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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

 1 package cn.sm1234.dao;
 2 
 3 import java.util.List;
 4 
 5 import cn.sm1234.domain.Customer;
 6 
 7 public interface CustomerDao {
 8 
 9     public void saveCustomer(Customer customer);
10     
11     public void updateCustomer(Customer customer);
12     
13     public void deleteCustomer(Integer id);
14     
15     public List<Customer> queryAllCustomer();
16     
17     public Customer queryCustomerById(Integer id);
18     
19     public List<Customer> queryCustomerByName(String name);
20 }

Dao实现：

  1 package cn.sm1234.dao.impl;
  2 
  3 import java.util.List;
  4 
  5 import org.apache.ibatis.session.SqlSession;
  6 
  7 import cn.sm1234.dao.CustomerDao;
  8 import cn.sm1234.domain.Customer;
  9 import cn.sm1234.utils.SessionUtils;
 10 
 11 public class CustomerDaoImpl implements CustomerDao {
 12 
 13     @Override
 14     public void saveCustomer(Customer customer) {
 15         SqlSession sqlSession = null;
 16         try {
 17             sqlSession = SessionUtils.getSesion();
 18             sqlSession.insert("insertCustomer", customer);
 19             sqlSession.commit();
 20         } catch (Exception e) {
 21             e.printStackTrace();
 22             sqlSession.rollback();
 23         } finally {
 24             sqlSession.close();
 25         }
 26     }
 27 
 28     @Override
 29     public void updateCustomer(Customer customer) {
 30         SqlSession sqlSession = null;
 31         try {
 32             sqlSession = SessionUtils.getSesion();
 33             sqlSession.update("updateCustomer", customer);
 34             sqlSession.commit();
 35         } catch (Exception e) {
 36             e.printStackTrace();
 37             sqlSession.rollback();
 38         } finally {
 39             sqlSession.close();
 40         }
 41 
 42     }
 43 
 44     @Override
 45     public void deleteCustomer(Integer id) {
 46         SqlSession sqlSession = null;
 47         try {
 48             sqlSession = SessionUtils.getSesion();
 49             sqlSession.delete("deleteCustomer", id);
 50             sqlSession.commit();
 51         } catch (Exception e) {
 52             e.printStackTrace();
 53             sqlSession.rollback();
 54         } finally {
 55             sqlSession.close();
 56         }
 57 
 58     }
 59 
 60     @Override
 61     public List<Customer> queryAllCustomer() {
 62         SqlSession sqlSession = null;
 63         try {
 64             sqlSession = SessionUtils.getSesion();
 65             return sqlSession.selectList("queryAllCustomer");
 66         } catch (Exception e) {
 67             e.printStackTrace();
 68         } finally {
 69             sqlSession.close();
 70         }
 71         return null;
 72     }
 73 
 74     @Override
 75     public Customer queryCustomerById(Integer id) {
 76         SqlSession sqlSession = null;
 77         try {
 78             sqlSession = SessionUtils.getSesion();
 79             return sqlSession.selectOne("queryCustomerById", id);
 80         } catch (Exception e) {
 81             e.printStackTrace();
 82         } finally {
 83             sqlSession.close();
 84         }
 85         return null;
 86     }
 87 
 88     @Override
 89     public List<Customer> queryCustomerByName(String name) {
 90         SqlSession sqlSession = null;
 91         try {
 92             sqlSession = SessionUtils.getSesion();
 93             return sqlSession.selectList("queryCustomerById", name);
 94         } catch (Exception e) {
 95             e.printStackTrace();
 96         } finally {
 97             sqlSession.close();
 98         }
 99         return null;
100     }
101 
102 }

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：

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE mapper
 3 PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
 4 "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 5 <!-- 该文件存放CRUD的sql语句 -->
 6 <mapper namespace="test">
 7     <!-- 添加 -->
 8     <insert id="insertCustomer" parameterType="customer">
 9         INSERT INTO t_customer(NAME,gender,telephone) VALUES(#{name},#{gender},#{telephone})
10     </insert>
11 
12     <!-- 修改 -->    
13     <!-- parameterType传入对象，包含需要使用的值 -->
14     <update id="updateCustomer" parameterType="customer">
15         UPDATE t_customer SET NAME = #{name} WHERE id = #{id}
16     </update>
17     
18     <!-- 查询所有数据 -->
19     <!-- 输出映射 resultType -->
20     <!-- parameterType可以省略，resultType不可以省略 -->
21     <select id="queryAllCustomer" resultType="customer">
22         SELECT * FROM t_customer
23     </select>
24     
25     <!-- 根据id查询 -->
26     <select id="queryCustomerById" parameterType="_int" resultType="customer">
27         SELECT * FROM t_customer WHERE id=#{value}
28     </select>
29     
30     <!-- 根据name模糊查询 -->
31     <select id="queryCustomerByName" parameterType="string" resultType="customer">
32         <!-- 方法一 -->
33         SELECT * FROM t_customer WHERE NAME LIKE #{value}
34         <!-- 方法二 -->
35         <!-- SELECT * FROM t_customer WHERE NAME LIKE '%${value}%' -->
36     </select>
37     
38     <!-- 删除 -->
39     <delete id="deleteCustomer" parameterType="int">
40         DELETE FROM t_customer WHERE id=#{value}
41     </delete>    
42 
43 </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：

