建手机网站公司,网站建设公司郴州,网站建设各模块功能简述,百度热搜榜第一MP入门
Mybatis-Plus#xff08;简称MP#xff09;是一个Mybatis的增强工具#xff0c;在Mybatis的基础上只做增强不做改变#xff0c;为简化开发、提高效率而生。
Mybatis-Plus已经封装好了大量增删改查的方法#xff0c;程序员只需要继承BaseMapper就可以使用这些方法…MP入门
Mybatis-Plus简称MP是一个Mybatis的增强工具在Mybatis的基础上只做增强不做改变为简化开发、提高效率而生。
Mybatis-Plus已经封装好了大量增删改查的方法程序员只需要继承BaseMapper就可以使用这些方法了无需自己再开发。
官网地址https://baomidou.com/
案例实现 向数据库保存一个User对象 创建数据表
create table tb_user (id bigint(20) primary key auto_increment,username varchar(30) unique not null,name varchar(30) not null,password varchar(32) not null,age int(3) not null ,tel varchar(32) not null,create_time datetime,update_time datetime
);
insert into tb_user values(1,heima1,tom,123456,12,12345678911,now(),now());
insert into tb_user values(2,heima2,jack,123456,8,12345678912,now(),now());
insert into tb_user values(3,heima3,jerry,123456,15,12345678910,now(),now());
insert into tb_user values(4,heima4,tom,123456,9,12345678910,now(),now());
insert into tb_user values(5,heima5,snake,123456,28,12345678910,now(),now());
insert into tb_user values(6,heima6,张益达,123456,22,12345678910,now(),now());
insert into tb_user values(7,heima7,张大炮,123456,16,12345678910,now(),now());创建工程 parentgroupIdorg.springframework.boot/groupIdartifactIdspring-boot-starter-parent/artifactIdversion2.7.3/version/parentdependencies!--mysql驱动--dependencygroupIdmysql/groupIdartifactIdmysql-connector-java/artifactId/dependency!--连接池--dependencygroupIdcom.alibaba/groupIdartifactIddruid-spring-boot-starter/artifactIdversion1.2.3/version/dependency!--mybatis plus依赖--dependencygroupIdcom.baomidou/groupIdartifactIdmybatis-plus-boot-starter/artifactIdversion3.4.1/version/dependency!--lombok简化对象书写--dependencygroupIdorg.projectlombok/groupIdartifactIdlombok/artifactId/dependency!--hutool工具包--dependencygroupIdcn.hutool/groupIdartifactIdhutool-all/artifactIdversion5.7.20/version/dependency!--整合测试--dependencygroupIdorg.springframework.boot/groupIdartifactIdspring-boot-starter-test/artifactId/dependency!--web环境依赖--dependencygroupIdorg.springframework.boot/groupIdartifactIdspring-boot-starter-web/artifactId/dependency/dependencies创建实体类
package com.itheima.domain;import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;
import java.time.LocalDateTime;Builder
Data
NoArgsConstructor
AllArgsConstructor
public class User {private Long id;private String username;private String name;private String password;private Integer age;private String tel;private LocalDateTime createTime;private LocalDateTime updateTime;
}创建接口 自定义的Mapper接口需要实现BaseMapper实体类,然后就可以继承到BaseMapper中定义的方法了 package com.itheima.mapper;import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.itheima.domain.User;
import org.apache.ibatis.annotations.Mapper;Mapper
public interface UserMapper extends BaseMapperUser {//声明方法注解实现sql}添加配置文件 在resources中添加配置文件application.yml然后在里面加入下面配置 spring:datasource:driver-class-name: com.mysql.cj.jdbc.Driverurl: jdbc:mysql://localhost:3306/mpusername: rootpassword: root# druid 阿里 HkariCp(springBoot)type: com.alibaba.druid.pool.DruidDataSourcemybatis-plus:configuration:log-impl: org.apache.ibatis.logging.stdout.StdOutImpl # 日志打印map-underscore-to-camel-case: true # 驼峰映射创建启动类
package com.itheima;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;SpringBootApplication
public class MpApplication {public static void main(String[] args) {SpringApplication.run(MpApplication.class,args);}
}测试
package com.itheima.test;import com.itheima.domain.User;
import com.itheima.mapper.UserMapper;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;SpringBootTest
public class UserMapperTest {Autowiredprivate UserMapper userMapper;Testpublic void testInsert() {//1. 封装user对象User user User.builder().username(baima1).name(tom).password(123456).age(18).tel(13700137001).build();//2. 调用mapper方法userMapper.insert(user);}
}案例细节
TableName 标注在实体类上用于声明实体类对应的表如果表名和类名一致可以省略 //标注在实体类上用于声明实体类对应的表如果表名和类名一致可以省略
TableName(tb_user)
public class User {....
