【知识积累】利用BeanDefinitionRegistryPostProcessor修改Mybatis的mapper代理对象

1、配置MyMapperScannerConfigurer


package com.darren.spring;
 
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
 
/**
 * mybatis
 * 
 *
 * @author : Darren
 * @date : 2022年07月31日 01:17:52
 **/
@Configuration
public class MyBatisConfig {
 
    private static final String BASE_PACKAGE = "com.darren.dao1";
 
    @Bean
    public MyMapperScannerConfigurer myMapperScannerConfigurer(){
        MyMapperScannerConfigurer myMapperScannerConfigurer = new MyMapperScannerConfigurer();
        myMapperScannerConfigurer.setBasePackage(BASE_PACKAGE);
        return myMapperScannerConfigurer;
    }
 
}

2、修改postProcessBeanDefinitionRegistry方法


/**
 * Copyright 2010-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.darren.spring;
 
import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionTemplate;
import org.springframework.beans.PropertyValue;
import org.springframework.beans.PropertyValues;
import org.springframework.beans.factory.BeanNameAware;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.beans.factory.config.PropertyResourceConfigurer;
import org.springframework.beans.factory.config.TypedStringValue;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;
import org.springframework.beans.factory.support.BeanNameGenerator;
import org.springframework.beans.factory.support.DefaultListableBeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.core.env.Environment;
import org.springframework.util.StringUtils;
 
import java.lang.annotation.Annotation;
import java.util.Map;
import java.util.Optional;
 
import static org.springframework.util.Assert.notNull;
 
/**
 * BeanDefinitionRegistryPostProcessor that searches recursively starting from a base package for interfaces and
 * registers them as {@code MapperFactoryBean}. Note that only interfaces with at least one method will be registered;
 * concrete classes will be ignored.
 * 
 * This class was a {code BeanFactoryPostProcessor} until 1.0.1 version. It changed to
 * {@code BeanDefinitionRegistryPostProcessor} in 1.0.2. See https://jira.springsource.org/browse/SPR-8269 for the
 * details.
 * 
 * The {@code basePackage} property can contain more than one package name, separated by either commas or semicolons.
 * 
 * This class supports filtering the mappers created by either specifying a marker interface or an annotation. The
 * {@code annotationClass} property specifies an annotation to search for. The {@code markerInterface} property
 * specifies a parent interface to search for. If both properties are specified, mappers are added for interfaces that
 * match either criteria. By default, these two properties are null, so all interfaces in the given
 * {@code basePackage} are added as mappers.
 * 
 * This configurer enables autowire for all the beans that it creates so that they are automatically autowired with the
 * proper {@code SqlSessionFactory} or {@code SqlSessionTemplate}. If there is more than one {@code SqlSessionFactory}
 * in the application, however, autowiring cannot be used. In this case you must explicitly specify either an
 * {@code SqlSessionFactory} or an {@code SqlSessionTemplate} to use via the bean name properties. Bean names
 * are used rather than actual objects because Spring does not initialize property placeholders until after this class
 * is processed.
 * 
 * Passing in an actual object which may require placeholders (i.e. DB user password) will fail. Using bean names defers
 * actual object creation until later in the startup process, after all placeholder substitution is completed. However,
 * note that this configurer does support property placeholders of its own properties. The
 * basePackage and bean name properties all support ${property} style substitution.
 * 
 * Configuration sample:
 *
 * 
 * {@code
 *   
 *       
 *       
 *       
 *   
 * }
 *

