基于mybatis-plus实现数据源动态切换、加载
简介
基于springboot，mybatis plus集成了一套多数据源的解决方案，在使用时引入相应的插件dynamic-datasource-spring-boot-starter，可以实现数据源的动态添加、删除等功能，对于多租户或者分库等操作可以根据AOP切面代理到不同的数据源、实现单一系统数据隔离的目的。
代码示例
mavne依赖
<!--mybatis-plus-->
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus-boot-starter</artifactId>
<version>3.4.3.4</version>
</dependency>
<!--dynamic-datasource-->
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>dynamic-datasource-spring-boot-starter</artifactId>
<version>3.4.1</version>
</dependency>
数据源增加、移除
@RestController
@RequestMapping("/datasources")
public class DataSourceController {
@Resource
private DataSource dataSource;
@Resource
private DefaultDataSourceCreator dataSourceCreator;
@GetMapping("list")
public Set<String> list() {
DynamicRoutingDataSource ds = (DynamicRoutingDataSource) dataSource;
return ds.getDataSources().keySet();
}
@PostMapping("add")
public Set<String> add(@Validated @RequestBody DataSourceDTO dto) {
DataSourceProperty dataSourceProperty = new DataSourceProperty();
BeanUtils.copyProperties(dto, dataSourceProperty);
DynamicRoutingDataSource ds = (DynamicRoutingDataSource) dataSource;
DataSource dataSource = dataSourceCreator.createDataSource(dataSourceProperty);
ds.addDataSource(dto.getPollName(), dataSource);
return ds.getDataSources().keySet();
}
@DeleteMapping("remove")
public void remove(String name) {
DynamicRoutingDataSource ds = (DynamicRoutingDataSource) dataSource;
ds.removeDataSource(name);
}
}
默认的数据源连接池加载顺序为: druid>hikaricp>beecp>dbcp>spring basic
数据源切换
基于AOP切换
添加注解,排除不做切换的接口
package com.starsray.dynamic.datasource.annotation;
import java.lang.annotation.*;
/**
* <p>
* 用户标识仅可以使用默认数据源
* </p>
*
* @author starsray
* @since 2021-11-10
*/
@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface DefaultDs {
}
切面具体实现
package com.starsray.dynamic.datasource.interceptor;
import com.baomidou.dynamic.datasource.toolkit.DynamicDataSourceContextHolder;
import com.starsray.dynamic.datasource.annotation.DefaultDs;
import com.starsray.dynamic.datasource.exception.ExceptionEnum;
import com.starsray.dynamic.datasource.exception.GlobalException;
import lombok.RequiredArgsConstructor;
import org.apache.commons.lang3.StringUtils;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.Signature;
import org.aspectj.lang.annotation.AfterReturning;
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.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.web.context.request.RequestAttributes;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;
import org.springframework.web.servlet.HandlerInterceptor;
import javax.servlet.http.HttpServletRequest;
import java.lang.reflect.Method;
/**
* <p>
* 数据源选择器切面
* </p>
*
* @author starsray
* @since 2021-11-10
*/
@Aspect
@Component
@RequiredArgsConstructor(onConstructor_ = @Autowired)
public class DsInterceptor implements HandlerInterceptor {
@Pointcut("execution(public * com.starsray.dynamic.datasource.controller.*.*(..))")
public void datasourcePointcut() {
}
/**
* 前置操作，拦截具体请求，获取header里的数据源id，设置线程变量里，用于后续切换数据源
*/
@Before("datasourcePointcut()")
public void doBefore(JoinPoint joinPoint) {
Signature signature = joinPoint.getSignature();
MethodSignature methodSignature = (MethodSignature) signature;
Method method = methodSignature.getMethod();
// 排除不可切换数据源的方法
DefaultDs annotation = method.getAnnotation(DefaultDs.class);
if (null != annotation) {
DynamicDataSourceContextHolder.push("master");
} else {
RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();
ServletRequestAttributes attributes = (ServletRequestAttributes) requestAttributes;
assert attributes != null;
HttpServletRequest request = attributes.getRequest();
String header = request.getHeader("tenantName");
if (StringUtils.isNotBlank(header)) {
DynamicDataSourceContextHolder.push(header);
} else {
throw new GlobalException(ExceptionEnum.NOT_TENANT);
}
}
}
/**
* 后置操作，设置回默认的数据源id
*/
@AfterReturning("datasourcePointcut()")
public void doAfter() {
DynamicDataSourceContextHolder.push("master");
}
}
基于重写处理器
mybatis plus提供了默认处理器来决定使用的数据源，可以重写处理器实现自定义参数，比如从请求header里面获取参数切换数据源。
@DS("#header.tenantId")
自定义处理器
public class HeaderProcessor extends DsProcessor {
private static final String HEADER = "#header";
@Override
