原文：https://blog.csdn.net/wsbgmofo/article/details/79260896

1,数据源配置文件,如下

datasource.readSize=1
spring.datasource.type=com.alibaba.druid.pool.DruidDataSource

# 主数据源，默认的
spring.master.driver-class-name=com.mysql.jdbc.Driver
spring.master.url=jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=UTF-8&zeroDateTimeBehavior=convertToNull
spring.master.username=root
spring.master.password=root
spring.master.initialSize=5
spring.master.minIdle=5
spring.master.maxActive=50
spring.master.maxWait=60000
spring.master.timeBetweenEvictionRunsMillis=60000
spring.master.minEvictableIdleTimeMillis=300000
spring.master.poolPreparedStatements=true
spring.master.maxPoolPreparedStatementPerConnectionSize=20

# 从数据源
spring.slave.driver-class-name=com.mysql.jdbc.Driver
spring.slave.url=jdbc:mysql://localhost:3306/data_source_02?useUnicode=true&characterEncoding=UTF-8&zeroDateTimeBehavior=convertToNull
spring.slave.username=root
spring.slave.password=root
spring.slave.initialSize=5
spring.slave.minIdle=5
spring.slave.maxActive=50
spring.slave.maxWait=60000
spring.slave.timeBetweenEvictionRunsMillis=60000
spring.slave.minEvictableIdleTimeMillis=300000
spring.slave.poolPreparedStatements=true
spring.slave.maxPoolPreparedStatementPerConnectionSize=20

2,新建数据库配置类DataSourceConfiguration,如下

package com.aop.writeAndRead.config;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import javax.sql.DataSource;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.autoconfigure.jdbc.DataSourceBuilder;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
@Configuration
public class DataSourceConfiguration {
private static Logger log = LoggerFactory.getLogger(DataSourceConfiguration.class);
@Value(“${spring.datasource.type}”)
private Class<? extends DataSource> dataSourceType;
@Bean(name=”writeDataSource”, destroyMethod = “close”, initMethod=”init”)
@Primary
@ConfigurationProperties(prefix = “spring.master”)
public DataSource writeDataSource() {
log.info(“——————– writeDataSource init ———————“);
return DataSourceBuilder.create().type(dataSourceType).build();
}
/**
* 有多少个从库就要配置多少个
* @return
*/
@Bean(name = “readDataSource”, destroyMethod = “close”, initMethod=”init”)
@ConfigurationProperties(prefix = “spring.slave”)
public DataSource readDataSourceOne(){
log.info(“——————– readDataSourceOne init ———————“);
return DataSourceBuilder.create().type(dataSourceType).build();
}
/**
* 这里的list是多个从库的情况下为了实现简单负载均衡
* @return
* @throws SQLException
*/
@Bean(“readDataSources”)
public List<DataSource> readDataSources() throws SQLException{
List<DataSource> dataSources=new ArrayList<>();
dataSources.add(readDataSourceOne());
return dataSources;
}
}

3,新建DataSourceContextHolder类,根据ThreadLocal来实现数据源的动态改变,如下

package com.aop.writeAndRead.config;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class DataSourceContextHolder {
private static Logger log = LoggerFactory.getLogger(DataSourceContextHolder.class);
private static final ThreadLocal<String> local = new ThreadLocal<String>();
public static ThreadLocal<String> getLocal() {
return local;
}
/**
* 读可能是多个库
*/
public static void read() {
local.set(DataSourceType.read.getType());
System.out.println(“==:” + DataSourceType.read.getType());
log.info(“数据库切换到读库…”);
}
/**
* 写只有一个库
*/
public static void write() {
local.set(DataSourceType.write.getType());
log.info(“数据库切换到写库…”);
}
public static String getJdbcType() {
return local.get();
}
}

4,新建一个枚举类DataSourceType,如下

package com.aop.writeAndRead.config;
public enum DataSourceType {
read(“read”, “从库”),
write(“write”, “主库”);
private String type;
private String name;
DataSourceType(String type, String name) {
this.type = type;
this.name = name;
}
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}

5,新建MybatisConfiguration类,如下

package com.aop.writeAndRead.config;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.annotation.Resource;
import javax.sql.DataSource;
import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.core.io.support.ResourcePatternResolver;
import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;
import org.springframework.transaction.annotation.EnableTransactionManagement;

