tkMybatis数据持久层框架入门

gitee链接

Spring Boot版本：2.3.4.RELEASE

tkMybatis封装了底层SQL，使开发者在操作单表的情况下可以不考虑SQL的写法，通过Java函数接口操作数据库。

并且tkMybatis是基于Mybaits的，所以也能编写XML文件来执行复杂的SQL语句。

Maven依赖

<dependencies>
    <!--springboot启动器-->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <scope>test</scope>
    </dependency>

    <!-- Spring-data-jpa依赖 -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
    </dependency>

    <!--MySQL数据库驱动-->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.21</version>
    </dependency>

    <!--tkMybatis通用mapper-->
    <dependency>
        <groupId>tk.mybatis</groupId>
        <artifactId>mapper-spring-boot-starter</artifactId>
        <version>2.0.2</version>
    </dependency>
</dependencies>
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配置文件

application.yml：

server:
  port: 8888
spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://myserverhost:3306/mytest?createDatabaseIfNotExist=true&characterEncoding=utf-8&useSSL=false&serverTimezone=UTC
    username: root
    password: admin
  # 开启hibernate表自动更新
  jpa:
    hibernate:
      ddl-auto: update
    show-sql: true
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配置文件中开启了hibernate自动建表方便测试，建表前检查下数据库有没有同名表，有则删除。

新建两个实体类

TbUser和TbProduct

- src
    - main
        - java
            - com
                - cc
                    - model
                        - entity
                            TbProduct
                            TbUser
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TbUser：

package com.cc.model.entity;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
import java.io.Serializable;

@Entity
@Table(name = "tb_user")
public class TbUser implements Serializable {
    @Id
    @Column(name = "id", columnDefinition = "BIGINT(20) UNSIGNED NOT NULL auto_increment COMMENT '主键id'")
    private Long id;

    @Column(name = "username", columnDefinition = "VARCHAR(64) UNIQUE NOT NULL COMMENT '用户名，唯一'")
    private String username;

    @Column(name = "password", columnDefinition = "VARCHAR(64) NOT NULL COMMENT '密码'")
    private String password;

    private static final long serialVersionUID = 1L;

    ...
}
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TbProduct：

package com.cc.model.entity;

import java.math.BigDecimal;
import java.io.Serializable;
import javax.persistence.Entity;
import javax.persistence.Table;
import javax.persistence.Column;
import javax.persistence.Id;

@Entity
@Table(name = "tb_product")
public class TbProduct implements Serializable {
    @Id
    @Column(name = "id", columnDefinition = "BIGINT(20) UNSIGNED NOT NULL auto_increment COMMENT '主键id'")
    private Long id;

    @Column(name = "name", columnDefinition = "VARCHAR(64) UNIQUE NOT NULL COMMENT '用户名，唯一'")
    private String name;

    @Column(name = "price", columnDefinition = "DECIMAL(10,2) NOT NULL DEFAULT 0.00 COMMENT '价格'")
    private BigDecimal price;

    @Column(name = "user_id", columnDefinition = "BIGINT(20) UNSIGNED NOT NULL DEFAULT 0 COMMENT '用户id'")
    private Long userId;

    private static final long serialVersionUID = 1L;

    ...
}
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创建操作user表和product表的dao类：

UserDao：

package com.cc.dao;

import com.cc.model.entity.TbUser;
import org.springframework.stereotype.Repository;
import tk.mybatis.mapper.common.Mapper;

@Repository
public interface UserDao extends Mapper<TbUser> {
}
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ProductDao：

package com.cc.dao;

import com.cc.model.entity.TbProduct;
import org.springframework.stereotype.Repository;
import tk.mybatis.mapper.common.Mapper;

@Repository
public interface ProductDao extends Mapper<TbProduct> {
}
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tkmybatis配置类

为了使dao类能被扫描到，还需要mybatis测试类：

package com.cc.config;

import org.springframework.context.annotation.Configuration;
import tk.mybatis.spring.annotation.MapperScan;

/**
 * MyBatis配置类
 * @author cc
 * @date 2021-07-09 14:38
 */
@Configuration
@MapperScan({"com.cc.dao"})
public class MyBatisConfig {
}
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创建一个controller来测试

