插件介绍
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。
项目结构
导入依赖
1
3
4 tk.mybatis
5 mapper-spring-boot-starter
6 2.1.5
7
8
10
11 com.github.pagehelper
12 pagehelper-spring-boot-starter
13 1.2.10
14
15
16
17 mysql
18 mysql-connector-java
19
20
21
22 org.springframework.boot
23 spring-boot-starter-web
24
属性配置
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=false
spring.datasource.username=root
spring.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*.xml
10
11 true
12
13
14
15
16 org.springframework.boot
17 spring-boot-maven-plugin
18
19
20
具体编码
1、表结构
创建一张 user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 @Id
16 @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 {
int countByUsername(String username);
}
4、映射文件UserMapper.xml
1 <?xml version="1.0" encoding="UTF-8" ?>
2
3
4
5
6 SELECT count(1) FROM user WHERE username = #{username}
7
8
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);
}
}
测试
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 @SpringBootTest
18 public class SpringbootMapperPagehelperApplicationTests {
19
20 private final Logger logger = LoggerFactory.getLogger(this.getClass());
21
22 @Autowired
23 private UserMapper userMapper;
24
25 @Test
26 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 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 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 }