@Configuration
@ConditionalOnClass({EnableTransactionManagement.class})
@Import({ DataSourceConfiguration.class})
@MapperScan(basePackages={“com.aop.writeAndRead.mapper”})
public class MybatisConfiguration {
@Value(“${spring.datasource.type}”)
private Class<? extends DataSource> dataSourceType;
@Value(“${datasource.readSize}”)
private String dataSourceSize;
// @Resource(name = “writeDataSource”)
// private DataSource writeDataSource;
// @Qualifier(“readDataSource”)
// private DataSource readDataSource;
@Bean
@ConditionalOnMissingBean
public SqlSessionFactory sqlSessionFactory(ApplicationContext ac) throws Exception {
SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
sqlSessionFactoryBean.setDataSource(roundRobinDataSouceProxy(ac));
ResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
sqlSessionFactoryBean.setMapperLocations(resolver.getResources(“classpath:mappings/**/*.xml”));
sqlSessionFactoryBean.setTypeAliasesPackage(“com.aop.writeAndRead.entity”);
sqlSessionFactoryBean.getObject().getConfiguration().setMapUnderscoreToCamelCase(true);
return sqlSessionFactoryBean.getObject();
}
/**
* 有多少个数据源就要配置多少个bean
* @return
*/
@Bean
public AbstractRoutingDataSource roundRobinDataSouceProxy(ApplicationContext ac) {
int size = Integer.parseInt(dataSourceSize);
System.out.println(“size:” + size);
MyAbstractRoutingDataSource proxy = new MyAbstractRoutingDataSource(size);
Map<Object, Object> targetDataSources = new HashMap<Object, Object>();
//多个读数据库时
DataSource writeDataSource = (DataSource)ac.getBean(“writeDataSource”);
List<DataSource> readDataSources = (List<DataSource>)ac.getBean(“readDataSources”);
for (int i = 0; i < size; i++) {
targetDataSources.put(i, readDataSources.get(i));
}
proxy.setDefaultTargetDataSource(writeDataSource);
proxy.setTargetDataSources(targetDataSources);
return proxy;
}
}
把第2步注册的bean放入一个map里面,后面就可以动态从这个map里面获取对应的数据源

注意:之前报错的地方就是在这里,用@Resource和@Qualifier这两种方式都无法获取到第2步注册的bean,只能是通过applicationContext上下文获取,应该是跟注解的优先级有关,Resource和Qualifier先执行,这个时候第2步的bean还未注册,所以娶不到,如果有知道更详细原因的朋友,请留言告知

6,,新建MyAbstractRoutingDataSource,如下

package com.aop.writeAndRead.config;
import java.util.concurrent.atomic.AtomicInteger;
import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;
public class MyAbstractRoutingDataSource extends AbstractRoutingDataSource{
private final int dataSourceNumber;
private AtomicInteger count = new AtomicInteger(0);
public MyAbstractRoutingDataSource(int dataSourceNumber) {
this.dataSourceNumber = dataSourceNumber;
}
@Override
protected Object determineCurrentLookupKey() {
String typeKey = DataSourceContextHolder.getJdbcType();
if (typeKey.equals(DataSourceType.write.getType())) {
return DataSourceType.write.getType();
}
// 读 简单负载均衡
int number = count.getAndAdd(1);
int lookupKey = number % dataSourceNumber;
return new Integer(lookupKey);
}
}
这里的determineCurrentLookupKey方法是根据DataSourceContextHolder这个类所改变的数据源而返回对应的bean的key,
这里的key要跟第5步放入map里面的key对应上

7,新建springAOP类,如下

package com.aop.writeAndRead.config;
import java.lang.reflect.Method;
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.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;
@Aspect
@Component
public class DataSourceAop {
private static Logger log = LoggerFactory.getLogger(DataSourceAop.class);
@Pointcut(“@annotation(com.aop.writeAndRead.config.WriteDataSource)”)
public void writeMethod(){}
@Pointcut(“@annotation(com.aop.writeAndRead.config.ReadDataSource)”)
public void readMethod(){}
@Before(“writeMethod()”)
public void beforeWrite(JoinPoint point) {
DataSourceContextHolder.write();
String className = point.getTarget().getClass().getName();
String methodName = point.getSignature().getName();
System.out.println(“开始执行:”+className+”.”+methodName+”()方法…”);
log.info(“dataSource切换到：write”);
}
@Before(“readMethod()”)
public void beforeRead(JoinPoint point) throws ClassNotFoundException {
//设置数据库为读数据
DataSourceContextHolder.read();

