【Springboot】mybatis进阶操作
动态sql
动态SQL是Mybatis的强⼤特性之⼀，能够完成不同条件下不同的sql拼接。根据需求，动态拼接sql.
1.增加
根据用户的输入情况，进行插入。
-- 全部输入
insert into userinfo(username,password,age,gender,phone) values (?,?,?,?,?);
-- 如果性别为空
insert into userinfo(username,password,age,phone) values (?,?,?,?);
-- 如果年龄为空
insert into userinfo(username,password,age,phone) values (?,?,?,?);
if 标签
在xml文件中使用：
DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.example.mybatisdemo.mapper.User2Mapper">
<insert id="insertByXML" useGeneratedKeys="true" keyProperty="id">
insert into userinfo(
<if test="username != null">
username,
if>
<if test="password != null">
password,
if>
<if test="age != null">
age,
if>
<if test="gender != null">
gender,
if>
<if test="phone != null">
phone
if>
)
values (
<if test="username != null">
#{username},
if>
<if test="password != null">
#{password},
if>
<if test="age != null">
#{age},
if>
<if test="gender != null">
#{gender},
if>
<if test="phone != null">
#{phone}
if>
);
insert>
mapper>
实体层代码：
@Mapper
public interface User2Mapper {
Integer insertByXML(UserInfo userInfo);
}
在注解中实现：
1.把全部的sql放在script标签下
2.使用if标签
@Insert("")
Integer insert(UserInfo userInfo);
script标签中和xml中的内容是一样的。xml更加易读，书写有提示。
如果自由选择mybatis实现方式：
- 简单SQL 使用注解
- 动态SQL 使用xml
trim标签
trim标签帮我们去除多余的字符。比如上面如果phone为null,那么后面多余的逗号是没有办法处理的。我们解决方案就是使用trim标签。
<?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.mybatisdemo.mapper.User2Mapper">
<insert id="insertByXML" useGeneratedKeys="true" keyProperty="id">
insert into userinfo
<trim suffixOverrides="," prefix="(" suffix=")">
<if test="username != null">
username,
</if>
<if test="password != null">
password,
</if>
<if test="age != null">
age,
</if>
<if test="gender != null">
gender,
</if>
<if test="phone != null">
phone
</if>
</trim>
values
<trim suffixOverrides="," prefix="(" suffix=")">
<if test="username != null">
#{username},
</if>
<if test="password != null">
#{password},
</if>
<if test="age != null">
#{age},
</if>
<if test="gender != null">
#{gender},
</if>
<if test="phone != null">
#{phone}
</if>
</trim>
</insert>
</mapper>
prefixOverrides：去除trim标签代码块最前面指定的字符
prefix：在trim标签代码块最前面添加指定的字符
suffix：在trim标签代码块最后面添加指定的字符
suffixOverrides：去除trim标签代码块最后面指定的字符
2.查询
List select(UserInfo userInfo);
如果使用trim+if标签处理没有任何参数的时候，需要加上条件1=1.
<select id="select" resultType="com.example.mybatisdemo.entity.UserInfo">
select * from userinfo
where 1=1
<trim prefixOverrides="and">
<if test="username!=null">
and username = #{username}
</if>
<if test="age!=null">
and age = #{age}
</if>
<if test="gender!=null">
and gender = #{gender}
</if>
</trim>
</select>
除此之外也可以使用where标签
where标签
<select id="select" resultType="com.example.mybatisdemo.entity.UserInfo">
select * from userinfo
<where>
<if test="username!=null">
username = #{username}
if>
<if test="age!=null">
and age = #{age}
if>
<if test="gender!=null">
and gender = #{gender}
if>
where>
select>
3.修改
Integer update(UserInfo userInfo);
xml文件中使用trim + if代码：
<update id="update">
update userinfo set
<trim suffixOverrides=",">
<if test="username != null">
username = #{username},
if>
<if test="password != null">
password = #{password},
if>
<if test="gender != null">
gender = #{gender}
if>
trim>
where id = #{id}
update>
set标签
<update id="update">
update userinfo
<set>
<if test="username!=null">
username = #{username},
if>
<if test="password!=null">
password = #{password},
if>
<if test="gender!=null">
gender = #{gender}
if>
set>
where id = #{id}
update>
测试代码：
@Test
void update() {
UserInfo userInfo = new UserInfo();
userInfo.setId(5);
userInfo.setPassword("12123456");
