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SpringBoot集成Mybatis-Plus及Mybatis-Plus的实例操作

一、SpringBoot集成Mybatis-Plus方法

  1. 创建springboot项目SpringBoot集成Mybatis-Plus及Mybatis-Plus的实例操作插图

    这里可以选择MySQL坐标,也可以不选然后自己手动添加

    SpringBoot集成Mybatis-Plus及Mybatis-Plus的实例操作插图1

  2. 添加依赖
    <!--mybatis-plus-->
    <dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.5.0</version>
    </dependency>
    
    <!--MySQL依赖-->
    <dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <scope>runtime</scope>
    </dependency>
    
    <!--druid-->
    <dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid-spring-boot-starter</artifactId>
    <version>1.2.9</version>
    </dependency>
    
    <!--lombok-->
    <dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    </dependency>
    
  3. 在application.yml中配置数据库
    server:
    port: 8080
    servlet:
    context-path: /
    spring:
    datasource:
    druid: #数据源使用druid
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/ssm_db?useUnicode=true&characterEncoding=UTF-8&useJDBC49CompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=GMT%2B8
    username: root
    password: root
    
  4. 使用Lombok创建实体类
    Book实体类:
    @Data
    public class Book {
    private Integer id;
    private String type;
    private String name;
    private String description;
    }
    
  5. 使用Mybatis-Plus创建dao层方法使用继承 BaseMapper<实体类>的方法,mp帮我们就创建了常用的sql
    import com.baomidou.mybatisplus.core.mapper.BaseMapper;
    import com.example.domain.Book;
    import org.apache.ibatis.annotations.Mapper;
    
    @Mapper
    public interface BookMapper extends BaseMapper<Book> {
    
    }
    
  6. 附:使用到的数据库的创建语句:
    SET NAMES utf8mb4;
    SET FOREIGN_KEY_CHECKS = 0;
    
    -- ----------------------------
    -- Table structure for book
    -- ----------------------------
    DROP TABLE IF EXISTS `book`;
    CREATE TABLE `book`(
    `id` int(0) NOT NULL AUTO_INCREMENT,
    `type` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
    `name` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
    `description` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
    PRIMARY KEY (`id`) USING BTREE
    ) ENGINE = InnoDB AUTO_INCREMENT = 739889170 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;
    
    SET FOREIGN_KEY_CHECKS = 1;
    
    

二、测试增删改查

@Autowired
private BookMapper bookMapper;
//测试查询
@Test
void testGetById(){
System.out.println(bookMapper.selectById(3));
}
//测试查询所有
@Test
void testGetAll(){
System.out.println(bookMapper.selectList(null));
}
//测试保存
@Test
void testSave(){
Book book = new Book();
book.setName("汤家凤2023考研高数辅导书");
book.setType("考研");
book.setDescription("2023考研高数汤家凤");
bookMapper.insert(book);
}
//测试修改
@Test
void testUpdate(){
Book book = new Book();
book.setId(739889166);
book.setType("数学");
bookMapper.updateById(book);

}
//测试删除
@Test
void testDelete(){
bookMapper.deleteById(739889166);
}

三、配置使用数据库默认id自增策略

mybatis-plus执行时对于id的处理默认是使用雪花算法随机生成id,但是我们在数据库表中给id设置的是自增(没有生效),设置默认使用数据库id自增策略的方式有两种

1.在application.yml配置文件中配置:

mybatis-plus:
global-config:
db-config:
id-type: auto #使用数据库默认id自增策略

2.在实体类中使用注解@TableId(value = "id",type = IdType.AUTO)配置

//lombok
@Data// = @Getter+@Setter
public class Book {
@TableId(value = "id",type = IdType.AUTO)
private Integer id;
private String type;
private String name;
private String description;
}

四、开启Mybatis-plus日志

mybatis-plus执行时,默认是不显示执行过程以及执行的sql语句的,这样调试时很是不方便,所以要打开日志功能

在application.yml中开启mybatis-plus日志,设置日志显示方式为打印在控制台,配置代码如下:

mybatis-plus:
global-config:
db-config:
id-type: auto #使用数据库默认id自增策略
configuration:
log-impl: org.apache.ibatis.logging.stdout.StdOutImpl#日志打印到控制台

执行效果(显示完整的执行过程):

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@1e4c6583] was not registered for synchronization because synchronization is not active
JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@76fe6cdc] will not be managed by Spring
==>Preparing: SELECT id,type,name,description FROM book
==> Parameters: 
<==Columns: id, type, name, description
<==Row: -2019983359, 考研, 汤家凤2023考研高数辅导书, 2023考研高数汤家凤
<==Row: -1986453503, 考研, 汤家凤2023考研高数辅导书, 2023考研高数汤家凤
<==Row: -304508927, 考研, 汤家凤2023考研高数辅导书, 2023考研高数汤家凤
<==Row: 1, 科技, Java编程思想, Java学习教程
<==Row: 2, 科技, C++ primer plus, C++学习教程
<==Row: 3, 人文, 阿甘正传, 在工作中学习
<==Row: 4, 考研, 张宇高数18讲, 考研高数复习资料----张宇
<==Row: 5, 考研, 句句真研, 田静考研英语
<==Row: 739889167, 考研, 汤家凤2023考研高数辅导书, 2023考研高数汤家凤
<==Row: 739889168, 考研, 汤家凤2023考研高数辅导书, 2023考研高数汤家凤
<==Row: 739889169, 考研, 汤家凤2023考研高数辅导书, 2023考研高数汤家凤
<==Total: 11
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@1e4c6583]

