spring mybatis circular reference

摘要: Error creating bean with name 'ＸＸＸ': Requested bean is currently in creation: Is there an unresolvable circular reference?; nested exception is org.springframework.beans.factory.BeanCurrentlyInCreationException:

如果把MapperScan单独配置，就不会有警告

DataSource，SqlSessionFactory，MapperScan有依赖关系．

如果把MapperScan单独配置，就不会有警告，例如：

code：

DataSource:

import com.alibaba.druid.spring.boot.autoconfigure.DruidDataSourceBuilder;

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;

import javax.sql.DataSource;

@Configuration

public class DataSourceConfig {

    @ConfigurationProperties("spring.datasource.druid")

    @Bean

    public DataSource equipDataSource() {

        return DruidDataSourceBuilder.create().build();

    }

}

SqlSessionFactory:

import org.apache.ibatis.session.SqlSessionFactory;

import org.mybatis.spring.SqlSessionFactoryBean;

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.Configuration;

import org.springframework.core.io.support.PathMatchingResourcePatternResolver;

import javax.sql.DataSource;

@SuppressWarnings("SpringJavaAutowiringInspection")

@Configuration

public class MyBatisConfig {

    @Bean

    public SqlSessionFactory sqlSessionFactory(DataSource dataSource) throws Exception {

        PathMatchingResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();

        SqlSessionFactoryBean factoryBean = new SqlSessionFactoryBean();

        factoryBean.setDataSource(dataSource);

        factoryBean.setTypeAliasesPackage("com.app.domain.entity");// 指定基包

        factoryBean.setMapperLocations(resolver.getResources("classpath:mapper/**/*.xml"));//

        return factoryBean.getObject();

    }

}

MapperScannerConfigurer

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.Configuration;

import tk.mybatis.mapper.common.BaseMapper;

import tk.mybatis.spring.mapper.MapperScannerConfigurer;

import java.util.Properties;

@Configuration

public class MapperConfig {

    @Bean

    public MapperScannerConfigurer mapperScannerConfigurer() {

        MapperScannerConfigurer mapperScannerConfigurer = new MapperScannerConfigurer();

        mapperScannerConfigurer.setBasePackage("com.app.domain.mapper");

        Properties properties = new Properties();

        // 这里要特别注意，不要把BaseMapper放到 basePackage 中，也就是不能同其他Mapper一样被扫描到。

        properties.setProperty("notEmpty", "false");

        properties.setProperty("IDENTITY", "MYSQL");

        mapperScannerConfigurer.setProperties(properties);

        mapperScannerConfigurer.setMarkerInterface(BaseMapper.class);

        return mapperScannerConfigurer;

    }

}

https://my.oschina.net/doctor2014/blog/386431

Requested bean is currently in creation: Is there an unresolvable circular reference?

getBean的时候由于bean之间存在循环依赖出现类似的错误，先做一个简单实验模拟一下这个异常出现的原因：

bean.xml配置如下：

<?xml version="1.0" encoding="GBK"?>

<beans xmlns="http://www.springframework.org/schema/beans"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"

default-autowire="byName">

</beans>

BeanA类如下：

public class BeanA

{

private BeanB b;

public BeanB getB() {

return b;

}

public void setB(BeanB b) {

this.b = b;

}

BeanB类如下：

public class BeanB

{

private BeanA a;

public BeanA getA() {

return a;

}

public void setA(BeanA a) {

this.a = a;

}

程序执行的堆栈信息：

bean在初始化的同时会初始化相应的属性（byName），a在初始化的时候会创建a.b，a.b在初始化的时候会创建a.b.a，形成了一个环，所以在AbstractBeanFactory.doGetBean（这里会出现递归调用）时候，走到：

if (isPrototypeCurrentlyInCreation(beanName)) {

throw new BeanCurrentlyInCreationException(beanName);

}

会抛出一个异常：Requested bean is currently in creation: Is there an unresolvable circular reference，然后scope是singlton或者其他的时候bean的创建过程不一样，不会有一个这样子的判断，因而不会抛出这样子的错误。

因为scope=prototype，所以每次请求对应不同的bean，所以在创建的时候有一个依赖的先后顺序，而如果bean配置成singleton，则属性间初始化的顺序可以无所谓了，所有的bean都只有一份，所以在bean是singleton时候不会报unresolvable circular reference的错误。