【入门】Spring-Boot项目配置Mysql数据库 - 好文

前言

    前面参照SpringBoot官网，自动生成了简单项目点击打开链接
<https://blog.csdn.net/qq_29266921/article/details/80249655>

配置数据库和代码遇到的问题

    问题1：cannot load driver class :com.mysql.jdbc.Driver不能加载mysql

    原因：没有添加依赖

    解决：pom.xml添加依赖
<dependency> <groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId> </dependency>
    问题2：Consider defining a bean of type 'com.xx.dao.XxDao' in your
configuration.注入UserDao失败

    原因：UserDao没有添加注解

    解决：在接口UserDao外层加上注解:@Mapper

    问题3：controller中注入service失败
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No
qualifying bean of type [com.boot.service.DemoService] found for dependency:
expected at least 1 bean which qualifies as autowire candidate for this
dependency. Dependency annotations:
{@org.springframework.beans.factory.annotation.Autowired(required=true)}
    原因：application.java文件默认扫描相同包名下的service，dao。

    解决：application.java文件添加注解:@ComponentScan(basePackages = "com.xxx")

配置Mysql数据库

在pom.xml添加依赖
<dependency>     <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>1.2.0</version> </dependency><dependency>
    <groupId>mysql</groupId>     <artifactId>mysql-connector-java</artifactId>
</dependency>
在application.properties添加
spring.datasource.url=jdbc:mysql://127.0.0.1:3306/girls
spring.datasource.username=root spring.datasource.password=chendashan
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.max-idle=10 spring.datasource.max-wait=10000
spring.datasource.min-idle=5 spring.datasource.initial-size=5 server.port=8080
server.session.timeout=10 server.tomcat.uri-encoding=UTF-8
mybatis.configLocations= classpath:mybatis-config.xml
mybatis.mapper-locations=classpath:mapper/*.xml
    建立库表省略，文章末尾附带

mapper文件

    操作数据库，靠它完成。
<?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.housekeeper.dao.UserDao">  <resultMap
id="BaseResultMap" type="com.housekeeper.model.User" >  <result column="user_id" property="userId"/>
<result column="user_name" property="userName"/> <result column="user_password"
property="userPassword"/> </resultMap>  <select
id="selectUserByUserName" parameterType="String" resultMap="BaseResultMap">
SELECT * FROM girls_info WHERE user_name = #{userName} </select> </mapper>
综上得知，UserDao通过映射文件mapper，执行了sql语句，返回了实体类User

UserDao接口
@Mapper public interface UserDao { /** * 根据user_name查询数据库 *
(映射执行mapper文件中的sql语句selectUserByUserName) * @param userName 名字 * @return User
*/ public User selectUserByUserName(String userName); }
User实体类
public class User { private String userName; private String userPassword;
public String getUserName() { return userName; } public void setName(String
userName) { this.userName = userName; } public String getUserPassword() {
return userPassword; } public void setPassword(String userPassword) {
this.userPassword = userPassword; } }
逻辑结构

逻辑层在controller里处理，已知，执行Userdao的接口方法，即可操作数据库。为了更好处理逻辑分层，加入Service层，调用UserDao。在Service实现层，注入UserDao即可调用其方法。
@Service public class UserServiceImp implements UserService { @Autowired
private UserDao userDao;//注入UserDao @Override public User
selectUserByName(String userName) { return
userDao.selectUserByUserName(userName); } }public interface UserService { /** *
通过姓名查找User * @param userName * @return */ User selectUserByName(String
useName); }
controller

    最后，controller层对外提供接口，返回查询数据结果
@Controller public class UserController { @Autowired private UserService
userService;//注入Service @ResponseBody @RequestMapping(value = "/login", method
= RequestMethod.POST) public Map<String, Object> login(@RequestParam(value =
"userName", required = true) String userName, @RequestParam(value =
"userPassword", required = true) String userPassword) { Map<String,Object>
result = new HashMap<String, Object>(); User user = null; String retCode = "";
String retMsg = ""; if(StringUtils.isEmpty(userName) ||
StringUtils.isEmpty(userPassword)){ retCode = "01"; retMsg = "用户名和密码不能为空";
}else{ user = userService.selectUserByName(userName); if(null == user){ retCode
= "01"; retMsg = "用户不存在"; }else{
if(userPassword.equals(user.getUserPassword())){ retCode = "00"; retMsg =
"登录成功"; }else{ retCode = "01"; retMsg = "密码有误"; } } }
result.put(SystemConst.retCode, retCode); result.put(SystemConst.retMsg,
retMsg); return result; } }
girls.sql文件
SET FOREIGN_KEY_CHECKS=0; -- ---------------------------- -- Table structure
for `girls_info` -- ---------------------------- DROP TABLE IF EXISTS
`girls_info`; CREATE TABLE `girls_info` ( `user_id` int(11) NOT NULL
AUTO_INCREMENT, `user_name` varchar(30) NOT NULL, `user_password` varchar(10)
NOT NULL, PRIMARY KEY (`user_id`) ) ENGINE=InnoDB AUTO_INCREMENT=8 DEFAULT
CHARSET=utf8; -- ---------------------------- -- Records of girls_info --
---------------------------- INSERT INTO `girls_info` VALUES ('1', '张帆',
'123456'); INSERT INTO `girls_info` VALUES ('2', '李北', '123456'); INSERT INTO
`girls_info` VALUES ('3', '陈珊珊', '123456'); INSERT INTO `girls_info` VALUES
('4', '王国立', '123456'); INSERT INTO `girls_info` VALUES ('5', '张三', '123456');
INSERT INTO `girls_info` VALUES ('6', '李四', '123456'); INSERT INTO `girls_info`
VALUES ('7', 'Biligle', '123456');
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<https://download.csdn.net/download/qq_29266921/10457479>

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