IntelliJ IDEA ，springboot 2.0 +mybatis 创建和访问数据库

环境：

JDK8+windows10

步骤 New Module —>Spring Initializr—>next

1

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2.

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3。web勾选web，sql里面可以不勾，后续添加，另外，勾选了MyBatis会报错Property 'sqlSessionFactory' or 'sqlSessionTemplate' are required 这样的错误。这里我勾选了是为了待会解决这个错误

​

选完直接下一步到最后就行了

自动生成的pom文件如下

<?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>2.0.8.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</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>

## 目录结构​

因为没有配置数据库和任何文件，application是空的 ，默认端口是8080

我们需要在 在启动累忽略数据库配置

@SpringBootApplication(exclude = {DataSourceAutoConfiguration.class})

然后 用postman访问一下  说明项目是正常的

​

4.配置数据库 application.yml 文件

server:
  port: 8080
  tomcat:
    uri-encoding: UTF-8
  servlet:
    context-path: /
spring:
  dataSource:
    url: jdbc:mysql://localhost:3306/db-test?useUnicode=true&characterEncoding=utf8&tinyInt1isBit=false
    username: root
    password: 123456
    driverClassName: com.mysql.jdbc.Driver
mybatis:
  mapper-locations: classpath:com/example/demo/mapper/*Mapper.xml #注意：一定要对应mapper映射xml文件的所在路径
  type-aliases-package: com.example.demo.model # 注意：对应实体类的路径
  configuration:
    call-setters-on-nulls: true # 解决使用map类型接收查询结果的时候为null的字段会没有的情况

这时候 com.mysql.jdbc.Driver 标红 说明mysql架包找不到

​

把<scope>runtime</scope> 去掉，  他的意思是运行时不需要，实际上是需要的

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <scope>runtime</scope>
</dependency>

改成  版本默认就行

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
</dependency>

然后driverClassName 恢复正常

导入 service dao xml (这里没有使用实体类返回，使用的是map返回，所以表我们可以随意自建)

UserController

@Controller
@RequestMapping("/usersDemo")
public class UserController {
    private static Logger log = LoggerFactory.getLogger(UserController.class);
    @Resource
    UserService userService;

    @ResponseBody
    @RequestMapping(value = "/test", produces = "application/json;charset=UTF-8", method = {RequestMethod.POST, RequestMethod.GET})
    public List<Map<String, Object>> test(){
        log.info("进入了test方法！");
        List<Map<String,Object>> list=userService.userQueryAll();
        return list;
    }
}

UserService

public interface UserService {
    List<Map<String, Object>> userQueryAll();
}

UserserviceImpl

@Service
public class UserserviceImpl  implements UserService {
    @Resource
    UserMapper userDao;
    @Override
    public List<Map<String, Object>> userQueryAll() {
        return userDao.userQueryAll();
    }
}

UserMapper

@Mapper
public interface UserMapper {
    List<Map<String, Object>> userQueryAll();
}

UserMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.example.demo.dao.UserMapper">
    <select id="userQueryAll" parameterType="Map" resultType="Map">
        SELECT * FROM `users`
    </select>
</mapper>

DemoApplication

@SpringBootApplication(exclude = {DataSourceAutoConfiguration.class})
@MapperScan("com.example.demo.dao")
@ComponentScan(basePackages = {"com.example.demo.*"})
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }

}

好了 ，

接下来就是启动了

5启动

注意 ：依赖注入后 如果没有去掉 exclude = {DataSourceAutoConfiguration.class}

启动会报如下错误：

Caused by: java.lang.IllegalArgumentException: Property 'sqlSessionFactory' or 'sqlSessionTemplate' are required

错误原因1：

很多人说 创建项目的时候勾选了mybatis导致
  实际上是这个架包的原因
如果不要的话也不能使用mybatis了
<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>2.0.0</version>
</dependency>

错误原因2 ，

dataSource.type 使用默认的连接池导致的

解决方案1 ：去掉 exclude = {DataSourceAutoConfiguration.class} ，就能正常启动

解决方案2 :使用其他连接池 ，比如阿里 druid 连接池

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid-spring-boot-starter</artifactId>
    <version>1.1.13</version>
</dependency>

然后修改application.yml  里面的  spring.dataSource.type=com.alibaba.druid.pool.DruidDataSource

就可以不删除 exclude = {DataSourceAutoConfiguration.class}了 ，实际上意义不大，属于低级错误

​

6 继续启动，

日志是没错了， 然后访问数据库的时候 可能会出现

这样的错误

org.apache.ibatis.binding.BindingException: Invalid bound statement (not found): com.example.demo.dao.UserMapper.userQueryAll

错误可能原因 1.   mapper.xml   select 的 id写错了

解决方案：检查代码

错误可能原因 2. 程序没有编译xml文件

解决方案：pom.xml 文件 build里面 增加代码

<resources>
<resource>
    <directory>src/main/java</directory>
    <includes>
        <include>**/*.xml</include>
    </includes>
    <filtering>false</filtering>
</resource>
</resources>

再次启动 ：

成功

​

最终 pom.xml文件如下

<?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>2.0.8.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</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>
        <!-- alibaba的druid数据库连接池监控依赖 -->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid-spring-boot-starter</artifactId>
            <version>1.1.13</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>${mysql.version}</version>
        </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>
        <resources>
        <resource>
            <directory>src/main/java</directory>
            <includes>
                <include>**/*.xml</include>
            </includes>
            <filtering>false</filtering>
        </resource>
        </resources>
    </build>

</project>

跳转网页404 错误解决方案 ：https://blog.csdn.net/q18771811872/article/details/88051260

转载请附带原地址：https://blog.csdn.net/q18771811872/article/details/88126835