protected WebApplicationContext createWebApplicationContext(@Nullable ApplicationContext parent) {
    Class<?> contextClass = getContextClass();
    if (!ConfigurableWebApplicationContext.class.isAssignableFrom(contextClass)) {
      throw new ApplicationContextException(
          "Fatal initialization error in servlet with name '" + getServletName() +
          "': custom WebApplicationContext class [" + contextClass.getName() +
          "] is not of type ConfigurableWebApplicationContext");
    }
    ConfigurableWebApplicationContext wac =
        (ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);

    wac.setEnvironment(getEnvironment());
    //wac 就是web ioc容器
    //parent 就是root ioc容器
    //web容器设置root容器为父容器，所以web容器可以引用root容器
    wac.setParent(parent);
    String configLocation = getContextConfigLocation();
    if (configLocation != null) {
      wac.setConfigLocation(configLocation);
    }
    configureAndRefreshWebApplicationContext(wac);

    return wac;
  }

public class MyWebAppInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {

  //指定root容器对应的配置类
  //root容器的配置类
  @Override
  protected Class<?>[] getRootConfigClasses() {
    return new Class<?>[] { ServiceJavaConfig.class,MapperJavaConfig.class };
  }
  
  //指定web容器对应的配置类 webioc容器的配置类
  @Override
  protected Class<?>[] getServletConfigClasses() {
    return new Class<?>[] { WebJavaConfig.class };
  }
  
  //指定dispatcherServlet处理路径，通常为 / 
  @Override
  protected String[] getServletMappings() {
    return new String[] { "/" };
  }
}

@Data
public class Employee {

    private Integer empId;
    private String empName;
    private Double empSalary;
}

/**
 * projectName: com.atguigu.config
 * 
 * 1.实现Springmvc组件声明标准化接口WebMvcConfigurer 提供了各种组件对应的方法
 * 2.添加配置类注解@Configuration
 * 3.添加mvc复合功能开关@EnableWebMvc
 * 4.添加controller层扫描注解
 * 5.开启默认处理器,支持静态资源处理
 */
@Configuration
@EnableWebMvc
@ComponentScan("com.atguigu.controller")
public class WebJavaConfig implements WebMvcConfigurer {

    //开启静态资源
    @Override
    public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
        configurer.enable(); 
    }
}

/**
 * projectName: com.atguigu.config
 * 
 * 1. 声明@Configuration注解,代表配置类
 * 2. 声明@EnableTransactionManagement注解,开启事务注解支持
 * 3. 声明@EnableAspectJAutoProxy注解,开启aspect aop注解支持
 * 4. 声明@ComponentScan("com.atguigu.service")注解,进行业务组件扫描
 * 5. 声明transactionManager(DataSource dataSource)方法,指定具体的事务管理器
 */
@EnableTransactionManagement
@EnableAspectJAutoProxy
@Configuration
@ComponentScan("com.atguigu.service")
public class ServiceJavaConfig {
    
    @Bean
    public DataSourceTransactionManager transactionManager(DataSource dataSource){
        DataSourceTransactionManager transactionManager = new DataSourceTransactionManager();
        transactionManager.setDataSource(dataSource);
        return transactionManager;
    }
    
}

//1.读取外部配置文件
InputStream ips = Resources.getResourceAsStream("mybatis-config.xml");

//2.创建sqlSessionFactory
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(ips);

//3.创建sqlSession
SqlSession sqlSession = sqlSessionFactory.openSession();
//4.获取mapper代理对象
EmpMapper empMapper = sqlSession.getMapper(EmpMapper.class);
//5.数据库方法调用
int rows = empMapper.deleteEmpById(1);
System.out.println("rows = " + rows);
//6.提交和回滚
sqlSession.commit();
sqlSession.close();

@Bean
public SqlSessionFactory sqlSessionFactory(){
   //1.读取外部配置文件
  InputStream ips = Resources.getResourceAsStream("mybatis-config.xml");
  
  //2.创建sqlSessionFactory
  SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(ips);
  
  return sqlSessionFactory;
}

package org.mybatis.spring;

public class SqlSessionFactoryBean
    implements FactoryBean<SqlSessionFactory>, InitializingBean, ApplicationListener<ContextRefreshedEvent> {
    
