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:
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
- 创建新的maven项目
- 配置pom.xml
- 配置全局配置文件
- 配置数据库属性文件
- 日志配置文件
- 创建实体类
- 创建接口
- 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
- 编写测试类
<?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();
}
}