*
* @author Hunter Presnall
* @author Eduardo Macarron
*
* @see MapperFactoryBean
*/
public class MyMapperScannerConfigurer
implements BeanDefinitionRegistryPostProcessor, InitializingBean, ApplicationContextAware, BeanNameAware {
private String basePackage;
private boolean addToConfig = true;
private String lazyInitialization;
private SqlSessionFactory sqlSessionFactory;
private SqlSessionTemplate sqlSessionTemplate;
private String sqlSessionFactoryBeanName;
private String sqlSessionTemplateBeanName;
private Classextends Annotation> annotationClass;
private Class markerInterface;
private Classextends MyMapperFactoryBean> mapperFactoryBeanClass;
private ApplicationContext applicationContext;
private String beanName;
private boolean processPropertyPlaceHolders;
private BeanNameGenerator nameGenerator;
/**
* This property lets you set the base package for your mapper interface files.
*
* You can set more than one package by using a semicolon or comma as a separator.
*
* Mappers will be searched for recursively starting in the specified package(s).
*
* @param basePackage
* base package name
*/
public void setBasePackage(String basePackage) {
this.basePackage = basePackage;
}
/**
* Same as {@code MapperFactoryBean#setAddToConfig(boolean)}.
*
* @param addToConfig
* a flag that whether add mapper to MyBatis or not
* @see MapperFactoryBean#setAddToConfig(boolean)
*/
public void setAddToConfig(boolean addToConfig) {
this.addToConfig = addToConfig;
}
/**
* Set whether enable lazy initialization for mapper bean.
*
* Default is {@code false}.
*
*
* @param lazyInitialization
* Set the @{code true} to enable
* @since 2.0.2
*/
public void setLazyInitialization(String lazyInitialization) {
this.lazyInitialization = lazyInitialization;
}
/**
* This property specifies the annotation that the scanner will search for.
*
* The scanner will register all interfaces in the base package that also have the specified annotation.
*
* Note this can be combined with markerInterface.
*
* @param annotationClass
* annotation class
*/
public void setAnnotationClass(Class annotationClass) {
this.annotationClass = annotationClass;
}
/**
* This property specifies the parent that the scanner will search for.
*
* The scanner will register all interfaces in the base package that also have the specified interface class as a
* parent.
*
* Note this can be combined with annotationClass.
*
* @param superClass
* parent class
*/
public void setMarkerInterface(Class superClass) {
this.markerInterface = superClass;
}
/**
* Specifies which {@code SqlSessionTemplate} to use in the case that there is more than one in the spring context.
* Usually this is only needed when you have more than one datasource.
*
*
* @deprecated Use {@link #setSqlSessionTemplateBeanName(String)} instead
*
* @param sqlSessionTemplate
* a template of SqlSession
*/
@Deprecated
public void setSqlSessionTemplate(SqlSessionTemplate sqlSessionTemplate) {
this.sqlSessionTemplate = sqlSessionTemplate;
}
/**
* Specifies which {@code SqlSessionTemplate} to use in the case that there is more than one in the spring context.
* Usually this is only needed when you have more than one datasource.
*
* Note bean names are used, not bean references. This is because the scanner loads early during the start process and
* it is too early to build mybatis object instances.
*
* @since 1.1.0
*
* @param sqlSessionTemplateName
* Bean name of the {@code SqlSessionTemplate}
*/
public void setSqlSessionTemplateBeanName(String sqlSessionTemplateName) {
this.sqlSessionTemplateBeanName = sqlSessionTemplateName;
}
/**
* Specifies which {@code SqlSessionFactory} to use in the case that there is more than one in the spring context.
* Usually this is only needed when you have more than one datasource.
*
*
* @deprecated Use {@link #setSqlSessionFactoryBeanName(String)} instead.
*
* @param sqlSessionFactory
* a factory of SqlSession
*/
@Deprecated
public void setSqlSessionFactory(SqlSessionFactory sqlSessionFactory) {
this.sqlSessionFactory = sqlSessionFactory;
}
/**
* Specifies which {@code SqlSessionFactory} to use in the case that there is more than one in the spring context.
* Usually this is only needed when you have more than one datasource.
*
* Note bean names are used, not bean references. This is because the scanner loads early during the start process and
* it is too early to build mybatis object instances.
*
* @since 1.1.0
*
* @param sqlSessionFactoryName
* Bean name of the {@code SqlSessionFactory}
*/
public void setSqlSessionFactoryBeanName(String sqlSessionFactoryName) {
this.sqlSessionFactoryBeanName = sqlSessionFactoryName;
}
/**
* Specifies a flag that whether execute a property placeholder processing or not.
*
* The default is {@literal false}. This means that a property placeholder processing does not execute.
*
* @since 1.1.1
*
* @param processPropertyPlaceHolders
* a flag that whether execute a property placeholder processing or not
*/
public void setProcessPropertyPlaceHolders(boolean processPropertyPlaceHolders) {
this.processPropertyPlaceHolders = processPropertyPlaceHolders;
