1、数据库建表
# 创建用户表
CREATE TABLE user (
id BIGINT(20) PRIMARY KEY NOT NULL COMMENT '主键',
name VARCHAR(30) DEFAULT NULL COMMENT '姓名',
age INT(11) DEFAULT NULL COMMENT '年龄',
email VARCHAR(50) DEFAULT NULL COMMENT '邮箱',
manager_id BIGINT(20) DEFAULT NULL COMMENT '直属上级id',
create_time DATETIME DEFAULT NULL COMMENT '创建时间',
CONSTRAINT manager_fk FOREIGN KEY (manager_id)
REFERENCES user (id)
) ENGINE=INNODB CHARSET=UTF8;
# 初始化数据:
INSERT INTO user (id, name, age, email, manager_id
, create_time)
VALUES (1087982257332887553, '大boss', 40, '[email protected]', NULL
, '2019-01-11 14:20:20'),
(1088248166370832385, '王天风', 25, '[email protected]', 1087982257332887553
, '2019-02-05 11:12:22'),
(1088250446457389058, '李艺伟', 28, '[email protected]', 1088248166370832385
, '2019-02-14 08:31:16'),
(1094590409767661570, '张雨琪', 31, '[email protected]', 1088248166370832385
, '2019-01-14 09:15:15'),
(1094592041087729666, '刘红雨', 32, '[email protected]', 1088248166370832385
, '2019-01-14 09:48:16');
2、依赖
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-configuration-processor</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus-boot-starter</artifactId>
<version>3.1.2</version>
</dependency>
3、SpringBoot 配置文件
spring:
datasource:
driver-class-name: com.mysql.cj.jdbc.Driver
username: root
password: root
url: jdbc:mysql://localhost:3306/test?serverTimezone=CTT&useUnicode=true&characterEncoding=utf-8&allowMultiQueries=true
logging:
level:
root: warn
org.ywb.demo.dao: trace
pattern:
console: '%p%m%n'
4、创建相关包,如图
5、在pojo包中新建和数据库user表映射的类
@Data
public class User {
private Long id;
private String name;
private Integer age;
private String email;
private String managerId;
private LocalDateTime createTime;
}
6、在dao包中创建mapper接口,并集成mybatisPlus的BaseMapper
public interface UserMapper extends BaseMapper<User> {
}
7、在springboot启动类添加@MapperScan
扫描dao层接口
@MapperScan("org.ywb.demo.dao")
@SpringBootApplication
public class MybatisPlusDemoApplication {
public static void main(String[] args) {
SpringApplication.run(MybatisPlusDemoApplication.class, args);
}
}
8、编写测试类
@RunWith(SpringRunner.class)
@SpringBootTest
public class MybatisPlusDemoApplicationTests {
@Resource
private UserMapper userMapper;
@Test
public void select(){
List<User> users = userMapper.selectList(null);
users.forEach(System.out::println);
}
}
9、运行结果
新增方法
UserMapper代码
package com.neo.mapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.neo.model.User;
import org.apache.ibatis.annotations.Mapper;
//要使用mp,就要集成BaseMapper
@Mapper
public interface UserMapper extends BaseMapper<User> {
}
在测试方法中调用userMapper中的insert方法
@Test
public void insert(){
User user = new User();
user.setName("黄小明");
user.setAge(20);
user.setManagerId(1088248166370832385L);
user.setCreateTime(LocalDateTime.now());
int rows = userMapper.insert(user);
System.out.println("影响记录数:"+rows);
}
测试结果
DEBUG==> Preparing: INSERT INTO user ( id, name, age, manager_id, create_time ) VALUES ( ?, ?, ?, ?, ? ) DEBUG==> Parameters: 1223961279246393345(Long), 黄小明(String), 20(Integer), 1088248166370832385(Long), 2020-02-02T21:28:03.621(LocalDateTime) DEBUG<== Updates: 1 影响记录数:1
常用注解
MyBatisPlus提供了一些注解供我们在实体类和表信息出现不对应的时候使用。通过使用注解完成逻辑上匹配。
注解名称 | 说明 |
---|---|
@TableName |
实体类的类名和数据库表名不一致 |
@TableId |
实体类的主键名称和表中主键名称不一致 |
@TableField |
实体类中的成员名称和表中字段名称不一致 |
@TabName注解
当修改数据库表明却不想修改实体类型时,可以通过@TabName("数据库表名")来指定表名,否则会运行报错。
@Data
@TableName("mp_user")
public class User {
//主键
