Springboot中mapper的配置

关于mapper怎么配置，如果去网上查资料大概分下面两类配置方法：

配置一：

mybatis.type-aliases-package=
mybatis.mapper-locations =classpath:/mappers/*.xml

配置二：

mybatis.typeAliasesPackage=com.sivalabs.demo.domain
mybatis.mapperLocations=classpath*:/mappers/*.xml

具体是采用哪一种呢？ 是否跟引用的mybatis版本有关系？ 带着一系列的疑问，去求索：

分析源码，在org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration、org.mybatis.spring.boot.autoconfigure.MybatisProperties两个类文件中有对应的解析属性定义：

其中MybatisAutoConfiguration的源码：

package org.mybatis.spring.boot.autoconfigure;

import java.util.List;

import javax.annotation.PostConstruct;
import javax.sql.DataSource;

import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.mapping.DatabaseIdProvider;
import org.apache.ibatis.plugin.Interceptor;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.ExecutorType;
import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.SqlSessionTemplate;
import org.mybatis.spring.mapper.ClassPathMapperScanner;
import org.mybatis.spring.mapper.MapperFactoryBean;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

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.EnableAutoConfiguration;
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.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;

/**
 * {@link EnableAutoConfiguration Auto-Configuration} for Mybatis. Contributes a
 * {@link SqlSessionFactory} and a {@link SqlSessionTemplate}.
 *
 * If {@link org.mybatis.spring.annotation.MapperScan} is used, or a
 * configuration file is specified as a property, those will be considered,
 * otherwise this auto-configuration will attempt to register mappers based on
 * the interface definitions in or under the root auto-configuration package.
 *
 * @author Edd煤 Mel茅ndez
 * @author Josh Long
 * @author Kazuki Shimizu
 * @author Eduardo Macarr贸n
 */
@org.springframework.context.annotation.Configuration
@ConditionalOnClass({ SqlSessionFactory.class, SqlSessionFactoryBean.class })
@ConditionalOnBean(DataSource.class)
@EnableConfigurationProperties(MybatisProperties.class)
@AutoConfigureAfter(DataSourceAutoConfiguration.class)
public class MybatisAutoConfiguration {

  private static final Logger logger = LoggerFactory.getLogger(MybatisAutoConfiguration.class);

  private final MybatisProperties properties;

  private final Interceptor[] interceptors;

  private final ResourceLoader resourceLoader;

  private final DatabaseIdProvider databaseIdProvider;

  private final List<ConfigurationCustomizer> configurationCustomizers;

  public MybatisAutoConfiguration(MybatisProperties properties,
                                  ObjectProvider<Interceptor[]> interceptorsProvider,
                                  ResourceLoader resourceLoader,
                                  ObjectProvider<DatabaseIdProvider> databaseIdProvider,
                                  ObjectProvider<List<ConfigurationCustomizer>> configurationCustomizersProvider) {
    this.properties = properties;
    this.interceptors = interceptorsProvider.getIfAvailable();
    this.resourceLoader = resourceLoader;
    this.databaseIdProvider = databaseIdProvider.getIfAvailable();
    this.configurationCustomizers = 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 {
    SqlSessionFactoryBean factory = new SqlSessionFactoryBean();
    factory.setDataSource(dataSource);
    factory.setVfs(SpringBootVFS.class);
    if (StringUtils.hasText(this.properties.getConfigLocation())) {
      factory.setConfigLocation(this.resourceLoader.getResource(this.properties.getConfigLocation()));
    }
    Configuration configuration = this.properties.getConfiguration();
    if (configuration == null && !StringUtils.hasText(this.properties.getConfigLocation())) {
      configuration = new Configuration();
    }
    if (configuration != null && !CollectionUtils.isEmpty(this.configurationCustomizers)) {
      for (ConfigurationCustomizer customizer : this.configurationCustomizers) {
        customizer.customize(configuration);
      }
    }
    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.getTypeHandlersPackage())) {
      factory.setTypeHandlersPackage(this.properties.getTypeHandlersPackage());
    }
    if (!ObjectUtils.isEmpty(this.properties.resolveMapperLocations())) {
      factory.setMapperLocations(this.properties.resolveMapperLocations());
    }

    return factory.getObject();
  }

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

  /**
   * This will just scan the same base package as Spring Boot does. If you want
   * more power, you can explicitly use
   * {@link org.mybatis.spring.annotation.MapperScan} but this will get typed
   * mappers working correctly, out-of-the-box, similar to using Spring Data JPA
   * repositories.
   */
  public static class AutoConfiguredMapperScannerRegistrar
      implements BeanFactoryAware, ImportBeanDefinitionRegistrar, ResourceLoaderAware {

    private BeanFactory beanFactory;

    private ResourceLoader resourceLoader;

    @Override
    public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {

      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 (logger.isDebugEnabled()) {
          for (String pkg : packages) {
            logger.debug("Using auto-configuration base package '{}'", pkg);
          }
        }

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

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

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

  /**
   * {@link org.mybatis.spring.annotation.MapperScan} ultimately ends up
   * creating instances of {@link MapperFactoryBean}. If
   * {@link org.mybatis.spring.annotation.MapperScan} is used then this
   * auto-configuration is not needed. If it is _not_ used, however, then this
   * will bring in a bean registrar and automatically register components based
   * on the same component-scanning path as Spring Boot itself.
   */
  @org.springframework.context.annotation.Configuration
  @Import({ AutoConfiguredMapperScannerRegistrar.class })
  @ConditionalOnMissingBean(MapperFactoryBean.class)
  public static class MapperScannerRegistrarNotFoundConfiguration {