TestController：

package com.cc.controller;

import com.cc.dao.ProductDao;
import com.cc.dao.UserDao;
import com.cc.model.entity.TbUser;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class TestController {
    private final UserDao userDao;
    private final ProductDao productDao;

    public TestController(UserDao userDao, ProductDao productDao) {
        this.userDao = userDao;
        this.productDao = productDao;
    }
}
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启动程序使其生效。

实战

实战的内容为：

• 插入一个user数据
• 更新一个user数据
• 查询所有user数据
• 查询指定名称的user
• 插入几条product数据
• 根据userId查询关联的所有product数据（连表查询）
• 删除user数据

为了简单，接口的参数都是写死的。

插入一个user数据

@GetMapping("/insertUser")
public void insertUser(@RequestBody TbUser user) {
    user = new TbUser();
    user.setId(1L);
    user.setUsername("cc");
    user.setPassword("1");

    int r = userDao.insertSelective(user);
    if (r <= 0) {
        throw new RuntimeException("插入失败");
    }
}
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更新一个user数据

@GetMapping("/updateUser")
public void updateUser(@RequestBody TbUser user) {
    user = new TbUser();
    user.setId(1L);
    user.setUsername("cc");
    user.setPassword("123456");

    int r = userDao.updateByPrimaryKeySelective(user);
    if (r <= 0) {
        throw new RuntimeException("更新失败");
    }
}
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查询所有user数据

@GetMapping("/selectAllUser")
public List<TbUser> selectAllUser(@RequestBody TbUser user) {
    user = new TbUser();
    user.setId(1L);
    user.setUsername("cc");
    user.setPassword("123456");

    return userDao.selectAll();
}
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查询指定id/名称的user

@GetMapping("/selectUserById")
public TbUser selectUserById(@RequestBody TbUser user) {
    return userDao.selectByPrimaryKey(1L);
}

@GetMapping("/selectUserByUsername")
public TbUser selectUserByUsername(@RequestBody TbUser user) {
    user = new TbUser();
    user.setUsername("cc");

    Example example = new Example(TbUser.class);
    Example.Criteria criteria = example.createCriteria();
    criteria.andEqualTo("username", user.getUsername());

    return userDao.selectOneByExample(example);
}
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插入几条product数据

@GetMapping("/insertSomeProduct")
public void insertSomeProduct() {
    for (long i = 0; i < 5; i++) {
        TbProduct product = new TbProduct();
        product.setId(i);
        product.setName("test" + i);
        productDao.insertSelective(product);
    }
}
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根据userId查询关联的所有product数据（连表查询）

因为dao只能操作单表，所以我们需要编写xml来实现连表操作。

首先要在配置文件文件中添加包扫描：

application.yml

## dao.xml的路径配置
mybatis:
  mapper-locations:
    - classpath:dao/*.xml # resource下的dao
  configuration:
    map-underscore-to-camel-case: true # 下划线自动转驼峰
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然后在resources下创建dao文件夹，并且新建product.xml：

<?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.cc.dao.ProductDao">
    <select id="selectByUserId" resultType="com.cc.model.entity.TbProduct">
        SELECT
            *
        FROM
            tb_product AS p
                LEFT JOIN tb_user u ON u.id = p.user_id
        WHERE
            u.id = #{userId}
    </select>
</mapper>
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在ProductDao下新增函数：

package com.cc.dao;

import com.cc.model.entity.TbProduct;
import org.springframework.stereotype.Repository;
import tk.mybatis.mapper.common.Mapper;

import java.util.List;

@Repository
public interface ProductDao extends Mapper<TbProduct> {
    List<TbProduct> selectByUserId(Long userId);
}
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然后编写接口：

@GetMapping("/selectProductByUserId")
public List<TbProduct> selectProductByUserId() {
    return productDao.selectByUserId(1L);
}
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删除user数据

@GetMapping("/deleteUser")
public void deleteUser() {
    int r = userDao.deleteByPrimaryKey(1L);
    if (r <= 0) {
        throw new RuntimeException("删除用户失败");
    }
}
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例子虽然不多，但是已经足够了解到，借助tkMybatis框架，我们操作单表的时候不用再写SQL语句，可以省略许多的代码，我们不用再为每一个实体类编写增删改查语句，仅仅只要新建一个映射实体类的Dao，不过几行通用代码而已。

还有当单表操作不满足于我们需求的时候，可以自行编写SQL语句并应用到XML下，真正做到按需开发，能省则省。