}如果大部分表都是以固定前缀开头可以全局配置表前缀但优先级比注解配置低 mybatis-plus:global-config:db-config:table-prefix: tb_ #表前缀TableId 标注在主键字段上用于声明主键生成策略 //主键生成策略//AUTO : 数据库的自增//INPUT: 让用户自己输入主键//ASSIGN_ID: 雪花算法生成的一个纯数字//ASSIGN_UUID: UUID生成一个不重复字符串//ASSIGN_NONE: INPUTASSIGN_IDTableId(type IdType.AUTO)private Long id;值描述AUTO数据库主键自增INPUT手动设置主键值ASSIGN_ID由雪花算法生成的纯数字ASSIGN_UUIDUUID生成的字符串NONE默认值相当于INPUTASSIGN_ID 如果大部分表主键都是自增可以进行全局设置但优先级比注解配置低 mybatis-plus:global-config:db-config:id-type: auto #主键策略table-prefix: tbl_ #表前缀Mapper接口 BaseMapper通用 CRUD 接口内部声明了大量的单表操作方法泛型 T 为任意实体对象 Mapper
public interface ProductMapper extends BaseMapperProduct {}基本使用 MybatisPlus提供了单表的增删改查方法常用的如下 // 插入一条记录
int insert(T entity);// 主键查询
T selectById(Serializable id);
// 主键批量查询
ListT selectBatchIds(Collection idList); // 根据ID修改不为空的字段
int updateById(T entity);// 根据ID删除
int deleteById(Serializable id);// 根据ID集合批量删除
int deleteBatchIds(Collection idList);package com.itheima.test;import cn.hutool.core.collection.ListUtil;
import com.itheima.domain.User;
import com.itheima.mapper.UserMapper;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;import java.util.ArrayList;
import java.util.List;SpringBootTest
public class UserMapperTest {Autowiredprivate UserMapper userMapper;//插入一条记录//int insert(T entity);Testpublic void testInsert() {//1. 封装user对象User user User.builder().username(baima1).name(tom).password(123456).age(18).tel(13700137001).build();//2. 调用mapper方法userMapper.insert(user);}//主键查询//T selectById(Serializable id);Testpublic void testSelectById() {User user userMapper.selectById(1L);System.out.println(user);}//主键批量查询//ListT selectBatchIds(Collection idList);Testpublic void testSelectBatchIds() {//1. 构建id集合ListLong idList ListUtil.of(1L, 2L, 3L);//2. 执行查询ListUser userList userMapper.selectBatchIds(idList);System.out.println(userList);}//根据ID修改不为空的字段//int updateById(T entity);Testpublic void testUpdateById() {//1. 封装user对象User user User.builder().username(baima2).name(tom2).tel(13700137002).id(2L)//不要忘记设置id.build();userMapper.updateById(user);}//根据ID删除//int deleteById(Serializable id);Testpublic void testDeleteById() {userMapper.deleteById(7L);}//根据ID集合批量删除//int deleteBatchIds(Collection idList);Testpublic void testDeleteBatchIds() {ListLong idList ListUtil.of(1L, 2L, 3L);userMapper.deleteBatchIds(idList);}
}条件查询 MybatisPlus提供了Wrapper对象来封装各种条件比如条件、分页、排序、分组、过滤等等 // 条件查询当查询结果最多为一条记录时使用 手机号 身份证号 用户名 唯一约束
T selectOne(WrapperT queryWrapper);// 条件查询当查询结果可能为多条记录时使用
ListT selectList(WrapperT queryWrapper);书写格式 MybatisPlus支持使用多种格式组装条件我们推荐使用Lambda格式 package com.itheima.test;import cn.hutool.core.util.StrUtil;
import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.itheima.domain.User;
import com.itheima.mapper.UserMapper;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;import java.util.List;SpringBootTest
