前言

前面参照SpringBoot官网，自动生成了简单项目点击打开链接

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">
<!-- namespace用于绑定Dao接口 -->
<mapper namespace="com.housekeeper.dao.UserDao">
<!-- 用用查询映射结果 -->
<resultMap id="BaseResultMap" type="com.housekeeper.model.User" >
<!-- column代表数据库列名，property代表实体类属性名 -->
<result column="user_id" property="userId"/>
<result column="user_name" property="userName"/>
<result column="user_password" property="userPassword"/>
</resultMap>
<!-- 查询名字记录sql -->
<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');
下载地址：https://download.csdn.net/download/qq_29266921/10457479
---------------------
作者：Biligle
来源：CSDN
原文：https://blog.csdn.net/qq_29266921/article/details/80513146
版权声明：本文为博主原创文章，转载请附上博文链接！