五、Mybatis-plus分页功能的实现

1.设定分页对象IPage

IPage ipage = new Page(2,5);
//执行分页查询
bookMapper.selectPage(ipage,null);

在这里插入图片描述

2.要想让上面的查询生效,还需要配置MyBatisPlus拦截器

在启动类的同级或上一级目录下新建config包,在config包中新建一个类命名为MPConfig.java(可以自己随意命名)

SpringBoot集成Mybatis-Plus及Mybatis-Plus的实例操作插图3

在MPConfig中定义分页需要的拦截器,该拦截器会在执行查询时在sql语句后面添加LIMIT ?,?

@Configuration
public class MPConfig {
@Bean
public MybatisPlusInterceptor mybatisPlusInterceptor(){
//1.定义mp拦截器
MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
//2.添加指定的拦截器
interceptor.addInnerInterceptor(new PaginationInnerInterceptor());
return interceptor;
}

}

测试分页:

测试代码:
 @Test
void testGetPage(){
IPage ipage = new Page(2,5);
//执行分页查询
bookMapper.selectPage(ipage,null);
System.out.println("当前页为: "+ipage.getCurrent());
System.out.println("每一页的条数 "+ipage.getSize());
System.out.println("表中数据总条数: "+ipage.getTotal());
System.out.println("一共的页数: "+ipage.getPages());
System.out.println("查到的数据: "+ipage.getRecords());
}
测试结果:
Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@1acb74ad] was not registered for synchronization because synchronization is not active
JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@21263314] will not be managed by Spring
==>Preparing: SELECT COUNT(*) AS total FROM book
==> Parameters: 
<==Columns: total
<==Row: 11
<==Total: 1
==>Preparing: SELECT id,type,name,description FROM book LIMIT ?,?
==> Parameters: 5(Long), 5(Long)
<==Columns: id, type, name, description
<==Row: 3, 人文, 阿甘正传, 在工作中学习
<==Row: 4, 考研, 张宇高数18讲, 考研高数复习资料----张宇
<==Row: 5, 考研, 句句真研, 田静考研英语
<==Row: 739889167, 考研, 汤家凤2023考研高数辅导书, 2023考研高数汤家凤
<==Row: 739889168, 考研, 汤家凤2023考研高数辅导书, 2023考研高数汤家凤
<==Total: 5
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@1acb74ad]
当前页为: 2
每一页的条数 5
表中数据总条数: 11
一共的页数: 3
查到的数据: [Book(id=3, type=人文, name=阿甘正传, description=在工作中学习), Book(id=4, type=考研, name=张宇高数18讲, description=考研高数复习资料----张宇), Book(id=5, type=考研, name=句句真研, description=田静考研英语), Book(id=739889167, type=考研, name=汤家凤2023考研高数辅导书, description=2023考研高数汤家凤), Book(id=739889168, type=考研, name=汤家凤2023考研高数辅导书, description=2023考研高数汤家凤)]

六、条件查询

1、方法一:QueryWrapper

@Test
void testGetBy(){
//1.新建QueryWrapper对象,Book是实体类
QueryWrapper<Book> qw = new QueryWrapper<>();
//2.条件
qw.like("type","考研");
//3.根据条件查询
bookMapper.selectList(qw);
}

运行结果:

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7cac93fe] was not registered for synchronization because synchronization is not active
JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@65a9ea3c] will not be managed by Spring
==>Preparing: SELECT id,type,name,description FROM book WHERE (type LIKE ?)
==> Parameters: %考研%(String)
<==Columns: id, type, name, description
<==Row: -2019983359, 考研, 汤家凤2023考研高数辅导书, 2023考研高数汤家凤
<==Row: -1986453503, 考研, 汤家凤2023考研高数辅导书, 2023考研高数汤家凤
<==Row: -304508927, 考研, 汤家凤2023考研高数辅导书, 2023考研高数汤家凤
<==Row: 4, 考研, 张宇高数18讲, 考研高数复习资料----张宇
<==Row: 5, 考研, 句句真研, 田静考研英语
<==Row: 739889167, 考研, 汤家凤2023考研高数辅导书, 2023考研高数汤家凤
<==Row: 739889168, 考研, 汤家凤2023考研高数辅导书, 2023考研高数汤家凤
<==Row: 739889169, 考研, 汤家凤2023考研高数辅导书, 2023考研高数汤家凤
<==Total: 8
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7cac93fe]

2、方法二LambdaQueryWrapper:

 @Test
void testGetBy2(){
//1.新建QueryWrapper对象
LambdaQueryWrapper<Book> lqw = new LambdaQueryWrapper<>();
//2.条件
lqw.like(Book::getType,"汤家凤");
//3.根据条件查询
bookMapper.selectList(lqw);
}

运行结果:

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@2f14b0f6] was not registered for synchronization because synchronization is not active
JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@4c6b4ed7] will not be managed by Spring
==>Preparing: SELECT id,type,name,description FROM book WHERE (name LIKE ?)
==> Parameters: %汤家凤%(String)
<==Columns: id, type, name, description
<==Row: -2019983359, 考研, 汤家凤2023考研高数辅导书, 2023考研高数汤家凤
<==Row: -1986453503, 考研, 汤家凤2023考研高数辅导书, 2023考研高数汤家凤
<==Row: -304508927, 考研, 汤家凤2023考研高数辅导书, 2023考研高数汤家凤
<==Row: 739889167, 考研, 汤家凤2023考研高数辅导书, 2023考研高数汤家凤
<==Row: 739889168, 考研, 汤家凤2023考研高数辅导书, 2023考研高数汤家凤
<==Row: 739889169, 考研, 汤家凤2023考研高数辅导书, 2023考研高数汤家凤
<==Total: 6
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@2f14b0f6]

使用LambdaQueryWrapper进行查询时,当参数为空时会出现错误,例如:

@Test
void testGetBy2(){
String name=null;
//1.新建QueryWrapper对象
LambdaQueryWrapper<Book> lqw = new LambdaQueryWrapper<>();
//2.条件
lqw.like(Book::getName,name);
//3.根据条件查询
bookMapper.selectList(lqw);
}

运行结果:

SpringBoot集成Mybatis-Plus及Mybatis-Plus的实例操作插图4

解决办法:判断参数是否为空

@Test
void testGetBy2(){
String name=null;
//1.新建QueryWrapper对象
LambdaQueryWrapper<Book> lqw = new LambdaQueryWrapper<>();
//2.条件
//if(name!=null) lqw.like(Book::getName,name); //第一种解决参数为空的办法
//第二种解决参数为空的方法
lqw.like(name != null,Book::getName,name);
//3.根据条件查询
bookMapper.selectList(lqw);
}

执行结果:(sql语句后面没有连接条件)

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@4ace284d] was not registered for synchronization because synchronization is not active
JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@73aeef7d] will not be managed by Spring
==>Preparing: SELECT id,type,name,description FROM book
==> Parameters: 
<==Columns: id, type, name, description
<==Row: -2019983359, 考研, 汤家凤2023考研高数辅导书, 2023考研高数汤家凤
<==Row: -1986453503, 考研, 汤家凤2023考研高数辅导书, 2023考研高数汤家凤
<==Row: -304508927, 考研, 汤家凤2023考研高数辅导书, 2023考研高数汤家凤
<==Row: 1, 科技, Java编程思想, Java学习教程
<==Row: 2, 科技, C++ primer plus, C++学习教程
<==Row: 3, 人文, 阿甘正传, 在工作中学习
<==Row: 4, 考研, 张宇高数18讲, 考研高数复习资料----张宇
<==Row: 5, 考研, 句句真研, 田静考研英语
<==Row: 739889167, 考研, 汤家凤2023考研高数辅导书, 2023考研高数汤家凤
<==Row: 739889168, 考研, 汤家凤2023考研高数辅导书, 2023考研高数汤家凤
<==Row: 739889169, 考研, 汤家凤2023考研高数辅导书, 2023考研高数汤家凤
<==Total: 11
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@4ace284d]

对应的条件可以在官网查询:

https://baomidou.com/pages/10c804/#abstractwrapper

七、业务层快速开发

1.服务层接口继承IService<要操作的实体类>

2.接口实现类继承ServiceImpl<数据层接口, 要操作的实体类>

3.除了MyBatisPlus提供的方法接口,要自定义方法的话直接在接口中写,在实现类中实现即可

业务层接口:
public interface IBookService extends IService<Book> {
/*
自定义的方法
 */
Boolean saveBook(Book book);
Boolean modify(Book book);
Boolean deleteById(Integer id);
}
业务层实现类
@Service
public class IBookServerImpl extends ServiceImpl<BookMapper, Book> implements IBookService {
//自定义方法的实现
@Autowired
private BookMapper bookMapper;
@Override
public Boolean saveBook(Book book) {
return bookMapper.insert(book)>0;
}

@Override
public Boolean modify(Book book) {
return bookMapper.updateById(book)>0;
}

@Override
public Boolean deleteById(Integer id) {
return bookMapper.deleteById(id)>0;
}
}
数据层接口及实现
@Mapper
public interface BookMapper extends BaseMapper<Book> {

}
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