称使用相应的数据源）

其实现原理如下：

通过Spring AOP对dao层接口进行拦截，并对需要指定数据源的接口在ThradLocal中设置其数据源类型及名称
通过MyBatsi的插件，对根据更新或者查询操作在ThreadLocal中设置数据源（dao层没有指定的情况下）
继承AbstractRoutingDataSource类。

在此直接写死使用HikariCP作为数据源

其实现步骤如下：

定义其数据源配置文件并进行解析为数据源
定义AbstractRoutingDataSource类及其它注解
定义Aop拦截
定义MyBatis插件
整合在一起

1.配置及解析类

其配置参数直接使用HikariCP的配置，其具体参数可以参考HikariCP。

在此使用yaml格式，名称为datasource.yaml,内容如下：

dds:
 write:
  jdbcUrl: jdbc:mysql://localhost:3306/order
  password: liu123
  username: root
  maxPoolSize: 10
  minIdle: 3
  poolName: master
 read:
  - jdbcUrl: jdbc:mysql://localhost:3306/test
   password: liu123
   username: root
   maxPoolSize: 10
   minIdle: 3
   poolName: slave1
  - jdbcUrl: jdbc:mysql://localhost:3306/test2
   password: liu123
   username: root
   maxPoolSize: 10
   minIdle: 3
   poolName: slave2

定义该配置所对应的Bean，名称为DBConfig,内容如下：

@Component
@ConfigurationProperties(locations = "classpath:datasource.yaml", prefix = "dds")
public class DBConfig {
  private List<HikariConfig> read;
  private HikariConfig write;

  public List<HikariConfig> getRead() {
    return read;
  }

  public void setRead(List<HikariConfig> read) {
    this.read = read;
  }

  public HikariConfig getWrite() {
    return write;
  }

  public void setWrite(HikariConfig write) {
    this.write = write;
  }
}

把配置转换为DataSource的工具类，名称：DataSourceUtil，内容如下：

import com.zaxxer.hikari.HikariConfig;
import com.zaxxer.hikari.HikariDataSource;

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

public class DataSourceUtil {
  public static DataSource getDataSource(HikariConfig config) {
    return new HikariDataSource(config);
  }

  public static List<DataSource> getDataSource(List<HikariConfig> configs) {
    List<DataSource> result = null;
    if (configs != null && configs.size() > 0) {
      result = new ArrayList<>(configs.size());
      for (HikariConfig config : configs) {
        result.add(getDataSource(config));
      }
    } else {
      result = new ArrayList<>(0);
    }

    return result;
  }
}

2.注解及动态数据源

定义注解@DataSource，其用于需要对个别方法指定其要使用的数据源（如某个读操作需要在master上执行，但另一读方法b需要在读数据源的具体一台上面执行）

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface DataSource {
  /**
   * 类型，代表是使用读还是写
   * @return
   */
  DataSourceType type() default DataSourceType.WRITE;

  /**
   * 指定要使用的DataSource的名称
   * @return
   */
  String name() default "";
}

定义数据源类型，分为两种：READ,WRITE，内容如下：

public enum DataSourceType {
  READ, WRITE;
}

定义保存这此共享信息的类DynamicDataSourceHolder，在其中定义了两个ThreadLocal和一个map，holder用于保存当前线程的数据源类型（读或者写），pool用于保存数据源名称（如果指定），其内容如下：

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

public class DynamicDataSourceHolder {
  private static final Map<String, DataSourceType> cache = new ConcurrentHashMap<>();
  private static final ThreadLocal<DataSourceType> holder = new ThreadLocal<>();
  private static final ThreadLocal<String> pool = new ThreadLocal<>();

  public static void putToCache(String key, DataSourceType dataSourceType) {
    cache.put(key,dataSourceType);
  }

  public static DataSourceType getFromCach(String key) {
    return cache.get(key);
  }

  public static void putDataSource(DataSourceType dataSourceType) {
    holder.set(dataSourceType);
  }

  public static DataSourceType getDataSource() {
    return holder.get();
  }

  public static void putPoolName(String name) {
    if (name != null && name.length() > 0) {
      pool.set(name);
    }
  }

  public static String getPoolName() {
    return pool.get();
  }

  public static void clearDataSource() {
    holder.remove();
    pool.remove();
  }
}