 1 package cn.sm1234.dao;
 2 
 3 import java.util.List;
 4 
 5 import cn.sm1234.domain.Customer;
 6 
 7 public interface CustomerDao {
 8 
 9     public void saveCustomer(Customer customer);
10     
11     public void updateCustomer(Customer customer);
12     
13     public void deleteCustomer(Integer id);
14     
15     public List<Customer> queryAllCustomer();
16     
17     public Customer queryCustomerById(Integer id);
18     
19     public List<Customer> queryCustomerByName(String name);
20 }

Customer.xml：

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE mapper
 3 PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
 4 "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 5 <!-- 该文件存放CRUD的sql语句 -->
 6 <!-- 
 7     如果是动态代理方式
 8       1）namespace必须和Dao接口的路径保持一致
 9       2）Dao接口里面的方法和sql语句的id保持一致
10       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
11  -->
12 <mapper namespace="cn.sm1234.dao.CustomerDao">
13     <!-- 添加 -->
14     <insert id="saveCustomer" parameterType="customer">
15         INSERT INTO t_customer(NAME,gender,telephone) VALUES(#{name},#{gender},#{telephone})
16     </insert>
17 
18     <!-- 修改 -->    
19     <!-- parameterType传入对象，包含需要使用的值 -->
20     <update id="updateCustomer" parameterType="customer">
21         UPDATE t_customer SET NAME = #{name} WHERE id = #{id}
22     </update>
23     
24     <!-- 查询所有数据 -->
25     <!-- 输出映射 resultType -->
26     <!-- parameterType可以省略，resultType不可以省略 -->
27     <select id="queryAllCustomer" resultType="customer">
28         SELECT * FROM t_customer
29     </select>
30     
31     <!-- 根据id查询 -->
32     <select id="queryCustomerById" parameterType="_int" resultType="customer">
33         SELECT * FROM t_customer WHERE id=#{value}
34     </select>
35     
36     <!-- 根据name模糊查询 -->
37     <select id="queryCustomerByName" parameterType="string" resultType="customer">
38         <!-- 方法一 -->
39         SELECT * FROM t_customer WHERE NAME LIKE #{value}
40         <!-- 方法二 -->
41         <!-- SELECT * FROM t_customer WHERE NAME LIKE '%${value}%' -->
42     </select>
43     
44     <!-- 删除 -->
45     <delete id="deleteCustomer" parameterType="int">
46         DELETE FROM t_customer WHERE id=#{value}
47     </delete>    
48 
49 </mapper>

测试代码：

 1 package cn.sm1234.test;
 2 
 3 import java.util.List;
 4 
 5 import org.apache.ibatis.session.SqlSession;
 6 import org.junit.Test;
 7 
 8 import cn.sm1234.dao.CustomerDao;
 9 import cn.sm1234.domain.Customer;
10 import cn.sm1234.utils.SessionUtils;
11 
12 public class Demo2 {
13 
14     @Test
15     public void test1(){
16         Customer c = new Customer();
17         c.setName("陈六333");
18         c.setGender("男");
19         c.setTelephone("13244445555");
20         
21         SqlSession sqlSession = SessionUtils.getSession();
22         //getMapper(): 返回指定接口的动态代理的实现类对象
23         CustomerDao dao = sqlSession.getMapper(CustomerDao.class);
24         dao.saveCustomer(c);
25         sqlSession.commit();
26         sqlSession.close();
27     }
28     
29     @Test
30     public void test2(){
31         Customer c = new Customer();
32         c.setId(1);
33         c.setName("李四222");
34         
35         SqlSession sqlSession = SessionUtils.getSession();
36         //getMapper(): 返回指定接口的动态代理的实现类对象
37         CustomerDao dao = sqlSession.getMapper(CustomerDao.class);
38         dao.updateCustomer(c);
39         sqlSession.commit();
40         sqlSession.close();
41     }
42     
43     @Test
44     public void test3(){
45         SqlSession sqlSession = SessionUtils.getSession();
46         CustomerDao dao = sqlSession.getMapper(CustomerDao.class);
47         dao.deleteCustomer(19);
48         sqlSession.commit();
49         sqlSession.close();
50     }
51     
52     @Test
53     public void test4(){
54         SqlSession sqlSession = SessionUtils.getSession();
55         CustomerDao dao = sqlSession.getMapper(CustomerDao.class);
56         List<Customer> list = dao.queryAllCustomer();
57         for (Customer customer : list) {
58             System.out.println(customer);
59         }
60     }
61     
62     @Test
63     public void test5(){
64         SqlSession sqlSession = SessionUtils.getSession();
65         CustomerDao dao = sqlSession.getMapper(CustomerDao.class);
66         Customer customer = dao.queryCustomerById(1);
67         System.out.println(customer);
68     }
69     
70     @Test
71     public void test6(){
72         SqlSession sqlSession = SessionUtils.getSession();
73         CustomerDao dao = sqlSession.getMapper(CustomerDao.class);
74         List<Customer> list = dao.queryCustomerByName("%陈%");
75         for (Customer customer : list) {
76             System.out.println(customer);
77         }
78     }
79 }

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

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原文地址：https://www.cnblogs.com/116970u/p/10158956.html