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Mapper动态代理方式,开发规范:
Mapper接口开发需要遵循以下规范:
1、 Mapper.xml文件中的namespace与mapper接口的类路径相同。
2、 Mapper接口方法名和Mapper.xml中定义的每个statement的id相同
3、 Mapper接口方法的输入参数类型和mapper.xml中定义的每个sql 的parameterType的类型相同
4、 Mapper接口方法的输出参数类型和mapper.xml中定义的每个sql的resultType的类型相同
整体工程架构
定义Mapper接口文件
package com.jxliu.mybatis.mapper;
import java.util.List;
import com.jxliu.mybatis.po.User;
/**
* 用户管理mapper
*/
public interface UserMapper{
//根据用户id查询用户信息
public User getUserById(int id) throws Exception;
//查询用户列表
public List<User> getUserByName(String username) throws Exception;
//添加用户信息
public void insertUser(User user)throws Exception;
}
定义Mapper.xml文件
<?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">
<!-- namespace是命名空间,作用sql语句的隔离,后面还有重要作用
#{}作用就是占位符,相当于jdbc的“?”
parameterType:查询的参数类型
resultType:查询结果的数据类型,如果时候pojo应该给全路径。
-->
<!-- mapper代理的开发规则:
1、namespace必须时候接口的全限定名
2、Statementid必须和接口的方法名称一致
3、接口方法的参数类型要和parameterType要一致
4、接口方法的返回值类型要和resultType一致
-->
<mapper namespace="com.jxliu.mybatis.mapper.UserMapper">
<!-- 别名不区分大小写 -->
<select id="getUserById" parameterType="int" resultType="com.jxliu.mybatis.po.User">
SELECT * FROM `user` WHERE id=#{id};
</select>
<!-- 如果查询结果返回list, resultType设置为list中一个元素的数据类型
${}字符串拼接指令
-->
<select id="getUserByName" parameterType="string" resultType="com.jxliu.mybatis.po.User">
SELECT * FROM `user` WHERE username LIKE '%${value}%'
</select>
<!-- 参数时候pojo时,#{}中的名称就是pojo的属性 -->
<insert id="insertUser" parameterType="com.jxliu.mybatis.po.User">
<!-- keyProperty:对于pojo的主键属性
resultType:对应主键的数据类型
order:是在insert语句执行之前或者之后。
如果使用uuid做主键,应该先生成主键然后插入数据,此时应该使用Before
-->
<selectKey keyProperty="id" resultType="int" order="AFTER">
SELECT LAST_INSERT_ID()
</selectKey>
INSERT into user (username,birthday,sex,address)
values (#{username}, #{birthday}, #{sex}, #{address})
</insert>
</mapper>
在SqlMapConfig.xml文件中加载UserMapper.xml文件
<!-- 加载映射文件 -->
<mappers>
<mapper resource="mapper/UserMapper.xml"/>
</mappers>
Mapper接口方式测试
package mybatis_demo;
import static org.junit.Assert.*;
import java.io.InputStream;
import java.util.List;
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 org.junit.Before;
import org.junit.Test;
import com.jxliu.mybatis.mapper.UserMapper;
import com.jxliu.mybatis.po.User;
public class UserMapperTest {
private SqlSessionFactory sqlSessionFactory = null;
@Before
public void init() throws Exception {
// 第一步:创建一个SQLSessionFactoryBuilder对象。
SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
// 第二步:加载配置文件。
InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");
// 第三步:创建SQLSessionFactory对象
sqlSessionFactory = sqlSessionFactoryBuilder.build(inputStream);
}
@Test
public void testGetUserById() {
//和spring整合后省略
SqlSession sqlSession = sqlSessionFactory.openSession();
//获得代理对象
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
User user;
try {
user = userMapper.getUserById(5);
System.out.println(user);
} catch (Exception e) {
e.printStackTrace();
}
//和spring整合后省略
sqlSession.close();
}
@Test
public void testGetUserByName() {
SqlSession sqlSession = sqlSessionFactory.openSession();
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
List<User> list;
try {
list = userMapper.getUserByName("小");
for (User user : list) {
System.out.println(user);
}
} catch (Exception e) {
e.printStackTrace();
}
sqlSession.close();
}
@Test
public void testInsertUser() {
fail("Not yet implemented");
}
}
原始Dao开发
定义dao接口和实现类
package com.jxliu.mybatis.dao;
import com.jxliu.mybatis.po.User;
public interface UserDao {
public User findUserById(int id) throws Exception;
public void insertUser(User user) throws Exception;
}
package com.jxliu.mybatis.dao;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import com.jxliu.mybatis.po.User;
public class UserDaoImpl implements UserDao {
private SqlSessionFactory sqlSessionFactory;
//注入SqlSessionFactory
public UserDaoImpl(SqlSessionFactory sqlSessionFactory){
this.sqlSessionFactory = sqlSessionFactory;
}
@Override
public User findUserById(int id) throws Exception {
SqlSession sqlSession = sqlSessionFactory.openSession();
User user = null;
try {
user = sqlSession.selectOne("findUserById",id);