private Long id;
//姓名
private String name;
//年龄
private Integer age;
//邮箱
private String email;
//直属上级
private Long managerId;
//创建时间
private LocalDateTime createTime;
}
@TabId注解
当实例中主键与数据库中的主键名称不一致时(例如实例中为驼峰命名,数据库表中为下划线命名),可使用该注解。
@TableField注解
当实例中的字段与数据库中的字段不同时,就可以使用该注解映射,如下例
@TableField("name")
private String realName;
排除非表字段的三种方式
第一:在声明类属性时使用 transient 关键字声明。
第二:如上方法可能无法序列化该字段,故可以在声明类属性时:使用 static 关键字声明为静态变量(注意,用static 声明的静态变量lombok不会为其添加set和get方法)。
第三:使用@TableField(exist = false)注解注解 其中括号中的 exist = false 表示该字段不是数据库表中的字段,无需映射。
基本查询方法
通过id查询:selectById()方法
@Test
public void selectById() {
User user = userMapper.selectById(1094590409767661570L);
System.out.println(user);
}
批量查询:selectBatchIds()
@Test
public void selectByIds() {
List<Long> idsList = Arrays.asList(1094592041087729666L, 1223961279246393345L, 1088250446457389058L);
List<User> users = userMapper.selectBatchIds(idsList);
users.forEach(System.out::println);
}
通过map查询
@Test
public void selectByMap() {
Map<String,Object> columnMap = new HashMap<>();
columnMap.put("name","王天风");
columnMap.put("age",25);
//通过此map会执行类似 where name="王天风" and age=25 的sql
List<User> userList = userMapper.selectByMap(columnMap);
userList.forEach(System.out::println);
}
注意:此map中的键名为数据表中列名,并非实体类中的属性名
以条件构造器为参数的查询方法
/*
查询要求:
1、名字中包含雨并且年龄小于40
name like '%雨%' and age<40
*/
@Test
public void selectByWrapper() {
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
//等同于
//QueryWrapper<User> query = Wrappers.<User>query();
queryWrapper.like("name","雨").lt("age",40);
//注意:此处的键名依旧为数据库中的列名
List<User> userList = userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
/*
2、名字中包含雨年并且龄大于等于20且小于等于40并且email不为空
name like '%雨%' and age between 20 and 40 and email is not null
*/
@Test
public void selectByWrapper2() {
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
//等同于
//QueryWrapper<User> query = Wrappers.<User>query();
queryWrapper.like("name","雨").between("age",20,40).isNotNull("email");
//注意:此处的键名依旧为数据库中的列名
List<User> userList = userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
/*
3、名字为王姓或者年龄大于等于25,按照年龄降序排列,年龄相同按照id升序排列
name like '王%' or age>=25 order by age desc,id asc
*/
@Test
public void selectByWrapper3() {
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
//等同于
//QueryWrapper<User> query = Wrappers.<User>query();
queryWrapper.likeRight("name","王").or()
.ge("age",25).orderByDesc("age").orderByAsc("id");
//注意:此处的键名依旧为数据库中的列名
List<User> userList = userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
/*
4、创建日期为2019年2月14日并且直属上级为名字为王姓
date_format(create_time,'%Y-%m-%d')='2019-02-14' and manager_id in (select id from user where name like '王%')
*/
@Test
public void selectByWrapper4() {
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
//等同于
//QueryWrapper<User> query = Wrappers.<User>query();
queryWrapper.apply("date_format(create_time,'%Y-%m-%d')={0}","2019-02-14")
.inSql("manager_id","select id from user where name like '王%'");
//注意:此处的键名依旧为数据库中的列名
List<User> userList = userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
// 注意:以上方法查询为推荐查询,不建议写如下方式查询:会导致sql注入风险
//queryWrapper.apply("date_format(create_time,'%Y-%m-%d')="2019-02-14")
/*
5、名字为王姓并且(年龄小于40或邮箱不为空)
name like '王%' and (age<40 or email is not null)
*/
@Test
public void selectByWrapper5() {
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
//等同于
//QueryWrapper<User> query = Wrappers.<User>query();
queryWrapper.likeRight("name","王").
