通用 Mapper 是一个可以实现任意 MyBatis 通用方法的框架，项目提供了常规的增删改查操作以及 Example 相关的单表操作。通用 Mapper 是为了解决 MyBatis 使用中 90% 的基本操作，PageHelper则提供通用的分页查询功能，使用它们可以很方便的进行开发，可以节省开发人员大量的时间。
通用Mapper的GIT地址： https://gitee.com/free/Mapper
分页插件的GIT地址： https://github.com/pagehelper/Mybatis-PageHelper
1 <!-- 通用Mapper插件 2 文档地址：https://gitee.com/free/Mapper/wikis/Home --> 3 <dependency> 4 <groupId>tk.mybatis</groupId> 5 <artifactId>mapper-spring-boot-starter</artifactId> 6 <version>2.1.5</version> 7 </dependency> 8 <!-- 分页插件 9 文档地址：https://github.com/pagehelper/Mybatis-PageHelper/blob/master/wikis/zh/HowToUse.md -->10 <dependency>11 <groupId>com.github.pagehelper</groupId>12 <artifactId>pagehelper-spring-boot-starter</artifactId>13 <version>1.2.10</version>14 </dependency>15 <!-- MYSQL包 -->16 <dependency>17 <groupId>mysql</groupId>18 <artifactId>mysql-connector-java</artifactId>19 </dependency>20 <!-- 默认就内嵌了Tomcat 容器，如需要更换容器也极其简单-->21 <dependency>22 <groupId>org.springframework.boot</groupId>23 <artifactId>spring-boot-starter-web</artifactId>24 </dependency> 在 application.properties 文件中分别添加上数据库、Mybatis、通用Mapper、PageHelper的属性配置
spring.datasource.url=jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=UTF-8&zeroDateTimeBehavior=convertToNull&allowMultiQueries=true&useSSL=falsespring.datasource.username=rootspring.datasource.password=123456# 如果想看到mybatis日志需要做如下配置logging.level.com.carry=DEBUG######### Mybatis 自身配置 ##########mybatis.mapper-locations=classpath:com/carry/mapper/*Mapper.xmlmybatis.type-aliases-package=com.carry.entity# 驼峰命名规范 如：数据库字段是 order_id 那么 实体字段就要写成 orderIdmybatis.configuration.map-underscore-to-camel-case=true
######### 通用Mapper ########### 主键自增回写方法,默认值MYSQL,详细说明请看文档mapper.identity=MYSQLmapper.mappers=tk.mybatis.mapper.common.Mapper# 设置 insert 和 update 中，是否判断字符串类型!=‘‘mapper.not-empty=true# 枚举按简单类型处理mapper.enum-as-simple-type=true######### 分页插件 ##########pagehelper.helper-dialect=mysqlpagehelper.params=count=countSqlpagehelper.reasonable=falsepagehelper.support-methods-arguments=true
由于 mybatis.mapper-locations=classpath:com/carry/mapper/*.xml配置的在java package中，而Spring Boot默认只打入java package -> *.java，所以我们需要给pom.xml文件添加如下内容
1 <build> 2 <resources> 3 <resource> 4 <directory>src/main/resources</directory> 5 </resource> 6 <resource> 7 <directory>src/main/java</directory> 8 <includes> 9 <include>**/*.xml</include>10 </includes>11 <filtering>true</filtering>12 </resource>13 </resources>14 <plugins>15 <plugin>16 <groupId>org.springframework.boot</groupId>17 <artifactId>spring-boot-maven-plugin</artifactId>18 </plugin>19 </plugins>20 </build>
1、表结构
创建一张 user表
1 2 3 4 5 6 | CREATE TABLE `user` ( `id` int(8) NOT NULL AUTO_INCREMENT COMMENT ‘主键自增‘, `username` varchar(50) NOT NULL COMMENT ‘用户名‘, `password` varchar(50) NOT NULL COMMENT ‘密码‘, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT=‘用户表‘; |
2、实体类
1 package com.carry.entity; 2 3 import java.io.Serializable; 4 5 import javax.persistence.GeneratedValue; 6 import javax.persistence.GenerationType; 7 import javax.persistence.Id; 8 import javax.persistence.Table; 9 10 @Table(name = "user")11 public class User implements Serializable {12 13 private static final long serialVersionUID = -8057591359892731452L;14 15 @Id16 @GeneratedValue(strategy = GenerationType.IDENTITY)17 private Long id;18 private String username;19 private String password;20 public Long getId() {21 return id;22 }23 public void setId(Long id) {24 this.id = id;25 }26 public String getUsername() {27 return username;28 }29 public void setUsername(String username) {30 this.username = username;31 }32 public String getPassword() {33 return password;34 }35 public void setPassword(String password) {36 this.password = password;37 }38 39 40 public User() {}41 public User(String username, String password) {42 super();43 this.username = username;44 this.password = password;45 }46 } 3、持久层
