Mybatis示例讲解注解开发中的单表操作

目录

• Mybatis注解开发单表操作
• MyBatis的常用注解
• MyBatis的增删改查
• 注解开发总结
• 常用注解
• 配置映射关系
• 练习项目代码

Mybatis注解开发单表操作

MyBatis的常用注解

Mybatis也可以使用注解开发方式，这样我们就可以减少编写Mapper映射文件了。我们先围绕一些基本的CRUD来学习，再学习复杂映射多表操作。

MyBatis的增删改查

我们完成简单的student表的增删改查的操作

步骤一:创建mapper接口

public interface StudentMapper {
    //查询全部
    @Select("SELECT * FROM student")
    public abstract List<Student> selectAll();
    //新增操作
    @Insert("INSERT INTO student VALUES (#{id},#{name},#{age})")
    public abstract Integer insert(Student stu);
    //修改操作
    @Update("UPDATE student SET name=#{name},age=#{age} WHERE id=#{id}")
    public abstract Integer update(Student stu);
    //删除操作
    @Delete("DELETE FROM student WHERE id=#{id}")
    public abstract Integer delete(Integer id);
}

步骤二：测试类

public class Test01 {
    @Test
    public void selectAll() throws Exception{
        //1.加载核心配置文件
        InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml");
        //2.获取SqlSession工厂对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
        //3.通过工厂对象获取SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        //4.获取StudentMapper接口的实现类对象
        StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);
        //5.调用实现类对象中的方法，接收结果
        List<Student> list = mapper.selectAll();
        //6.处理结果
        for (Student student : list) {
            System.out.println(student);
        }
        //7.释放资源
        sqlSession.close();
        is.close();
    }
    @Test
    public void insert() throws Exception{
        //1.加载核心配置文件
        InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml");
        //2.获取SqlSession工厂对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
        //3.通过工厂对象获取SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        //4.获取StudentMapper接口的实现类对象
        StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);
        //5.调用实现类对象中的方法，接收结果
        Student stu = new Student(4,"赵六",26);
        Integer result = mapper.insert(stu);
        //6.处理结果
        System.out.println(result);
        //7.释放资源
        sqlSession.close();
        is.close();
    }
    @Test
    public void update() throws Exception{
        //1.加载核心配置文件
        InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml");
        //2.获取SqlSession工厂对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
        //3.通过工厂对象获取SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        //4.获取StudentMapper接口的实现类对象
        StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);
        //5.调用实现类对象中的方法，接收结果
        Student stu = new Student(4,"赵六",36);
        Integer result = mapper.update(stu);
        //6.处理结果
        System.out.println(result);
        //7.释放资源
        sqlSession.close();
        is.close();
    }
    @Test
    public void delete() throws Exception{
        //1.加载核心配置文件
        InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml");
        //2.获取SqlSession工厂对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
        //3.通过工厂对象获取SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        //4.获取StudentMapper接口的实现类对象
        StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);
        //5.调用实现类对象中的方法，接收结果
        Integer result = mapper.delete(4);
        //6.处理结果
        System.out.println(result);
        //7.释放资源
        sqlSession.close();
        is.close();
    }
}

例如运行test1结果如下：

注意：

修改MyBatis的核心配置文件，我们使用了注解替代的映射文件，所以我们只需要加载使用了注解的Mapper接口即可

<mappers>
    <!--扫描使用注解的类-->
    <mapper class="com.yyl.mapper.UserMapper"></mapper>
</mappers>

​ 或者指定扫描包含映射关系的接口所在的包也可以

<mappers>
    <!--扫描使用注解的类所在的包-->
    <package name="com.yyl.mapper"></package>
</mappers>

注解开发总结

注解可以简化开发操作，省略映射配置文件的编写。

常用注解

@Select(“查询的 SQL 语句”)：执行查询操作注解
@Insert(“查询的 SQL 语句”)：执行新增操作注解
@Update(“查询的 SQL 语句”)：执行修改操作注解
@Delete(“查询的 SQL 语句”)：执行删除操作注解