and(wq->wq.lt("age",40)
.or().isNotNull("email"));
//注意:此处的键名依旧为数据库中的列名
List<User> userList = userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
/*
6、名字为王姓或者(年龄小于40并且年龄大于20并且邮箱不为空)
name like '王%' or (age<40 and age>20 and email is not null)
*/
@Test
public void selectByWrapper6() {
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
//等同于
//QueryWrapper<User> query = Wrappers.<User>query();
queryWrapper.likeRight("name","王")
.or(wq->wq.lt("age",40).gt("age",20).isNotNull("email"));
//注意:此处的键名依旧为数据库中的列名
List<User> userList = userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
/*
7、(年龄小于40或邮箱不为空)并且名字为王姓
(age<40 or email is not null) and name like '王%'
*/
@Test
public void selectByWrapper7() {
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
//等同于
//QueryWrapper<User> query = Wrappers.<User>query();
queryWrapper.nested(wq->wq.lt("age",40).or().
isNotNull("email"))
.likeRight("name","王");
//注意:此处的键名依旧为数据库中的列名
List<User> userList = userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
/*
8、年龄为30、31、34、35
age in (30、31、34、35)
*/
@Test
public void selectByWrapper8() {
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
//等同于
//QueryWrapper<User> query = Wrappers.<User>query();
queryWrapper.in("age",Arrays.asList(30,31,34,35));
//注意:此处的键名依旧为数据库中的列名
List<User> userList = userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
/**
* 无视优化规则直接拼接到 sql 的最后(有sql注入的风险,请谨慎使用)
* <p>例: last("limit 1")</p>
* <p>注意只能调用一次,多次调用以最后一次为准</p>
*
* @param condition 执行条件
* @param lastSql sql语句
* @return children
*/
Children last(boolean condition, String lastSql);
/**
* 9. 只返回满足条件的一条语句即可
* limit 1
*/
@Test
public void selectWrapper7(){
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.in("age", Arrays.asList(30,31,34,35)).last("limit 1");
List<User> userList = userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
- last 有SQL注入的风险!!!