}
/**
* The class of the {@link MapperFactoryBean} to return a mybatis proxy as spring bean.
*
* @param mapperFactoryBeanClass
* The class of the MapperFactoryBean
* @since 2.0.1
*/
public void setMapperFactoryBeanClass(Class mapperFactoryBeanClass) {
this.mapperFactoryBeanClass = mapperFactoryBeanClass;
}
/**
* {@inheritDoc}
*/
@Override
public void setApplicationContext(ApplicationContext applicationContext) {
this.applicationContext = applicationContext;
}
/**
* {@inheritDoc}
*/
@Override
public void setBeanName(String name) {
this.beanName = name;
}
/**
* Gets beanNameGenerator to be used while running the scanner.
*
* @return the beanNameGenerator BeanNameGenerator that has been configured
* @since 1.2.0
*/
public BeanNameGenerator getNameGenerator() {
return nameGenerator;
}
/**
* Sets beanNameGenerator to be used while running the scanner.
*
* @param nameGenerator
* the beanNameGenerator to set
* @since 1.2.0
*/
public void setNameGenerator(BeanNameGenerator nameGenerator) {
this.nameGenerator = nameGenerator;
}
/**
* {@inheritDoc}
*/
@Override
public void afterPropertiesSet() throws Exception {
notNull(this.basePackage, "Property 'basePackage' is required");
}
/**
* {@inheritDoc}
*/
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
// left intentionally blank
}
/**
* {@inheritDoc}
*
* @since 1.0.2
*/
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
if (this.processPropertyPlaceHolders) {
processPropertyPlaceHolders();
}
MyClassPathMapperScanner scanner = new MyClassPathMapperScanner(registry);
scanner.setAddToConfig(this.addToConfig);
scanner.setAnnotationClass(this.annotationClass);
scanner.setMarkerInterface(this.markerInterface);
scanner.setSqlSessionFactory(this.sqlSessionFactory);
scanner.setSqlSessionTemplate(this.sqlSessionTemplate);
scanner.setSqlSessionFactoryBeanName(this.sqlSessionFactoryBeanName);
scanner.setSqlSessionTemplateBeanName(this.sqlSessionTemplateBeanName);
scanner.setResourceLoader(this.applicationContext);
scanner.setBeanNameGenerator(this.nameGenerator);
scanner.setMapperFactoryBeanClass(this.mapperFactoryBeanClass);
if (StringUtils.hasText(lazyInitialization)) {
scanner.setLazyInitialization(Boolean.valueOf(lazyInitialization));
}
scanner.registerFilters();
scanner.scan(
StringUtils.tokenizeToStringArray(this.basePackage, ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS));
}
/*
* BeanDefinitionRegistries are called early in application startup, before BeanFactoryPostProcessors. This means that
* PropertyResourceConfigurers will not have been loaded and any property substitution of this class' properties will
* fail. To avoid this, find any PropertyResourceConfigurers defined in the context and run them on this class' bean
* definition. Then update the values.
*/
private void processPropertyPlaceHolders() {
Map prcs = applicationContext.getBeansOfType(PropertyResourceConfigurer.class,
false, false);
if (!prcs.isEmpty() && applicationContext instanceof ConfigurableApplicationContext) {
BeanDefinition mapperScannerBean = ((ConfigurableApplicationContext) applicationContext).getBeanFactory()
.getBeanDefinition(beanName);
// PropertyResourceConfigurer does not expose any methods to explicitly perform
// property placeholder substitution. Instead, create a BeanFactory that just
// contains this mapper scanner and post process the factory.
DefaultListableBeanFactory factory = new DefaultListableBeanFactory();
factory.registerBeanDefinition(beanName, mapperScannerBean);
for (PropertyResourceConfigurer prc : prcs.values()) {
prc.postProcessBeanFactory(factory);
}
PropertyValues values = mapperScannerBean.getPropertyValues();
this.basePackage = updatePropertyValue("basePackage", values);
this.sqlSessionFactoryBeanName = updatePropertyValue("sqlSessionFactoryBeanName", values);
this.sqlSessionTemplateBeanName = updatePropertyValue("sqlSessionTemplateBeanName", values);
this.lazyInitialization = updatePropertyValue("lazyInitialization", values);
}
this.basePackage = Optional.ofNullable(this.basePackage).map(getEnvironment()::resolvePlaceholders).orElse(null);
this.sqlSessionFactoryBeanName = Optional.ofNullable(this.sqlSessionFactoryBeanName)
.map(getEnvironment()::resolvePlaceholders).orElse(null);
this.sqlSessionTemplateBeanName = Optional.ofNullable(this.sqlSessionTemplateBeanName)
.map(getEnvironment()::resolvePlaceholders).orElse(null);
this.lazyInitialization = Optional.ofNullable(this.lazyInitialization).map(getEnvironment()::resolvePlaceholders)
.orElse(null);
}
private Environment getEnvironment() {
return this.applicationContext.getEnvironment();
}
private String updatePropertyValue(String propertyName, PropertyValues values) {
PropertyValue property = values.getPropertyValue(propertyName);
if (property == null) {
return null;
}
Object value = property.getValue();
if (value == null) {
return null;
} else if (value instanceof String) {
return value.toString();
} else if (value instanceof TypedStringValue) {
return ((TypedStringValue) value).getValue();
} else {
return null;
}
}
}

