Spring Boot的数据库之旅（一）

使用mybatis操作数据库

1.配置mybatis依赖和mysql依赖

<!-- MyBatis依赖 -->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.1.1</version>
        </dependency>
        <!-- MySQL依赖 -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>

2.mybatis配置文件及数据库配置

#检查MyBatis配置是否存在，一般命名为mybatis-config.xml
mybatis.check-config-location=true
#配置文件位置
mybatis.config-location=classpath:mybatis/mybatis-config.xml
#mapper xml位置
mybatis.mapper-locations=classpath*:mapper/*Mapper.xml
#日志级别
logging.level.com.com.example.demo.mapper.UserMapper=debug

#数据库配置
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/test?characterEncoding=utf-8&useSSL=false&serverTimezone=GMT%2B8&allowPublicKeyRetrieval=true
spring.datasource.username=root
spring.datasource.password=123456abc

3.创建mybatis全局配置文件mybatis-config.xml

<?xml version="1.0" encoding="UTF-8"?>
<!-- mybatis全局配置文件 -->
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD SQL Map Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<!-- 类型别名 -->
    <typeAliases>
        <typeAlias alias="Integer" type="java.lang.Integer" />
        <typeAlias alias="Long" type="java.lang.Long" />
        <typeAlias alias="HashMap" type="java.util.HashMap" />
        <typeAlias alias="LinkedHashMap" type="java.util.LinkedHashMap" />
        <typeAlias alias="ArrayList" type="java.util.ArrayList" />
        <typeAlias alias="LinkedList" type="java.util.LinkedList" />
<!--自行配置-->
        <typeAlias alias="user" type="com.example.demo.pojo.User"/>
    </typeAliases>
</configuration>

4.创建一个实体类User

@Alias(value = "user")
public class User {
    private String id;
    private String user_name;
    private String user_password;
//相应的构造方法，注意不要让无参的被覆盖
//setter getter
}

5.基于xml的使用，创建UserMapper接口

基于注解也可以，用的时候再说

//这个注解很好用，1.不用再在mybatis-config.xml里写xml映射文件2.直接就可以有相应的对象实例使用了

//同时如果有多个mapper一个个加@Mapper比较麻烦，可以在启动类上加上@MapperScan(basePackages = "com.example.demo.dao")扫描此包下的所有mapper
@Mapper
public interface UserMapper {
    User findUserByUsername(String username);
    void updateUserByUsername(User user);
    void deleteUserByUsername(String username);
    void saveUser(User user);
    List<User> getUserList();
}

6.创建UserMapper.xml

<?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.demo.mapper.UserMapper">
    <resultMap id="user" type="com.example.demo.pojo.User"/>
    <parameterMap id="user" type="com.example.demo.pojo.User"/>
    <select id="findUserByUsername" parameterType="String" resultMap="user">
        SELECT * FROM user
        WHERE user_name=#{1}
    </select>

    <update id="updateUserByUsername" parameterMap="user">
        UPDATE USER SET USER_PASSWORD=#{user_password} WHERE USER_NAME=#{user_name}
    </update>

    <delete id="deleteUserByUsername" parameterType="String">
        DELETE FROM USER WHERE USER_NAME=#{1}
    </delete>

    <!-- 使用alias自定义的parameterType-->
    <insert id="saveUser" parameterType="user">
        INSERT INTO USER (user_password,user_name) VALUES (#{user_password},#{user_name})
    </insert>

    <select id="getUserList" resultMap="user">
        SELECT  * FROM USER
    </select>
</mapper>

7.创建controller运行测试

@RestController
public class UserController {
    
    @Autowired
    private UserMapper userMapper;

    //http://localhost:8080/getUser?username=xiaoli2
    @GetMapping("/getUser")
    public String getUser(String username){
        User user =userMapper.findUserByUsername(username);
        return user!=null ? username+"的密码是："+user.getUser_password():"不存在用户名为"+username+"的用户";
    }

    //http://localhost:8080/updateUser?username=xiaoli2&password=123
    @GetMapping("/updateUser")
    public String updateUser(String password,String username){
        User user = new User(username,password);
        userMapper.updateUserByUsername(user);
        return "success!";
    }

    //http://localhost:8080/addUser?username=xiaoli2&password=123
    @GetMapping("/addUser")
    public String addUser(String username,String password){
        User user = new User(username,password);
        userMapper.saveUser(user);
        return "success!";
    }

