聊聊、手写Mybatis 注解配置方式
导航：
在《聊聊、手写Mybatis XML配置方式》中聊了通过 XML配置方式 来实现 Mybatis，也聊到了 Mybatis 中用到的动态代理技术。我手动实现了 AccountMapperFactoryBean，但是有一个缺点，需要 XML 配置才可以用。类似 MapperFactoryBean。
这篇文章主要是聊聊通过注解方式来手写 Mybatis。我们向 Spring 注册 Bean 的方式有很多种，这里会用到 ImportBeanDefinitionRegistrar，它就是今天的主角。
自定义 AccountImportBeanDefinitionRegistrar 实现 ImportBeanDefinitionRegistrar
AccountImportBeanDefinitionRegistrar
package org.rockcode.factory;
import org.rockcode.mappers.AccountMapper;
import org.springframework.beans.factory.support.AbstractBeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
import org.springframework.core.type.AnnotationMetadata;
public class AccountImportBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar {
@Override
public void registerBeanDefinitions(AnnotationMetadata annotationMetadata, BeanDefinitionRegistry beanDefinitionRegistry) {
BeanDefinitionBuilder beanDefinitionBuilder = BeanDefinitionBuilder.genericBeanDefinition(AccountMapperFactoryBean.class);
AbstractBeanDefinition beanDefinition = beanDefinitionBuilder.getBeanDefinition();
beanDefinition.getPropertyValues().add("mapperInterface", AccountMapper.class);
beanDefinitionRegistry.registerBeanDefinition("accountMapperFactoryBean",beanDefinition);
}
}
AccountConfig
package org.rockcode.config;
import com.alibaba.druid.pool.DruidDataSource;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.rockcode.factory.AccountImportBeanDefinitionRegistrar;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import javax.sql.DataSource;
@Configuration
@Import(AccountImportBeanDefinitionRegistrar.class)
public class AccountConfig {
@Bean
public SqlSessionFactoryBean sqlSessionFactoryBean(DataSource dataSource){
SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
sqlSessionFactoryBean.setDataSource(dataSource);
return sqlSessionFactoryBean;
}
@Bean
public DataSource dataSource(){
DruidDataSource driverManagerDataSource = new DruidDataSource();
driverManagerDataSource.setDriverClassName("com.mysql.jdbc.Driver");
driverManagerDataSource.setUrl("jdbc:mysql://127.0.0.1:3306/test?useSSL=false");
driverManagerDataSource.setUsername("root");
driverManagerDataSource.setPassword("root");
return driverManagerDataSource;
}
}
AccountMapperFactoryBean
package org.rockcode.factory;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.support.SqlSessionDaoSupport;
import org.springframework.beans.factory.FactoryBean;
import org.springframework.beans.factory.annotation.Autowired;
import static org.springframework.util.Assert.notNull;
public class AccountMapperFactoryBean extends SqlSessionDaoSupport implements FactoryBean {
private Class mapperInterface;
public void setMapperInterface(Class mapperInterface) {
this.mapperInterface = mapperInterface;
}
@Autowired
public void setSqlSessionFactory(SqlSessionFactory sqlSessionFactory) {
super.setSqlSessionFactory(sqlSessionFactory);
}
@Override
protected void checkDaoConfig() {
super.checkDaoConfig();
notNull(this.mapperInterface, "Property ‘mapperInterface‘ is required");
Configuration configuration = getSqlSession().getConfiguration();
configuration.addMapper(this.mapperInterface);
}
@Override
public Object getObject() throws Exception {
return getSqlSession().getMapper(this.mapperInterface);
}
@Override
public Class<?> getObjectType() {
return this.mapperInterface;
}
}
Main方法
package org.rockcode.config;
import org.rockcode.mappers.AccountMapper;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
public class Main {
public static void main(String[] args) {
AnnotationConfigApplicationContext ac = new AnnotationConfigApplicationContext(AccountConfig.class);
AccountMapper accountMapper = (AccountMapper) ac.getBean("accountMapperFactoryBean");
System.out.println(accountMapper.queryAll());
}
}
上面代码的重点在于 @Import(AccountImportBeanDefinitionRegistrar.class)，这是 Spring 很重要的一个扩展点，与 ImportBeanDefinitionRegistrar 相同的扩展点还有 ImportSelector，它们都可以实现 Bean 的注册。