       //封装了实例化流程
       public SqlSessionFactory getObject() throws Exception {
          if (this.sqlSessionFactory == null) {
            //实例化对象逻辑
            afterPropertiesSet();
          }
          //返回对象逻辑
          return this.sqlSessionFactory;
       }
   
} 

@Configuration
@PropertySource("classpath:jdbc.properties")
public class MapperJavaConfig {

    @Value("${jdbc.user}")
    private String user;
    @Value("${jdbc.password}")
    private String password;
    @Value("${jdbc.url}")
    private String url;
    @Value("${jdbc.driver}")
    private String driver;


    //数据库连接池配置
    @Bean
    public DataSource dataSource(){
        DruidDataSource dataSource = new DruidDataSource();
        dataSource.setUsername(user);
        dataSource.setPassword(password);
        dataSource.setUrl(url);
        dataSource.setDriverClassName(driver);
        return dataSource;
    }

    /**
     * 配置SqlSessionFactoryBean,指定连接池对象和外部配置文件即可
     * @param dataSource 需要注入连接池对象
     * @return 工厂Bean
     */
    @Bean
    public SqlSessionFactoryBean sqlSessionFactoryBean(DataSource dataSource){
        //实例化SqlSessionFactory工厂
        SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();

        //设置连接池
        sqlSessionFactoryBean.setDataSource(dataSource);

        //设置配置文件
        //包裹外部配置文件地址对象
        Resource resource = new ClassPathResource("mybatis-config.xml");
        sqlSessionFactoryBean.setConfigLocation(resource);

        return sqlSessionFactoryBean;
    }

    /**
     * 配置Mapper实例扫描工厂,配置 <mapper <package 对应接口和mapperxml文件所在的包
     * @return
     */
    @Bean
    public MapperScannerConfigurer mapperScannerConfigurer(){
        MapperScannerConfigurer mapperScannerConfigurer = new MapperScannerConfigurer();
        //设置mapper接口和xml文件所在的共同包
        mapperScannerConfigurer.setBasePackage("com.atguigu.mapper");
        return mapperScannerConfigurer;
    }

}

/**
 * projectName: com.atguigu.config
 *
 * description: 持久层配置和Druid和Mybatis配置 使用一个配置文件
 */
@Configuration
public class MapperJavaConfigNew {

    /**
     * 配置SqlSessionFactoryBean,指定连接池对象和外部配置文件即可
     * @param dataSource 需要注入连接池对象
     * @return 工厂Bean
     */
    @Bean
    public SqlSessionFactoryBean sqlSessionFactoryBean(DataSource dataSource){
        //实例化SqlSessionFactory工厂
        SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();

        //设置连接池
        sqlSessionFactoryBean.setDataSource(dataSource);

        //TODO: 替代xml文件的java配置
        /*

            <settings>
                <!-- 开启驼峰式映射-->
                <setting name="mapUnderscoreToCamelCase" value="true"/>
                <!-- 开启logback日志输出-->
                <setting name="logImpl" value="SLF4J"/>
                <!--开启resultMap自动映射 -->
                <setting name="autoMappingBehavior" value="FULL"/>
            </settings>

            <typeAliases>
                <!-- 给实体类起别名 -->
                <package name="com.atguigu.pojo"/>
            </typeAliases>

            <plugins>
                <plugin interceptor="com.github.pagehelper.PageInterceptor">
                    <!--
                        helperDialect：分页插件会自动检测当前的数据库链接，自动选择合适的分页方式。
                        你可以配置helperDialect属性来指定分页插件使用哪种方言。配置时，可以使用下面的缩写值：
                        oracle,mysql,mariadb,sqlite,hsqldb,postgresql,db2,sqlserver,informix,h2,sqlserver2012,derby
                        （完整内容看 PageAutoDialect） 特别注意：使用 SqlServer2012 数据库时，
                        https://github.com/pagehelper/Mybatis-PageHelper/blob/master/wikis/zh/HowToUse.md#%E5%A6%82%E4%BD%95%E9%85%8D%E7%BD%AE%E6%95%B0%E6%8D%AE%E5%BA%93%E6%96%B9%E8%A8%80
                     -->
                    <property name="helperDialect" value="mysql"/>
                </plugin>
            </plugins>