public class UserMapperTest2 {Autowiredprivate UserMapper userMapper;//根据name白马1和age18查询(支持动态sql)Testpublic void testSelectList1() {//0. 模仿前端传入参数String name null;Integer age 18;//1. 构建查询条件QueryWrapperUser wrapper new QueryWrapper();if (StrUtil.isNotEmpty(name)) {wrapper.eq(name, name); //where name 白马}if (age ! null) {wrapper.gt(age, age);//and age 18}//2. 查询ListUser userList userMapper.selectList(wrapper);userList.forEach(System.out::println);}//Lambda 根据name白马1和age18查询(支持动态sql)Testpublic void testSelectList2() {//0. 模仿前端传入参数String name 白马;Integer age 18;//1. 构建查询条件LambdaQueryWrapperUser wrapper new LambdaQueryWrapper();//参数1位置是一个boolean值,只有这个值为true,当前条件才会生效wrapper.eq(StrUtil.isNotEmpty(name), User::getName, name);//where name 白马wrapper.gt(age ! null, User::getAge, age);//and age 18//2. 查询ListUser userList userMapper.selectList(wrapper);userList.forEach(System.out::println);}//Lambda链式 根据name白马1和age18查询(支持动态sql)Testpublic void testSelectList3() {//0. 模仿前端传入参数String name 白马;Integer age 18;//1. 构建查询条件LambdaQueryWrapperUser wrapper new LambdaQueryWrapper();//参数1位置是一个boolean值,只有这个值为true,当前条件才会生效wrapper.eq(StrUtil.isNotEmpty(name), User::getName, name)//where name 白马.gt(age ! null, User::getAge, age);//and age 18//2. 查询ListUser userList userMapper.selectList(wrapper);userList.forEach(System.out::println);}
}查询条件
查询方法说明例子eq、ne、gt、ge、lt、le、isNull、isNotNull比较运算eq(“name”, “老王”)---name ‘老王’like、notLike、likeLeft、likeRight模糊查询likeRight(“name”, “王”)---name like ‘王%’in、notIn、between、notBetween范围运算in(“age”,{1,2,3})---age in (1,2,3)or、and拼接eq(“id”,1).or().eq(“name”,“老王”)---id 1 or name ‘老王’ //select * from tb_user where//id 1//and username baima//and name like %马//and age between 10 and 30//or tel in (1370013001,1370013002)Testpublic void testSelectList4() {//0. 模仿前端传入参数String name 白马;Integer age 18;//1. 构建查询条件LambdaQueryWrapperUser wrapper new LambdaQueryWrapper();wrapper.ge(User::getId,1).eq(User::getUsername,baima).likeLeft(User::getName,马).between(User::getAge,10,30).or().in(User::getTel,List.of(1370013001,1370013002));//2. 查询ListUser userList userMapper.selectList(wrapper);userList.forEach(System.out::println);}其他条件 除了设置查询条件外MP还支持投影、排序、分组、过滤等功能 查询方法说明例子select投影select(“name”,“password”)---select name,password from 表orderByAsc、orderByDesc排序orderByDesc(“id”, “name”)---order by id DESC,name DESCgroupBy分组groupBy(“id”, “name”)---group by id,namehaving过滤having(“sum(age) 10”)---having sum(age) 10
package com.itheima.test;import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.itheima.domain.User;
import com.itheima.mapper.UserMapper;
import com.itheima.vo.Re;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;import java.util.List;
import java.util.Map;SpringBootTest
public class UserMapperTest2 {Autowiredprivate UserMapper userMapper;//投影和排序//select name,age from tb_user where id 1 order by age descTestpublic void testSelectList1() {//1. 构建查询条件LambdaQueryWrapperUser wrapper new LambdaQueryWrapper();wrapper.gt(User::getId,1);//id 1wrapper.select(User::getName,User::getAge);//select name,agewrapper.orderByDesc(User::getAge);//order by age descwrapper.orderByAsc(User::getId);//order by id asc//2. 查询ListUser userList userMapper.selectList(wrapper);userList.forEach(System.out::println);}//分组和过滤//select age,count(*) from tb_user group by age having count(*) 2Testpublic void testSelectList2() {//1. 构建查询条件(LambdaQueryWrapper不支持分组和过滤)QueryWrapperUser wrapper new QueryWrapper();wrapper.select(age,count(*));//select age,count(*)wrapper.groupBy(age);//group by agewrapper.having(count(*) 2);//having count(*) 2//2. 查询ListMapString, Object list userMapper.selectMaps(wrapper);list.forEach(System.out::println);}//分组和过滤//select age,count(*) from tb_user group by age having count(*) 2Testpublic void testSelectList3() {ListMapString, Object list userMapper.count1();list.forEach(System.out::println);}Testpublic void testSelectList4() {ListRe list userMapper.count2();list.forEach(System.out::println);}
