springboot2.0+mybatis+mysql实例（注解）

矫情吗；* 2022-03-12 10:19 348阅读 0赞

### 文章目录 ###

*   *   *  一、项目介绍和下载
         *  二、项目结构
         *  三、步骤
         *   *  1.创建用户表
             *  2.新建项目
             *  3.修改配置文件application.properties
             *  4.代码
             *   *  4.1实体类user.java
                 *  4.2接口层userMapper.java
                 *  4.3服务类userService.java
                 *  4.4前端控制类userController.java
                 *  4.5启动类application.java
         *  四、运行结果
         *   *   *  1.显示helloworld
                 *  2.插入用户
                 *  3.根据年龄查询用户
                 *  4.缺少参数，查询用户，出错
         *  五、遇到的问题

### 一、项目介绍和下载 ###

我们springboot2.0+mybatis+mysql搭建javaweb项目，全部都使用注解，实现数据库的插入和查询。

**项目下载：** [https://github.com/enjoyu/mybatis][https_github.com_enjoyu_mybatis]

### 二、项目结构 ###

1、application.properties配置文件中填写数据库信息。  
2、工程中包括实体类、接口层、服务层、前端控制层。  
3  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hqdTIy_size_16_color_FFFFFF_t_70]

### 三、步骤 ###

#### 1.创建用户表 ####

create database test;
    use test;
    create table user(
    id int primary key auto_increment,
    name varchar(20),
    age int
    );

![在这里插入图片描述][20190305182032417.]

#### 2.新建项目 ####

**1、新建项目create new project**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hqdTIy_size_16_color_FFFFFF_t_70 1]  
**2、Spring Initializr,点击next**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hqdTIy_size_16_color_FFFFFF_t_70 2]  
**3、group填写com.springboot，Artifact填写mybatis，点击next**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hqdTIy_size_16_color_FFFFFF_t_70 3]  
**4、添加依赖，选择web、mysql、mybatis，点击next**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hqdTIy_size_16_color_FFFFFF_t_70 4]  
**5、点击finish，项目创建成功**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hqdTIy_size_16_color_FFFFFF_t_70 5]  
**6、项目目录结构如下：**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hqdTIy_size_16_color_FFFFFF_t_70 6]  
**7、查看pom.xml：**

<?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>2.1.3.RELEASE</version>
            <relativePath/> 
        </parent>
        <groupId>com.springboot</groupId>
        <artifactId>mybatis</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <name>mybatis</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-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>

#### 3.修改配置文件application.properties ####

#mysql数据库配置（数据库驱动、数据库地址、用户名、密码）
    spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
    spring.datasource.url=jdbc:mysql://localhost:3306/test?useSSL=false&useUnicode=true&characterEncoding=UTF-8
    spring.datasource.username=root
    spring.datasource.password=root123

#### 4.代码 ####

##### 4.1实体类user.java #####

在com.springboot.mybatis包下创建子包entity，在entity下创建user.java。

package com.springboot.mybatis.entity;
    
    public class User {
    
        private int id;
        private String name;
        private int age;
    
        public int getId() {
            return id;
        }
    
        public void setId(int id) {
            this.id = id;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public int getAge() {
            return age;
        }
    
        public void setAge(int age) {
            this.age = age;
        }
    }

##### 4.2接口层userMapper.java #####

在com.springboot.mybatis包下创建子包mapper，在mapper下创建userMapper.java。

package com.springboot.mybatis.mapper;
    
    import com.springboot.mybatis.entity.User;
    import org.apache.ibatis.annotations.*;
    
    import java.util.List;
    @Mapper //声明UserMapper为一个Mapper接口
    public interface UserMapper {
        /*@Result是结果映射列表
        property是User类的属性名，colomn是数据库表的字段名
         */
        @Results({
                @Result(property = "id", column = "id"),
                @Result(property = "name", column = "name"),
                @Result(property = "age", column = "age")
        })
    
        //插入用户
        @Insert("INSERT INTO user(name, age) VALUES (#{name}, #{age})")
        void insert(User user);
    
        //根据年龄查询用户
        @Select("SELECT * FROM user WHERE age = #{age}")
        List<User> select(int age);
    }

##### 4.3服务类userService.java #####

在com.springboot.mybatis包下创建子包service，在service下创建userService.java。

package com.springboot.mybatis.service;
    
    
    import com.springboot.mybatis.entity.User;
    import com.springboot.mybatis.mapper.UserMapper;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Service;
    
    import java.util.List;
    @Service //声明为服务
    public class UserService {
    
        @Autowired //注入userMapper
        private UserMapper userMapper;
    
        public String show() {
            return "Hello World!";
        }
    
        //插入用户
        public String insert(String name, int age) { //插入一条记录
            User user = new User();
            user.setName(name);
            user.setAge(age);
            userMapper.insert(user);
            return "Insert ( \""+name+"\", age"+age+") OK!";
        }
    
        //根据年龄查询用户
        public List<User> select(int age) {
            return userMapper.select(age);
        }
    
