一小时迅速入门Mybatis之增删查改篇
目录
- 一、说明
- 二、开搞
- 2.1 数据库表
- 2.1 创建实体类
- 2.2 创建接口
- 2.3 创建XML
- 2.5 测试类
- 2.6 唠唠
一、说明
这二篇涉及到映射Java实体类、面向接口编写Mybatis、增删查改示例
怎么引入jar包,怎么配置数据库看上一篇哦~
二、开搞
2.1 数据库表
上一篇好像丢了数据库创建语句
-- 主键自增 DROP TABLE IF EXISTS `test`; CREATE TABLE `test` ( `id` bigint(20) NOT NULL AUTO_INCREMENT, `name` varchar(200) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL, `salary` decimal(10, 2) NOT NULL, PRIMARY KEY (`id`) USING BTREE ) ENGINE = InnoDB AUTO_INCREMENT = 4 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic; -- ---------------------------- -- 插入测试数据 -- ---------------------------- INSERT INTO `test` VALUES (1, '小明', 30000.00);
2.1 创建实体类
package entity; import java.math.BigDecimal; /** * @author 发现更多精彩 关注公众号:木子的昼夜编程 * 一个生活在互联网底层,做着增删改查的码农,不谙世事的造作 * @create 2021-08-25 22:05 */ public class TestEntity { private Long id; private String name; private BigDecimal salary; public Long getId() { return id; } public void setId(Long id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public BigDecimal getSalary() { return salary; } public void setSalary(BigDecimal salary) { this.salary = salary; } @Override public String toString() { return "TestEntity{" + "id=" + id + ", name='" + name + '\'' + ", salary=" + salary + '}'; } }
2.2 创建接口
package dao; import entity.TestEntity; import java.util.List; /** * @author 发现更多精彩 关注公众号:木子的昼夜编程 分享一个生活在互联网底层做着增删改查的码农的感悟与学习 * @create 2021-08-25 22:07 */ public interface TestMapper { // 新增 void save(TestEntity testEntity); // 修改 void update(TestEntity testEntity); // 删除 这里就一个参数 所以不用@Param 也不用Map 自定义实体类等 void delete(Long id); // 根据主键查询 TestEntity get(Long id); // 查询所有数据 List<TestEntity> list(); // 根据名称模糊查询 List<TestEntity> listByNameLike(String name); }
2.3 创建XML
mybatis-config.xml
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd"> <configuration> <environments default="development"> <environment id="development"> <transactionManager type="JDBC"/> <dataSource type="POOLED"> <property name="driver" value="com.mysql.jdbc.Driver"/> <property name="url" value="jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone=GMT%2B8"/> <property name="username" value="root"/> <property name="password" value="123456"/> </dataSource> </environment> </environments> <mappers> <mapper resource="TestMapper.xml"/> </mappers> </configuration>
TestMapper.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="dao.TestMapper"> <!--增加--> <insert id="save" > INSERT INTO `test`( `name`, `salary`) VALUE (#{name}, #{salary}); </insert> <!--删除--> <delete id="delete"> delete from test where id = #{id} </delete> <!--根据主键查询--> <select id="get" resultType="entity.TestEntity"> select * from test where id = #{id} </select> <!--查询所有数据--> <select id="list" resultType="entity.TestEntity"> select * from test </select> <!--根据名称模糊查询--> <select id="listByNameLike" resultType="entity.TestEntity"> select * from test where name like CONCAT('%',#{name},'%') </select> <update id="update"> update test set name =#{name}, salary = #{salary} where id = #{id} </update> </mapper>
2.5 测试类
先看一下数据库数据
新增数据
import dao.TestMapper; import entity.TestEntity; import org.apache.ibatis.io.Resources; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder; import java.io.InputStream; import java.math.BigDecimal; import java.util.List; import java.util.Map; /** * @author 发现更多精彩 关注公众号:木子的昼夜编程 * 一个生活在互联网底层,做着增删改查的码农,不谙世事的造作 * @create 2021-08-25 21:26 */ public class TestMain { public static void main(String[] args) throws Exception { String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); try (SqlSession session = sqlSessionFactory.openSession()) { // 通过sesson获取Mapper 这个Mapper会编程Mybatis的代理Mapper TestMapper mapper = session.getMapper(TestMapper.class); System.out.println(mapper); // 1. 插入数据 TestEntity entity = new TestEntity(); entity.setName("小月鸟"); entity.setSalary(new BigDecimal(50000)); mapper.save(entity); TestEntity entity02 = new TestEntity(); entity02.setName("小强01"); entity02.setSalary(new BigDecimal(50000)); mapper.save(entity02); TestEntity entity03 = new TestEntity(); entity03.setName("小强02"); entity03.setSalary(new BigDecimal(50000)); mapper.save(entity03); // 手动提交 session.commit(); } } }
执行完查看数据库数据:
根据Id 查询数据
