Mybatis进阶学习笔记——动态代理方式开发Dao接口、Dao层（推荐第二种）

1.原始方法开发Dao

Dao接口

 package cn.sm1234.dao;

 import java.util.List;

 import cn.sm1234.domain.Customer;

 public interface CustomerDao {

     public void saveCustomer(Customer customer);

     public void updateCustomer(Customer customer);

     public void deleteCustomer(Integer id);

     public List<Customer> queryAllCustomer();

     public Customer queryCustomerById(Integer id);

     public List<Customer> queryCustomerByName(String name);
 }

Dao实现：

 package cn.sm1234.dao.impl;

 import java.util.List;

 import org.apache.ibatis.session.SqlSession;

 import cn.sm1234.dao.CustomerDao;
 import cn.sm1234.domain.Customer;
 import cn.sm1234.utils.SessionUtils;

 public class CustomerDaoImpl implements CustomerDao {

     @Override
     public void saveCustomer(Customer customer) {
         SqlSession sqlSession = null;
         try {
             sqlSession = SessionUtils.getSesion();
             sqlSession.insert("insertCustomer", customer);
             sqlSession.commit();
         } catch (Exception e) {
             e.printStackTrace();
             sqlSession.rollback();
         } finally {
             sqlSession.close();
         }
     }

     @Override
     public void updateCustomer(Customer customer) {
         SqlSession sqlSession = null;
         try {
             sqlSession = SessionUtils.getSesion();
             sqlSession.update("updateCustomer", customer);
             sqlSession.commit();
         } catch (Exception e) {
             e.printStackTrace();
             sqlSession.rollback();
         } finally {
             sqlSession.close();
         }

     }

     @Override
     public void deleteCustomer(Integer id) {
         SqlSession sqlSession = null;
         try {
             sqlSession = SessionUtils.getSesion();
             sqlSession.delete("deleteCustomer", id);
             sqlSession.commit();
         } catch (Exception e) {
             e.printStackTrace();
             sqlSession.rollback();
         } finally {
             sqlSession.close();
         }

     }

     @Override
     public List<Customer> queryAllCustomer() {
         SqlSession sqlSession = null;
         try {
             sqlSession = SessionUtils.getSesion();
             return sqlSession.selectList("queryAllCustomer");
         } catch (Exception e) {
             e.printStackTrace();
         } finally {
             sqlSession.close();
         }
         return null;
     }

     @Override
     public Customer queryCustomerById(Integer id) {
         SqlSession sqlSession = null;
         try {
             sqlSession = SessionUtils.getSesion();
             return sqlSession.selectOne("queryCustomerById", id);
         } catch (Exception e) {
             e.printStackTrace();
         } finally {
             sqlSession.close();
         }
         return null;
     }

     @Override
     public List<Customer> queryCustomerByName(String name) {
         SqlSession sqlSession = null;
         try {
             sqlSession = SessionUtils.getSesion();
             return sqlSession.selectList("queryCustomerById", name);
         } catch (Exception e) {
             e.printStackTrace();
         } finally {
             sqlSession.close();
         }
         return null;
     }

 }

测试类：

package cn.sm1234.test;

import java.util.List;

import org.junit.Test;

import cn.sm1234.dao.CustomerDao;
import cn.sm1234.dao.impl.CustomerDaoImpl;
import cn.sm1234.domain.Customer;

public class Demo1 {

    @Test
    public void test1(){
        Customer c = new Customer();
        c.setName("陈六222");
        c.setGender("男");
        c.setTelephone("13244445555");

        CustomerDao dao = new CustomerDaoImpl();
        dao.saveCustomer(c);
    }

    @Test
    public void test2(){
        Customer c = new Customer();
        c.setId(1);
        c.setName("李四");

        CustomerDao dao = new CustomerDaoImpl();
        dao.updateCustomer(c);
    }

    @Test
    public void test3(){
        CustomerDao dao = new CustomerDaoImpl();
        dao.deleteCustomer(14);
    }

    @Test
    public void test4(){
        CustomerDao dao = new CustomerDaoImpl();
        List<Customer> list = dao.queryAllCustomer();
        for (Customer customer : list) {
            System.out.println(customer);
        }
    }

    @Test
    public void test5(){
        CustomerDao dao = new CustomerDaoImpl();
        Customer customer = dao.queryCustomerById(1);
        System.out.println(customer);
    }

    @Test
    public void test6(){
        CustomerDao dao = new CustomerDaoImpl();
        List<Customer> list = dao.queryCustomerByName("%陈%");
        for (Customer customer : list) {
            System.out.println(customer);
        }
    }
}

Customer.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">
 <!-- 该文件存放CRUD的sql语句 -->
 <mapper namespace="test">
     <!-- 添加 -->
     <insert id="insertCustomer" parameterType="customer">
         INSERT INTO t_customer(NAME,gender,telephone) VALUES(#{name},#{gender},#{telephone})
     </insert>

     <!-- 修改 -->
     <!-- parameterType传入对象，包含需要使用的值 -->
     <update id="updateCustomer" parameterType="customer">
         UPDATE t_customer SET NAME = #{name} WHERE id = #{id}
     </update>

     <!-- 查询所有数据 -->
     <!-- 输出映射 resultType -->
     <!-- parameterType可以省略，resultType不可以省略 -->
     <select id="queryAllCustomer" resultType="customer">
         SELECT * FROM t_customer
     </select>

     <!-- 根据id查询 -->
     <select id="queryCustomerById" parameterType="_int" resultType="customer">
         SELECT * FROM t_customer WHERE id=#{value}
     </select>