package com.carry.mapper;import com.carry.entity.User;import tk.mybatis.mapper.common.Mapper;
public interface UserMapper extends Mapper<User> {
/**
* 根据用户名统计（假设它是一个很复杂的SQL）
* @param username 用户名
* @return 统计结果
*/
int countByUsername(String username);
} 4、映射文件UserMapper.xml
1 <?xml version="1.0" encoding="UTF-8" ?>2 <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >3 <mapper namespace="com.carry.mapper.UserMapper">4 5 <select id="countByUsername" resultType="java.lang.Integer">6 SELECT count(1) FROM user WHERE username = #{username}7 </select>8 </mapper> 5、启动类
import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import tk.mybatis.spring.annotation.MapperScan;@SpringBootApplication@MapperScan(basePackages = "com.carry.mapper")public class SpringbootMapperPagehelperApplication { public static void main(String[] args) {
SpringApplication.run(SpringbootMapperPagehelperApplication.class, args); } }
完成数据访问层接口后，编写一个junit测试类来检验代码的正确性。
1 package com.carry; 2 3 import org.junit.Test; 4 import org.junit.runner.RunWith; 5 import org.slf4j.Logger; 6 import org.slf4j.LoggerFactory; 7 import org.springframework.beans.factory.annotation.Autowired; 8 import org.springframework.boot.test.context.SpringBootTest; 9 import org.springframework.test.context.junit4.SpringRunner;10 11 import com.carry.entity.User;12 import com.carry.mapper.UserMapper;13 import com.github.pagehelper.PageHelper;14 import com.github.pagehelper.PageInfo;15 16 @RunWith(SpringRunner.class)17 @SpringBootTest18 public class SpringbootMapperPagehelperApplicationTests {19 20 private final Logger logger = LoggerFactory.getLogger(this.getClass());21 22 @Autowired23 private UserMapper userMapper;24 25 @Test26 public void test() {27 try {28 final User user1 = new User("u1", "p1");29 final User user2 = new User("u1", "p2");30 final User user3 = new User("u3", "p3");31 userMapper.insertSelective(user1);32 logger.info("[user1回写主键] - [{}]", user1.getId());33 userMapper.insertSelective(user2);34 logger.info("[user2回写主键] - [{}]", user2.getId());35 userMapper.insertSelective(user3);36 logger.info("[user3回写主键] - [{}]", user3.getId());37 final int count = userMapper.countByUsername("u1");38 logger.info("[调用自己写的SQL] - [{}]", count);39 40 // TODO 模拟分页41 for (int i = 0; i < 20; i++) {42 userMapper.insertSelective(new User("u" + i, "p" + i));43 }44 // TODO 分页 + 排序 this.userMapper.selectAll() 这一句就是我们需要写的查询，有了这两款插件无缝切换各种数据库45 final PageInfo<User> pageInfo = PageHelper.startPage(1, 10).setOrderBy("id desc")46 .doSelectPageInfo(() -> this.userMapper.selectAll());47 logger.info("[lambda写法] - [分页信息] - [{}]", pageInfo.toString());48 49 PageHelper.startPage(1, 10).setOrderBy("id desc");50 final PageInfo<User> userPageInfo = new PageInfo<>(this.userMapper.selectAll());51 logger.info("[普通写法] - [{}]", userPageInfo);52 } catch (Exception e) {53 logger.error(e.getMessage());54 }55 }56 57 }