} catch (Exception e) {
e.printStackTrace();
}finally{
sqlSession.close();
}
return user;
}
@Override
public void insertUser(User user) throws Exception {
SqlSession sqlSession = sqlSessionFactory.openSession();
try {
sqlSession.insert("insertUser", user);
sqlSession.commit();
} finally{
sqlSession.close();
}
}
}
定义user.xml文件
<?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="test">
<select id="findUserById" parameterType="int" resultType="com.jxliu.mybatis.po.User">
select * from User where id = #{id};
</select>
<select id="findUserByUsername" parameterType="string" resultType="com.jxliu.mybatis.po.User">
select * from User where username like "%${value}%"
</select>
<insert id="insertUser" parameterType="com.jxliu.mybatis.po.User">
<!-- selectKey将主键返回,需要再返回 -->
<selectKey keyProperty="id" order="AFTER" resultType="java.lang.Integer">
select LAST_INSERT_ID();
</selectKey>
insert into User(id,username,sex,birthday,address) values (#{id},#{username},#{sex},#{birthday},#{address})
</insert>
<!-- 删除用户 -->
<delete id="deleteUserById" parameterType="int">
delete from user where id=#{id}
</delete>
<!-- 更新用户 -->
<update id="updateUser" parameterType="com.jxliu.mybatis.po.User">
update user set username=#{username},birthday=#{birthday},sex=#{sex},address=#{address}
where id=#{id}
</update>
</mapper>
<mappers>
<mapper resource="sqlmap/user.xml"/>
</mappers>
测试Dao
package mybatis_demo;
import java.io.InputStream;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Before;
import org.junit.Test;
import com.jxliu.mybatis.dao.UserDao;
import com.jxliu.mybatis.dao.UserDaoImpl;
import com.jxliu.mybatis.po.User;
public class TestDao {
private SqlSessionFactory sqlSessionFactory;
@Before
public void init() throws Exception {
SqlSessionFactoryBuilder sessionFactoryBuilder = new SqlSessionFactoryBuilder();
InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");
sqlSessionFactory = sessionFactoryBuilder.build(inputStream);
}
@Test
public void testGetUserById() {
UserDao userDao = new UserDaoImpl(sqlSessionFactory);
User user;
try {
user = userDao.findUserById(0);
System.out.println(user.getUsername());
} catch (Exception e) {
e.printStackTrace();
}
}
}
两种方式相比较,大多数企业开发中使用mapper接口开发方式,因为可以省去了写dao实现类的这一步,开发效率提高了
SqlMapConfig.xml中配置的内容和顺序如下:
properties(属性)
settings(全局配置参数)
typeAliases(类型别名)
typeHandlers(类型处理器)
objectFactory(对象工厂)
plugins(插件)
environments(环境集合属性对象)
environment(环境子属性对象)
transactionManager(事务管理)
dataSource(数据源)
mappers(映射器)将SqlMapConfig.xml中数据库的配置隔离开,在db.properties中维护
定义db.properties文件
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mybatis?characterEncoding=utf-8
jdbc.username=root
jdbc.password=123456
在SqlMapConfig.xml中添加配置
<!-- 和spring整合后 environments配置将废除-->
<environments default="development">
<environment id="development">
<!-- 使用jdbc事务管理-->
<transactionManager type="JDBC" />
<!-- 数据库连接池-->
<dataSource type="POOLED">
<property name="driver" value="${jdbc.driver}" />
<property name="url" value="${jdbc.url}" />
<property name="username" value="${jdbc.username}" />
<property name="password" value="${jdbc.password}" />
</dataSource>
</environment>
</environments>
mybatis支持别名形式:
别名 | 映射的类型 |
_byte | byte |
_long | long |
_short | short |
_int | int |
_integer | int |
_double | double |
_float | float |
_boolean | boolean |
string | String |
byte | Byte |
long | Long |
short | Short |
int | Integer |
integer | Integer |
double | Double |
float | Float |
boolean | Boolean |
date | Date |
decimal | BigDecimal |
bigdecimal | BigDecimal |
map | Map |
在SqlMapConfig.xml中配置以下属性可以 自定义别名
<typeAliases>
<!-- 单个别名定义 -->
<typeAlias alias="user" type="com.jxliu.mybatis.po.User"/>
<!-- 批量别名定义,扫描整个包下的类,别名为类名(首字母大写或小写都可以) -->
<package name="com.jxliu.mybatis.po"/>
<package name="其它包"/>
</typeAliases>
Mapper的三种映射方式
1. <mapper resource=" " />
使用相对于类路径的资源
如:<mapper resource="sqlmap/User.xml"/>
2. <mapper class=" " />
使用mapper接口类路径
如:<mapperclass="com.jxliu.mybatis.mapper.UserMapper"/>
注意:此种方法要求mapper接口名称和mapper映射文件名称相同,且放在同一个目录中。
3. <package name=""/>
注册指定包下的所有mapper接口
如:<packagename="com.jxliu.mybatis.mapper"/>
注意:此种方法要求mapper接口名称和mapper映射文件名称相同,且放在同一个目录中。