# spring boot + mybatis 读取数据库

spring boot + mybatis 读取数据库

创建数据库

use testdb;
drop table if exists t_city;
create table t_city(
id int primary key auto_increment,
city varchar(20),
state varchar(10)
)engine = innodb default charset = utf8;
insert into t_city values(1,"zhengzhou","HN");

maven 的pom 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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>nulijiushimeili</groupId>
    <artifactId>spring-boot2-mybatis</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>
    <name>spring-boot2-mybatis</name>
    <description>Demo project for Spring Boot</description>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.5.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <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>1.3.2</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>
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
            <version>3.4</version>
        </dependency>
        <!-- alibaba的druid数据库连接池 -->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid-spring-boot-starter</artifactId>
            <version>1.1.9</version>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

spring boot 配置 application.yml

#默认使用配置
spring:
  profiles:
    active: dev
#公共配置与profiles选择无关 mapperLocations指的路径是src/main/resources
mybatis:
  typeAliasesPackage: com.xdd.entity
#  mapperLocations: classpath:mapper/*.xml
---
#开发配置
spring:
  profiles: dev
  datasource:
    url: jdbc:mysql://localhost:3306/testdb
    username: root
    password: 123456
    driver-class-name: com.mysql.jdbc.Driver
    # 使用druid数据源
    type: com.alibaba.druid.pool.DruidDataSource

spring boot 启动器

@SpringBootApplication
@EnableTransactionManagement //如果mybatis中service实现类中加入事务注解，需要此处添加该注解
@MapperScan("nulijiushimeili.springboot2mybatis.mapper")  //扫描的是mapper.xml中namespace指向值的包位置
public class SpringBoot2MybatisApplication {
    public static void main(String[] args) {
        SpringApplication.run(SpringBoot2MybatisApplication.class, args);
    }
}

City bean

public class City {
    private String city;
    private String state;
    public City(){}
    public City(String city, String state){
        this.city = city ;
        this.state = state;
    }
    public String getCity() {
        return city;
    }
    public void setCity(String city) {
        this.city = city;
    }
    public String getState() {
        return state;
    }
    public void setState(String state) {
        this.state = state;
    }
}

mapper

@Repository
public interface CityMapper {
    @Select("select * from t_city where state = #{state}")
    City findByState(@Param("state")String state);
}

controller

@Controller
@RequestMapping(value = "/abv")
public class RegistyController {
 @Autowired
    private CityMapper cityMapper;
    @RequestMapping(value = "/read", method = RequestMethod.GET)
    @ResponseBody
    public City readMybatis(@RequestParam String state) {
        return cityMapper.findByState(state);
    }
}

测试url

http://localhost:8080/abv/read?state=HN

踩坑记

1. 数据库的字段名和bean的字段名必须保持一致，前后台请求数据的key也必须是一致的。否则会加载不到数据
2. 映射url请求路径不对，比如在类名上添加了@RequestMapping(),在请求的时候只写了类名上了方法上的路径。

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