         */

        //settings [包裹到一个configuration对象,切记别倒错包]
        org.apache.ibatis.session.Configuration configuration = new org.apache.ibatis.session.Configuration();
        configuration.setMapUnderscoreToCamelCase(true);
        configuration.setLogImpl(Slf4jImpl.class);
        configuration.setAutoMappingBehavior(AutoMappingBehavior.FULL);
        sqlSessionFactoryBean.setConfiguration(configuration);

        //typeAliases
        sqlSessionFactoryBean.setTypeAliasesPackage("com.atguigu.pojo");

        //分页插件配置
        PageInterceptor pageInterceptor = new PageInterceptor();

        Properties properties = new Properties();
        properties.setProperty("helperDialect","mysql");
        pageInterceptor.setProperties(properties);
        sqlSessionFactoryBean.addPlugins(pageInterceptor);

        return sqlSessionFactoryBean;
    }

    /**
     * 配置Mapper实例扫描工厂,配置 <mapper <package 对应接口和mapperxml文件所在的包
     * @return
     */
    @Bean
    public MapperScannerConfigurer mapperScannerConfigurer(){
        MapperScannerConfigurer mapperScannerConfigurer = new MapperScannerConfigurer();
        //设置mapper接口和xml文件所在的共同包
        mapperScannerConfigurer.setBasePackage("com.atguigu.mapper");
        return mapperScannerConfigurer;
    }

}

public class MyWebAppInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {

  //指定root容器对应的配置类
  @Override
  protected Class<?>[] getRootConfigClasses() {
    return new Class<?>[] {MapperJavaConfig.class, ServiceJavaConfig.class, DataSourceJavaConfig.class };
  }
  
  //指定web容器对应的配置类
  @Override
  protected Class<?>[] getServletConfigClasses() {
    return new Class<?>[] { WebJavaConfig.class };
  }
  
  //指定dispatcherServlet处理路径，通常为 / 
  @Override
  protected String[] getServletMappings() {
    return new String[] { "/" };
  }
}

@Slf4j
@RestController
@RequestMapping("/employee")
public class EmployeeController {

    @Autowired
    private EmployeeService employeeService;

    @GetMapping("list")
    public List<Employee> retList(){
        List<Employee> employees = employeeService.findAll();
        log.info("员工数据:{}",employees);
        return employees;
    }
}

@Service
public class EmployeeServiceImpl implements EmployeeService {

    @Autowired
    private EmployeeMapper employeeMapper;

    /**
     * 查询所有员工信息
     */
    @Override
    public List<Employee> findAll() {
        List<Employee> employeeList =  employeeMapper.queryAll();
        return employeeList;
    }
}

public interface EmployeeMapper {

     List<Employee> queryAll();
}

/* 
需求说明
    查询全部数据页数据
请求uri
    schedule/{pageSize}/{currentPage}
请求方式 
    get   
响应的json
    {
        "code":200,
        "flag":true,
        "data":{
            //本页数据
            data:
            [
            {id:1,title:'学习java',completed:true},
            {id:2,title:'学习html',completed:true},
            {id:3,title:'学习css',completed:true},
            {id:4,title:'学习js',completed:true},
            {id:5,title:'学习vue',completed:true}
            ], 
            //分页参数
            pageSize:5, // 每页数据条数 页大小
            total:0 ,   // 总记录数
            currentPage:1 // 当前页码
        }
    }
*/

/* 
需求说明
    根据id删除日程
请求uri
    schedule/{id}
请求方式 
    delete
响应的json
    {
        "code":200,
        "flag":true,
        "data":null
    }
*/

/* 
需求说明
    增加日程
请求uri
    schedule
请求方式 
    post
请求体中的JSON
    {
        title: '',
        completed: false
    }
响应的json
    {
        "code":200,
        "flag":true,
        "data":null
    }
*/

/* 
需求说明
    根据id修改数据
请求uri
    schedule
请求方式 
    put
请求体中的JSON
    {
        id: 1,
        title: '',
        completed: false
    }
响应的json
    {
        "code":200,
        "flag":true,
        "data":null
    }
*/