    }

##### 4.4前端控制类userController.java #####

在com.springboot.mybatis包下创建子包controller，在controller下创建userController.java。

package com.springboot.mybatis.controller;
    
    import com.springboot.mybatis.service.UserService;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    @RestController //声明为一个Restful的Controller
    public class UserController {
        @Autowired //注入userService
        private UserService userService;
    
        //显示
        @RequestMapping(value = "/show")
        public String show() {
            return userService.show();
        }
    
        //插入用户
        @RequestMapping(value="/insert")
        public String insert(String name, int age) {
            return userService.insert(name, age);
        }
    
        //根据年龄查询用户
        @RequestMapping(value = "/select")
        public Object select(int age) {
            return userService.select(age);
        }
    
    }

##### 4.5启动类application.java #####

默认就行

package com.springboot.mybatis;
    
    import org.mybatis.spring.annotation.MapperScan;
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    
    @SpringBootApplication
    public class MybatisApplication {
    
        public static void main(String[] args) {
            SpringApplication.run(MybatisApplication.class, args);
        }
    }

### 四、运行结果 ###

**运行MybatisApplication类启动成功如下图所示：**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hqdTIy_size_16_color_FFFFFF_t_70 7]

##### 1.显示helloworld #####

访问 [http://localhost:8080/show][http_localhost_8080_show] ，结果如下  
![在这里插入图片描述][20190305200249223.]

##### 2.插入用户 #####

访问 [http://localhost:8080/insert?name=小明&age=20][http_localhost_8080_insert_name_age_20] ，结果如下：  
![在这里插入图片描述][20190305200515299.]  
用户表中插入了相关记录：  
![在这里插入图片描述][20190305200627396.]

##### 3.根据年龄查询用户 #####

访问 [http://localhost:8080/select?age=20][http_localhost_8080_select_age_20] ，结果如下  
![在这里插入图片描述][20190305201504976.]

##### 4.缺少参数，查询用户，出错 #####

访问 [http://localhost:8080/select][http_localhost_8080_select] ，结果如下：  
这个是一个白页，是说缺少参数age  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hqdTIy_size_16_color_FFFFFF_t_70 8]

### 五、遇到的问题 ###

**问题1：** Could not autowire. No beans of ‘UserMapper’ type found.  
**解决方法：** [https://blog.csdn.net/hju22/article/details/88136926][https_blog.csdn.net_hju22_article_details_88136926]

**问题2：** The server time zone value ‘ÖÐ¹ú±ê×¼Ê±¼ä’ is unrecognized  
**解决方法：** [https://blog.csdn.net/hju22/article/details/88192989][https_blog.csdn.net_hju22_article_details_88192989]

[https_github.com_enjoyu_mybatis]: https://github.com/enjoyu/mybatis
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hqdTIy_size_16_color_FFFFFF_t_70]: /images/20220312/e65ba89354524848985f8b3b62e70493.png
[20190305182032417.]: /images/20220312/0b47ace9bc374861b3d7d2ab193a8d1f.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hqdTIy_size_16_color_FFFFFF_t_70 1]: /images/20220312/07910b069bb0449a826ef73fa9136742.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hqdTIy_size_16_color_FFFFFF_t_70 2]: /images/20220312/b0f13ab7627845c4bc88f1baf7ed170c.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hqdTIy_size_16_color_FFFFFF_t_70 3]: /images/20220312/08f64e8b1cfd4b07bffc8e7949f9c6f1.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hqdTIy_size_16_color_FFFFFF_t_70 4]: /images/20220312/bbd0ab99b8ac45e682088d95b43a0270.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hqdTIy_size_16_color_FFFFFF_t_70 5]: /images/20220312/852b7b534eb14fa58c79643d0b4fed95.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hqdTIy_size_16_color_FFFFFF_t_70 6]: /images/20220312/7c2f6fcafb4f470fa72c60f1fe802a61.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hqdTIy_size_16_color_FFFFFF_t_70 7]: /images/20220312/b9654b3284b6417aa776ba70893ff01c.png
[http_localhost_8080_show]: http://localhost:8080/show
[20190305200249223.]: /images/20220312/9ee5160461e44428ad5e308eb32fa174.png
[http_localhost_8080_insert_name_age_20]: http://localhost:8080/insert?name=%E5%B0%8F%E6%98%8E&age=20
[20190305200515299.]: /images/20220312/6773de2fc1e94b38864135e8465de848.png
[20190305200627396.]: /images/20220312/d3b7cefabb254170a2db1c37f4204ef1.png
[http_localhost_8080_select_age_20]: http://localhost:8080/select?age=20
[20190305201504976.]: /images/20220312/8d906ba0d52145669c6853936da40cc9.png
[http_localhost_8080_select]: http://localhost:8080/select
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hqdTIy_size_16_color_FFFFFF_t_70 8]: /images/20220312/7001a860dd7c43d396060a85c8d487f5.png
[https_blog.csdn.net_hju22_article_details_88136926]: https://blog.csdn.net/hju22/article/details/88136926
[https_blog.csdn.net_hju22_article_details_88192989]: https://blog.csdn.net/hju22/article/details/88192989