}UserMapper
package com.itheima.mapper;import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.itheima.domain.User;
import com.itheima.vo.Re;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Select;import java.util.List;
import java.util.Map;//自定义的Mapper 要求继承BaseMapper实体类类型
Mapper
public interface UserMapper extends BaseMapperUser {//自定义Select(select age,count(*) from tb_user group by age having count(*) 2)ListMapString, Object count1();Select(select age,count(*) as num from tb_user group by age having num 2)ListRe count2();
}Re
package com.itheima.vo;import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;NoArgsConstructor
AllArgsConstructor
Data
public class Re {private String age;private Integer num;
}
分页查询 MybatisPlus内置了专门用于分页的插件使用起来非常简单它是基于拦截器原理实现分页的 ① 配置拦截器
package com.itheima.config;import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;Configuration
public class MybatisPlusConfig {Beanpublic MybatisPlusInterceptor mybatisPlusInterceptor(){//1 创建MybatisPlusInterceptor拦截器对象MybatisPlusInterceptor mpInterceptornew MybatisPlusInterceptor();//2 添加分页拦截器mpInterceptor.addInnerInterceptor(new PaginationInnerInterceptor());return mpInterceptor;}
}② 分页代码实现 //分页查询//select * from tb_user where id 1 limit 5,7Testpublic void testPage() {//1. 设置分页条件 当前页面 每页条数PageUser page new Page(2, 3);//2. 设置业务条件LambdaQueryWrapperUser wrapper new LambdaQueryWrapper();wrapper.eq(User::getAge, 18);//3. 调用分页方法page userMapper.selectPage(page, wrapper);//4. 获取分页结果System.out.println(总条数: page.getTotal());System.out.println(总页数: page.getPages());System.out.println(当前页数据集合: page.getRecords());}条件修改 // 参数1: 封装要修改的字段 参数2: 封装更新条件
int update(T entity,WrapperT updateWrapper);package com.itheima.test;import com.baomidou.mybatisplus.core.conditions.update.LambdaUpdateWrapper;
import com.itheima.domain.User;
import com.itheima.mapper.UserMapper;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;SpringBootTest
public class UserMapperTest4 {Autowiredprivate UserMapper userMapper;//条件更新//update tb_user set age 10,password 123123 where name tomTestpublic void testUpdate() {//1. 设置更新条件LambdaUpdateWrapperUser wrapper new LambdaUpdateWrapper();wrapper.eq(User::getName, tom);//2. 设置更新字段User user User.builder().age(10).password(123123).build();//3. 执行更新userMapper.update(user, wrapper);}
}条件删除 // 条件删除
int delete(WrapperT wrapper);//条件删除//delete from tb_user where name tom;Testpublic void testDelete() {//1. 设置删除条件LambdaQueryWrapperUser wrapper new LambdaQueryWrapper();wrapper.eq(User::getName, tom);//2. 执行删除userMapper.delete(wrapper);}实用功能