select中字段不全出现的处理方法
并非每次查询都要查询所有字段,测试可用如下方法查询
/*
10、名字中包含雨并且年龄小于40(需求1加强版)
第一种情况
select id,name
from user
where name like '%雨%' and age<40
*/
@Test
public void selectByWrapperSuper() {
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.select("id","name").like("name","雨").lt("age",40);
List<User> userList =userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
/*
第二种情况
select id,name,age,email
from user
where name like '%雨%' and age<40
*/
@Test
public void selectByWrapperSuper2() {
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.like("name","雨").lt("age",40)
.select(User.class,info->!info.getColumn().equals("create_time")
&&!info.getColumn().equals("manager_id"));
List<User> userList =userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
条件构造器中condition作用
@Test
public void testCondition() {
String name="王";
String email="";
condition(name,email);
}
public void condition(String name,String email){
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
// if(StringUtils.isNotEmpty(name)){
// queryWrapper.like("name",name);
// }
// if(StringUtils.isNotEmpty(email)){
// queryWrapper.like("email",email);
// }
// 以上代码过于臃肿,可采用如下代码代替
queryWrapper.like(StringUtils.isNotEmpty(name),"name",name)
.like(StringUtils.isNotEmpty(email),"email",email);
List<User> userList =userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
创建条件构造器时传入实体对象
如果想通过对象中某些属性进行模糊查询,我们可以在跟数据库表对应的实体类中相应的属性标注注解即可。
比如我们想通过姓名进行模糊查询用户列表。
@TableField(condition = SqlCondition.LIKE)
private String name;
@Test
public void selectWrapper10(){
User user = new User();
user.setName("红");
user.setAge(32);
QueryWrapper<User> queryWrapper = new QueryWrapper<>(user);
List<User> userList = userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
- 当然可以通过源码对照 SqlCondition 对应的作用
- 如果源码中没有找到想要的功能,还可以自定义,如图
条件构造器中allEq用法
/**
* allEq
*/
@Test
public void selectList_allEq() {
QueryWrapper<User> query = new QueryWrapper<>();
Map<String, Object> params = new HashMap<>();
params.put("name", "刘明强");
params.put("age", 31);
params.put("email", null);
// query.allEq(params,false);//第二个参数表示如果列值为null是否按IS NULL查询,false则忽略null列的查询
query.allEq((k, v) -> !k.equals("name"), params, false);//第一个参数是过滤器
List<User> list = userMapper.selectList(query);
list.forEach(System.out::println);
}
其他以条件构造器为参数的查询方法
/**
* selectMaps的应用场景1:当表中的列特别多,但实际只需要几个列时,这时返回一个实体类有些不必要
*/
@Test
public void selectMaps() {
QueryWrapper<User> query = new QueryWrapper<>();
query.like("name", "雨").lt("age", 40).select("name", "age");
List<Map<String, Object>> maps = userMapper.selectMaps(query);
maps.forEach(System.out::println);
}
/**
* selectMaps的应用场景2:查询统计结果
* 按照直属上级分组,查询每组的平均年龄、最大年龄、最小年龄,并且只取年龄总和小于100的组
* SELECT AVG(age) avg_age,MIN(age) min_age,MAX(age) max_age
* FROM `user`
* GROUP BY `manager_id`
* HAVING SUM(age)<100;
*/
@Test
public void selectMaps2() {
QueryWrapper<User> query = new QueryWrapper<>();
query.select("AVG(age) avg_age", "MIN(age) min_age", "MAX(age) max_age")
.groupBy("manager_id")
.having("SUM(age)<{0}", 100);
List<Map<String, Object>> maps = userMapper.selectMaps(query);
maps.forEach(System.out::println);
}
/**
* selectObjs只返回第一列,其它列被遗弃
* 应用场景:只需返回一列的时候
*/
@Test
public void selectObjs() {
QueryWrapper<User> query = new QueryWrapper<>();
query.like("name", "雨").lt("age", 40).select("name", "age");
List<Object> list = userMapper.selectObjs(query);
list.forEach(System.out::println);
}
/**
* 返回总记录数