/*spring AOP测试代码*/
String currentClassName = point.getTarget().getClass().getName();//根据切点获取当前调用的类名
String methodName = point.getSignature().getName();//根据切点获取当前调用的类方法
Object[] args = point.getArgs();//根据切点获取当前类方法的参数
System.out.println(“开始执行:”+currentClassName+”.”+methodName+”()方法…”);
Class reflexClassName = Class.forName(currentClassName);//根据反射获取当前调用类的实例
Method[] methods = reflexClassName.getMethods();//获取该实例的所有方法
for(Method method : methods){
if(method.getName().equals(methodName)){
String desrciption = method.getAnnotation(ReadDataSource.class).description();//获取该实例方法上注解里面的描述信息
System.out.println(“desrciption:” + desrciption);
}
}

log.info(“dataSource切换到：Read”);
}
}
利用springAOP对方法的切入,在方法执行前判断使用哪个数据源

@Pointcut(“@annotation(com.aop.writeAndRead.config.WriteDataSource)”)
这里是对自定义注解作切点,双引号里面也可以换成对方法,但是个人觉得如果对方法作切点的话,如果方法多了这里写的就很长了

8,新建注解类,如下

package com.aop.writeAndRead.config;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface ReadDataSource {
String description() default “”;
}

package com.aop.writeAndRead.config;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface WriteDataSource {
String description() default “”;
}
这样在对需要控制数据源的方法前加上这个注解,springAOP就能控制这个方法,先选择数据源再执行方法

测试:

在方法上加入注解,如下

package com.aop.writeAndRead.service;

import java.util.Map;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Isolation;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;

import com.aop.writeAndRead.config.ReadDataSource;
import com.aop.writeAndRead.config.WriteDataSource;
import com.aop.writeAndRead.entity.User;
import com.aop.writeAndRead.mapper.UserMapper;

@Service
public class UserService {

@Autowired UserMapper userMapper;

@WriteDataSource(description=”WRITE”)
public void writeUser(User user){
userMapper.writeUser(user);
}

@ReadDataSource(description=”READ”)
@Transactional(propagation=Propagation.REQUIRED,isolation=Isolation.DEFAULT,readOnly=true)
public Map<String, String> readUser(){
return userMapper.readUser();
}
}
接口分别调用writeUser跟readUser,如下

9,MySQL数据同步

修改主库的配置文件my.ini,在末尾加上

#数据库ID号， 为1时表示为Master,其中master_id必须为1到232–1之间的一个正整数值;
server-id = 1
#启用二进制日志；
log-bin=mysql-bin
#需要同步的二进制数据库名；
binlog-do-db=minishop
#不同步的二进制数据库名,如果不设置可以将其注释掉;
binlog-ignore-db=information_schema
binlog-ignore-db=mysql
binlog-ignore-db=personalsite
binlog-ignore-db=test
#设定生成的log文件名；
log-bin=”D:/Database/materlog”
#把更新的记录写到二进制文件中；
log-slave-updates
修改从库的配置文件my.ini,在文件末尾加上

#如果需要增加Slave库则，此id往后顺延；
server-id = 2
log-bin=mysql-bin
#主库host
master-host = 192.168.168.253
#在主数据库服务器中建立的用于该从服务器备份使用的用户
master-user = forslave
master-password = ******
master-port = 3306
#如果发现主服务器断线，重新连接的时间差；
master-connect-retry=60
#不需要备份的数据库；
replicate-ignore-db=mysql
#需要备份的数据库
replicate-do-db=minishop
log-slave-update

———————
作者：猴样鬼相
来源：CSDN
原文：https://blog.csdn.net/wsbgmofo/article/details/79260896
版权声明：本文为博主原创文章，转载请附上博文链接！