【1】pom文件添加依赖
依赖如下所示：
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!--mybatis-->
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>1.3.1</version>
</dependency>
<!-- mysql-connector-java-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>
<!-- https://mvnrepository.com/artifact/com.alibaba/druid -->
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid</artifactId>
<version>1.1.10</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>【2】配置数据源，数据库建立表，并生成pojo
数据源配置如下：
spring:
datasource:
url: jdbc:mysql://localhost:3306/test
username: root
password: 123456
driver-class-name: com.mysql.jdbc.Driver
type: com.alibaba.druid.pool.DruidDataSource
initialSize: 5
minIdle: 5
maxActive: 20
maxWait: 60000
timeBetweenEvictionRunsMillis: 60000
minEvictableIdleTimeMillis: 300000
validationQuery: SELECT 1 FROM DUAL
testWhileIdle: true
testOnBorrow: true
testOnReturn: false
poolPreparedStatements: true
# 配置监控统计拦截的filters，去掉后监控界面sql无法统计，'wall'用于防火墙
filters: stat,wall,log4j
maxPoolPreparedStatementPerConnectionSize: 20
useGlobalDataSourceStat: true
connectionProperties: druid.stat.mergeSql=true;druid.stat.slowSqlMillis=500这里使用两个类，department和employee，分别如下：
Department源码如下：
public class Department implements Serializable {
private Integer id;
private String departmentName;
public void setId(Integer id) {
this.id = id;
}
public void setDepartmentName(String departmentName) {
this.departmentName = departmentName;
}
public Integer getId() {
return id;
}
public String getDepartmentName() {
return departmentName;
}
}Employee源码如下：
public class Employee implements Serializable {
private Integer id;
private String lastName;
private Integer gender;
private String email;
private Integer dId;
public void setId(Integer id) {
this.id = id;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public void setGender(Integer gender) {
this.gender = gender;
}
public void setEmail(String email) {
this.email = email;
}
public void setdId(Integer dId) {
this.dId = dId;
}
public Integer getId() {
return id;
}
public String getLastName() {
return lastName;
}
public Integer getGender() {
return gender;
}
public String getEmail() {
return email;
}
public Integer getdId() {
return dId;
}
}【3】编写注解版的Mapper
DepartmentMapper 源码如下：
//指定这是一个操作数据库的mapper
@Mapper
public interface DepartmentMapper {
@Select("select id,department_name as departmentName from department where id=#{id}")
public Department getDeptById(Integer id);
@Delete("delete from department where id=#{id}")
public int deleteDeptById(Integer id);
@Options(useGeneratedKeys = true,keyProperty = "id")
@Insert("insert into department(department_name) values(#{departmentName})")
public int insertDept(Department department);
@Update("update department set department_name=#{departmentName} where id=#{id}")
public int updateDept(Department department);
}EmployeeMapper源码如下：
//@Mapper或者@MapperScan将接口扫描装配到容器中
public interface EmployeeMapper {
@Select("select * from employee where id=#{id}")
public Employee getEmpById(Integer id);
@Insert("insert into employee(lastName,email,gender,d_id) values(#{lastName},#{email},#{gender},#{dId})")
public void insertEmp(Employee employee);
}这里需要注意两点：
第一对象的属性与数据表列属性不完全一直，如department的departmentName与数据表中department_name列对应。
解决方法：
① SQL中使用别名方式；
② 向容器中注册自定义的ConfigurationCustomizer
@org.springframework.context.annotation.Configuration
public class MyBatisConfig {
@Bean
public ConfigurationCustomizer configurationCustomizer(){
return new ConfigurationCustomizer(){
@Override
public void customize(Configuration configuration) {
//这里表示开启驼峰命名
configuration.setMapUnderscoreToCamelCase(true);
}
};
}
}第二，数据表中department的id为自增，则默认情况下插入department后，department对象的id为null(数据表有值，id列为自增),如下图所示：
解决办法如下：添加@Options注解
@Options(useGeneratedKeys = true,keyProperty = "id")
@Insert("insert into department(department_name) values(#{departmentName})")
public int insertDept(Department department);可以编写Controller进行简单测试。
DeptController 源码如下：
@RestController
public class DeptController {
@Autowired
DepartmentMapper departmentMapper;
@RequestMapping("/dept/{id}")
public Department getDepartment(@PathVariable("id") Integer id){
return departmentMapper.getDeptById(id);
}
@GetMapping("/dept")
public Department insertDept(Department department){
departmentMapper.insertDept(department);
System.out.println(department);
return department;
}
}
【4】@MapperScan注解
配置该注解即可不用在每个mapper上面添加注解，示例如下：
@org.springframework.context.annotation.Configuration
@MapperScan(basePackages = {"com.springboot.datasource.mapper"})
public class MyBatisConfig {
@Bean
public ConfigurationCustomizer configurationCustomizer(){
return new ConfigurationCustomizer(){
@Override
public void customize(Configuration configuration) {
configuration.setMapUnderscoreToCamelCase(true);
}
};
}
}查看该注解源码如下：
/**
* Use this annotation to register MyBatis mapper interfaces when using Java
* Config. It performs when same work as {@link MapperScannerConfigurer} via
* {@link MapperScannerRegistrar}.
