一、创建项目

IDEA中采用spring initialzer...创建，jdk选择8，maven,jar。。。springboot版本2.5.0（稳定）

项目依赖：

二、项目结构：

原始pom.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.5.0</version><relativePath/> <!-- lookup parent from repository --></parent><groupId>com.itheima</groupId><artifactId>springboot_09_ssm</artifactId><version>0.0.1-SNAPSHOT</version><name>springboot_09_ssm</name><description>Demo project for Spring Boot</description><properties><java.version>1.8</java.version></properties><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.mybatis.spring.boot</groupId><artifactId>mybatis-spring-boot-starter</artifactId><version>2.2.0</version></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><scope>runtime</scope></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><!--TODO 添加必要的依赖坐标--><dependency><groupId>com.alibaba</groupId><artifactId>druid</artifactId><version>1.1.16</version></dependency></dependencies><build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin></plugins></build></project>

 原始application.yml

spring:datasource:type: com.alibaba.druid.pool.DruidDataSourcedriver-class-name: com.mysql.cj.jdbc.Driverurl: jdbc:mysql://localhost:3306/www #?servierTimezone=UTCusername: rootpassword: root
server:port: 80

domain层

用于存储实体类

public class Book {private Integer id;private String type;private String name;private String description;@Overridepublic String toString() {return "Book{" +"id=" + id +", type='" + type + '\'' +", name='" + name + '\'' +", description='" + description + '\'' +'}';}public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getType() {return type;}public void setType(String type) {this.type = type;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getDescription() {return description;}public void setDescription(String description) {this.description = description;}
}

dao层

用于操作数据库 

@Mapper  //注意mapper
public interface BookDao {@Insert("insert into tbl_book (type,name,description) values(#{type},#{name},#{description})")public int save(Book book);@Update("update tbl_book set type = #{type}, name = #{name}, description = #{description} where id = #{id}")public int update(Book book);@Delete("delete from tbl_book where id = #{id}")public int delete(Integer id);@Select("select * from tbl_book where id = #{id}")public Book getById(Integer id);@Select("select * from tbl_book")public List<Book> getAll();
}

service层

用于业务实现

接口：

@Transactional
public interface BookService {/*** 保存* @param book* @return*/public boolean save(Book book);/*** 修改* @param book* @return*/public boolean update(Book book);/*** 按id删除* @param id* @return*/public boolean delete(Integer id);/*** 按id查询* @param id* @return*/public Book getById(Integer id);/*** 查询全部* @return*/public List<Book> getAll();
}

类：

@Service
public class BookServiceImpl implements BookService {@Autowiredprivate BookDao bookDao;public boolean save(Book book) {return bookDao.save(book) > 0;}public boolean update(Book book) {return bookDao.update(book) > 0;}public boolean delete(Integer id) {return bookDao.delete(id) > 0;}public Book getById(Integer id) {return bookDao.getById(id);}public List<Book> getAll() {return bookDao.getAll();}
}

controller层

用于控制业务流程

@RestController
@RequestMapping("/books")
public class BookController {@Autowiredprivate BookService bookService;@PostMappingpublic Result save(@RequestBody Book book) {boolean flag = bookService.save(book);return new Result(flag ? Code.SAVE_OK:Code.SAVE_ERR,flag);}@PutMappingpublic Result update(@RequestBody Book book) {boolean flag = bookService.update(book);return new Result(flag ? Code.UPDATE_OK:Code.UPDATE_ERR,flag);}@DeleteMapping("/{id}")public Result delete(@PathVariable Integer id) {boolean flag = bookService.delete(id);return new Result(flag ? Code.DELETE_OK:Code.DELETE_ERR,flag);}@GetMapping("/{id}")public Result getById(@PathVariable Integer id) {Book book = bookService.getById(id);Integer code = book != null ? Code.GET_OK : Code.GET_ERR;String msg = book != null ? "" : "数据查询失败，请重试！";return new Result(code,book,msg);}@GetMappingpublic Result getAll() {List<Book> bookList = bookService.getAll();Integer code = bookList != null ? Code.GET_OK : Code.GET_ERR;String msg = bookList != null ? "" : "数据查询失败，请重试！";return new Result(code,bookList,msg);}
}

tip: Code 类和 Result 和ProjectExceptionAdvice在Controller层中

code类用于规定result返回的编码类别

public class Code {public static final Integer SAVE_OK = 20011;public static final Integer DELETE_OK = 20021;public static final Integer UPDATE_OK = 20031;public static final Integer GET_OK = 20041;public static final Integer SAVE_ERR = 20010;public static final Integer DELETE_ERR = 20020;public static final Integer UPDATE_ERR = 20030;public static final Integer GET_ERR = 20040;public static final Integer SYSTEM_ERR = 50001;public static final Integer SYSTEM_TIMEOUT_ERR = 50002;public static final Integer SYSTEM_UNKNOW_ERR = 59999;public static final Integer BUSINESS_ERR = 60002;}

result用于封装返回的结果，让后台数据进行统一化处理

public class Result {private Object data;private Integer code;private String msg;public Result() {}public Result(Integer code,Object data) {this.data = data;this.code = code;}public Result(Integer code, Object data, String msg) {this.data = data;this.code = code;this.msg = msg;}public Object getData() {return data;}public void setData(Object data) {this.data = data;}public Integer getCode() {return code;}public void setCode(Integer code) {this.code = code;}public String getMsg() {return msg;}public void setMsg(String msg) {this.msg = msg;}
}

ProjectExceptionAdvice类用于规定 系统异常都抛到业务控制层，也就是controller层

@RestControllerAdvice
public class ProjectExceptionAdvice {@ExceptionHandler(SystemException.class)public Result doSystemException(SystemException ex){//记录日志//发送消息给运维//发送邮件给开发人员,ex对象发送给开发人员return new Result(ex.getCode(),null,ex.getMessage());}@ExceptionHandler(BusinessException.class)public Result doBusinessException(BusinessException ex){return new Result(ex.getCode(),null,ex.getMessage());}@ExceptionHandler(Exception.class)public Result doOtherException(Exception ex){//记录日志//发送消息给运维//发送邮件给开发人员,ex对象发送给开发人员return new Result(Code.SYSTEM_UNKNOW_ERR,null,"系统繁忙，请稍后再试！");}
}

exception层

封装异常类

BusinessException ，业务异常

public class BusinessException extends RuntimeException{private Integer code;public Integer getCode() {return code;}public void setCode(Integer code) {this.code = code;}public BusinessException(Integer code, String message) {super(message);this.code = code;}public BusinessException(Integer code, String message, Throwable cause) {super(message, cause);this.code = code;}}

SystemException  系统异常 

public class SystemException extends RuntimeException{private Integer code;public Integer getCode() {return code;}public void setCode(Integer code) {this.code = code;}public SystemException(Integer code, String message) {super(message);this.code = code;}public SystemException(Integer code, String message, Throwable cause) {super(message, cause);this.code = code;}}

测试：

@SpringBootTest
public class BookServiceTest {@Autowiredprivate BookService bookService;  //测试哪个  装配哪个//    @Test
//    public void testGetById(){
//        Book book = bookService.getById(2);
//        System.out.println(book);
//    }@Testpublic void testGetAll(){List<Book> all = bookService.getAll();System.out.println(all);}}