配置映射关系

<mappers>
    <package name="接口所在包"/>
</mappers>

练习项目代码

bean

package com.yyl.bean;
public class Student {
    private Integer id;
    private String name;
    private Integer age;
    public Student() {
    }
    public Student(Integer id, String name, Integer age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

mapper.class

package com.yyl.mapper;
import com.yyl.bean.Student;
import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;
import java.util.List;
public interface StudentMapper {
    //查询全部
    @Select("SELECT * FROM student")
    public abstract List<Student> selectAll();
    //新增操作
    @Insert("INSERT INTO student VALUES (#{id},#{name},#{age})")
    public abstract Integer insert(Student stu);
    //修改操作
    @Update("UPDATE student SET name=#{name},age=#{age} WHERE id=#{id}")
    public abstract Integer update(Student stu);
    //删除操作
    @Delete("DELETE FROM student WHERE id=#{id}")
    public abstract Integer delete(Integer id);
}

test

package com.yyl.test;
import com.yyl.bean.Student;
import com.yyl.mapper.StudentMapper;
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 org.junit.Test;
import java.io.InputStream;
import java.util.List;
public class Test01 {
    @Test
    public void selectAll() throws Exception{
        //1.加载核心配置文件
        InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml");
        //2.获取SqlSession工厂对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
        //3.通过工厂对象获取SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        //4.获取StudentMapper接口的实现类对象
        StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);
        //5.调用实现类对象中的方法，接收结果
        List<Student> list = mapper.selectAll();
        //6.处理结果
        for (Student student : list) {
            System.out.println(student);
        }
        //7.释放资源
        sqlSession.close();
        is.close();
    }
    @Test
    public void insert() throws Exception{
        //1.加载核心配置文件
        InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml");
        //2.获取SqlSession工厂对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
        //3.通过工厂对象获取SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        //4.获取StudentMapper接口的实现类对象
        StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);
        //5.调用实现类对象中的方法，接收结果
        Student stu = new Student(4,"赵六",26);
        Integer result = mapper.insert(stu);
        //6.处理结果
        System.out.println(result);
        //7.释放资源
        sqlSession.close();
        is.close();
    }
    @Test
    public void update() throws Exception{
        //1.加载核心配置文件
        InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml");
        //2.获取SqlSession工厂对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
        //3.通过工厂对象获取SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        //4.获取StudentMapper接口的实现类对象
        StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);
        //5.调用实现类对象中的方法，接收结果
        Student stu = new Student(4,"赵六",36);
        Integer result = mapper.update(stu);
        //6.处理结果
        System.out.println(result);
        //7.释放资源
        sqlSession.close();
        is.close();
    }
    @Test
    public void delete() throws Exception{
        //1.加载核心配置文件
        InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml");
        //2.获取SqlSession工厂对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
        //3.通过工厂对象获取SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        //4.获取StudentMapper接口的实现类对象
        StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);
        //5.调用实现类对象中的方法，接收结果
        Integer result = mapper.delete(4);
        //6.处理结果
        System.out.println(result);
        //7.释放资源
        sqlSession.close();
        is.close();
    }
}

xml

<?xml version="1.0" encoding="UTF-8" ?>
<!--MyBatis的DTD约束-->
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">
<!--configuration 核心根标签-->
<configuration>
    <!--引入数据库连接的配置文件-->
    <properties resource="jdbc.properties"/>
    <!--配置LOG4J-->
    <settings>
        <setting name="logImpl" value="log4j"/>
    </settings>
    <!--起别名-->
    <typeAliases>
        <package name="com.yyl.bean"/>
    </typeAliases>
    <!--environments配置数据库环境，环境可以有多个。default属性指定使用的是哪个-->
    <environments default="mysql">
        <!--environment配置数据库环境  id属性唯一标识-->
        <environment id="mysql">
            <!-- transactionManager事务管理。  type属性，采用JDBC默认的事务-->
            <transactionManager type="JDBC"></transactionManager>
            <!-- dataSource数据源信息   type属性 连接池-->
            <dataSource type="POOLED">
                <!-- property获取数据库连接的配置信息 -->
                <property name="driver" value="${driver}" />
                <property name="url" value="${url}" />
                <property name="username" value="${username}" />
                <property name="password" value="${password}" />
            </dataSource>
        </environment>
    </environments>
    <!--配置映射关系-->
    <mappers>
        <package name="com.yyl.mapper"/>
    </mappers>
</configuration>

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