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Java中使用MyBatis-Plus操作数据库的实例

作者：像向日葵一样~

本文主要介绍了Java中使用MyBatis-Plus操作数据库的实例，文中通过示例代码介绍的非常详细，对大家的学习或者工作具有一定的参考学习价值，需要的朋友们下面随着小编来一起学习学习吧

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

     <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.6.3</version>
        <relativePath/>
    </parent>
 
    <dependencies>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-test</artifactId>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
        </dependency>
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.5.1</version>
        </dependency>
        <!--Druid连接池-->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid-spring-boot-starter</artifactId>
            <version>1.1.9</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.25</version>
        </dependency>
    </dependencies>

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

@Data
public 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<User> {
 
}

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<User> 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<User> 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<User> 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！");
        }
    }

 到此这篇关于Java中使用MyBatis-Plus操作数据库的实例的文章就介绍到这了,更多相关MyBatis-Plus操作数据内容请搜索脚本之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持脚本之家！

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