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

}

其中类文件的头部：@EnableConfigurationProperties(MybatisProperties.class) 开启了关于mybatis的properties文件的配置！

MybatisProperties.java源码

/**
 * Configuration properties for MyBatis.
 *
 * @author Eddú Meléndez
 * @author Kazuki Shimizu
 */
@ConfigurationProperties(prefix = MybatisProperties.MYBATIS_PREFIX)
public class MybatisProperties {

  public static final String MYBATIS_PREFIX = "mybatis";

  /**
   * Location of MyBatis xml config file.
   */
  private String configLocation;

  /**
   * Locations of MyBatis mapper files.（看这个属性）
   */
  private String[] mapperLocations;

  /**
   * Packages to search type aliases. (Package delimiters are ",; \t\n")（看这个属性）
   */
  private String typeAliasesPackage;

  /**
   * Packages to search for type handlers. (Package delimiters are ",; \t\n")
   */
  private String typeHandlersPackage;

  /**
   * Indicates whether perform presence check of the MyBatis xml config file.
   */
  private boolean checkConfigLocation = false;

  /**
   * Execution mode for {@link org.mybatis.spring.SqlSessionTemplate}.
   */
  private ExecutorType executorType;

  /**
   * Externalized properties for MyBatis configuration.
   */
  private Properties configurationProperties;

  /**
   * A Configuration object for customize default settings. If {@link #configLocation}
   * is specified, this property is not used.
   */
  @NestedConfigurationProperty
  private Configuration configuration;

  /**
   * @since 1.1.0
   */
  public String getConfigLocation() {
    return this.configLocation;
  }

  /**
   * @since 1.1.0
   */
  public void setConfigLocation(String configLocation) {
    this.configLocation = configLocation;
  }

  @Deprecated
  public String getConfig() {
    return this.configLocation;
  }

  @Deprecated
  public void setConfig(String config) {
    this.configLocation = config;
  }

  public String[] getMapperLocations() {
    return this.mapperLocations;
  }

  public void setMapperLocations(String[] mapperLocations) {
    this.mapperLocations = mapperLocations;
  }

  public String getTypeHandlersPackage() {
    return this.typeHandlersPackage;
  }

  public void setTypeHandlersPackage(String typeHandlersPackage) {
    this.typeHandlersPackage = typeHandlersPackage;
  }

  public String getTypeAliasesPackage() {
    return this.typeAliasesPackage;
  }

  public void setTypeAliasesPackage(String typeAliasesPackage) {
    this.typeAliasesPackage = typeAliasesPackage;
  }

  public boolean isCheckConfigLocation() {
    return this.checkConfigLocation;
  }

  public void setCheckConfigLocation(boolean checkConfigLocation) {
    this.checkConfigLocation = checkConfigLocation;
  }

  public ExecutorType getExecutorType() {
    return this.executorType;
  }

  public void setExecutorType(ExecutorType executorType) {
    this.executorType = executorType;
  }

  /**
   * @since 1.2.0
   */
  public Properties getConfigurationProperties() {
    return configurationProperties;
  }

  /**
   * @since 1.2.0
   */
  public void setConfigurationProperties(Properties configurationProperties) {
    this.configurationProperties = configurationProperties;
  }

  public Configuration getConfiguration() {
    return configuration;
  }

  public void setConfiguration(Configuration configuration) {
    this.configuration = configuration;
  }

  public Resource[] resolveMapperLocations() {
    ResourcePatternResolver resourceResolver = new PathMatchingResourcePatternResolver();
    List<Resource> resources = new ArrayList<Resource>();
    if (this.mapperLocations != null) {
      for (String mapperLocation : this.mapperLocations) {
        try {
          Resource[] mappers = resourceResolver.getResources(mapperLocation);
          resources.addAll(Arrays.asList(mappers));
        } catch (IOException e) {
          // ignore
        }
      }
    }
    return resources.toArray(new Resource[resources.size()]);
  }
}

其中类文件的头部：

@ConfigurationProperties(prefix = MybatisProperties.MYBATIS_PREFIX)

使用@ConfigurationProperties注解，系统就可以识别以“mybatis”为前缀的配置信息~~~，要特别说明的是@ConfigurationProperties支持元数据（Meta-data）, 请看一下上面截图中的：spring-configuration-metadata.json 文件，其中是一段配置数据如下：

 {
      "sourceType": "org.mybatis.spring.boot.autoconfigure.MybatisProperties",
      "name": "mybatis.mapper-locations",
      "description": "Locations of MyBatis mapper files.",
      "type": "java.lang.String[]"
    },
    {
      "sourceType": "org.mybatis.spring.boot.autoconfigure.MybatisProperties",
      "name": "mybatis.type-aliases-package",
      "description": "Packages to search type aliases. (Package delimiters are \",; \\t\\n\")",
      "type": "java.lang.String"
    },

从中可以看出来，是可以解析文章开头所说的配置一的！

看一下重点属性的注释：
mapperLocations：Locations of MyBatis mapper files. mybatis映射器文件的位置
typeAliasesPackage：Packages to search type aliases. (Package delimiters are “,; \t\n”). 要搜索的包类型别名