SpringBoot集成MyBatis查詢數據庫

代碼已上傳，GitHub地址

準備數據庫：

1. 配置maven倉庫

		<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>2.1.0</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-tomcat</artifactId>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <!-- Gson -->
        <dependency>
            <groupId>com.google.code.gson</groupId>
            <artifactId>gson</artifactId>
            <version>2.8.5</version>
        </dependency>

2. application.properties中添加mybatis映射文件配置
   這一步是配置xml文件的位置，如果不配置，找不到xml映射文件

#配置mybatis #指定sql映射文件位置  claspath:resources文件夾
mybatis.mapper-locations=classpath:mapper/*.xml

3. 添加映射對象dao

public class User {
    private int id;
    private String head_pic;
    private String user_name;
    private String account;
    private String pw;
    @Override
    public String toString() {
        JSONObject jsonObject = new JSONObject();
        jsonObject.put("account",account);
        jsonObject.put("pw",pw);
        return jsonObject.toString();
    }
    //getters...
    //setters...
}

4. 添加關聯映射對象的java類
   @Repository可以換成@Mapper

@Repository//映射mapper文件，替代@mapper
public interface UserMapper {
    User Sel(int id);
}

5. 添加數據service

@Service//service標識
public class UserService {
    @Autowired//自動初始化對象
    UserMapper userMapper;
    public User Sel(int id){
        return userMapper.Sel(id);
    }
}

6. 添加控制器controller

注意寫法，get請求參數不需要配置，如果配置成/getUser/{id}這種形式，瀏覽器會報錯

Whitelabel Error Page
This application has no explicit mapping for /error, so you are seeing this as a fallback.
Fri Nov 01 14:56:52 CST 2019
There was an unexpected error (type=Not Found, status=404).
No message available

@RestController//controller標識
@RequestMapping("/abc")//請求路徑
public class UserController{
    @Autowired//自動初始化對象
    UserService userService;
    @GetMapping("/getUser")//請求路徑
    public String getUser(int id){
        System.out.print("id = "+id);
        return userService.Sel(id).toString();
    }
}

7. 瀏覽器顯示查詢結果
   輸入網址：http://localhost:8888/abc/getUser?id=1
   顯示結果：