Mybatis之XML、注解
前言
上篇简单介绍了Mybatis的简单实用，本篇先对上次实验环境的一些内容进行优化，然后验证Mybatis的XML配置以及注解方式。
实验环境优化
数据库配置
在mybatis的配置文件中，引入数据库配置文件db.properties，然后修改配置文件
driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis
name=root
password=admin
mybatis配置文件 mybatis-config.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<!-- 数据库配置文件 -->
<properties resource="db.properties"/>
<!--
development : 开发模式
work : 工作模式
-->
<environments default="development">
<environment id="development">
<transactionManager type="JDBC" />
<dataSource type="POOLED">
<property name="driver" value="${driver}" />
<property name="url" value="${url}" />
<property name="username" value="${name}" />
<property name="password" value="${password}" />
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="com/lion/mapper/UserMapper.xml" />
</mappers>
</configuration>
实体类定义别名
没有为实体定义别名时，在sql映射xml中应用实体时，比如parameterType resultType 中就需要配置实体的全路径名（全限定名）。
当为实体定义了别名后，映射文件中可以直接配置实体的别名即可。因此为实体类定义别名，可以简化Sql映射xml文件中对实体的引用配置。
mybatis配置文件中<typeAlises>定义实体别名有两种方式：
- typeAlias 单个为每个实体定义别名 当实体类比较多是 配置增多 不方便
- package 指定实体的包 会自动为改包下的所有实体自动设定各自的类名为别名
优化后的Mybatis配置文件mybatis-config.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<!-- 数据库配置文件 -->
<properties resource="db.properties"/>
<!-- 配置实体的别名 -->
<typeAliases>
<!-- 此种方式是分别为每一个实体设置别名 mapper xml 中resultType即为alias的值-->
<!-- <typeAlias type="com.lion.pojo.User" alias="_User"/> -->
<!-- package 设置别名的方式会自动为该包下的所有JavaBean设置别名为其类名称 -->
<package name="com.lion.pojo"/>
</typeAliases>
<!--
development : 开发模式
work : 工作模式
-->
<environments default="development">
<environment id="development">
<transactionManager type="JDBC" />
<dataSource type="POOLED">
<property name="driver" value="${driver}" />
<property name="url" value="${url}" />
<property name="username" value="${name}" />
<property name="password" value="${password}" />
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="com/lion/mapper/UserMapper.xml" />
</mappers>
</configuration>
Mybatis实现方式
分别使用XML和注解的方式实现对User的CURD。
XML方式
sql中参数定义为 #{} 在Mybatis配置文件中已经配置对实体类的自动设置别名，因此此处可以直接使用实体类的别名进行引用。
<?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">
<mapper namespace="com.lion.mapper.UserMapper">
<select id="selectUser" parameterType="int" resultType="User">
select * from users where id = #{id}
</select>
<delete id="deleteUser" parameterType="int">
delete from users where id = #{id}
</delete>
<update id="updateUser" parameterType="User">
update users set name = #{name},age = #{age} where id = #{id}
</update>
<insert id="addUser" parameterType="User">
insert into users(name,age) values(#{name},#{age})
</insert>
<select id="selectAll" resultType="User" >
select * from users
</select>
</mapper>
1 package com.lion.test;
2
3 import java.io.IOException;
4 import java.util.List;
5
6 import org.apache.ibatis.session.SqlSession;
7 import org.apache.ibatis.session.SqlSessionFactory;
8 import org.junit.Test;
9
10 import com.lion.pojo.User;
11 import com.lion.util.MybatisUtils;
12
13 public class TestUserCURDByXML {
14
15 @Test
16 public void testAdd() {
17 try {
18 SqlSessionFactory factory = MybatisUtils.getFactory();
19 SqlSession session = factory.openSession();
20
21 String statement = "com.lion.mapper.UserMapper.addUser";
22 // id mysql设置的自增长 此处设为 -1
23 User user = new User(-1, "Spring", 25);
24 session.insert(statement, user);
25
26 // 不提交的话 数据无法提交到数据库
27 session.commit();
28 session.close();
29 } catch (IOException e) {
30 e.printStackTrace();
31 }
32 }
33
34 @Test
35 public void testDelete() {
36 try {
37 SqlSessionFactory factory = MybatisUtils.getFactory();
38 // 自动提交事务
39 SqlSession session = factory.openSession(true);
40
41 String statement = "com.lion.mapper.UserMapper.deleteUser";