逻辑删除 逻辑删除指的是当执行删除操作时并不是将对应记录真正从数据库删掉而是使用一个标识列将要删除的数据标识为删除状态 MP使用TableLogic就可以轻松实现这个功能 ①在user表中添加逻辑删除标记字段并设置默认值为0 ②实体类中添加对应字段设定为当前字段为逻辑删除标记字段 //逻辑删除字段value用于指定未删除状态的值, delval用于指定删除状态的值TableLogic(value 0, delval 1)private Integer deleted;③ 删除其中一个用户观察效果 TableLogic 只是单个表设置逻辑删除字段如果多张表都需要配置逻辑删除则可以做全局配置 mybatis-plus:global-config:db-config:logic-delete-field: deleted # 全局逻辑删除的实体字段名logic-delete-value: 1 # 逻辑已删除值(默认为 1)logic-not-delete-value: 0 # 逻辑未删除值(默认为 0)自动填充 对于数据表中的一些公共字段我们可以使用mybatisplus的自动填充功能来统一设置值 TableField注解的fill属性可以完成这个功能 [1. 什么时候填充 2. 填充什么值] ① 在实体类的字段上添加注解
TableField(fill FieldFill.INSERT)
private LocalDateTime createTime;TableField(fill FieldFill.INSERT_UPDATE)
private LocalDateTime updateTime;值描述INSERT插入时填充字段UPDATE更新时填充字段INSERT_UPDATE插入和更新时填充字段
② 在配置类中设置要填充的值
package com.itheima.config;import com.baomidou.mybatisplus.core.handlers.MetaObjectHandler;
import lombok.extern.slf4j.Slf4j;
import org.apache.ibatis.reflection.MetaObject;
import org.springframework.stereotype.Component;import java.time.LocalDateTime;Slf4j
Component
public class MyMetaObjectHandler implements MetaObjectHandler {//新增时执行此方法Overridepublic void insertFill(MetaObject metaObject) {log.info(start insert fill ....);this.strictInsertFill(metaObject, createTime, LocalDateTime.class, LocalDateTime.now());this.strictInsertFill(metaObject, updateTime, LocalDateTime.class, LocalDateTime.now());}//修改时执行此方法Overridepublic void updateFill(MetaObject metaObject) {log.info(start update fill ....);this.strictUpdateFill(metaObject, updateTime, LocalDateTime.class, LocalDateTime.now()); }
}③ 测试 //自动填充Testpublic void testFill(){//1. 封装user对象User user User.builder().username(baima10).name(tom10).password(123456).age(18).tel(13700137001).build();//2. 调用mapper方法userMapper.insert(user);}多余属性 多余属性指的是实体类中存在但是在数据表没有对应字段的属性 此时需要使用TableField(exist false)标识此属性 package com.itheima.domain;import com.baomidou.mybatisplus.annotation.*;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;import java.time.LocalDateTime;Builder
Data
NoArgsConstructor
AllArgsConstructor
//标注在实体类上用于声明实体类对应的表如果表名和类名一致可以省略
//TableName(tb_user)
public class User {//type: 声明主键生成策略TableId(type IdType.AUTO)private Long id;private String username;private String name;private String password;TableField(exist false)//表示当前属性仅在实体类中存在,在数据表中没有对应的字段private String password2;private Integer age;private String tel;TableField(fill FieldFill.INSERT)private LocalDateTime createTime;TableField(fill FieldFill.INSERT_UPDATE)private LocalDateTime updateTime;//逻辑删除字段value用于指定未删除状态的值, delval用于指定删除状态的值//TableLogic(value 1, delval 0)private Integer deleted;
}综合案例
添加页面运行程序访问页面
UserController
package com.itheima.controller;import com.itheima.domain.User;
import com.itheima.service.UserService;
import com.itheima.vo.Result;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;import java.util.List;RestController
public class UserController {Autowiredprivate UserService userService;GetMapping(/user)public Result findList(){ListUser userList userService.findList();return Result.success(userList);}PostMapping(/user)public Result save(RequestBody User user){userService.save(user);return Result.success();}DeleteMapping(/user/{id})public Result deleteById(PathVariable(id) Long id){userService.deleteById(id);return Result.success();}GetMapping(/user/{id})public Result findById(PathVariable(id) Long id){User user userService.findById(id);return Result.success(user);}PutMapping(/user)public Result update(RequestBody User user){userService.update(user);return Result.success();}
