springboot项目搭建（三）SpringBoot+Mybatis+mysql

1.首先在数据库里面新建一张表customer,表的设计如下：

然后在表中插入几条数据。

2.  整个项目的结构如下所示：

3.在application.properties中配置mysql，以及mybatis的映射路径，这里的url的数据库名记得改成自己的哦。注意：
这里的mybatis映射路径的classpath*与classpath的区别，WEB-INF/classes,lib才是classpath,classpath* 会查找根目录下所有的文件，直到找到为止。

#mysql配置
spring.datasource.password=123456
spring.datasource.url=jdbc:mysql://localhost:3306/mysql?useUnicode=true&characterEncoding=utf8&useSSL=\
  false&allowPublicKeyRetrieval=true&serverTimezone=GMT%2B8
spring.datasource.username=root
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
#mybatis映射路径
mybatis.mapper-locations:classpath*:userMapper.xml

4.model包新建实体类User，这里的@Setter,@Getter,是添加lombok的插件依赖

@Setter
@Getter
public class User {

    private String userId;
    private String userName;
    private String phone;
    private Date createDate;
    private Date updateDate;
}

5.service包下新建接口UserService，根据用户Id获取用户信息

public interface UserService {
    User getUserName(String userId);
}

6.dao包下新建接口UserDao

@Mapper
public interface UserDao {
    User getUserName(String userId);
}

7.serviceImpl包下新建实现类UserServiceImpl

@Service
public class UserServiceImpl implements UserService {

    @Autowired
    private UserDao userDao;
    @Override
    public User getUserName(String userId) {
        return userDao.getUserName(userId);
    }
}

8.UserMapper.xml文件如下：

<?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.springbootdemo.dao.UserDao">


    <resultMap id="BaseResultMap" type="com.example.springbootdemo.model.User">
        <id  column="userId"   jdbcType="VARCHAR"   property="userId" />
        <result column="userName"  jdbcType="VARCHAR"  property="userName"    />
        <result column="phone"  jdbcType="VARCHAR"  property="phone"    />
        <result column="createDate" jdbcType="TIMESTAMP"  property="createDate"   />
        <result column="updateDate" jdbcType="TIMESTAMP"   property="updateDate"   />
    </resultMap>

    <select id="getUserName" resultMap="BaseResultMap">
        select * from customer  where userId = #{userId}
    </select>

</mapper>

9.UserController类的代码如下：
 

@RestController
public class UserController {

    @Autowired
    private UserService userService;


    @RequestMapping("/userName")
    public User getUserName(String userId){
        return userService.getUserName(userId);
    }

}

10.启动项目，在浏览器里面输入：http://127.0.0.1:8080/userName?userId=1,即可得到用户id=1的信息。如下图所示：

就此，一个简单的雏形就搭建成功啦。

下面，简单的实现一个操作：根据id获取用户信息的时候，先从redis里面获取数据，如果redis里面没有数据，则从mysql数据库中读取数据，由于本地操作没有数据，所以我先将数据库中的数据插入redis.实现类的代码修改为如下：

启动前，记得要将redis的服务运行哦。

启动之后，浏览器中输入http://127.0.0.1:8080/userName?userId=1，发现报如下的错误：

2020-02-16 07:40:57.282 ERROR 13532 --- [nio-8080-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.data.redis.serializer.SerializationException: Cannot serialize; nested exception is org.springframework.core.serializer.support.SerializationFailedException: Failed to serialize object using DefaultSerializer; nested exception is java.lang.IllegalArgumentException: DefaultSerializer requires a Serializable payload but received an object of type [com.example.springbootdemo.model.User]] with root cause

java.lang.IllegalArgumentException: DefaultSerializer requires a Serializable payload but received an object of type [com.example.springbootdemo.model.User]
    at org.springframework.core.serializer.DefaultSerializer.serialize(DefaultSerializer.java:43) ~[spring-core-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.core.serializer.support.SerializingConverter.convert(SerializingConverter.java:63) ~[spring-core-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.core.serializer.support.SerializingConverter.convert(SerializingConverter.java:35) ~[spring-core-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.data.redis.serializer.JdkSerializationRedisSerializer.serialize(JdkSerializationRedisSerializer.java:94) ~[spring-data-redis-2.2.4.RELEASE.jar:2.2.4.RELEASE]
    at org.springframework.data.redis.core.AbstractOperations.rawValue(AbstractOperations.java:127) ~[spring-data-redis-2.2.4.RELEASE.jar:2.2.4.RELEASE]
    at org.springframework.data.redis.core.DefaultValueOperations.set(DefaultValueOperations.java:235) ~[spring-data-redis-2.2.4.RELEASE.jar:2.2.4.RELEASE]
    at com.example.springbootdemo.serviceImpl.UserServiceImpl.getUserName(UserServiceImpl.java:24) ~[classes/:na]
    at com.example.springbootdemo.controller.UserController.getUserName(UserController.java:23) ~[classes/:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_121]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_121]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_121]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_121]
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190) ~[spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
   原因是：缓存时，spring会将对象先序列化再存入redis,所以我们要将实体类对象实现Serializable。

最后，再运行一遍，成功！