问题
I am working on a mysql master slave replication. I am using spring data jpa(spring boot).
What I needed is all write operations to go to master server and read-only operations to be equally distributed among multiple read-only slaves.
For that I need to:
Use special JDBC driver: com.mysql.jdbc.ReplicationDriver
Set replication: in the URL:
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
Auto commit needs to be turned off. (*) Connection needs to be set to read-only.
To ensure JDBC Connection is set to read-only, I created an annotation and a simple AOP interceptor.
Annotation
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 {
}
Interceptor
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();
}
}
}
Following is my spring data repository
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);
}
Following is my Manager(Service) class.
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);
}
}
In the above code @ReadOnlyConnection annotation is specified in manager or service layer. Above pieces of code works fine for me. It is a trivial case where in the service layer I am only reading from slave db and writing into master db.
Having said that my actual requirement is I should be able to use @ReadOnlyConnection in repository level itself because I have quite a few business logic where I do both read/write operation in other classes of service layer.Therefore I can't put @ReadOnlyConnection in service layer.
I should be able to use something like this
public interface TopicRepository extends Repository<Topic,Integer>{
Topic save(Topic topic);
@ReadOnlyConnection
Topic findByTopicIdAndIsDeletedFalse(Integer topicId);
@ReadOnlyConnection
List<Topic> findByIsDeletedOrderByTopicOrderAsc(Boolean isDelete);
}
Like spring's @Transactional or @Modifying or @Query annotation. Following is an example of what I am referring.
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);
}
I am novice to aspectj and aop world, I tried quite a few pointcut regex in the ConnectionInterceptor but none of them worked. I have been trying this since a long time but no luck yet.
How to achieve the asked task.
回答1:
I couldn't get a workaround of having my custom annotation @ReadOnlyConnection(like @Transactional) at a method level,but a small heck did work for me.
I am pasting the code snippet below.
@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();
}
}
So in the above code I am using a pointcut like following
@Pointcut("this(org.springframework.data.repository.Repository)")
public void inRepositoryLayer() {}
and what it does is
any join point (method execution only in Spring AOP) where the proxy implements the Repository interface
You can have a look it at http://docs.spring.io/spring/docs/current/spring-framework-reference/html/aop.html
Now all my repository read query methods either start with a prefix "findByXXX"(default spring-data-jpa readable method) or "readXXX"(custom read method with @Query annotation) which in my around method executions matched by the above pointcut. According to my requirement I am setting the JDBC Connection readOnly true.
Session session = entityManager.unwrap(Session.class);
ConnectionReadOnly readOnlyWork = new ConnectionReadOnly();
And my ConnectionReadOnly look like following
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);
}
}
So above settings work for my requirement.
来源：https://stackoverflow.com/questions/33527737/applying-custom-annotation-advice-to-spring-data-jpa-repository