// 实现自己的MyMapperFactoryBean
private Class mapperFactoryBeanClass;

/**
     * {@inheritDoc}
     *
     * @since 1.0.2
     */
    @Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
        if (this.processPropertyPlaceHolders) {
            processPropertyPlaceHolders();
        }

        MyClassPathMapperScanner scanner = new MyClassPathMapperScanner(registry);
        scanner.setAddToConfig(this.addToConfig);
        scanner.setAnnotationClass(this.annotationClass);
        scanner.setMarkerInterface(this.markerInterface);
        scanner.setSqlSessionFactory(this.sqlSessionFactory);
        scanner.setSqlSessionTemplate(this.sqlSessionTemplate);
        scanner.setSqlSessionFactoryBeanName(this.sqlSessionFactoryBeanName);
        scanner.setSqlSessionTemplateBeanName(this.sqlSessionTemplateBeanName);
        scanner.setResourceLoader(this.applicationContext);
        scanner.setBeanNameGenerator(this.nameGenerator);
        scanner.setMapperFactoryBeanClass(this.mapperFactoryBeanClass);
        if (StringUtils.hasText(lazyInitialization)) {
            scanner.setLazyInitialization(Boolean.valueOf(lazyInitialization));
        }
        scanner.registerFilters();
        scanner.scan(
                StringUtils.tokenizeToStringArray(this.basePackage, ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS));
    }

注：
MyMapperScannerConfigurer是实现了BeanDefinitionRegistryPostProcessor，BeanDefinitionRegistryPostProcessor由继承了BeanFactoryPostProcessor，在spring容器启动的时候会调用所有BeanFactoryPostProcessor接口的实现的postProcessBeanDefinitionRegistry方法，MyMapperScannerConfigurer在postProcessBeanDefinitionRegistry方法用来修改BeanDefinition。

3、MyClassPathMapperScanner的doScan方法种调用父类的doScan方法


/**
 * Copyright 2010-2019 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.mybatis.spring.mapper;
 
import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.logging.Logger;
import org.mybatis.logging.LoggerFactory;
import org.mybatis.spring.SqlSessionTemplate;
import org.springframework.beans.factory.annotation.AnnotatedBeanDefinition;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.BeanDefinitionHolder;
import org.springframework.beans.factory.config.RuntimeBeanReference;
import org.springframework.beans.factory.support.AbstractBeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.GenericBeanDefinition;
import org.springframework.context.annotation.ClassPathBeanDefinitionScanner;
import org.springframework.core.type.filter.AnnotationTypeFilter;
import org.springframework.core.type.filter.AssignableTypeFilter;
import org.springframework.util.StringUtils;
 
import java.lang.annotation.Annotation;
import java.util.Arrays;
import java.util.Set;
 
/**
 * A {@link ClassPathBeanDefinitionScanner} that registers Mappers by {@code basePackage}, {@code annotationClass}, or
 * {@code markerInterface}. If an {@code annotationClass} and/or {@code markerInterface} is specified, only the
 * specified types will be searched (searching for all interfaces will be disabled).
 * 
 * This functionality was previously a private class of {@link MapperScannerConfigurer}, but was broken out in version
 * 1.2.0.
 *
 * @author Hunter Presnall
 * @author Eduardo Macarron
 * 
 * @see MapperFactoryBean
 * @since 1.2.0
 */
public class ClassPathMapperScanner extends ClassPathBeanDefinitionScanner {
 
  private static final Logger LOGGER = LoggerFactory.getLogger(ClassPathMapperScanner.class);
 
  private boolean addToConfig = true;
 
  private boolean lazyInitialization;
 
  private SqlSessionFactory sqlSessionFactory;
 
  private SqlSessionTemplate sqlSessionTemplate;
 
  private String sqlSessionTemplateBeanName;
 
  private String sqlSessionFactoryBeanName;
 
  private Classextends Annotation> annotationClass;
 
  private Class markerInterface;
 
  private Classextends MapperFactoryBean> mapperFactoryBeanClass = MapperFactoryBean.class;
 
  public ClassPathMapperScanner(BeanDefinitionRegistry registry) {
    super(registry, false);
  }
 
  public void setAddToConfig(boolean addToConfig) {
    this.addToConfig = addToConfig;
  }
 
  public void setAnnotationClass(Class annotationClass) {
    this.annotationClass = annotationClass;
  }
 