     <!-- 根据name模糊查询 -->
     <select id="queryCustomerByName" parameterType="string" resultType="customer">
         <!-- 方法一 -->
         SELECT * FROM t_customer WHERE NAME LIKE #{value}
         <!-- 方法二 -->
         <!-- SELECT * FROM t_customer WHERE NAME LIKE '%${value}%' -->
     </select>

     <!-- 删除 -->
     <delete id="deleteCustomer" parameterType="int">
         DELETE FROM t_customer WHERE id=#{value}
     </delete>    

 </mapper>

缺点：代码繁琐。

解决方法：利用动态代理方式Dao接口开发。Dao层只需要接口，不需要重复的Dao层实现。

2.动态代理方式开发Dao层（推荐使用）

好处：无需再去编写Dao层的实现类。

Dao接口：

 package cn.sm1234.dao;

 import java.util.List;

 import cn.sm1234.domain.Customer;

 public interface CustomerDao {

     public void saveCustomer(Customer customer);

     public void updateCustomer(Customer customer);

     public void deleteCustomer(Integer id);

     public List<Customer> queryAllCustomer();

     public Customer queryCustomerById(Integer id);

     public List<Customer> queryCustomerByName(String name);
 }

Customer.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">
 <!-- 该文件存放CRUD的sql语句 -->
 <!--
     如果是动态代理方式
       1）namespace必须和Dao接口的路径保持一致
       2）Dao接口里面的方法和sql语句的id保持一致
       3）Dao接口的方法的参数和返回值类型 和 映射文件的parameterType和resultType要对应
  -->
 <mapper namespace="cn.sm1234.dao.CustomerDao">
     <!-- 添加 -->
     <insert id="saveCustomer" parameterType="customer">
         INSERT INTO t_customer(NAME,gender,telephone) VALUES(#{name},#{gender},#{telephone})
     </insert>

     <!-- 修改 -->
     <!-- parameterType传入对象，包含需要使用的值 -->
     <update id="updateCustomer" parameterType="customer">
         UPDATE t_customer SET NAME = #{name} WHERE id = #{id}
     </update>

     <!-- 查询所有数据 -->
     <!-- 输出映射 resultType -->
     <!-- parameterType可以省略，resultType不可以省略 -->
     <select id="queryAllCustomer" resultType="customer">
         SELECT * FROM t_customer
     </select>

     <!-- 根据id查询 -->
     <select id="queryCustomerById" parameterType="_int" resultType="customer">
         SELECT * FROM t_customer WHERE id=#{value}
     </select>

     <!-- 根据name模糊查询 -->
     <select id="queryCustomerByName" parameterType="string" resultType="customer">
         <!-- 方法一 -->
         SELECT * FROM t_customer WHERE NAME LIKE #{value}
         <!-- 方法二 -->
         <!-- SELECT * FROM t_customer WHERE NAME LIKE '%${value}%' -->
     </select>

     <!-- 删除 -->
     <delete id="deleteCustomer" parameterType="int">
         DELETE FROM t_customer WHERE id=#{value}
     </delete>    

 </mapper>

测试代码：

 package cn.sm1234.test;

 import java.util.List;

 import org.apache.ibatis.session.SqlSession;
 import org.junit.Test;

 import cn.sm1234.dao.CustomerDao;
 import cn.sm1234.domain.Customer;
 import cn.sm1234.utils.SessionUtils;

 public class Demo2 {

     @Test
     public void test1(){
         Customer c = new Customer();
         c.setName("陈六333");
         c.setGender("男");
         c.setTelephone("13244445555");

         SqlSession sqlSession = SessionUtils.getSession();
         //getMapper(): 返回指定接口的动态代理的实现类对象
         CustomerDao dao = sqlSession.getMapper(CustomerDao.class);
         dao.saveCustomer(c);
         sqlSession.commit();
         sqlSession.close();
     }

     @Test
     public void test2(){
         Customer c = new Customer();
         c.setId(1);
         c.setName("李四222");

         SqlSession sqlSession = SessionUtils.getSession();
         //getMapper(): 返回指定接口的动态代理的实现类对象
         CustomerDao dao = sqlSession.getMapper(CustomerDao.class);
         dao.updateCustomer(c);
         sqlSession.commit();
         sqlSession.close();
     }

     @Test
     public void test3(){
         SqlSession sqlSession = SessionUtils.getSession();
         CustomerDao dao = sqlSession.getMapper(CustomerDao.class);
         dao.deleteCustomer(19);
         sqlSession.commit();
         sqlSession.close();
     }

     @Test
     public void test4(){
         SqlSession sqlSession = SessionUtils.getSession();
         CustomerDao dao = sqlSession.getMapper(CustomerDao.class);
         List<Customer> list = dao.queryAllCustomer();
         for (Customer customer : list) {
             System.out.println(customer);
         }
     }

     @Test
     public void test5(){
         SqlSession sqlSession = SessionUtils.getSession();
         CustomerDao dao = sqlSession.getMapper(CustomerDao.class);
         Customer customer = dao.queryCustomerById(1);
         System.out.println(customer);
     }

     @Test
     public void test6(){
         SqlSession sqlSession = SessionUtils.getSession();
         CustomerDao dao = sqlSession.getMapper(CustomerDao.class);
         List<Customer> list = dao.queryCustomerByName("%陈%");
         for (Customer customer : list) {
             System.out.println(customer);
         }
     }
 }

要点总结：

如果是动态代理方式
1）namespace必须和Dao接口的路径保持一致
2）Dao接口里面的方法和sql语句的id保持一致
3） Dao接口的方法的参数和返回值类型 和 映射文件的parameterType和resultType要对应