42 session.delete(statement, 4);
43
44 session.close();
45 } catch (IOException e) {
46 e.printStackTrace();
47 }
48 }
49
50 @Test
51 public void testUpdate() {
52 try {
53 SqlSessionFactory factory = MybatisUtils.getFactory();
54 // 自动提交事务
55 SqlSession session = factory.openSession(true);
56
57 String statement = "com.lion.mapper.UserMapper.updateUser";
58 User user = new User(1, "mali", 18);
59 session.update(statement, user);
60
61 session.close();
62 } catch (IOException e) {
63 e.printStackTrace();
64 }
65 }
66
67 @Test
68 public void testSelect() {
69 try {
70 SqlSessionFactory factory = MybatisUtils.getFactory();
71 // 自动提交事务
72 SqlSession session = factory.openSession(true);
73
74 String statement = "com.lion.mapper.UserMapper.selectAll";
75 List<User> users = session.selectList(statement);
76 for (User user : users) {
77 System.out.println(user);
78 }
79
80 session.close();
81 } catch (IOException e) {
82 e.printStackTrace();
83 }
84 }
85
86 }
注解方式
package com.lion.testAnnotation;
import java.util.List;
import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;
import com.lion.pojo.User;
public interface UserMapper {
@Insert("insert into users(name,age) values(#{name},#{age})")
int insertUser(User user);
@Delete("delete from users where id = #{id}")
int deleteUser(int id);
@Update("update users set name = #{name},age = #{age} where id = #{id}")
int updateUser(User user);
@Select("select * from users where id = #{id}")
User selectUser(int id);
@Select("select * from users")
List<User> selectAll();
}
Mybatis配置文件中注册映射接口 class
<mappers>
<mapper resource="com/lion/mapper/UserMapper.xml" />
<mapper class="com.lion.testAnnotation.UserMapper"/>
</mappers>
针对同一实体的映射文件不能放到同一个包中。
1 package com.lion.testAnnotation;
2
3 import java.io.IOException;
4 import java.util.List;
5
6 import org.apache.ibatis.session.SqlSession;
7 import org.apache.ibatis.session.SqlSessionFactory;
8 import org.junit.Before;
9 import org.junit.Test;
10
11 import com.lion.pojo.User;
12 import com.lion.util.MybatisUtils;
13
14 public class TestUserCURDByAnnotaion2 {
15
16 private SqlSessionFactory factory;
17
18 @Before
19 public void loadFactory() {
20 try {
21 factory = MybatisUtils.getFactory();
22 } catch (IOException e) {
23 e.printStackTrace();
24 }
25 }
26
27 @Test
28 public void testAdd() {
29 SqlSession session = factory.openSession(true);
30 // 映射器
31 UserMapper mapper = session.getMapper(UserMapper.class);
32
33 int i = mapper.insertUser(new User(-1, "xiazis", 24));
34
35 System.out.println(i);
36
37 session.close();
38
39 }
40
41 @Test
42 public void testDelete() {
43 SqlSession session = factory.openSession(true);
44 // 映射器
45 UserMapper mapper = session.getMapper(UserMapper.class);
46
47 int i = mapper.deleteUser(1);
48
49 System.out.println(i);
50
51 session.close();
52
53 }
54
55 @Test
56 public void testUpdate() {
57 SqlSession session = factory.openSession(true);
58 // 映射器
59 UserMapper mapper = session.getMapper(UserMapper.class);
60
61 int i = mapper.updateUser(new User());
62
63 System.out.println(i);
64
65 session.close();
66
67 }
68
69 @Test
70 public void testSelect() {
71 SqlSession session = factory.openSession(true);
72 // 映射器
73 UserMapper mapper = session.getMapper(UserMapper.class);
74
75 User user = mapper.selectUser(2);
76
77 System.out.println(user);
78
79 session.close();
80
81 }
82
83 @Test
84 public void testSelectAll() {
85 SqlSession session = factory.openSession(true);
86 // 映射器
87 UserMapper mapper = session.getMapper(UserMapper.class);
88
89 List<User> users = mapper.selectAll();
90
91 for (User user : users) {
92 System.out.println(user);
93 }
94
95 session.close();
96
97 }
98
99 }
