Mybatis进阶学习笔记——动态sql

1.if标签

 1     <select id="queryByNameAndTelephone" parameterType="Customer"
 2         resultType="Customer">
 3         SELECT * FROM t_customer
 4         WHERE 1=1
 5         <if test="name!=null and name!=''">
 6             AND NAME LIKE #{name}
 7         </if>
 8         <if test="telephone!=null and telephone!=''">
 9             AND telephone LIKE #{telephone}
10         </if>
11     </select>

 1 public List<Customer> queryByNameAndTelephone(Customer customer); 

 1     /**
 2      * if标签使用
 3      */
 4     @Test
 5     public void test1() {
 6         SqlSession sqlSession = SessionUtils.getSession();
 7         // getMapper(): 返回指定接口的动态代理的实现类对象
 8         CustomerDao dao = sqlSession.getMapper(CustomerDao.class);
 9         Customer c = new Customer();
10         //c.setName("%陈%");
11         c.setTelephone("%55%");
12         List<Customer> list = dao.queryByNameAndTelephone(c);
13         for (Customer customer : list) {
14             System.out.println(customer);
15         }
16         sqlSession.commit();
17         sqlSession.close();
18     }

2.where标签：自动把第一个条件的and去掉

 1     <select id="queryByNameAndTelephone" parameterType="Customer"
 2         resultType="Customer">
 3         SELECT * FROM t_customer
 4         <!-- <where>：where条件，自动把第一个条件的and去掉 -->
 5         <where>
 6             <if test="name!=null and name!=''">
 7                 AND NAME LIKE #{name}
 8             </if>
 9             <if test="telephone!=null and telephone!=''">
10                 AND telephone LIKE #{telephone}
11             </if>
12         </where>
13     </select>

3.sql片段

作用：把相同的sql片段抽取出来

1     <!-- sql片段 -->
2     <sql id="customerField">
3         id,name,gender,telephone
4     </sql>

 1     <select id="queryByNameAndTelephone" parameterType="Customer"
 2         resultType="Customer">
 3         SELECT
 4         <include refid="customerField"/>
 5         FROM t_customer
 6         <!-- <where>：where条件，自动把第一个条件的and去掉 -->
 7         <where>
 8             <if test="name!=null and name!=''">
 9                 AND NAME LIKE #{name}
10             </if>
11             <if test="telephone!=null and telephone!=''">
12                 AND telephone LIKE #{telephone}
13             </if>
14         </where>
15     </select>

4.foreach标签

 1     <delete id="deleteCustomerByIn" parameterType="Customer">
 2         DELETE FROM t_customer WHERE 
 3         <!-- 
 4             collection: 需要遍历的属性
 5             item: 遍历的变量
 6             open: 循环前面的 sql语句
 7             close： 循环后面的 sql语句
 8             separator：分隔符
 9             
10             id IN(1,2,3)
11          -->
12          <!-- id为ids数组中的每个元素 -->
13         <foreach collection="ids" item="id" open="id IN (" close=")" separator=",">
14             #{id}
15         </foreach>
16     </delete>

 1 public void deleteCustomerByIn(Customer customer); 

 1     /**
 2      * foreach标签
 3      */
 4     @Test
 5     public void test2() {
 6         SqlSession sqlSession = SessionUtils.getSession();
 7         // getMapper(): 返回指定接口的动态代理的实现类对象
 8         CustomerDao dao = sqlSession.getMapper(CustomerDao.class);
 9         Customer c = new Customer();
10         Integer[] ids = {23,24,25};
11         c.setIds(ids);
12         dao.deleteCustomerByIn(c);
13         sqlSession.commit();
14         sqlSession.close();
15     }

Customer.java：

 1 package cn.sm1234.domain;
 2 
 3 import java.util.Arrays;
 4 
 5 public class Customer {
 6 
 7     private Integer id;
 8     private String name;
 9     private String gender;
10     private String telephone;
11     
12     private Integer ids[];
13     
14     public Integer getId() {
15         return id;
16     }
17     public void setId(Integer id) {
18         this.id = id;
19     }
20     public String getName() {
21         return name;
22     }
23     public void setName(String name) {
24         this.name = name;
25     }
26     public String getGender() {
27         return gender;
28     }
29     public void setGender(String gender) {
30         this.gender = gender;
31     }
32     public String getTelephone() {
33         return telephone;
34     }
35     public void setTelephone(String telephone) {
36         this.telephone = telephone;
37     }
38     public Integer[] getIds() {
39         return ids;
40     }
41     public void setIds(Integer[] ids) {
42         this.ids = ids;
43     }
44     @Override
45     public String toString() {
46         return "Customer [id=" + id + ", name=" + name + ", gender=" + gender + ", telephone=" + telephone + ", ids="
47                 + Arrays.toString(ids) + "]";
48     }
49     
50     
51 }