spingboot和mybatis，純註解方式

spingboot和mybatis整合

純註解方式，不使用xml

1. 創建數據庫

DROP DATABASE IF EXISTS `socks`;
CREATE DATABASE `socks`;
USE `SOCKS`;
DROP TABLE IF EXISTS `t_user`;
CREATE TABLE `t_user` (
  `USER_ID` varchar(50) ,
  `USERNAME` varchar(50) ,
  `PASSWORD` varchar(50) ,
  `PHONE_NUM` varchar(15) 
) ;

INSERT INTO `t_user` VALUES ('1', 'admin', 'admin','15011791234');
INSERT INTO `t_user` VALUES ('2', 'roots', 'roots','18812342017');

2. 建立工程，spring initizer: web + jbdc + mysql + mybatis,pom.xml如下：

<?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 http://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>2.1.3.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.mybatis</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>demo</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-jdbc</artifactId>
        </dependency>
        <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>2.0.0</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>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

3. 針對表t_user創建一個類，針對一個表數據，也可以叫做結構體，數據類型，一般的實體（也就是數據類型）放在pojo下面：

4. 爲這個表創建方法，這個方法還必須和mysql map起來，也就是一個方法對應着對應的sql語句，對數據庫的操作都是放在mapper下面

這裏面的問題是，User的數據名和數據庫裏面的數據名不一致，數據庫裏面喜歡用下劃線，要麼開啓駝峯映射，要麼直接使用@Results一一對應這個是一勞永逸的方法。

@Mapper
public interface UserMapper {
    @Select("select * from t_user")
    @Results({
            @Result(property = "userId", column = "USER_ID"),
            @Result(property = "username", column = "USERNAME"),
            @Result(property = "password", column = "PASSWORD"),
            @Result(property = "mobileNum", column = "PHONE_NUM")
    })
    List<User> list();

}

5. 顯示出來，controller裏面調用對應的方法：

(先寫函數或者變量，在寫註解，註解是作用其上的)

@RestController
@RequestMapping("/user/*")
public class UserController {
    @SuppressWarnings("all")
    @Autowired
    UserMapper userMapper;

    @GetMapping("list")
    public List<User> list() {
        return userMapper.list();
    }
}

6. 附錄

application.yml

spring:
  datasource:
    #連接MySQL
    url: jdbc:mysql://localhost:3306/socks?useSSL=false&serverTimezone=GMT%2B8
    username: root
    password: 880808
    driver-class-name: com.mysql.jdbc.Driver

mybatis:
  configuration:
    #配置項：開啓下劃線到駝峯的自動轉換. 作用：將數據庫字段根據駝峯規則自動注入到對象屬性。
    map-underscore-to-camel-case: true

logging:
  level:
    #打印SQL信息
    com.mybatis.demo.mapper: debug

pojo.User.java

public class User {
    private String userId;
    private String username;
    private String password;
    private String mobileNum;

    public String getUserId() {
        return userId;
    }

    public void setUserId(String userId) {
        this.userId = userId;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getMobileNum() {
        return mobileNum;
    }

    public void setMobileNum(String mobileNum) {
        this.mobileNum = mobileNum;
    }
}

mapper.UserMapper.java

@Mapper
public interface UserMapper {
    @Select("select * from t_user")
    @Results({
            @Result(property = "userId", column = "USER_ID"),
            @Result(property = "username", column = "USERNAME"),
            @Result(property = "password", column = "PASSWORD"),
            @Result(property = "mobileNum", column = "PHONE_NUM")
    })
    List<User> list();

}

controller.UserController.java

@RestController
@RequestMapping("/user/*")
public class UserController {
    @SuppressWarnings("all")
    @Autowired
    UserMapper userMapper;

    @GetMapping("list")
    public List<User> list() {
        return userMapper.list();
    }
}