    //http://localhost:8080/deleteUser?username=xiaoli2
    @GetMapping("/deleteUser")
    public String deleteUser(String username){
        userMapper.deleteUserByUsername(username);
        return "success!";
    }

    //http://localhost:8080/getUserList
    @GetMapping("/getUserList")
    public List getUserList(){
        return userMapper.getUserList();
    }
}

使用Mybatis-Generator插件

1.在pom文件里加入Mybatis-Generator插件

<build>
        <plugins>
            <plugin>
                <groupId>org.mybatis.generator</groupId>
                <artifactId>mybatis-generator-maven-plugin</artifactId>
                <version>1.3.2</version>
                <executions>
                    <execution>
                        <id>mybatis-generator</id>
                        <phase>deploy</phase>
                        <goals>
                            <goal>generate</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <!-- Mybatis-Generator 工具配置文件的位置 -->
                    <configurationFile>src/main/resources/mybatis-generator/generatorConfig.xml</configurationFile>
                    <verbose>true</verbose>
                    <overwrite>true</overwrite>
                </configuration>
                <dependencies>
                    <dependency>
                        <groupId>mysql</groupId>
                        <artifactId>mysql-connector-java</artifactId>
                        <version>5.1.46</version>
                    </dependency>
                    <dependency>
                        <groupId>org.mybatis.generator</groupId>
                        <artifactId>mybatis-generator-core</artifactId>
                        <version>1.3.2</version>
                    </dependency>
                </dependencies>
            </plugin>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <classifier>exec</classifier>
                </configuration>
            </plugin>
        </plugins>
    </build>

2.创建Mybatis-Generator配置文件generatorConfig.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE generatorConfiguration
        PUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN"
        "http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd">
<!-- 配置生成器 -->
<generatorConfiguration>
    <!--执行generator插件生成文件的命令： call mvn mybatis-generator:generate -e -->
    <!-- 引入配置文件 -->
    <properties resource="application.properties"/>
    <!--classPathEntry:数据库的JDBC驱动,换成你自己的驱动位置 可选 -->
    <!--<classPathEntry location="D:generator_mybatismysql-connector-java-5.1.24-bin.jar" /> -->

    <!-- 一个数据库一个context -->
    <!--defaultModelType="flat" 大数据字段，不分表 -->
    <!--     MyBatis3Simple没有生成selective结尾的方法，设置为MyBatis3即可生成 -->
    <context id="MysqlTables" targetRuntime="MyBatis3Simple" defaultModelType="flat">
        <!-- 自动识别数据库关键字，默认false，如果设置为true，根据SqlReservedWords中定义的关键字列表；
        一般保留默认值，遇到数据库关键字（Java关键字），使用columnOverride覆盖 -->
        <property name="autoDelimitKeywords" value="true" />
        <!-- 生成的Java文件的编码 -->
        <property name="javaFileEncoding" value="utf-8" />
        <!-- beginningDelimiter和endingDelimiter：指明数据库的用于标记数据库对象名的符号，比如ORACLE就是双引号，MYSQL默认是`反引号； -->
        <property name="beginningDelimiter" value="`" />
        <property name="endingDelimiter" value="`" />

        <!-- 格式化java代码 -->
        <property name="javaFormatter" value="org.mybatis.generator.api.dom.DefaultJavaFormatter"/>
        <!-- 格式化XML代码 -->
        <property name="xmlFormatter" value="org.mybatis.generator.api.dom.DefaultXmlFormatter"/>
        <plugin type="org.mybatis.generator.plugins.SerializablePlugin" />

        <plugin type="org.mybatis.generator.plugins.ToStringPlugin" />

        <!-- 注释 -->
        <commentGenerator >
            <property name="suppressAllComments" value="false"/><!-- 是否取消注释 -->
            <property name="suppressDate" value="true" /> <!-- 是否生成注释代时间戳-->
        </commentGenerator>

        <!-- jdbc连接 -->
        <jdbcConnection driverClass="${spring.datasource.driver-class-name}" connectionURL="${spring.datasource.url}" userId="${spring.datasource.username}" password="${spring.datasource.password}" />
        <!-- 类型转换 -->
        <javaTypeResolver>
            <!-- 是否使用bigDecimal， false可自动转化以下类型（Long, Integer, Short, etc.） -->
            <property name="forceBigDecimals" value="false"/>
        </javaTypeResolver>