动态数据源类为DynamicDataSoruce,其继承自AbstractRoutingDataSource，可以根据返回的key切换到相应的数据源，其内容如下：

import com.zaxxer.hikari.HikariDataSource;
import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;

import javax.sql.DataSource;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ThreadLocalRandom;

public class DynamicDataSource extends AbstractRoutingDataSource {
  private DataSource writeDataSource;
  private List<DataSource> readDataSource;
  private int readDataSourceSize;
  private Map<String, String> dataSourceMapping = new ConcurrentHashMap<>();

  @Override
  public void afterPropertiesSet() {
    if (this.writeDataSource == null) {
      throw new IllegalArgumentException("Property 'writeDataSource' is required");
    }
    setDefaultTargetDataSource(writeDataSource);
    Map<Object, Object> targetDataSource = new HashMap<>();
    targetDataSource.put(DataSourceType.WRITE.name(), writeDataSource);
    String poolName = ((HikariDataSource)writeDataSource).getPoolName();
    if (poolName != null && poolName.length() > 0) {
      dataSourceMapping.put(poolName,DataSourceType.WRITE.name());
    }
    if (this.readDataSource == null) {
      readDataSourceSize = 0;
    } else {
      for (int i = 0; i < readDataSource.size(); i++) {
        targetDataSource.put(DataSourceType.READ.name() + i, readDataSource.get(i));
        poolName = ((HikariDataSource)readDataSource.get(i)).getPoolName();
        if (poolName != null && poolName.length() > 0) {
          dataSourceMapping.put(poolName,DataSourceType.READ.name() + i);
        }
      }
      readDataSourceSize = readDataSource.size();
    }
    setTargetDataSources(targetDataSource);
    super.afterPropertiesSet();
  }


  @Override
  protected Object determineCurrentLookupKey() {
    DataSourceType dataSourceType = DynamicDataSourceHolder.getDataSource();
    String dataSourceName = null;
    if (dataSourceType == null ||dataSourceType == DataSourceType.WRITE || readDataSourceSize == 0) {
      dataSourceName = DataSourceType.WRITE.name();
    } else {
      String poolName = DynamicDataSourceHolder.getPoolName();
      if (poolName == null) {
        int idx = ThreadLocalRandom.current().nextInt(0, readDataSourceSize);
        dataSourceName = DataSourceType.READ.name() + idx;
      } else {
        dataSourceName = dataSourceMapping.get(poolName);
      }
    }
    DynamicDataSourceHolder.clearDataSource();
    return dataSourceName;
  }

  public void setWriteDataSource(DataSource writeDataSource) {
    this.writeDataSource = writeDataSource;
  }

  public void setReadDataSource(List<DataSource> readDataSource) {
    this.readDataSource = readDataSource;
  }
}

3.AOP拦截

如果在相应的dao层做了自定义配置（指定数据源），则在些处理。解析相应方法上的@DataSource注解，如果存在，并把相应的信息保存至上面的DynamicDataSourceHolder中。在此对com.hfjy.service.order.dao包进行做拦截。内容如下：

import com.hfjy.service.order.anno.DataSource;
import com.hfjy.service.order.wr.DynamicDataSourceHolder;
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.aspectj.lang.annotation.Pointcut;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.stereotype.Component;

import java.lang.reflect.Method;

/**
 * 使用AOP拦截，对需要特殊方法可以指定要使用的数据源名称(对应为连接池名称）
 */
@Aspect
@Component
public class DynamicDataSourceAspect {

  @Pointcut("execution(public * com.hfjy.service.order.dao.*.*(*))")
  public void dynamic(){}

  @Before(value = "dynamic()")
  public void beforeOpt(JoinPoint point) {
    Object target = point.getTarget();
    String methodName = point.getSignature().getName();
    Class<?>[] clazz = target.getClass().getInterfaces();
    Class<?>[] parameterType = ((MethodSignature)point.getSignature()).getMethod().getParameterTypes();
    try {
      Method method = clazz[0].getMethod(methodName,parameterType);
      if (method != null && method.isAnnotationPresent(DataSource.class)) {
        DataSource datasource = method.getAnnotation(DataSource.class);
        DynamicDataSourceHolder.putDataSource(datasource.type());
        String poolName = datasource.name();
        DynamicDataSourceHolder.putPoolName(poolName);
        DynamicDataSourceHolder.putToCache(clazz[0].getName() + "." + methodName, datasource.type());
      }
    } catch (Exception e) {
      e.printStackTrace();
    }
  }