}
UserService
package com.itheima.service;import com.itheima.domain.User;import java.util.List;public interface UserService {ListUser findList();void save(User user);void deleteById(Long id);User findById(Long id);void update(User user);
}
UserServiceImpl
package com.itheima.service.impl;import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.itheima.domain.User;
import com.itheima.mapper.UserMapper;
import com.itheima.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;import java.util.List;Service
public class UserServiceImpl implements UserService {Autowiredprivate UserMapper userMapper;Overridepublic ListUser findList() {return userMapper.selectList(new LambdaQueryWrapper());}Overridepublic void save(User user) {userMapper.insert(user);}Overridepublic void deleteById(Long id) {userMapper.deleteById(id);}Overridepublic User findById(Long id) {return userMapper.selectById(id);}Overridepublic void update(User user) {userMapper.updateById(user);}
}ID精度损失问题
后端返回一个Long的id时候,前端接收到的数据精度有损失
pom.xml dependencygroupIdcom.fasterxml.jackson.datatype/groupIdartifactIdjackson-datatype-jsr310/artifactIdversion2.13.0/version/dependencyWebMvcConfig
package com.itheima.config;import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.module.SimpleModule;
import com.fasterxml.jackson.databind.ser.std.ToStringSerializer;
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;import java.math.BigInteger;
import java.util.List;import static com.fasterxml.jackson.databind.DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES;Configuration
public class WebMvcConfig implements WebMvcConfigurer {//扩展mvc框架的消息转换器public void extendMessageConverters(ListHttpMessageConverter? converters) {//创建消息转换器对象MappingJackson2HttpMessageConverter messageConverter new MappingJackson2HttpMessageConverter();//设置对象转换器底层使用Jackson将Java对象转为jsonmessageConverter.setObjectMapper(new JacksonObjectMapper());//将上面的消息转换器对象追加到mvc框架的转换器集合中converters.add(0, messageConverter);}/*** 对象映射器:基于jackson将Java对象转为json或者将json转为Java对象* 将JSON解析为Java对象的过程称为 [从JSON反序列化Java对象]* 从Java对象生成JSON的过程称为 [序列化Java对象到JSON]*/public class JacksonObjectMapper extends ObjectMapper {public JacksonObjectMapper() {super();//对应JDK8 时间类型处理需要添加的模块this.registerModule(new JavaTimeModule());//收到未知属性时不报异常this.configure(FAIL_ON_UNKNOWN_PROPERTIES, false);//反序列化时属性不存在的兼容处理this.getDeserializationConfig().withoutFeatures(FAIL_ON_UNKNOWN_PROPERTIES);//自定义转换规则SimpleModule simpleModule new SimpleModule().addSerializer(BigInteger.class, ToStringSerializer.instance)//将BigInteger转换为String.addSerializer(Long.class, ToStringSerializer.instance);//将Long转换成Stringthis.registerModule(simpleModule);}}
}Service接口
介绍
为了简化service代码编写mybatisPlus也提供了的基础接口和实现类
我们只需要让我们自己的service去继承它提供的service就可以使用里面的方法
进一步封装 CRUD 采用 get 查询单行 remove 删除 list 查询集合 page 分页 前缀命名方式区分 Mapper 层避免混淆
