本文分享自华为云社区《SpringBoot整合MybatisPlus项目存在Mapper时运行报错的问题分析与修复》，作者：攻城狮Chova 。

异常信息

• 在SpringBoot运行测试Mybatis-Plus测试的时候报错:

rg.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'com.oxford.test.ApplicationTests':

原因

• 自定义的mapper文件不受Spring管理所以不会注入到Spring容器中

• mybatis-config中只是会为对应的mapper创建代理类

• 想真正包装成bean, 注入到spring容器中,需要使用到AutoConfiguredMapperScannerRegistrar它会根据扫描 @Mapper注释或是 @MapperScan指定的包下的接口,将其注册为bean

• AutoConfiguredMapperScannerRegistrar:

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

package com.baomidou.mybatisplus.spring.boot.starter;

import com.baomidou.mybatisplus.MybatisConfiguration;
import com.baomidou.mybatisplus.MybatisXMLLanguageDriver;
import com.baomidou.mybatisplus.spring.MybatisSqlSessionFactoryBean;
import java.util.Iterator;
import java.util.List;
import javax.annotation.PostConstruct;
import javax.sql.DataSource;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.logging.Log;
import org.apache.ibatis.logging.LogFactory;
import org.apache.ibatis.mapping.DatabaseIdProvider;
import org.apache.ibatis.plugin.Interceptor;
import org.apache.ibatis.session.ExecutorType;
import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionTemplate;
import org.mybatis.spring.mapper.ClassPathMapperScanner;
import org.mybatis.spring.mapper.MapperFactoryBean;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.ObjectProvider;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.boot.autoconfigure.AutoConfigurationPackages;
import org.springframework.boot.autoconfigure.AutoConfigureAfter;
import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.ResourceLoaderAware;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceLoader;
import org.springframework.core.type.AnnotationMetadata;
import org.springframework.util.Assert;
import org.springframework.util.CollectionUtils;
import org.springframework.util.ObjectUtils;
import org.springframework.util.StringUtils;

@Configuration
@ConditionalOnClass({SqlSessionFactory.class, MybatisSqlSessionFactoryBean.class})
@ConditionalOnBean({DataSource.class})
@EnableConfigurationProperties({MybatisPlusProperties.class})
@AutoConfigureAfter({DataSourceAutoConfiguration.class})
public class MybatisPlusAutoConfiguration {
    private static final Log logger = LogFactory.getLog(MybatisPlusAutoConfiguration.class);
    private final MybatisPlusProperties properties;
    private final Interceptor[] interceptors;
    private final ResourceLoader resourceLoader;
    private final DatabaseIdProvider databaseIdProvider;
    private final List<ConfigurationCustomizer> configurationCustomizers;

    public MybatisPlusAutoConfiguration(MybatisPlusProperties properties, ObjectProvider<Interceptor[]> interceptorsProvider, ResourceLoader resourceLoader, ObjectProvider<DatabaseIdProvider> databaseIdProvider, ObjectProvider<List<ConfigurationCustomizer>> configurationCustomizersProvider) {
        this.properties = properties;
        this.interceptors = (Interceptor[])interceptorsProvider.getIfAvailable();
        this.resourceLoader = resourceLoader;
        this.databaseIdProvider = (DatabaseIdProvider)databaseIdProvider.getIfAvailable();
        this.configurationCustomizers = (List)configurationCustomizersProvider.getIfAvailable();
    }

    @PostConstruct
    public void checkConfigFileExists() {
        if (this.properties.isCheckConfigLocation() && StringUtils.hasText(this.properties.getConfigLocation())) {
            Resource resource = this.resourceLoader.getResource(this.properties.getConfigLocation());
            Assert.state(resource.exists(), "Cannot find config location: " + resource + " (please add config file or check your Mybatis configuration)");
        }

    }

    @Bean
    @ConditionalOnMissingBean
    public SqlSessionFactory sqlSessionFactory(DataSource dataSource) throws Exception {
        MybatisSqlSessionFactoryBean factory = new MybatisSqlSessionFactoryBean();
        factory.setDataSource(dataSource);
        factory.setVfs(SpringBootVFS.class);
        if (StringUtils.hasText(this.properties.getConfigLocation())) {
            factory.setConfigLocation(this.resourceLoader.getResource(this.properties.getConfigLocation()));
        }

