【Java闭关修炼】MyBatis-接口代理的方式实现Dao层

实现规则

• 映射配置文件中的名称空间必须和Dao层接口的全类名相同
• 映射配置文件的增删改查标签的id属性必须和Dao层接口方法的参数相同
• 映射配置文件中的增删改查标签的parameterType属性必须和Dao层接口方法的参数相同
• 映射配置文件中的增删改查标签中的resultType属性必须和Dao层接口方法的返回值相同

代码实现

• 删除mapper层接口的实现类

• 修改映射配置文件

• 修改service层接口的实现类 采用接口代理方式实现功能

• mapper层接口

package com.itheima.mapper;import com.itheima.bean.Student;import java.util.List;/*持久层接口*/// 接口的名称要和namespace一样
public interface StudentMapper {//查询全部public abstract List<Student> selectAll();//根据id查询public abstract Student selectById(Integer id);//新增数据public abstract Integer insert(Student stu);//修改数据public abstract Integer update(Student stu);//删除数据public abstract Integer delete(Integer id);//多条件查询public abstract List<Student> selectCondition(Student stu);//根据多个id查询public abstract List<Student> selectByIds(List<Integer> ids);
}

• 映射配置文件

<?xml version="1.0" encoding="UTF-8" ?>
<!--MyBatis的DTD约束-->
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd"><!--mapper：核心根标签namespace属性：名称空间
--><!--名称空间要和接口的路径保持一致-->
<mapper namespace="com.itheima.mapper.StudentMapper"><sql id="select" >SELECT * FROM student</sql><!--select：查询功能的标签id属性：唯一标识resultType属性：指定结果映射对象类型  返回值类型parameterType属性：指定参数映射对象类型--><!--    id必须和方法名保持一致--><select id="selectAll" resultType="student"><include refid="select"/></select><select id="selectById" resultType="student" parameterType="int"><include refid="select"/> WHERE id = #{id}</select><insert id="insert" parameterType="student">INSERT INTO student VALUES (#{id},#{name},#{age})</insert><update id="update" parameterType="student">UPDATE student SET name = #{name},age = #{age} WHERE id = #{id}</update><delete id="delete" parameterType="int">DELETE FROM student WHERE id = #{id}</delete><select id="selectCondition" resultType="student" parameterType="student"><include refid="select"/><where><if test="id != null">id = #{id}</if><if test="name != null">AND name = #{name}</if><if test="age != null">AND age = #{age}</if></where></select><select id="selectByIds" resultType="student" parameterType="list"><include refid="select"/><where><foreach collection="list" open="id IN (" close=")" item="id" separator=",">#{id}</foreach></where></select>
</mapper>

• StudentServiceImpl

package com.itheima.service.impl;import com.itheima.bean.Student;
import com.itheima.mapper.StudentMapper;
import com.itheima.service.StudentService;
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;
/*业务层实现类*/
public class StudentServiceImpl implements StudentService {@Overridepublic List<Student> selectAll() throws IOException {List<Student> students = null;SqlSession sqlSession = null;InputStream is = null;// 没有了持久层实现对象  只有持久层的接口try{// 加载核心配置文件is = Resources.getResourceAsStream("MyBatisConfig.xml");// 返回一个字节输入流对象// 获取sqlSession工厂对象SqlSessionFactory build = new SqlSessionFactoryBuilder().build(is);// 通过工厂对象获取SqlSession对象sqlSession = build.openSession(true);// 代表自动提交事务// 获取StudentMapper接口的实现类对象// 父类的接口指向实现类对象StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);// 通过实现类对象调用方法  接受结果students = mapper.selectAll();// 释放资源// 返回结果}catch(Exception e){e.printStackTrace();}finally {// 释放资源if(sqlSession != null){sqlSession.close();}if(is != null){is.close();}}// 返回结果return students;}@Overridepublic Student selectById(Integer id) throws IOException {// 根据id来查询对象Student stu = null;SqlSession sqlSession = null;InputStream is = null;try{// 加载核心配置文件is = Resources.getResourceAsStream("MyBatisConfig.xml");//获取工厂对象SqlSessionFactory build = new SqlSessionFactoryBuilder().build(is);// 通过工厂对象获取SqlSessionsqlSession = build.openSession(true);// 代表自动提交事务// 获取StudentMapper接口的实现类对象StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);// 通过实现类对象调用方法  接受结果stu = mapper.selectById(id);// 获取学生对象}catch (Exception e){e.printStackTrace();}finally {if(sqlSession != null){sqlSession.close();}if(is != null){is.close();}}// 获取学生对象return stu;}// 新增学生对象@Overridepublic Integer insert(Student stu) throws IOException {// 根据id来查询对象Integer result = null;SqlSession sqlSession = null;InputStream is = null;try{// 加载核心配置文件is = Resources.getResourceAsStream("MyBatisConfig.xml");//获取工厂对象SqlSessionFactory build = new SqlSessionFactoryBuilder().build(is);// 通过工厂对象获取SqlSessionsqlSession = build.openSession(true);// 代表自动提交事务// 获取StudentMapper接口的实现类对象StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);// 通过实现类对象调用方法  接受结果result = mapper.insert(stu);// 返回影响的行数}catch (Exception e){e.printStackTrace();}finally {if(sqlSession != null){sqlSession.close();}if(is != null){is.close();}}// 获取学生对象return result;}@Overridepublic Integer update(Student stu) throws IOException {// 根据id来查询对象Integer result = null;SqlSession sqlSession = null;InputStream is = null;try{// 加载核心配置文件is = Resources.getResourceAsStream("MyBatisConfig.xml");//获取工厂对象SqlSessionFactory build = new SqlSessionFactoryBuilder().build(is);// 通过工厂对象获取SqlSessionsqlSession = build.openSession(true);// 代表自动提交事务// 获取StudentMapper接口的实现类对象StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);// 通过实现类对象调用方法  接受结果result = mapper.update(stu);// 返回影响的行数}catch (Exception e){e.printStackTrace();}finally {if(sqlSession != null){sqlSession.close();}if(is != null){is.close();}}// 获取学生对象return result;}@Overridepublic Integer delete(Integer id) throws IOException {// 根据id来查询对象Integer result = null;SqlSession sqlSession = null;InputStream is = null;try{// 加载核心配置文件is = Resources.getResourceAsStream("MyBatisConfig.xml");//获取工厂对象SqlSessionFactory build = new SqlSessionFactoryBuilder().build(is);// 通过工厂对象获取SqlSessionsqlSession = build.openSession(true);// 代表自动提交事务// 获取StudentMapper接口的实现类对象StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);// 通过实现类对象调用方法  接受结果result = mapper.delete(id);// 返回影响的行数}catch (Exception e){e.printStackTrace();}finally {if(sqlSession != null){sqlSession.close();}if(is != null){is.close();}}// 获取学生对象return result;}
}

代理对象分析

接口代理方式小结

• 接口代理方式可以让我们之编写接口即可，而实现类对象由MyBatis生成

• 实现规则

  • 映射配置文件中的名称空间必须和Dao层接口的全类名相同
  • 映射配置文件中的增删改查标签的id属性必须和Dao层接口的方法名相同
  • 映射配置文件中的增删改查标签的parameterType属性必须和Dao层接口方法的参数相同
  • 映射配置文件中的增删改查标签的resultType属性必须和Dao层接口方法的返回值相同

• 获取动态代理对象

  • SqlSession功能类中的getMapper()方法