  /**
   * Set whether enable lazy initialization for mapper bean.
   * 
   * Default is {@code false}.
   * 
   *
   * @param lazyInitialization
   *          Set the @{code true} to enable
   * @since 2.0.2
   */
  public void setLazyInitialization(boolean lazyInitialization) {
    this.lazyInitialization = lazyInitialization;
  }
 
  public void setMarkerInterface(Class markerInterface) {
    this.markerInterface = markerInterface;
  }
 
  public void setSqlSessionFactory(SqlSessionFactory sqlSessionFactory) {
    this.sqlSessionFactory = sqlSessionFactory;
  }
 
  public void setSqlSessionTemplate(SqlSessionTemplate sqlSessionTemplate) {
    this.sqlSessionTemplate = sqlSessionTemplate;
  }
 
  public void setSqlSessionTemplateBeanName(String sqlSessionTemplateBeanName) {
    this.sqlSessionTemplateBeanName = sqlSessionTemplateBeanName;
  }
 
  public void setSqlSessionFactoryBeanName(String sqlSessionFactoryBeanName) {
    this.sqlSessionFactoryBeanName = sqlSessionFactoryBeanName;
  }
 
  /**
   * @deprecated Since 2.0.1, Please use the {@link #setMapperFactoryBeanClass(Class)}.
   */
  @Deprecated
  public void setMapperFactoryBean(MapperFactoryBean mapperFactoryBean) {
    this.mapperFactoryBeanClass = mapperFactoryBean == null ? MapperFactoryBean.class : mapperFactoryBean.getClass();
  }
 
  /**
   * Set the {@code MapperFactoryBean} class.
   *
   * @param mapperFactoryBeanClass
   *          the {@code MapperFactoryBean} class
   * @since 2.0.1
   */
  public void setMapperFactoryBeanClass(Class mapperFactoryBeanClass) {
    this.mapperFactoryBeanClass = mapperFactoryBeanClass == null ? MapperFactoryBean.class : mapperFactoryBeanClass;
  }
 
  /**
   * Configures parent scanner to search for the right interfaces. It can search for all interfaces or just for those
   * that extends a markerInterface or/and those annotated with the annotationClass
   */
  public void registerFilters() {
    boolean acceptAllInterfaces = true;
 
    // if specified, use the given annotation and / or marker interface
    if (this.annotationClass != null) {
      addIncludeFilter(new AnnotationTypeFilter(this.annotationClass));
      acceptAllInterfaces = false;
    }
 
    // override AssignableTypeFilter to ignore matches on the actual marker interface
    if (this.markerInterface != null) {
      addIncludeFilter(new AssignableTypeFilter(this.markerInterface) {
        @Override
        protected boolean matchClassName(String className) {
          return false;
        }
      });
      acceptAllInterfaces = false;
    }
 
    if (acceptAllInterfaces) {
      // default include filter that accepts all classes
      addIncludeFilter((metadataReader, metadataReaderFactory) -> true);
    }
 
    // exclude package-info.java
    addExcludeFilter((metadataReader, metadataReaderFactory) -> {
      String className = metadataReader.getClassMetadata().getClassName();
      return className.endsWith("package-info");
    });
  }
 
  /**
   * Calls the parent search that will search and register all the candidates. Then the registered objects are post
   * processed to set them as MapperFactoryBeans
   */
  @Override
  public Set doScan(String... basePackages) {
    Set beanDefinitions = super.doScan(basePackages);
 
    if (beanDefinitions.isEmpty()) {
      LOGGER.warn(() -> "No MyBatis mapper was found in '" + Arrays.toString(basePackages)
          + "' package. Please check your configuration.");
    } else {
      processBeanDefinitions(beanDefinitions);
    }
 
    return beanDefinitions;
  }
 
  private void processBeanDefinitions(Set beanDefinitions) {
    GenericBeanDefinition definition;
    for (BeanDefinitionHolder holder : beanDefinitions) {
      definition = (GenericBeanDefinition) holder.getBeanDefinition();
      String beanClassName = definition.getBeanClassName();
      LOGGER.debug(() -> "Creating MapperFactoryBean with name '" + holder.getBeanName() + "' and '" + beanClassName
          + "' mapperInterface");
 
