mybatis接口

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定义

接口interface:用于定义规则;内容:常量/抽象方法

public interface Speak {
    // 常量:一般大写
    /* 接口中常量的修饰符public static final省略会自动加上*/ int AGE = 18;

    // 抽象方法
    /* public abstract也可省略 */ void say();

}

接口和继承的区别:

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之前项目存在的问题:方法不能直接调用,需要设置resultType;多个参数处理麻烦;项目没有规范可言,不利于面向接口编程思想

接口绑定方案

  1. 创建新的maven项目
  2. 配置pom.xml
  3. 配置全局配置文件
  4. 配置数据库属性文件
  5. 日志配置文件
  6. 创建实体类
  7. 创建接口
  8. 创建映射文件:namespace取值必须是接口的全限定路径、标签中的id属性值必须和方法名对应
  9. 编写测试类

uTools_1691309621293.png

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config //EN"
        "https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <properties resource="db.properties"></properties>
    <typeAliases>
        <package name="com.msb.pojo"/>
    </typeAliases>
    <environments default="mysql">
        <environment id="mysql">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="${driver}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/msb/mapper/BookMapper.xml"></mapper>
    </mappers>
</configuration>
package com.msb.mapper;

import java.util.List;

public interface BookMapper {
    public abstract List selectAllBooks();
}
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper //EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.msb.mapper.BookMapper">    <!--namespace自定义-->
    <select id="selectAllBooks" resultType="Book">
        select * from t_book
    </select>
</mapper>
package com.ms b;

import com.msb.mapper.BookMapper;
import com.msb.pojo.Book;
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.IOException;
import java.io.InputStream;
import java.util.List;

public class Test {
    public static void main(String[] args) throws IOException {
        // 指定核心配置文件路径
        String resource = "mybatis.xml";
        // 获取加载配置文件的输入流:
        InputStream inputStream = Resources.getResourceAsStream(resource);
        // 加载配置文件,创建工厂类
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        // 通过工厂创建一个会话
        SqlSession sqlSession = sqlSessionFactory.openSession();
        // 动态代理模式:通过接口找到接口的实现类 BookMapper mapper = BookMapper实现类
        BookMapper mapper = sqlSession.getMapper(BookMapper.class);
        List list = mapper.selectAllBooks();        
        // 遍历
        for (int i = 0; i <= list.size() -1 ; i++) {
            Book b = (Book)list.get(i);
            System.out.println(b.getName());
        }
        // 关闭资源
        sqlSession.close();
    }
}