public boolean matches(String key) {
return key.startsWith(HEADER);
}
@Override
public String doDetermineDatasource(MethodInvocation invocation, String key) {
HttpServletRequest request = ((ServletRequestAttributes) RequestContextHolder.getRequestAttributes()).getRequest();
return request.getHeader(key.substring(8));
}
}
注册自定义处理器
@Configuration
public class CustomerDynamicDataSourceConfig{
@Bean
public DsProcessor dsProcessor() {
DsHeaderProcessor headerProcessor = new DsHeaderProcessor();
DsSessionProcessor sessionProcessor = new DsSessionProcessor();
DsSpelExpressionProcessor spelExpressionProcessor = new DsSpelExpressionProcessor();
headerProcessor.setNextProcessor(sessionProcessor);
sessionProcessor.setNextProcessor(spelExpressionProcessor);
return headerProcessor;
}
}
如果有场景需要手动切换数据源，可以使用组件提供的工具来实现。
DynamicDataSourceContextHolder.push("master");
自定义数据源
mybatis plus提供了一个接口来加载数据源信息。
public interface DynamicDataSourceProvider {
Map<String, DataSource> loadDataSources();
}
这个接口有一个抽象实现类AbstractDataSourceProvider,通过模板方法定义了加载数据源来源的方式，mybatis plus通过YmlDynamicDataSourceProvider实现了读取yml文件配置来初始化数据源的方式。
public abstract class AbstractDataSourceProvider implements DynamicDataSourceProvider {
private static final Logger log = LoggerFactory.getLogger(AbstractDataSourceProvider.class);
@Autowired
private DefaultDataSourceCreator defaultDataSourceCreator;
public AbstractDataSourceProvider() {
}
protected Map<String, DataSource> createDataSourceMap(Map<String, DataSourceProperty> dataSourcePropertiesMap) {
Map<String, DataSource> dataSourceMap = new HashMap(dataSourcePropertiesMap.size() * 2);
Iterator var3 = dataSourcePropertiesMap.entrySet().iterator();
while(var3.hasNext()) {
Entry<String, DataSourceProperty> item = (Entry)var3.next();
String dsName = (String)item.getKey();
DataSourceProperty dataSourceProperty = (DataSourceProperty)item.getValue();
String poolName = dataSourceProperty.getPoolName();
if (poolName == null || "".equals(poolName)) {
poolName = dsName;
}
dataSourceProperty.setPoolName(poolName);
dataSourceMap.put(dsName, this.defaultDataSourceCreator.createDataSource(dataSourceProperty));
}
return dataSourceMap;
}
}
如果有需要从数据库加载数据源信息，可以重写AbstractJdbcDataSourceProvider中的executeStmt方法来加载数据库配置信息。示例：
package com.digital.cnzz.dynamic.ds.provider;
import com.baomidou.dynamic.datasource.provider.AbstractJdbcDataSourceProvider;
import com.baomidou.dynamic.datasource.provider.DynamicDataSourceProvider;
import com.baomidou.dynamic.datasource.spring.boot.autoconfigure.DataSourceProperty;
import com.digital.cnzz.dynamic.ds.config.DefaultDsConfig;
import com.digital.cnzz.dynamic.ds.constant.DsDriverEnum;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import javax.annotation.Resource;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.HashMap;
import java.util.Map;
@Primary
@Configuration
public class DsProvider {
@Resource
private DefaultDsConfig defaultDsConfig;
@Bean
public DynamicDataSourceProvider jdbcDynamicDataSourceProvider() {
return new AbstractJdbcDataSourceProvider(defaultDsConfig.getDriverClassName(), defaultDsConfig.getUrl(), defaultDsConfig.getUsername(), defaultDsConfig.getPassword()) {
@Override
protected Map<String, DataSourceProperty> executeStmt(Statement statement) {
Map<String, DataSourceProperty> dataSourcePropertiesMap = null;
ResultSet rs = null;
try {
dataSourcePropertiesMap = new HashMap<>();
rs = statement.executeQuery("SELECT * FROM DYNAMIC_DATASOURCE_INSTANCE");
while (rs.next()) {
String name = rs.getString("name");
DataSourceProperty property = new DataSourceProperty();
property.setDriverClassName(rs.getString("driver"));
property.setUrl(rs.getString("url"));
property.setUsername(rs.getString("username"));
property.setPassword(rs.getString("password"));
dataSourcePropertiesMap.put(name, property);
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
if (rs != null) {
rs.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
try {
statement.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
return dataSourcePropertiesMap;
}
};
}
}
通过读取源码可以发现，如果还有其他需要自定义加载数据源的方式，只需要继承AbstractDataSourceProvider抽象类，实现DynamicDataSourceProvider接口，重写loadDataSources方法就可以实现自定义数据源。
本文来自博客园，作者：星光Starsray，转载请注明原文链接：https://www.cnblogs.com/starsray/p/15557151.html