      // the mapper interface is the original class of the bean
      // but, the actual class of the bean is MapperFactoryBean
      definition.getConstructorArgumentValues().addGenericArgumentValue(beanClassName); // issue #59
      definition.setBeanClass(this.mapperFactoryBeanClass);
 
      definition.getPropertyValues().add("addToConfig", this.addToConfig);
 
      boolean explicitFactoryUsed = false;
      if (StringUtils.hasText(this.sqlSessionFactoryBeanName)) {
        definition.getPropertyValues().add("sqlSessionFactory",
            new RuntimeBeanReference(this.sqlSessionFactoryBeanName));
        explicitFactoryUsed = true;
      } else if (this.sqlSessionFactory != null) {
        definition.getPropertyValues().add("sqlSessionFactory", this.sqlSessionFactory);
        explicitFactoryUsed = true;
      }
 
      if (StringUtils.hasText(this.sqlSessionTemplateBeanName)) {
        if (explicitFactoryUsed) {
          LOGGER.warn(
              () -> "Cannot use both: sqlSessionTemplate and sqlSessionFactory together. sqlSessionFactory is ignored.");
        }
        definition.getPropertyValues().add("sqlSessionTemplate",
            new RuntimeBeanReference(this.sqlSessionTemplateBeanName));
        explicitFactoryUsed = true;
      } else if (this.sqlSessionTemplate != null) {
        if (explicitFactoryUsed) {
          LOGGER.warn(
              () -> "Cannot use both: sqlSessionTemplate and sqlSessionFactory together. sqlSessionFactory is ignored.");
        }
        definition.getPropertyValues().add("sqlSessionTemplate", this.sqlSessionTemplate);
        explicitFactoryUsed = true;
      }
 
      if (!explicitFactoryUsed) {
        LOGGER.debug(() -> "Enabling autowire by type for MapperFactoryBean with name '" + holder.getBeanName() + "'.");
        definition.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_BY_TYPE);
      }
      definition.setLazyInit(lazyInitialization);
    }
  }
 
  /**
   * {@inheritDoc}
   */
  @Override
  protected boolean isCandidateComponent(AnnotatedBeanDefinition beanDefinition) {
    return beanDefinition.getMetadata().isInterface() && beanDefinition.getMetadata().isIndependent();
  }
 
  /**
   * {@inheritDoc}
   */
  @Override
  protected boolean checkCandidate(String beanName, BeanDefinition beanDefinition) {
    if (super.checkCandidate(beanName, beanDefinition)) {
      return true;
    } else {
      LOGGER.warn(() -> "Skipping MapperFactoryBean with name '" + beanName + "' and '"
          + beanDefinition.getBeanClassName() + "' mapperInterface" + ". Bean already defined with the same name!");
      return false;
    }
  }
 
}

/**
* Calls the parent search that will search and register all the candidates. Then the registered objects are post
* processed to set them as MapperFactoryBeans
*/
@Override
public Set doScan(String... basePackages) {
Set beanDefinitions = super.doScan(basePackages);

if (beanDefinitions.isEmpty()) {
LOGGER.warn(() -> "No MyBatis mapper was found in '" + Arrays.toString(basePackages)
+ "' package. Please check your configuration.");
} else {
processBeanDefinitions(beanDefinitions);
}

return beanDefinitions;
}

调用父类ClassPathBeanDefinitionScanner的doScan方法，返回所有扫描到的BeanDefinition对象

4、ClassPathBeanDefinitionScanner开始扫描maper接口，并注册到spring工厂中

注册：其实就是添加到BeanFactory（默认实现：DefaultListableBeanFactory）里面的Map beanDefinitionMap中


/**
	 * Perform a scan within the specified base packages.
	 * @param basePackages the packages to check for annotated classes
	 * @return number of beans registered
	 */
	public int scan(String... basePackages) {
		int beanCountAtScanStart = this.registry.getBeanDefinitionCount();
 
		doScan(basePackages);
 
		// Register annotation config processors, if necessary.
		if (this.includeAnnotationConfig) {
			AnnotationConfigUtils.registerAnnotationConfigProcessors(this.registry);
		}
 
		return (this.registry.getBeanDefinitionCount() - beanCountAtScanStart);
	}

doScan是真正扫描的地方，并注册的地方，传入的basePackages就是MyBatisConfig传入的要扫描的包路径

5、处理父类ClassPathBeanDefinitionScanner返回的所有扫描到的BeanDefinition对象，遍历修改

// 实现自己的MyMapperFactoryBean
private Class mapperFactoryBeanClass = MyMapperFactoryBean.class;
private void processBeanDefinitions(Set beanDefinitions) {
GenericBeanDefinition definition;
for (BeanDefinitionHolder holder : beanDefinitions) {

// 将拿到的BeanDefinition转换为普通的BeanDefinition
definition = (GenericBeanDefinition) holder.getBeanDefinition();

