Question

我正在开发一个mysql主从复制。我正在使用spring data jpa（spring boot）。

我需要的是所有写入操作，以便主服务器和只读操作在多个只读从属设备之间平均分配。

为此，我需要：

使用特殊的JDBC驱动程序：com.mysql.jdbc.ReplicationDriver

在URL中设置复制：

spring:
    datasource:
        driverClassName: com.mysql.jdbc.ReplicationDriver
        url: jdbc:mysql:replication://127.0.0.1:3306,127.0.0.1:3307/MyForum?user=root&password=password&autoReconnect=true
        test-on-borrow: true
        validation-query: SELECT 1
    database: MYSQL

需要关闭自动提交。（*）连接需要设置为只读。

为了确保JDBC Connection设置为只读，我创建了一个注释和一个简单的AOP拦截器。

注释

package com.xyz.forum.replication;

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

/**
 * Created by Bhupati Patel on 02/11/15.
 */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface ReadOnlyConnection {
}

拦截

package com.xyz.forum.replication;

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;
import org.hibernate.Session;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import javax.persistence.EntityManager;

/**
 * Created by Bhupati Patel on 02/11/15.
 */

@Aspect
@Component
public class ConnectionInterceptor {

    private Logger logger;

    public ConnectionInterceptor() {
        logger = LoggerFactory.getLogger(getClass());
        logger.info("ConnectionInterceptor Started");
    }

    @Autowired
    private EntityManager entityManager;

    @Pointcut("@annotation(com.xyz.forum.replication.ReadOnlyConnection)")
    public void inReadOnlyConnection(){}


    @Around("inReadOnlyConnection()")
    public Object proceed(ProceedingJoinPoint pjp) throws Throwable {
        Session session = entityManager.unwrap(Session.class);
        ConnectionReadOnly readOnlyWork = new ConnectionReadOnly();

        try{
            session.doWork(readOnlyWork);
            return pjp.proceed();
        } finally {
            readOnlyWork.switchBack();
        }
    }

}

以下是我的spring数据库

package com.xyz.forum.repositories;

import com.xyz.forum.entity.Topic;
import org.springframework.data.repository.Repository;

import java.util.List;

/**
 * Created by Bhupati Patel on 16/04/15.
 */
public interface TopicRepository extends Repository<Topic,Integer>{
    Topic save(Topic topic);
    Topic findByTopicIdAndIsDeletedFalse(Integer topicId);
    List<Topic> findByIsDeletedOrderByTopicOrderAsc(Boolean isDelete);

}

以下是我的经理（服务）课程。

package com.xyz.forum.manager;

import com.xyz.forum.domain.entry.impl.TopicEntry;

import com.xyz.forum.domain.exception.impl.AuthException;

import com.xyz.forum.domain.exception.impl.NotFoundException;
import com.xyz.forum.entity.Topic;
import com.xyz.forum.replication.ReadOnlyConnection;
import com.xyz.forum.repositories.TopicRepository;
import com.xyz.forum.utils.converter.TopicConverter;
import org.apache.commons.lang3.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Repository;
import org.springframework.transaction.annotation.Transactional;

import java.util.*;

/**
 * Created by Bhupati Patel on 16/04/15.
 */
@Repository
public class TopicManager {
    @Autowired
    TopicRepository topicRepository;

    @Transactional
    public TopicEntry save(TopicEntry topicEntry) {
        Topic topic = TopicConverter.fromEntryToEntity(topicEntry);
        return TopicConverter.fromEntityToEntry(topicRepository.save(topic));
    }

    @ReadOnlyConnection
    public TopicEntry get(Integer id) {
        Topic topicFromDb = topicRepository.findByTopicIdAndIsDeletedFalse(id);
        if(topicFromDb == null) {
            throw new NotFoundException("Invalid Id", "Topic Id [" + id + "] doesn't exist ");
        }
        return TopicConverter.fromEntityToEntry(topicFromDb);
    }
}

在上面的代码中，在管理层或服务层中指定了@ReadOnlyConnection注释。 以上代码对我来说很好。这是一个微不足道的案例，在服务层我只是从slave db读取并写入master db。

说到我的实际要求是我应该能够在存储库级别本身使用@ReadOnlyConnection，因为我有很多业务逻辑，我在其他类服务层中都进行读/写操作。因此我不能把@ReadOnlyConnection放在服务层。