user2Mapper.update(userInfo);
}
4.删除
foreach标签
属性：
- collection：绑定⽅法参数中的集合，如List，Set，Map或数组对象
- item：遍历时的每⼀个对象
- open：语句块开头的字符串
- close：语句块结束的字符串
- separator：每次遍历之间间隔的字符串
Integer batchDelete(List<Integer> ids);
xml文件中的代码：
<delete id="batchDelete">
delete from userinfo
where id in
<foreach collection="ids" separator="," item="id" open="(" close=")">
#{id}
foreach>
delete>
sql和include标签
把一些重复的sql可以提取出来,使用标签来标识，使用时,使用标签。
比如：
<sql id="selectTable">
select * from userinfo
sql>
<select id="select" resultType="com.example.mybatisdemo.entity.UserInfo">
<include refid="selectTable">include>
where 1=1
<trim prefixOverrides="and">
<if test="username!=null">
and username = #{username}
if>
<if test="age!=null">
and age = #{age}
if>
<if test="gender!=null">
and gender = #{gender}
if>
trim>
select>
<select id="select2" resultType="com.example.mybatisdemo.entity.UserInfo">
<include refid="selectTable">include>
<where>
<if test="username!=null">
username = #{username}
if>
<if test="age!=null">
and age = #{age}
if>
<if test="gender!=null">
and gender = #{gender}
if>
where>
select>
mybatis练习–表白墙
添加依赖：
<dependency>
<groupId>org.mybatis.spring.bootgroupId>
<artifactId>mybatis-spring-boot-starterartifactId>
<version>3.0.3version>
dependency>
<dependency>
<groupId>com.mysqlgroupId>
<artifactId>mysql-connector-jartifactId>
<scope>runtimescope>
dependency>
yml配置文件
spring:
datasource:
url: jdbc:mysql://127.0.0.1:3306/messagewall?characterEncoding=utf8&useSSL=false
username: root
password: abc123
mybatis:
configuration: # 配置打印 MyBatis日志
log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
map-underscore-to-camel-case: true #配置驼峰自动转换
# 配置 mybatis xml 的文件路径，在 resources/mapper 创建所有表的 xml 文件
mapper-locations: classpath:mapper/**Mapper.xml
数据库设计：
-- 创建数据库
CREATE DATABASE IF NOT EXISTS messagewall CHARSET utf8;
USE messagewall;
-- 创建表
DROP TABLE IF EXISTS
CREATE TABLE message_info(
id INT PRIMARY KEY AUTO_INCREMENT,
`from` VARCHAR(127) NOT NULL,
`to` VARCHAR(127) NOT NULL,
`message` VARCHAR(127) NOT NULL,
`delete_flag` TINYINT(4) DEFAULT 0, # 0正常，1删除
create_time DATETIME DEFAULT NOW(),
update_time DATETIME DEFAULT NOW()
);
实体类改变：
@Data
public class MessageInfo {
private Integer id;
private String from;
private String to;
private String message;
private String deleteFlag;
private Date createTime;
private Date updateTime;
}
实体层代码：
@Mapper
public interface MessageMapper {
@Insert("insert into message_info (`from`,`to`,`message`) values (#{from},#{to},#{message})")
public Integer insertMessage(MessageInfo messageInfo);
@Select("select * from message_info")
public List selectAllMessage();
}
service层代码：
@Service
public class MessageService {
@Autowired
MessageMapper messageMapper;
public Integer add(MessageInfo messageInfo){
Integer result = messageMapper.insertMessage(messageInfo);
return result;
}
public List getAllMessage(){
return messageMapper.selectAllMessage();
}
}
controller层代码：
@RestController
@RequestMapping("/message")
public class MessageController {
@Autowired
private MessageService messageService;
@RequestMapping("/publish")
public boolean publishMessage(@RequestBody MessageInfo messageInfo){
System.out.println(messageInfo);
if (!StringUtils.hasLength(messageInfo.getFrom()) ||
!StringUtils.hasLength(messageInfo.getTo()) ||
!StringUtils.hasLength(messageInfo.getMessage())){
return false;
}
messageService.add(messageInfo);
return true;
}
@RequestMapping("/getMessageList")
public List getMessageList(){
return messageService.getAllMessage();
}
}
前端代码和springMVC中一样，不需要进行改变。