*/
@Test
public void selectCount() {
QueryWrapper<User> query = new QueryWrapper<>();
query.like("name", "雨").lt("age", 40);
Integer count = userMapper.selectCount(query);
System.out.println("总记录数:" + count);
}
/**
* selectOne:只能查询一条记录,查询到多条会报错
*/
@Test
public void selectOne() {
QueryWrapper<User> query = new QueryWrapper<>();
query.like("name", "刘红雨").lt("age", 40);
User user = userMapper.selectOne(query);
System.out.println(user);
}
Lambda条件构造器
/**
* lambda条件构造器
*/
@Test
public void lambdaQueryWrapper1() {
// LambdaQueryWrapper<User> lambdaQ = new QueryWrapper<User>().lambda();
// LambdaQueryWrapper<User> lambdaQ = new LambdaQueryWrapper<>();
LambdaQueryWrapper<User> lambdaQ = Wrappers.<User>lambdaQuery();
lambdaQ.like(User::getName, "雨").lt(User::getAge, 40);
List<User> list = userMapper.selectList(lambdaQ);
list.forEach(System.out::println);
}
/**
* lambda条件构造器:防误写(例如列名"name"可能被误写)
*/
@Test
public void lambdaQueryWrapper2() {
LambdaQueryWrapper<User> query = new LambdaQueryWrapper<>();
query.likeRight(User::getName, "王")
.and(q -> q.lt(User::getAge, 40).or().isNotNull(User::getEmail));
List<User> list = userMapper.selectList(query);
list.forEach(System.out::println);
}
/**
* 链式lambda条件构造器:更优雅的书写方式
*/
@Test
public void lambdaQueryChainWrapper() {
List<User> list = new LambdaQueryChainWrapper<User>(userMapper)
.likeRight(User::getName, "王")
.and(
q -> q
.lt(User::getAge, 40)
.or()
.isNotNull(User::getEmail)
)
.list();
list.forEach(System.out::println);
}
使用条件构造器的自定义SQL
(要求版本大于等于3.0.7)
在UserMapper中定于接口方法(采用注解的方式)
@Select("select * from user ${ew.customSqlSegment}")
List<User> selectAll(@Param(Constants.WRAPPER)Wrapper<User> wrapper);
在测试中使用自定义方法
@Test
public void selectMy() {
// LambdaQueryWrapper<User> lambda = new QueryWrapper<User>().lambda();
// LambdaQueryWrapper<User> userLambdaQueryWrapper = new LambdaQueryWrapper<>();
LambdaQueryWrapper<User> lambdaQuery = Wrappers.<User>lambdaQuery();
lambdaQuery.like(User::getName,"雨").lt(User::getAge,40);
//where name like '%雨%'
List<User> userList = userMapper.selectAll(lambdaQuery);//此处使用自定义接口方法
userList.forEach(System.out::println);
}
如果不想把自定义sql写在接口中,例如写在xml中,还可以采用如下方法:
第一步:在yml配置文件中配置接口对应的xml路径
Mybatis-plus:
mapper-locations: classpath:mp/mapper/*.xml
在配置路径下新建UserMapper.xml文件,同时去除接口中的注解sql
<?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.neo.mapper.UserMapper" >
<select id="selectAll" resultType="com.neo.model.User">
select * from user ${ew.customSqlSegment}
</select>
</mapper>
mybatis中提供分页方法,但是该分页是逻辑分页,而非物理分页。
MP分页插件实现物理分页
新建配置包(com.neo.configuration)并新建配置分页类MybatisPlusConfig:
@Configuration
public class MybatisPlusConfig {
@Bean
public PaginationInterceptor paginationInterceptor() {
return new PaginationInterceptor();
}
}
测试(selectPage)
@Test
public void selectPage() {
QueryWrapper<User> queryWrapper = new QueryWrapper<User>();
queryWrapper.ge("age", 26);
Page<User> page = new Page<>(1, 2);
IPage<User> iPage = userMapper.selectPage(page, queryWrapper);
System.out.println("总页数:" + iPage.getPages());
System.out.println("总记录数:" + iPage.getTotal());
List<User> userlist = iPage.getRecords();
userlist.forEach(System.out::println);
}
运行日志:
DEBUG==> Preparing: SELECT COUNT(1) FROM user WHERE age >= ?
DEBUG==> Parameters: 26(Integer)
TRACE<== Columns: COUNT(1)
TRACE<== Row: 7
DEBUG==> Preparing: SELECT id,name,age,email,manager_id,create_time FROM user WHERE age >= ? LIMIT ?,?