// 拿到bean的名称
String beanClassName = definition.getBeanClassName();
LOGGER.debug(() -> "Creating MapperFactoryBean with name '" + holder.getBeanName() + "' and '" + beanClassName
+ "' mapperInterface");

// the mapper interface is the original class of the bean
// but, the actual class of the bean is MapperFactoryBean
// 构造器参数中传入mapper接口的名称

definition.getConstructorArgumentValues().addGenericArgumentValue(beanClassName); // issue #59

// 设置自己的实现的MyMapperFactoryBean
definition.setBeanClass(this.mapperFactoryBeanClass);

// 添加一个addToConfig的参数

definition.getPropertyValues().add("addToConfig", this.addToConfig);

boolean explicitFactoryUsed = false;
if (StringUtils.hasText(this.sqlSessionFactoryBeanName)) {
definition.getPropertyValues().add("sqlSessionFactory",
new RuntimeBeanReference(this.sqlSessionFactoryBeanName));
explicitFactoryUsed = true;
} else if (this.sqlSessionFactory != null) {
definition.getPropertyValues().add("sqlSessionFactory", this.sqlSessionFactory);
explicitFactoryUsed = true;
}

if (StringUtils.hasText(this.sqlSessionTemplateBeanName)) {
if (explicitFactoryUsed) {
LOGGER.warn(
() -> "Cannot use both: sqlSessionTemplate and sqlSessionFactory together. sqlSessionFactory is ignored.");
}
definition.getPropertyValues().add("sqlSessionTemplate",
new RuntimeBeanReference(this.sqlSessionTemplateBeanName));
explicitFactoryUsed = true;
} else if (this.sqlSessionTemplate != null) {
if (explicitFactoryUsed) {
LOGGER.warn(
() -> "Cannot use both: sqlSessionTemplate and sqlSessionFactory together. sqlSessionFactory is ignored.");
}
definition.getPropertyValues().add("sqlSessionTemplate", this.sqlSessionTemplate);
explicitFactoryUsed = true;
}

if (!explicitFactoryUsed) {
LOGGER.debug(() -> "Enabling autowire by type for MapperFactoryBean with name '" + holder.getBeanName() + "'.");

// 设置自动装配的模式
definition.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_BY_TYPE);
}

// 设置懒加载
definition.setLazyInit(lazyInitialization);
}
}

6、Spring在实例化Bean的时候会判断Bean是否是FactoryBean接口的实现，如果是通过FactoryBean的T getObject()方法返回用户自己实例化好的对象


/**
 * Copyright 2010-2019 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.darren.spring;
 
import static org.springframework.util.Assert.notNull;
 
import org.apache.ibatis.executor.ErrorContext;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.mybatis.spring.SqlSessionTemplate;
import org.mybatis.spring.support.SqlSessionDaoSupport;
import org.springframework.beans.factory.FactoryBean;
 
import java.io.IOException;
import java.io.InputStream;
 
/**
 * BeanFactory that enables injection of MyBatis mapper interfaces. It can be set up with a SqlSessionFactory or a
 * pre-configured SqlSessionTemplate.
 * 
 * Sample configuration:
 *
 * 
 * {@code
 *   
 *     
 *   
 *
 *   
 *     
 *   
 *
 *   
 *     
 *   
 * }
 *

*

* Note that this factory can only inject interfaces, not concrete classes.

*

* @author Eduardo Macarron

*

* @see SqlSessionTemplate

*/

public class MyMapperFactoryBean implements FactoryBean {

private SqlSessionFactory sqlSessionFactory;

private Class mapperInterface;

    private boolean addToConfig = true;

    public MyMapperFactoryBean() {

// intentionally empty

}

    public MyMapperFactoryBean(Class mapperInterface) {

this.mapperInterface = mapperInterface;

}

/**

* {@inheritDoc}

*/

@Override

    public T getObject() throws Exception {

this.getSqlSessionFactory();

        SqlSession sqlSession = sqlSessionFactory.openSession();

return sqlSession.getMapper(this.mapperInterface);

}

    private void getSqlSessionFactory(){

// 根据全局配置文件创建出SqlSessionFactory

// SqlSessionFactory:负责创建SqlSession对象的工厂

// SqlSession:表示跟数据库建议的一次会话

        String resource = "mybatis-config.xml";

        InputStream inputStream = null;

try {

inputStream = Resources.getResourceAsStream(resource);

} catch (IOException e) {

e.printStackTrace();