        MybatisConfiguration configuration = this.properties.getConfiguration();
        if (configuration == null && !StringUtils.hasText(this.properties.getConfigLocation())) {
            configuration = new MybatisConfiguration();
        }

        if (configuration != null && !CollectionUtils.isEmpty(this.configurationCustomizers)) {
            Iterator i$ = this.configurationCustomizers.iterator();

            while(i$.hasNext()) {
                ConfigurationCustomizer customizer = (ConfigurationCustomizer)i$.next();
                customizer.customize(configuration);
            }
        }

        configuration.setDefaultScriptingLanguage(MybatisXMLLanguageDriver.class);
        factory.setConfiguration(configuration);
        if (this.properties.getConfigurationProperties() != null) {
            factory.setConfigurationProperties(this.properties.getConfigurationProperties());
        }

        if (!ObjectUtils.isEmpty(this.interceptors)) {
            factory.setPlugins(this.interceptors);
        }

        if (this.databaseIdProvider != null) {
            factory.setDatabaseIdProvider(this.databaseIdProvider);
        }

        if (StringUtils.hasLength(this.properties.getTypeAliasesPackage())) {
            factory.setTypeAliasesPackage(this.properties.getTypeAliasesPackage());
        }

        if (StringUtils.hasLength(this.properties.getTypeEnumsPackage())) {
            factory.setTypeEnumsPackage(this.properties.getTypeEnumsPackage());
        }

        if (StringUtils.hasLength(this.properties.getTypeHandlersPackage())) {
            factory.setTypeHandlersPackage(this.properties.getTypeHandlersPackage());
        }

        if (!ObjectUtils.isEmpty(this.properties.resolveMapperLocations())) {
            factory.setMapperLocations(this.properties.resolveMapperLocations());
        }

        if (!ObjectUtils.isEmpty(this.properties.getGlobalConfig())) {
            factory.setGlobalConfig(this.properties.getGlobalConfig().convertGlobalConfiguration());
        }

        return factory.getObject();
    }

    @Bean
    @ConditionalOnMissingBean
    public SqlSessionTemplate sqlSessionTemplate(SqlSessionFactory sqlSessionFactory) {
        ExecutorType executorType = this.properties.getExecutorType();
        return executorType != null ? new SqlSessionTemplate(sqlSessionFactory, executorType) : new SqlSessionTemplate(sqlSessionFactory);
    }

    @Configuration
    @Import({MybatisPlusAutoConfiguration.AutoConfiguredMapperScannerRegistrar.class})
    @ConditionalOnMissingBean({MapperFactoryBean.class})
    public static class MapperScannerRegistrarNotFoundConfiguration {
        public MapperScannerRegistrarNotFoundConfiguration() {
        }

        @PostConstruct
        public void afterPropertiesSet() {
            MybatisPlusAutoConfiguration.logger.debug("No " + MapperFactoryBean.class.getName() + " found.");
        }
    }

    public static class AutoConfiguredMapperScannerRegistrar implements BeanFactoryAware, ImportBeanDefinitionRegistrar, ResourceLoaderAware {
        private BeanFactory beanFactory;
        private ResourceLoader resourceLoader;

        public AutoConfiguredMapperScannerRegistrar() {
        }

        public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
            MybatisPlusAutoConfiguration.logger.debug("Searching for mappers annotated with @Mapper");
            ClassPathMapperScanner scanner = new ClassPathMapperScanner(registry);

            try {
                if (this.resourceLoader != null) {
                    scanner.setResourceLoader(this.resourceLoader);
                }

                List<String> packages = AutoConfigurationPackages.get(this.beanFactory);
                if (MybatisPlusAutoConfiguration.logger.isDebugEnabled()) {
                    Iterator i$ = packages.iterator();

                    while(i$.hasNext()) {
                        String pkg = (String)i$.next();
                        MybatisPlusAutoConfiguration.logger.debug("Using auto-configuration base package '" + pkg + "'");
                    }
                }

                scanner.setAnnotationClass(Mapper.class);
                scanner.registerFilters();
                scanner.doScan(StringUtils.toStringArray(packages));
            } catch (IllegalStateException var7) {
                MybatisPlusAutoConfiguration.logger.debug("Could not determine auto-configuration package, automatic mapper scanning disabled." + var7);
            }

        }

        public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
            this.beanFactory = beanFactory;
        }

        public void setResourceLoader(ResourceLoader resourceLoader) {
            this.resourceLoader = resourceLoader;
        }
    }
}

解决办法

@Mapper

• 在mapper文件的类上添加 @Mapper注解

@MapperScan

• 在主类上添加 @MapperScan注解,指定mapper的扫描范围,注意值为mapper文件所在的包名

@MapperScan("com.oxford.mapper")

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