  @After(value = "dynamic()")
  public void afterOpt(JoinPoint point) {
    DynamicDataSourceHolder.clearDataSource();
  }
}

4.MyBatis插件

如果在dao层没有指定相应的要使用的数据源，则在此进行拦截，根据是更新还是查询设置数据源的类型，内容如下：

import org.apache.ibatis.executor.Executor;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.mapping.SqlCommandType;
import org.apache.ibatis.plugin.*;
import org.apache.ibatis.session.ResultHandler;
import org.apache.ibatis.session.RowBounds;

import java.util.Properties;

@Intercepts({
    @Signature(type = Executor.class, method = "update", args = {MappedStatement.class, Object.class}),
    @Signature(type = Executor.class, method = "query", args = {MappedStatement.class, Object.class,
        RowBounds.class, ResultHandler.class})
})
public class DynamicDataSourcePlugin implements Interceptor {

  @Override
  public Object intercept(Invocation invocation) throws Throwable {
    MappedStatement ms = (MappedStatement)invocation.getArgs()[0];
    DataSourceType dataSourceType = null;
    if ((dataSourceType = DynamicDataSourceHolder.getFromCach(ms.getId())) == null) {
      if (ms.getSqlCommandType().equals(SqlCommandType.SELECT)) {
        dataSourceType = DataSourceType.READ;
      } else {
        dataSourceType = DataSourceType.WRITE;
      }
      DynamicDataSourceHolder.putToCache(ms.getId(), dataSourceType);
    }
    DynamicDataSourceHolder.putDataSource(dataSourceType);
    return invocation.proceed();
  }

  @Override
  public Object plugin(Object target) {
    if (target instanceof Executor) {
      return Plugin.wrap(target, this);
    } else {
      return target;
    }
  }

  @Override
  public void setProperties(Properties properties) {

  }
}

5.整合

在里面定义MyBatis要使用的内容及DataSource，内容如下：

import com.hfjy.service.order.wr.DBConfig;
import com.hfjy.service.order.wr.DataSourceUtil;
import com.hfjy.service.order.wr.DynamicDataSource;
import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.jdbc.datasource.DataSourceTransactionManager;

import javax.annotation.Resource;
import javax.sql.DataSource;

@Configuration
@MapperScan(value = "com.hfjy.service.order.dao", sqlSessionFactoryRef = "sqlSessionFactory")
public class DataSourceConfig {
  @Resource
  private DBConfig dbConfig;

  @Bean(name = "dataSource")
  public DynamicDataSource dataSource() {
    DynamicDataSource dataSource = new DynamicDataSource();
    dataSource.setWriteDataSource(DataSourceUtil.getDataSource(dbConfig.getWrite()));
    dataSource.setReadDataSource(DataSourceUtil.getDataSource(dbConfig.getRead()));
    return dataSource;
  }

  @Bean(name = "transactionManager")
  public DataSourceTransactionManager dataSourceTransactionManager(@Qualifier("dataSource") DataSource dataSource) {
    return new DataSourceTransactionManager(dataSource);
  }

  @Bean(name = "sqlSessionFactory")
  public SqlSessionFactory sqlSessionFactory(@Qualifier("dataSource") DataSource dataSource) throws Exception {
    SqlSessionFactoryBean sessionFactoryBean = new SqlSessionFactoryBean();
    sessionFactoryBean.setConfigLocation(new ClassPathResource("mybatis-config.xml"));
    sessionFactoryBean.setMapperLocations(new PathMatchingResourcePatternResolver()
        .getResources("classpath*:mapper/*.xml"));
    sessionFactoryBean.setDataSource(dataSource);
    return sessionFactoryBean.getObject();
  }
}

如果不清楚，可以查看github上源码orderdemo

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