}

sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

}

/**

* {@inheritDoc}

*/

@Override

    public Class getObjectType() {

return this.mapperInterface;

}

/**

* {@inheritDoc}

*/

@Override

    public boolean isSingleton() {

return true;

}

// ------------- mutators --------------

/**

* Sets the mapper interface of the MyBatis mapper

*

* @param mapperInterface

* class of the interface

*/

    public void setMapperInterface(Class mapperInterface) {

this.mapperInterface = mapperInterface;

}

/**

* Return the mapper interface of the MyBatis mapper

*

* @return class of the interface

*/

    public Class getMapperInterface() {

return mapperInterface;

}

/**

     * If addToConfig is false the mapper will not be added to MyBatis. This means it must have been included in

* mybatis-config.xml.

*

     * If it is true, the mapper will be added to MyBatis in the case it is not already registered.

*

* By default addToConfig is true.

*

* @param addToConfig

* a flag that whether add mapper to MyBatis or not

*/

    public void setAddToConfig(boolean addToConfig) {

this.addToConfig = addToConfig;

}

/**

* Return the flag for addition into MyBatis config.

*

     * @return true if the mapper will be added to MyBatis in the case it is not already registered.

*/

    public boolean isAddToConfig() {

return addToConfig;

}

/**
* {@inheritDoc}
*/
@Override
public T getObject() throws Exception {

// 初始化SqlSessionFactory
this.getSqlSessionFactory();

// 打开一个SqlSession
SqlSession sqlSession = sqlSessionFactory.openSession();

// 返回mapper接口的代理对象
return sqlSession.getMapper(this.mapperInterface);
}

private void getSqlSessionFactory(){
// 根据全局配置文件创建出SqlSessionFactory
// SqlSessionFactory:负责创建SqlSession对象的工厂
// SqlSession:表示跟数据库建议的一次会话
String resource = "mybatis-config.xml";
InputStream inputStream = null;
try {
inputStream = Resources.getResourceAsStream(resource);
} catch (IOException e) {
e.printStackTrace();
}
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
}

7、测试


package com.darren;
 
import com.darren.bean.Emp;
import com.darren.dao.EmpDao;
import com.darren.dao1.EmpDao1;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
 
import java.util.List;
 
/**
 * mybatis
 * 
 *
 * @author : Darren
 * @date : 2022年07月24日 18:30:32
 **/
@ContextConfiguration(locations = {"classpath:spring.xml"})
@RunWith(SpringJUnit4ClassRunner.class)
public class MyBatisSpringTest {
 
  @Autowired
  private EmpDao dao;
  @Autowired
  private EmpDao1 dao1;
 
  @Test
  public void test01(){
    List empByEmpno = dao.selectAll();
    empByEmpno.stream().forEach(System.out::println);
 
    List empByEmpno1 = dao1.selectAll();
    empByEmpno1.stream().forEach(System.out::println);
  }
 
}

// 没有修改过的

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7203c7ff] was not registered for synchronization because synchronization is not active
JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@59252cb6] will not be managed by Spring
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7203c7ff]
Emp{empno=7369, ename='Darren', job='CEO', mgr=1000000, hiredate=Wed Jun 10 08:00:00 CST 2015, sal=1.0E7, common=null, deptno=0}
Emp{empno=7379, ename='Darren1', job='CEO', mgr=1000000, hiredate=Wed Jun 10 08:00:00 CST 2015, sal=1.0E7, common=null, deptno=0}

// 自己修改的（配置文件开启了logImpl，所以打了sql日志）
Opening JDBC Connection
Created connection 1033348658.
Setting autocommit to false on JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@3d97a632]
==> Preparing: select * from emp
==> Parameters:
<== Columns: empno, ename, job, mgr, hiredate, sal, common, deptno, create_time, update_time
<== Row: 7369, Darren, CEO, 1000000, 2015-06-10 00:00:00, 10000000.00, null, 0, 2022-07-24 09:38:43, 2022-07-24 09:38:43
<== Row: 7379, Darren1, CEO, 1000000, 2015-06-10 00:00:00, 10000000.00, null, 0, 2022-07-24 17:11:34, 2022-07-24 17:11:34
<== Total: 2
Emp{empno=7369, ename='Darren', job='CEO', mgr=1000000, hiredate=Wed Jun 10 08:00:00 CST 2015, sal=1.0E7, common=null, deptno=0}
Emp{empno=7379, ename='Darren1', job='CEO', mgr=1000000, hiredate=Wed Jun 10 08:00:00 CST 2015, sal=1.0E7, common=null, deptno=0}