SpringBoot Mybatis整理

MybatisAutoConfiguration

Mybaitis自动配置类，会根据datasource，配置相应的sqlSessionFactory和sqlSessionTemplate

AutoConfiguredMapperScannerRegistrar

数据访问层mapper接口的注册类，根据扫描策略注册相应的mapper接口的bean(mapper是接口类型，使用代理类创建实现类)

ClassPathMapperScanner

上面提到的用来扫描的扫描器，扫描@Mapper注解的类

@MapperScan

扫描mapper接口所在的包，代替@Mapper注解

MapperScannerConfigurer

作用类似@MapperScan，一般在xml配置中使用,详细使用参考官方文档

<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
    <property name="basePackage" value="org.mybatis.spring.sample.mapper" />
        <!-- optional unless there are multiple session factories defined -->
    <property name="sqlSessionFactoryBeanName" value="sqlSessionFactory" />
</bean>

MapperFactoryBean

mapper的创建工厂,spring创建mapper实例的具体类型

以一个简单的工程，实际操作下：SpringBoot中集成Mybatis

SpringBoot快速开发，使用data-jpa是最方便的，但是如果业务逻辑相对复杂，需要定制化各种复杂sql的情况下，就需要使用mybatis、hibernate等框架。

列出maven依赖

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter</artifactId>
</dependency>

<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>1.3.2</version>

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter</artifactId>
</dependency>

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <scope>runtime</scope>
</dependency>

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid</artifactId>
    <version>1.1.10</version>
</dependency>

<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <optional>true</optional>
</dependency>

首先进行mybatis相关配置，正常情况下我们需要在resource目录下新建一个mybatis-config.xml的配置文件，进行mybatis一些策略的配置。

下图是一个完整的setting配置

<settings>
  <setting name="cacheEnabled" value="true"/>
  <setting name="lazyLoadingEnabled" value="true"/>
  <setting name="multipleResultSetsEnabled" value="true"/>
  <setting name="useColumnLabel" value="true"/>
  <setting name="useGeneratedKeys" value="false"/>
  <setting name="autoMappingBehavior" value="PARTIAL"/>
  <setting name="defaultExecutorType" value="SIMPLE"/>
  <setting name="defaultStatementTimeout" value="25"/>
  <setting name="safeRowBoundsEnabled" value="false"/>
  <setting name="mapUnderscoreToCamelCase" value="false"/>
  <setting name="localCacheScope" value="SESSION"/>
  <setting name="jdbcTypeForNull" value="OTHER"/>
  <setting name="lazyLoadTriggerMethods" value="equals,clone,hashCode,toString"/>
</settings>

在Spring Boot中，我们可以application.properties配置，从而代替mybatis-config.xml配置文件。这里配置了几个属性(具体的作用就不做阐释了)

#mybatis配置
mybatis.configuration.use-generated-keys=true
mybatis.configuration.map-underscore-to-camel-case=true
mybatis.configuration.use-column-label=true
mybatis.type-aliases-package=com.faderw.school.domain

然后配置数据库相关属性，同样也在application.properties文件中配置，spring.dataource.type配置数据源的实现类型,这里我们用DruidDataSource代替默认的数据源

spring.datasource.type=com.alibaba.druid.pool.DruidDataSource
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.username=root
spring.datasource.password=123456
spring.datasource.url=jdbc:mysql://localhost:3306/demo?useUnicode=true&characterEncoding=utf-8&zeroDateTimeBehavior=convertToNull&useSSL=false

创建一个配置类DataSourceConfig,@MapperScan会自动扫描包下面的类，代替@mapper注解，告诉spring这是一个mapper。然后注入datasource以及sqlSessionFactory的bean，注意@ConfigurationProperties这个注解将会根据prefix属性自动装配application.porperties里面的配置

@Configuration
@MapperScan("com.faderw.school.dao")
public class DataSourceConfig {

    private static final String SPRING_DATASOURCE = "spring.datasource";
    private static final String MAPPER_LOCATIONS = "mapper/*.xml";

    @Value("${mybatis.type-aliases-package}")
    private String typeAliasesPackage; 

    @Bean(name = "dataSource")
    @ConfigurationProperties(prefix = SPRING_DATASOURCE)
    public DruidDataSource dataSource() {
        DruidDataSource dataSource = new DruidDataSource();
        return dataSource;
    }

    @Bean(name = "sqlSessionFactory")
    public SqlSessionFactoryBean sessionFactoryBean() throws IOException{
        SqlSessionFactoryBean sessionFactoryBean = new SqlSessionFactoryBean();
        sessionFactoryBean.setDataSource(dataSource());

        String patternPath = ResourcePatternResolver.CLASSPATH_URL_PREFIX + MAPPER_LOCATIONS;
        sessionFactoryBean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources(patternPath));
        sessionFactoryBean.setTypeAliasesPackage(typeAliasesPackage);

        return sessionFactoryBean;
    }
}

这里我们并没有配置事物管理器，因为springboot的自动装配会为我们默认配置一个DataSourceTransactionManager的事物管理器，我们只需要在程序入口类加上@EnableTransactionManagement开启注解事物的支持。