DEBUG==> Parameters: 26(Integer), 0(Long), 2(Long)
TRACE<== Columns: id, name, age, email, manager_id, create_time
TRACE<== Row: 1087982257332887553, 大boss, 40, [email protected], null, 2019-01-11 14:20:20
TRACE<== Row: 1088250446457389058, 李艺伟, 28, [email protected], 1088248166370832385, 2019-02-14 08:31:16
DEBUG<== Total: 2
总页数:4
总记录数:7
User(id=1087982257332887553, name=大boss, age=40, [email protected], managerId=null, createTime=2019-01-11T14:20:20)
User(id=1088250446457389058, name=李艺伟, age=28, [email protected], managerId=1088248166370832385, createTime=2019-02-14T08:31:16)
测试(selectMapsPage)
@Test
public void selectPage() {
QueryWrapper<User> queryWrapper = new QueryWrapper<User>();
// queryWrapper.ge("age",26);
Page<User> page = new Page<>(1, 2);
// IPage<User> iPage = userMapper.selectPage(page, queryWrapper);
// System.out.println("总页数:"+ iPage.getPages());
// System.out.println("总记录数:"+ iPage.getTotal());
// List<User> userlist = iPage.getRecords();
IPage<Map<String, Object>> iPage = userMapper.selectMapsPage(page, queryWrapper);
System.out.println("总页数:"+ iPage.getPages());
System.out.println("总记录数:"+ iPage.getTotal());
List<Map<String, Object>> userlist = iPage.getRecords();
userlist.forEach(System.out::println);
}
DEBUG==> Preparing: SELECT COUNT(1) FROM user
DEBUG==> Parameters:
TRACE<== Columns: COUNT(1)
TRACE<== Row: 13
DEBUG==> Preparing: SELECT id,name,age,email,manager_id,create_time FROM user LIMIT ?,?
DEBUG==> Parameters: 0(Long), 2(Long)
TRACE<== Columns: id, name, age, email, manager_id, create_time
TRACE<== Row: 1087982257332887553, 大boss, 40, [email protected], null, 2019-01-11 14:20:20
TRACE<== Row: 1088248166370832385, 王天风, 25, [email protected], 1087982257332887553, 2019-02-05 11:12:22
DEBUG<== Total: 2
总页数:7
总记录数:13
{createTime=2019-01-11 14:20:20.0, name=大boss, id=1087982257332887553, age=40, [email protected]}
{createTime=2019-02-05 11:12:22.0, name=王天风, id=1088248166370832385, managerId=1087982257332887553, age=25, [email protected]}
从以上两个例子看以看出每个是执行了两条sql语句,如果只想要查询结果,不想要查询总数,只需要将page的第三个参数变为false,即可:
Page<User> page = new Page<>(1, 2,false);
- 当我们在做多表联查时,就不能使用如上方式查询了,此时可以在xml文件中自定义sql。
根据id更新
@Test
public void updateById(){
User user= new User();
user.setId(1088248166370832385L);
user.setAge(26);
user.setEmail("[email protected]");
int rows = userMapper.updateById(user);
System.out.println("影响记录数:"+ rows);
}
运行日志:
DEBUG==> Preparing: UPDATE user SET age=?, email=? WHERE id=?
DEBUG==> Parameters: 26(Integer), [email protected](String), 1088248166370832385(Long)
DEBUG<== Updates: 1
影响记录数:1
以条件构造器作为参数的更新方法
@Test
public void updateByWrapper(){
UpdateWrapper<User> updateWrapper = new UpdateWrapper<>();
updateWrapper.eq("name","李艺伟").eq("age",28);
User user = new User();
user.setEmail("[email protected]");
user.setAge(29);
int rows = userMapper.update(user, updateWrapper);
System.out.println("影响行数:"+rows
);
}
运行日志:
DEBUG==> Preparing: UPDATE user SET age=?, email=? WHERE name = ? AND age = ?