分类方法描述新增boolean save(T entity)新增entity 实体对象boolean saveOrUpdate(T entity)id存在则更新记录否插入一条记录boolean saveBatch(Collection entityList)插入批量默认一次可以保存1000条数据修改boolean updateById(T entity)根据 ID 修改boolean update(T entity,Wrapper updateWrapper)根据 条件 修改查询T getById(Serializable id)根据 ID 查询List listByIds(Collection idList) 查询根据ID 批量查询List list() 查询所有List list(Wrapper queryWrapper)条件查询删除boolean removeById(Serializable id) 根据 ID 删除boolean removeByIds(Collection idList) 删除根据ID 批量删除boolean remove(Wrapper queryWrapper) 根据条件删除
修改Service
使用Service 接口使用
接口继承 IService实现类继承 ServiceImplM,T
UserService
package com.itheima.service;import com.baomidou.mybatisplus.extension.service.IService;
import com.itheima.domain.User;//自定义service接口
public interface UserService extends IServiceUser {}UserServiceImpl
package com.itheima.service.impl;import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.itheima.domain.User;
import com.itheima.mapper.UserMapper;
import com.itheima.service.UserService;
import org.springframework.stereotype.Service;Service
public class UserServiceImpl extends ServiceImplUserMapper, User implements UserService {}修改controller
package com.itheima.controller;import com.itheima.domain.User;
import com.itheima.service.UserService;
import com.itheima.vo.Result;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;import java.util.List;RestController
public class UserController {Autowiredprivate UserService userService;GetMapping(/user)public Result findList(){ListUser userList userService.list();return Result.success(userList);}PostMapping(/user)public Result save(RequestBody User user){userService.saveOrUpdate(user);return Result.success();}DeleteMapping(/user/{id})public Result deleteById(PathVariable(id) Long id){userService.removeById(id);return Result.success();}GetMapping(/user/{id})public Result findById(PathVariable(id) Long id){User user userService.getById(id);return Result.success(user);}PutMapping(/user)public Result update(RequestBody User user){userService.saveOrUpdate(user);return Result.success();}
}
代码生成器
mybatis-plus官方提供了代码生成器可以根据数据库表逆向生成 Controller Service Mapper代码
这里使用 IDEA的插件完成代码生成
安装插件配置数据源代码生成
安装插件 配置数据源
jdbc:mysql://localhost:3306/mp_demo?useUnicodetrueIntegerEncodingutf8useSSLfalseservertimeZoneAsia/Shanghai 代码生成 多表查询
表间关系 添加新表
CREATE TABLE tb_account (aid INT(11) PRIMARY KEY AUTO_INCREMENT,accountName VARCHAR(100) DEFAULT NULL,balance FLOAT(10,2) DEFAULT NULL,uid INT(11) DEFAULT NULL
);
INSERT INTO tb_account VALUES
(1,B01,100.00,1),
(2,B02,200.00,1),
(3,B03,300.00,1),
(4,B04,400.00,2);package com.itheima.domain;import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.*;
import lombok.experimental.Accessors;import java.io.Serializable;
import java.time.LocalDateTime;/*** p* 账户* /p** author gxm* since 2024-08-11*/
Data
AllArgsConstructor
NoArgsConstructor
EqualsAndHashCode(callSuper false)
Accessors(chain true)
TableName(tb_account)
Builder
public class Account implements Serializable {private static final long serialVersionUID 1L;TableId(value aid, type IdType.AUTO)private Long aid;TableField(accountName)private String accountName;TableField(balance)private Float balance;TableField(uid)private Integer uid;
}查询所有账户, 并且带出账户的用户信息
建立关系 接口 映射
?xml version1.0 encodingUTF-8?