*
* <p>Configuration example:</p>
* <pre class="code">
* @Configuration
* @MapperScan("org.mybatis.spring.sample.mapper")
* public class AppConfig {
*
* @Bean
* public DataSource dataSource() {
* return new EmbeddedDatabaseBuilder()
* .addScript("schema.sql")
* .build();
* }
*
* @Bean
* public DataSourceTransactionManager transactionManager() {
* return new DataSourceTransactionManager(dataSource());
* }
*
* @Bean
* public SqlSessionFactory sqlSessionFactory() throws Exception {
* SqlSessionFactoryBean sessionFactory = new SqlSessionFactoryBean();
* sessionFactory.setDataSource(dataSource());
* return sessionFactory.getObject();
* }
* }
* </pre>
*
* @author Michael Lanyon
* @author Eduardo Macarron
*
* @since 1.2.0
* @see MapperScannerRegistrar
* @see MapperFactoryBean
*/
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Import(MapperScannerRegistrar.class)
public @interface MapperScan {
/**
* Alias for the {@link #basePackages()} attribute. Allows for more concise
* annotation declarations e.g.:
* {@code @EnableMyBatisMapperScanner("org.my.pkg")} instead of {@code
* @EnableMyBatisMapperScanner(basePackages= "org.my.pkg"})}.
*/
String[] value() default {};
/**
* Base packages to scan for MyBatis interfaces. Note that only interfaces
* with at least one method will be registered; concrete classes will be
* ignored.
*/
String[] basePackages() default {};
/**
* Type-safe alternative to {@link #basePackages()} for specifying the packages
* to scan for annotated components. The package of each class specified will be scanned.
* <p>Consider creating a special no-op marker class or interface in each package
* that serves no purpose other than being referenced by this attribute.
*/
Class<?>[] basePackageClasses() default {};
/**
* The {@link BeanNameGenerator} class to be used for naming detected components
* within the Spring container.
*/
Class<? extends BeanNameGenerator> nameGenerator() default BeanNameGenerator.class;
/**
* This property specifies the annotation that the scanner will search for.
* <p>
* The scanner will register all interfaces in the base package that also have
* the specified annotation.
* <p>
* Note this can be combined with markerInterface.
*/
Class<? extends Annotation> annotationClass() default Annotation.class;
/**
* This property specifies the parent that the scanner will search for.
* <p>
* The scanner will register all interfaces in the base package that also have
* the specified interface class as a parent.
* <p>
* Note this can be combined with annotationClass.
*/
Class<?> markerInterface() default Class.class;
/**
* 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.
*/
String sqlSessionTemplateRef() default "";
/**
* 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.
*/
String sqlSessionFactoryRef() default "";
/**
* Specifies a custom MapperFactoryBean to return a mybatis proxy as spring bean.
*
*/
Class<? extends MapperFactoryBean> factoryBean() default MapperFactoryBean.class;
}
其中，最上面言简意赅地说明了该注解的作用：
Use this annotation to register MyBatis mapper interfaces when using Java Config.
It performs when same work as {@link MapperScannerConfigurer} via
{@link MapperScannerRegistrar}.【5】MyBatis的自动配置
如下图所示，添加后mybatis-spring-boot-starter依赖如下图：
其中MyBatis的自动配置如下图：
在类MybatisAutoConfiguration 注册了许多以前我们在XML中配置的bean，如SqlSessionFactory，源码如下：
@Configuration
@ConditionalOnClass({SqlSessionFactory.class, SqlSessionFactoryBean.class})
@ConditionalOnBean({DataSource.class})
//MyBatis的属性对应类
@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();
}
@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)");
}
}
//注册SqlSessionFactory
@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()));
}
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();
}
//注册SqlSessionTemplate
@Bean
@ConditionalOnMissingBean
public 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() {
}
@PostConstruct
public 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<String> packages = AutoConfigurationPackages.get(this.beanFactory);
if(MybatisAutoConfiguration.logger.isDebugEnabled()) {
Iterator var5 = packages.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(packages));
} 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;
}
}
}
【6】注解开启二级缓存
Spring与MyBatis整合时，MyBatis的一级缓存失效。SpringBoot中默认帮我们全局开启了二级缓存，如果想要使用二级缓存还需要在mapper上注明。
源码示例如下：
@CacheNamespace
public interface EmployeeMapper {
@Select("select * from employee where id=#{id}")
public Employee getEmpById(Integer id);
@Insert("insert into employee(lastName,email,gender,d_id) values(#{lastName},#{email},#{gender},#{dId})")
public void insertEmp(Employee employee);
}这里使用@CacheNamespace注解(为给定的命名空间（比如类）配置缓存，对应xml<cache>)在该mapper上使用二级缓存。
连续发起两次查询语句，查询同一个id的Employee，控制台日志如下：
@CacheNamespace源码如下：
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface CacheNamespace {
Class<? extends org.apache.ibatis.cache.Cache> implementation() default PerpetualCache.class;
Class<? extends org.apache.ibatis.cache.Cache> eviction() default LruCache.class;
long flushInterval() default 0;
int size() default 1024;
boolean readWrite() default true;
boolean blocking() default false;
/**
* Property values for a implementation object.
* @since 3.4.2
*/
Property[] properties() default {};
}