DEBUG==> Parameters: 29(Integer), [email protected](String), 李艺伟(String), 28(Integer)
DEBUG<== Updates: 1
影响行数:1
条件构造器中set方法使用
(只修改少量字段时)
@Test
public void updateByWrapper(){
UpdateWrapper<User> updateWrapper = new UpdateWrapper<>();
//通过条件构造器的链式编程设置更新信息
updateWrapper.eq("name","李艺伟").eq("age",29).set("email","[email protected]");
// User user = new User();
int rows = userMapper.update(null, updateWrapper);
System.out.println("影响行数:"+rows);
}
lambda条件构造器更新
@Test
public void updateByWrapperLambda(){
LambdaUpdateWrapper<User> lambdaUpdate = Wrappers.<User>lambdaUpdate();
lambdaUpdate.eq(User::getName,"李艺伟").eq(User::getAge,29).set(User::getAge,31);
int rows = userMapper.update(null, lambdaUpdate);
System.out.println("影响行数:"+rows);
}
根据id删除的方法
@Test
public void deleteById() {
int rows= userMapper.deleteById(1223976086888599553L);
System.out.println("影响行数:"+rows);
}
根据id批量删除
@Test
public void deleteBatchIds() {
int rows = userMapper.deleteBatchIds(
Arrays.asList(1223973741031141377L,
1223972327026405378L,1223970002606067714L));
System.out.println("影响行数:"+rows);
}
其他普通删除方法
@Test
public void deleteByMap() {
Map<String,Object> columnMap= new HashMap<>();
columnMap.put("name","向后");
columnMap.put("age","31");
int rows = userMapper.deleteByMap(columnMap);
System.out.println("影响行数:"+rows);
}
以条件构造器为参数的删除方法
AR模式(Active Record)
直接通过实体类完成对数据的增删改查。
实体类继承Model类
@Data
@EqualsAndHashCode(callSuper = false)
public class User extends Model<User> {
private Long id;
@TableField(condition = SqlCondition.LIKE)
private String name;
private Integer age;
private String email;
private Long managerId;
private LocalDateTime createTime;
}
Model类中封装了很多增删改查方法,不用使用UserMapper即可完成对数据的增删改查。
查询所有用户信息
@Test
public void test(){
User user = new User();
user.selectAll().forEach(System.out::println);
}
主键策略
MyBatisPlus的主键策略封装在IdType
枚举类中。
@Getter
public enum IdType {
/**
* 数据库ID自增
*/
AUTO(0),
/**
* 该类型为未设置主键类型(将跟随全局)
*/
NONE(1),
/**
* 用户输入ID
* <p>该类型可以通过自己注册自动填充插件进行填充</p>
*/
INPUT(2),
/* 以下3种类型、只有当插入对象ID 为空,才自动填充。 */
/**
* 全局唯一ID (idWorker)
*/
ID_WORKER(3),
/**
* 全局唯一ID (UUID)
*/
UUID(4),
/**
* 字符串全局唯一ID (idWorker 的字符串表示)
*/
ID_WORKER_STR(5);
private final int key;
IdType(int key) {
this.key = key;
}
}
在实体类中对应数据库中的主键id属性上标注注解TableId(type='xxx')
即可完成主键配置。
@TableId(type = IdType.AUTO)
private Long id;
这种配置方式的主键策略只能在该表中生效,但是其他表还需要进行配置,为了避免冗余,麻烦,MybatisPlus提供了全局配置,在配置文件中配置主键策略即可实现。
mybatis-plus:
mapper-locations: mapper/*.xml
global-config:
db-config:
id-type: auto
-
如果全局策略和局部策略全都设置,局部策略优先。
基本配置
mybatis-plus:
mapper-locations: mapper/*.xml
global-config:
db-config:
# 主键策略
id-type: auto
# 表名前缀
table-prefix: t
# 表名是否使用下划线间隔,默认:是
table-underline: true
# 添加mybatis配置文件路径
config-location: mybatis-config.xml
# 配置实体类包地址
type-aliases-package: org.ywb.demo.pojo
# 驼峰转下划线
configuration:
map-underscore-to-camel-case: true
- config-location & configuration 不能同时出现,否则报错。
通用Service
定义接口继承IService
public interface UserService extends IService<User>{}
定义接口的实现类
@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService{}