import dao.TestMapper; import entity.TestEntity; import org.apache.ibatis.io.Resources; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder; import java.io.InputStream; /** * @author 发现更多精彩 关注公众号:木子的昼夜编程 * 一个生活在互联网底层,做着增删改查的码农,不谙世事的造作 * @create 2021-08-25 21:26 */ public class TestMain { public static void main(String[] args) throws Exception { String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); try (SqlSession session = sqlSessionFactory.openSession()) { // 通过sesson获取Mapper 这个Mapper会编程Mybatis的代理Mapper TestMapper mapper = session.getMapper(TestMapper.class); System.out.println(mapper); // 1. 根据Id 查询数据 TestEntity testEntity = mapper.get(1L); System.out.println("查询数据为:"+testEntity); } } }
输出结果:
更新数据
把”小月鸟“ 工资改成40000
import dao.TestMapper; import entity.TestEntity; import org.apache.ibatis.io.Resources; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder; import java.io.InputStream; import java.math.BigDecimal; /** * @author 发现更多精彩 关注公众号:木子的昼夜编程 * 一个生活在互联网底层,做着增删改查的码农,不谙世事的造作 * @create 2021-08-25 21:26 */ public class TestMain { public static void main(String[] args) throws Exception { String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); try (SqlSession session = sqlSessionFactory.openSession()) { // 通过sesson获取Mapper 这个Mapper会编程Mybatis的代理Mapper TestMapper mapper = session.getMapper(TestMapper.class); System.out.println(mapper); // 更新 TestEntity entityUpdate = new TestEntity(); entityUpdate.setId(40L); entityUpdate.setName("小月鸟"); entityUpdate.setSalary(new BigDecimal(40000)); mapper.update(entityUpdate); session.commit(); } } }
执行完查看数据库数据:
查询全部数据
import dao.TestMapper; import entity.TestEntity; import org.apache.ibatis.io.Resources; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder; import java.io.InputStream; import java.util.List; /** * @author 发现更多精彩 关注公众号:木子的昼夜编程 * 一个生活在互联网底层,做着增删改查的码农,不谙世事的造作 * @create 2021-08-25 21:26 */ public class TestMain { public static void main(String[] args) throws Exception { String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); try (SqlSession session = sqlSessionFactory.openSession()) { // 通过sesson获取Mapper 这个Mapper会编程Mybatis的代理Mapper TestMapper mapper = session.getMapper(TestMapper.class); System.out.println(mapper); // 查询列表 List<TestEntity> list = mapper.list(); if (list.size() >0) { for (int i = 0; i < list.size(); i++) { System.out.println(list.get(i)); } } } } }
输出结果:
根据名称查询数据
import dao.TestMapper; import entity.TestEntity; import org.apache.ibatis.io.Resources; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder; import java.io.InputStream; import java.util.List; /** * @author 发现更多精彩 关注公众号:木子的昼夜编程 * 一个生活在互联网底层,做着增删改查的码农,不谙世事的造作 * @create 2021-08-25 21:26 */ public class TestMain { public static void main(String[] args) throws Exception { String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); try (SqlSession session = sqlSessionFactory.openSession()) { // 通过sesson获取Mapper 这个Mapper会编程Mybatis的代理Mapper TestMapper mapper = session.getMapper(TestMapper.class); System.out.println(mapper); // 根据名称模糊查询列表 List<TestEntity> list = mapper.listByNameLike("强"); if (list.size() >0) { for (int i = 0; i < list.size(); i++) { System.out.println(list.get(i)); } } } } }
输出结果:
删除数据
import dao.TestMapper; import entity.TestEntity; import org.apache.ibatis.io.Resources; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder; import java.io.InputStream; import java.util.List; /** * @author 发现更多精彩 关注公众号:木子的昼夜编程 * 一个生活在互联网底层,做着增删改查的码农,不谙世事的造作 * @create 2021-08-25 21:26 */ public class TestMain { public static void main(String[] args) throws Exception { String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); try (SqlSession session = sqlSessionFactory.openSession()) { // 通过sesson获取Mapper 这个Mapper会编程Mybatis的代理Mapper TestMapper mapper = session.getMapper(TestMapper.class); System.out.println(mapper); // 删除数据 mapper.delete(1L); session.commit(); } } }
执行完查看数据库数据:
项目结构:
2.6 唠唠
1.刚开始新增没有成功 是因为没有手动commit (改变数据库数据都需要commit)
现在大部分项目都是结合SpringBoot 事务都交给Spring管理了都不需要自己手动commit了
2.实体类没有用别名 直接用的全类路径 实际项目中有用别名的有用全类路径的
3.新增的时候没有返回自增主键的值 实际项目可能会用到这个值
4.更新的时候写死的字段 实际项目可能会根据不同的值进行不同列的更新
下篇预告:
- 实体类用别名
- 新增返回自增主键的值
- 多个参数的使用
- 动态Sql的常用标签
- 聊一聊 insert delete select update标签
补充一个知识点(应该不用深入研究):
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSessionFactoryBuilder有好几种方式创建SqlSessionFactory
除了使用xml还可以纯Java代码创建
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