spring boot(三) 集成mybatis

前言

还记得之前我们写接口也是基于SpringMVC+MyBatis环境下，项目入手就需要N个配置文件，N个步骤才能实现，不但繁琐，而且时间长了xml配置文件太多，难以维护。现在基于spring boot环境。3分钟就能编写一个基于MyBatis增删改查的demo。那么为什么这么神奇呢？

准备工作

1、环境依赖

  <dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>4.12</version></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot</artifactId><version>2.0.2.RELEASE</version></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId><version>2.0.2.RELEASE</version></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><version>2.0.2.RELEASE</version></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter</artifactId><version>2.0.2.RELEASE</version></dependency><!--mybatis --><dependency><groupId>org.mybatis.spring.boot</groupId><artifactId>mybatis-spring-boot-starter</artifactId><version>1.3.1</version></dependency><!--mysql--><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>5.1.46</version></dependency>

2、配置文件(applition.yml)

主要配置数据源(DataSource)和MyBatis。

spring:datasource:driver-class-name: com.mysql.jdbc.Driverurl: jdbc:mysql://192.168.80.129:3306/testusername: rootpassword: 123456mybatis:type-aliases-package: com.zhangfei.entitymapper-Locations: classpath:mybatis/*.xml

Example

1、程序入口

这里最关键的地方就是MapperScan注解，扫码Mapper接口所在地址。

@SpringBootApplication
@MapperScan(value = "com.zhangfei.dao")
public class DemoApplication {public static void main(String[] args){SpringApplication.run(DemoApplication.class,args);}}

2、Dao接口实现

也就是Mapper实现，放在resources/mybatis/*.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.zhangfei.dao.StudentDao"><select id="getStudentList" resultType="Student">select * from student;</select><select id="getById" resultType="Student">select * from student where id=#{id};</select><insert id="insert" parameterType="Student">insert into student (name,age) values (#{name},#{age})</insert><update id="update" parameterType="Student">update student set name=#{name},age=#{age} where id=#{id}</update><delete id="delete" parameterType="long">delete from student where id=#{id}</delete>
</mapper>

　　OK,有了接口、有了接口实现，第一个增删改查就搞定了，就是这么简单，来看单元测试。单元测试注意2.x环境下已经推荐使用SpringBootTest注解。

@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest
public class DemoApplicationTest {@AutowiredStudentDao studentDao;@Testpublic void test(){List<Student> students=studentDao.getStudentList();System.out.println("size:"+students.size());Student student=studentDao.getById(1);System.out.println(student.getId()+","+student.getName());}@Testpublic void test1(){//测试insertStudent student=new Student();student.setName("lisi");student.setAge(30);int result=studentDao.insert(student);}@Testpublic void test2(){//测试updateStudent student=new Student();student.setName("lisi222");student.setAge(35);student.setId(2);int result=studentDao.update(student);}@Testpublic void test3(){//测试updatelong id=3;int result=studentDao.delete(id);}}

总结：

还记得之前用SpringMVC+MyBatis开发接口应用时，基于spring托管mybatis时需要在xml中配置datasource、sqlsessionfactory、sqlsession。那么现在不需要自己亲力亲为了呢，那么这就是springboot、mybatis自动配置的工作所在。在org.mybatis.spring.boot.configure包下有两个关键类：

MyBatisProperties

这个类主要是读取你在applition.yml中配置的mybatis的基本属性用来配置数据源使用

@ConfigurationProperties(prefix = "mybatis"
)
public class MybatisProperties {public static final String MYBATIS_PREFIX = "mybatis";private String configLocation;private String[] mapperLocations;private String typeAliasesPackage;private String typeHandlersPackage;private boolean checkConfigLocation = false;private ExecutorType executorType;private Properties configurationProperties;@NestedConfigurationPropertyprivate Configuration configuration;public MybatisProperties() {}public String getConfigLocation() {return this.configLocation;}public void setConfigLocation(String configLocation) {this.configLocation = configLocation;}/** @deprecated */@Deprecatedpublic String getConfig() {return this.configLocation;}/** @deprecated */@Deprecatedpublic 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;}public Properties getConfigurationProperties() {return this.configurationProperties;}public void setConfigurationProperties(Properties configurationProperties) {this.configurationProperties = configurationProperties;}public Configuration getConfiguration() {return this.configuration;}public void setConfiguration(Configuration configuration) {this.configuration = configuration;}public Resource[] resolveMapperLocations() {PathMatchingResourcePatternResolver resourceResolver = new PathMatchingResourcePatternResolver();ArrayList resources = new ArrayList();if(this.mapperLocations != null) {String[] var3 = this.mapperLocations;int var4 = var3.length;for(int var5 = 0; var5 < var4; ++var5) {String mapperLocation = var3[var5];try {Resource[] mappers = resourceResolver.getResources(mapperLocation);resources.addAll(Arrays.asList(mappers));} catch (IOException var8) {;}}}return (Resource[])resources.toArray(new Resource[resources.size()]);}
}