!DOCTYPE mapper PUBLIC -//mybatis.org//DTD Mapper 3.0//EN http://mybatis.org/dtd/mybatis-3-mapper.dtd
mapper namespacecom.itheima.mapper.AccountMapper!--自定义结果映射--resultMap idBaseResultMap typecom.itheima.domain.Accountresult columnaid propertyaid/resultresult columnaccountName propertyaccountName/resultresult columnbalance propertybalance/resultresult columnuid propertyuid/resultassociation propertyuser javaTypecom.itheima.domain.Userresult columnid propertyid/resultresult columnusername propertyusername/resultresult columnname propertyname/resultresult columnpassword propertypassword/resultresult columnage propertyage/resultresult columntel propertytel/resultresult columncreate_time propertycreateTime/resultresult columnupdate_time propertyupdateTime/resultresult columndeleted propertydeleted/result/association/resultMap!-- 通用查询映射结果 --select idfindAllWithUser resultMapBaseResultMapselect * from tb_account a left join tb_user u on a.uid u.id/select
/mapper测试 查询所有用户, 并且带出用户的账户信息
建立关系 接口 映射
?xml version1.0 encodingUTF-8?
!DOCTYPE mapper PUBLIC -//mybatis.org//DTD Mapper 3.0//EN http://mybatis.org/dtd/mybatis-3-mapper.dtd
mapper namespacecom.itheima.mapper.UserMapper!-- 通用查询映射结果 --resultMap idBaseResultMap typecom.itheima.domain.Userid columnid propertyid /result columnusername propertyusername /result columnname propertyname /result columnpassword propertypassword /result columnage propertyage /result columntel propertytel /result columncreate_time propertycreateTime /result columnupdate_time propertyupdateTime /result columndeleted propertydeleted /collection propertyaccountList ofTypecom.itheima.domain.Accountresult columnaid propertyaid /result columnaccountName propertyaccountName /result columnbalance propertybalance /result columnuid propertyuid //collection/resultMapselect idfindAllWithAccount resultMapBaseResultMapselect * from tb_user u left join tb_account a on a.uid u.id/select/mapper测试 [外链图片转存中…(img-jtmFAVvw-1724395263711)]
接口
[外链图片转存中…(img-ryL3e27c-1724395263712)]
映射
?xml version1.0 encodingUTF-8?
!DOCTYPE mapper PUBLIC -//mybatis.org//DTD Mapper 3.0//EN http://mybatis.org/dtd/mybatis-3-mapper.dtd
mapper namespacecom.itheima.mapper.UserMapper!-- 通用查询映射结果 --resultMap idBaseResultMap typecom.itheima.domain.Userid columnid propertyid /result columnusername propertyusername /result columnname propertyname /result columnpassword propertypassword /result columnage propertyage /result columntel propertytel /result columncreate_time propertycreateTime /result columnupdate_time propertyupdateTime /result columndeleted propertydeleted /collection propertyaccountList ofTypecom.itheima.domain.Accountresult columnaid propertyaid /result columnaccountName propertyaccountName /result columnbalance propertybalance /result columnuid propertyuid //collection/resultMapselect idfindAllWithAccount resultMapBaseResultMapselect * from tb_user u left join tb_account a on a.uid u.id/select/mapper测试
[外链图片转存中…(img-MPWRWmeR-1724395263712)]