/**
 * projectName: com.atguigu.pojo
 *
 * description: 任务实体类
 */
@Data
public class Schedule {

    private Integer id;
    private String title;
    private Boolean completed;
}

**
 * projectName: com.atguigu.utils
 *
 * description: 返回结果类
 */
public class R {

    private int code = 200; //200成功状态码

    private boolean flag = true; //返回状态

    private Object data;  //返回具体数据


    public  static R ok(Object data){
        R r = new R();
        r.data = data;
        return r;
    }

    public static R  fail(Object data){
        R r = new R();
        r.code = 500; //错误码
        r.flag = false; //错误状态
        r.data = data;
        return r;
    }


    public int getCode() {
        return code;
    }

    public void setCode(int code) {
        this.code = code;
    }

    public boolean isFlag() {
        return flag;
    }

    public void setFlag(boolean flag) {
        this.flag = flag;
    }

    public Object getData() {
        return data;
    }

    public void setData(Object data) {
        this.data = data;
    }
}

@Data
@NoArgsConstructor
@AllArgsConstructor
public class PageBean<T> {
    private int currentPage;   // 当前页码
    private int pageSize;      // 每页显示的数据量
    private long total;    // 总数据条数
    private List<T> data;      // 当前页的数据集合
}

/*
    @CrossOrigin 注释在带注释的控制器方法上启用跨源请求
 */
@CrossOrigin
@RequestMapping("schedule")
@RestController
public class ScheduleController
{

    @Autowired
    private ScheduleService scheduleService;

    @GetMapping("/{pageSize}/{currentPage}")
    public R showList(@PathVariable(name = "pageSize") int pageSize, @PathVariable(name = "currentPage") int currentPage){
        PageBean<Schedule> pageBean = scheduleService.findByPage(pageSize,currentPage);
        return  R.ok(pageBean);
    }
}    

@Slf4j
@Service
public class ScheduleServiceImpl  implements ScheduleService {

    @Autowired
    private ScheduleMapper scheduleMapper;

    /**
     * 分页数据查询,返回分页pageBean
     *
     * @param pageSize
     * @param currentPage
     * @return
     */
    @Override
    public PageBean<Schedule> findByPage(int pageSize, int currentPage) {
        //1.设置分页参数
        PageHelper.startPage(currentPage,pageSize);
        //2.数据库查询
        List<Schedule> list = scheduleMapper.queryPage();
        //3.结果获取
        PageInfo<Schedule> pageInfo = new PageInfo<>(list);
        //4.pageBean封装
        PageBean<Schedule> pageBean = new PageBean<>(pageInfo.getPageNum(),pageInfo.getPageSize(),pageInfo.getTotal(),pageInfo.getList());

        log.info("分页查询结果:{}",pageBean);

        return pageBean;
    }

}

public interface ScheduleMapper {

    List<Schedule> queryPage();
}    

@PostMapping
public R saveSchedule(@RequestBody Schedule schedule){
    scheduleService.saveSchedule(schedule);
    return R.ok(null);
}

/**
 * 保存学习计划
 *
 * @param schedule
 */
@Override
public void saveSchedule(Schedule schedule) {
    scheduleMapper.insert(schedule);
}

void insert(Schedule schedule);

@DeleteMapping("/{id}")
public R removeSchedule(@PathVariable Integer id){
    scheduleService.removeById(id);
    return R.ok(null);
}

/**
 * 移除学习计划
 *
 * @param id
 */
@Override
public void removeById(Integer id) {
    scheduleMapper.delete(id);
}

void delete(Integer id);

@PutMapping
    public R changeSchedule(@RequestBody Schedule schedule){
    scheduleService.updateSchedule(schedule);
    return R.ok(null);
}

/**
 * 更新学习计划
 *
 * @param schedule
 */
@Override
public void updateSchedule(Schedule schedule) {
    scheduleMapper.update(schedule);
}

void update(Schedule schedule);

@CrossOrigin //允许其他源访问我们的controller 浏览器大哥就不拦截了!
@RestController
@RequestMapping("schedule")
@Slf4j
public class ScheduleController {
    
}