        <!-- 需要自行配置 ------------------------------------------------------------------------------------>
        <!-- 生成实体类地址 -->
        <javaModelGenerator targetPackage="com.springboot.entity" targetProject="${mybatis.project}" >
            <property name="enableSubPackages" value="false"/>
            <property name="trimStrings" value="true"/>
        </javaModelGenerator>
        <!-- 生成mapxml文件 -->
        <sqlMapGenerator targetPackage="mapper" targetProject="${mybatis.resources}" >
            <property name="enableSubPackages" value="false" />
        </sqlMapGenerator>
        <!-- 需要自行配置 ------------------------------------------------------------------------------------>
        <!-- 生成mapxml对应client，也就是接口dao -->
        <javaClientGenerator targetPackage="com.springboot.dao" targetProject="${mybatis.project}" type="XMLMAPPER" >
            <property name="enableSubPackages" value="false" />
        </javaClientGenerator>
        <!-- table可以有多个,每个数据库中的表都可以写一个table，tableName表示要匹配的数据库表,也可以在tableName属性中通过使用%通配符来匹配所有数据库表,只有匹配的表才会自动生成文件 -->
        <table tableName="user" enableCountByExample="true" enableUpdateByExample="true" enableDeleteByExample="true" enableSelectByExample="true" selectByExampleQueryId="true">
            <property name="useActualColumnNames" value="false" />
            <!-- 数据库表主键 -->
            <generatedKey column="id" sqlStatement="Mysql" identity="true" />
        </table>
    </context>
</generatorConfiguration>

3.Mybatis-Generator项目配置文件（项目配置文件就是写在默认配置文件里的）

#mapper xml位置
mybatis.mapper-locations=classpath*:mapper/*Mapper.xml

#数据库配置
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/test?characterEncoding=utf-8&useSSL=false&serverTimezone=GMT%2B8&allowPublicKeyRetrieval=true
spring.datasource.username=root
spring.datasource.password=123456abc

#mybatis generator配置
#dao类(或mapper类)和实体类位置
mybatis.project =src/main/java
#mapper文件位置
mybatis.resources=src/main/resources

4.运行生成

右键项目run as—>maven build:goal里输入mybatis-generator:generate  -e

PageHelper插件

1.引入PageHelper插件依赖

<!-- pagehelper插件 -->
        <dependency>
            <groupId>com.github.pagehelper</groupId>
            <artifactId>pagehelper-spring-boot-starter</artifactId>
            <version>1.2.12</version>
        </dependency>

2.在项目配置文件中配置

#pagehelper分页插件配置
pagehelper.helper-dialect=mysql

3.编写UserMapper类，加入方法

@Select("select * from user")
    List<User> getUserListPage();

4.编写Controller

//pageNum为页码，pageSize为每页的数量
    //http://localhost:8080/getUserListPage?pageNum=1&pageSize=2
    @GetMapping("/getUserListPage")
    public List<User> getUserListPage(Integer pageNum,Integer pageSize){
        PageHelper.startPage(pageNum, pageSize);
        return userMapper.getUserListPage();
    }

是不是非常简单，测试成功。

MyBatis-Plus插件

1.引入相关依赖

<dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatisplus-spring-boot-starter</artifactId>
            <version>1.0.5</version>
        </dependency>
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus</artifactId>
            <version>2.3</version>
        </dependency>

2.配置项目配置文件

#mybatis-plus mapper xml文件地址
mybatis-plus.mapper-locations=classpath*:mapper/*Mapper.xml
#mybatis-plus type-aliases文件地址
mybatis-plus.type-aliases-package=com.example.demo.pojo

3.MyBatis-Plus配置

@Configuration
public class MybatisPlusConfig {
    @Bean
    public PaginationInterceptor paginationInterceptor() {
        PaginationInterceptor page=new PaginationInterceptor();
        //设置方言类型
        page.setDialectType("mysql");
        return page;
    }
}

4.dao层需要继承MyBatis-Plus提供的BaseMapper

@Mapper
public interface UserMapper extends BaseMapper<User>{
    List<User> getUserList();
}

5.在mapper.xml里写出对应方法

<?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.demo.mapper.UserMapper">
    <resultMap id="user" type="com.example.demo.pojo.User"/>
    <parameterMap id="user" type="com.example.demo.pojo.User"/>
    <select id="getUserList" resultMap="user">
        SELECT  * FROM USER
    </select>
</mapper>

6.在写controller进行测试

MyBatis-Plus应该还有很多要学的东西，未完待续！