我应该可以使用这样的东西

public interface TopicRepository extends Repository<Topic,Integer>{
    Topic save(Topic topic);
    @ReadOnlyConnection
    Topic findByTopicIdAndIsDeletedFalse(Integer topicId);
    @ReadOnlyConnection
    List<Topic> findByIsDeletedOrderByTopicOrderAsc(Boolean isDelete);

}

像spring的@Transactional或@Modifying或@Query注释。以下是我所指的一个例子。

    public interface AnswerRepository extends Repository<Answer,Integer> {
    @Transactional
    Answer save(Answer answer);

    @Transactional
    @Modifying
    @Query("update Answer ans set ans.isDeleted = 1, ans.deletedBy = :deletedBy, ans.deletedOn = :deletedOn " +
            "where ans.questionId = :questionId and ans.isDeleted = 0")
    void softDeleteBulkAnswers(@Param("deletedBy") String deletedBy, @Param("deletedOn") Date deletedOn,
                               @Param("questionId") Integer questionId);
}

我是关于aspectj和aop世界的新手，我在ConnectionInterceptor中尝试了很多切入点正则表达式，但它们都没有工作。很久以来我一直在尝试这个但是没有运气。

如何实现提问任务。

Answer 1

我无法在方法级别获得自定义注释@ReadOnlyConnection（如@Transactional）的解决方法，但是小麻烦对我有效。

我正在粘贴下面的代码段。

@Aspect
@Component
@EnableAspectJAutoProxy
public class ConnectionInterceptor {

    private Logger logger;
    private static final String JPA_PREFIX = "findBy";
    private static final String CUSTOM_PREFIX = "read";

    public ConnectionInterceptor() {
        logger = LoggerFactory.getLogger(getClass());
        logger.info("ConnectionInterceptor Started");
    }

    @Autowired
    private EntityManager entityManager;

    @Pointcut("this(org.springframework.data.repository.Repository)")
    public void inRepositoryLayer() {}

    @Around("inRepositoryLayer()")
    public Object proceed(ProceedingJoinPoint pjp) throws Throwable {
        String methodName = pjp.getSignature().getName();
        if (StringUtils.startsWith(methodName, JPA_PREFIX) || StringUtils.startsWith(methodName, CUSTOM_PREFIX)) {
            System.out.println("I'm there!" );
            Session session = entityManager.unwrap(Session.class);
            ConnectionReadOnly readOnlyWork = new ConnectionReadOnly();

            try{
                session.doWork(readOnlyWork);
                return pjp.proceed();
            } finally {
                readOnlyWork.switchBack();
            }
        }
        return pjp.proceed();
    }
}

所以在上面的代码中我使用了一个像下面这样的切入点

@Pointcut("this(org.springframework.data.repository.Repository)")
public void inRepositoryLayer() {}

它的作用是

代理实现Repository接口的任何连接点（仅在Spring AOP中执行方法）

你可以看一下 http://docs.spring.io/spring/docs/current/spring-framework-reference/html/aop.html

现在我的所有存储库读取查询方法都以前缀“findByXXX”（默认的spring-data-jpa可读方法）或“readXXX”（带有@Query注释的自定义读取方法）开头，这在我的周围方法执行中与切入点以上。根据我的要求，我将JDBC Connection readOnly设置为true。

Session session = entityManager.unwrap(Session.class);
ConnectionReadOnly readOnlyWork = new ConnectionReadOnly();

我的ConnectionReadOnly看起来像是

package com.xyz.forum.replication;

import org.hibernate.jdbc.Work;

import java.sql.Connection;
import java.sql.SQLException;

/**
 * Created by Bhupati Patel on 04/11/15.
 */
public class ConnectionReadOnly implements Work {

    private Connection connection;
    private boolean autoCommit;
    private boolean readOnly;

    @Override
    public void execute(Connection connection) throws SQLException {
        this.connection = connection;
        this.autoCommit = connection.getAutoCommit();
        this.readOnly = connection.isReadOnly();
        connection.setAutoCommit(false);
        connection.setReadOnly(true);
    }

    //method to restore the connection state before intercepted
    public void switchBack() throws SQLException{
        connection.setAutoCommit(autoCommit);
        connection.setReadOnly(readOnly);
    }
}

所以上面的设置符合我的要求。

Answer 2

似乎@Pointcut && @Around应该以如下方式声明：

@Pointcut(value = "execution(public * *(..))")
public void anyPublicMethod() {
}

@Around("@annotation(readOnlyConnection)")

将自定义注释建议应用于spring数据jpa存储库

2 个答案: