Java中如何使用MyBatis-Plus操作数据库

这篇文章主要介绍Java中如何使用MyBatis-Plus操作数据库，文中介绍的非常详细，具有一定的参考价值，感兴趣的小伙伴们一定要看完！

MyBatis-Plus

MyBatis-Plus (opens new window)（简称 MP）是一个 MyBatis (opens new window)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可以直接在xml中通过SQL语句操作数据库，很灵活。但其操作都要通过SQL语句进行，就必须写大量的xml文件，很麻烦。mybatis-plus就很好的解决了这个问题。

官网

MyBatis-Plus 官方文档

使用

这里我用的数据库是mysql8，新建test数据库，并创建user表

建表语句

SET NAMES utf8mb4;SET FOREIGN_KEY_CHECKS = 0; -- ------------------------------ Table structure for user-- ----------------------------DROP TABLE IF EXISTS `user`;CREATE TABLE `user`  (  `id` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '主键',  `name` varchar(20) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '姓名',  `age` int(0) NULL DEFAULT NULL COMMENT '年龄',  `address` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '地址',  PRIMARY KEY (`id`) USING BTREE) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic; SET FOREIGN_KEY_CHECKS = 1;

引入依赖

这里我用的数据库是mysql8

             org.springframework.boot        spring-boot-starter-parent        2.6.3                                     org.projectlombok            lombok                            org.springframework.boot            spring-boot-starter                            org.springframework.boot            spring-boot-devtools            runtime            true                            org.springframework.boot            spring-boot-starter-test            test                            org.springframework.boot            spring-boot-test                            junit            junit                            org.springframework            spring-test                            com.baomidou            mybatis-plus-boot-starter            3.5.1                                    com.alibaba            druid-spring-boot-starter            1.1.9                            mysql            mysql-connector-java            8.0.25            

分别创建application.yml及application-dev.yml文件

application.yml

# Spring配置spring:  # 环境设置  profiles:    active: dev  # 模板引擎  thymeleaf:    mode: HTML    encoding: utf-8    # 禁用缓存    cache: false  # 服务模块  devtools:    restart:      # 热部署开关      enabled: true

application-dev.yml

# 开发环境配置server:  # 服务器的HTTP端口，默认为80  port: 8081 spring:  datasource:    type: com.alibaba.druid.pool.DruidDataSource    driver-class-name: com.mysql.cj.jdbc.Driver    druid:      url: jdbc:mysql://localhost:3307/test?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull&useSSL=true&serverTimezone=GMT%2B8      username: root      password: 123456      initial-size: 5      min-idle: 10      max-active: 20      max-wait: 60000      time-between-eviction-runs-millis: 60000      min-evictable-idle-time-millis: 300000      validation-query: select 'x'      test-while-idle: true      test-on-borrow: false      test-on-return: false      pool-prepared-statements: true      max-open-prepared-statements: 50      max-pool-prepared-statement-per-connection-size: 20

编写实体类User.java,这里用到lombok

@Datapublic class User {    private String id;    private String name;    private Integer age;    private String address;}

创建mapper文件夹,并编写 Mapper 类 UserMapper.java

public interface UserMapper extends BaseMapper { }

在 Spring Boot 启动类中添加 @MapperScan 注解，扫描 Mapper 文件夹：

@SpringBootApplication@MapperScan("com.mybatisplus.mapper")public class MainApplication {    public static void main(String[] args)    {        SpringApplication.run(MainApplication.class, args);    }}

添加测试类，进行功能测试：

测试数据插入数据库

    @Autowired    private UserMapper userMapper;     @Test    public void testInsert() {        System.out.println(("----- insert method test ------"));        User user = new User();        // 自动生成主键,例如550E8400-E29B-11D4-A716-446655440000        String id = UUID.randomUUID().toString();        String replaceAll = id.replaceAll("-", "");        //550E8400E29B11D4A716446655440000        user.setId(replaceAll);        user.setName("张三");        user.setAge(21);        user.setAddress("北京市海淀区");        int insert = userMapper.insert(user);        if(insert>0){            System.out.println("插入成功："+user);        }else{            System.out.println("插入失败！");        }    }

测试查询所有

    @Autowired    private UserMapper userMapper;            @Test    public void testSelect() {        System.out.println(("----- selectAll method test ------"));        List userList = userMapper.selectList(null);        userList.forEach(System.out::println);    }

测试删除数据

删除姓名等于"张三"的记录

    @Autowired    private UserMapper userMapper;        @Test    public void testDelete() {        System.out.println(("----- delete method test ------"));        LambdaQueryWrapper wrapper = new LambdaQueryWrapper<>();        User user = new User();        user.setName("张三");        wrapper.eq(User::getName, user.getName());        int delete = userMapper.delete(wrapper);        if(delete>0){            System.out.println("删除成功："+user);        }else{            System.out.println("删除失败！");        }    }

测试修改数据

修改前先执行下插入

修改还可以用userMapper.updateById(T entity)方法来修改，传入一个实体类

    @Autowired    private UserMapper userMapper;        @Test    public void testUpdate() {        System.out.println(("----- update method test ------"));        LambdaQueryWrapper wrapper = new LambdaQueryWrapper<>();        User user = new User();        user.setName("张三");        wrapper.eq(User::getName, user.getName());        User userNew = new User();        userNew.setName("李四");        int update = userMapper.update(userNew, wrapper);        if(update>0){            System.out.println("修改成功："+user);        }else{            System.out.println("修改失败！");        }    }

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