MyBatisAutoConfiguration

@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 = (Interceptor[])interceptorsProvider.getIfAvailable();this.resourceLoader = resourceLoader;this.databaseIdProvider = (DatabaseIdProvider)databaseIdProvider.getIfAvailable();this.configurationCustomizers = (List)configurationCustomizersProvider.getIfAvailable();}@PostConstructpublic 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@ConditionalOnMissingBeanpublic 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()));}org.apache.ibatis.session.Configuration configuration = this.properties.getConfiguration();if(configuration == null && !StringUtils.hasText(this.properties.getConfigLocation())) {configuration = new org.apache.ibatis.session.Configuration();}if(configuration != null && !CollectionUtils.isEmpty(this.configurationCustomizers)) {Iterator var4 = this.configurationCustomizers.iterator();while(var4.hasNext()) {ConfigurationCustomizer customizer = (ConfigurationCustomizer)var4.next();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@ConditionalOnMissingBeanpublic SqlSessionTemplate sqlSessionTemplate(SqlSessionFactory sqlSessionFactory) {ExecutorType executorType = this.properties.getExecutorType();return executorType != null?new SqlSessionTemplate(sqlSessionFactory, executorType):new SqlSessionTemplate(sqlSessionFactory);}@Configuration@Import({MybatisAutoConfiguration.AutoConfiguredMapperScannerRegistrar.class})@ConditionalOnMissingBean({MapperFactoryBean.class})public static class MapperScannerRegistrarNotFoundConfiguration {public MapperScannerRegistrarNotFoundConfiguration() {}@PostConstructpublic void afterPropertiesSet() {MybatisAutoConfiguration.logger.debug("No {} found.", MapperFactoryBean.class.getName());}}public static class AutoConfiguredMapperScannerRegistrar implements BeanFactoryAware, ImportBeanDefinitionRegistrar, ResourceLoaderAware {private BeanFactory beanFactory;private ResourceLoader resourceLoader;public AutoConfiguredMapperScannerRegistrar() {}public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {MybatisAutoConfiguration.logger.debug("Searching for mappers annotated with @Mapper");ClassPathMapperScanner scanner = new ClassPathMapperScanner(registry);try {if(this.resourceLoader != null) {scanner.setResourceLoader(this.resourceLoader);}List ex = AutoConfigurationPackages.get(this.beanFactory);if(MybatisAutoConfiguration.logger.isDebugEnabled()) {Iterator var5 = ex.iterator();while(var5.hasNext()) {String pkg = (String)var5.next();MybatisAutoConfiguration.logger.debug("Using auto-configuration base package \'{}\'", pkg);}}scanner.setAnnotationClass(Mapper.class);scanner.registerFilters();scanner.doScan(StringUtils.toStringArray(ex));} catch (IllegalStateException var7) {MybatisAutoConfiguration.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;}}
}

　　这个类里的内容是不是看起来会面熟很多，看到了熟悉的SqlSessionFactory、SqlSessionTemplate。SpringBoot在运行的时候会进行自动配置，在mybatis-spring-boot-autoconfigure里找到spring.factories。然后找到MyBatisAutoConfiguration。其中checkConfigFileExists 使用了PostContruct注解，在初始化时加载mybatis配置文件创建SqlSessionFactory。sqlSessionFactory、sqlSessionTemplate两个方法都添加了ConditionalOnMissingBean注解，在bean不存在时分别创建SqlSessionFactory和SqlSessionTemplate。

在回过头来看程序入口还有一个MapperScan注解，主程序运行时去扫描mapper接口实现类，为其注入sqlsessionfactory和sqlsession。OK。这就是spring boot和mybatis为我们所提供的基础功能。