mybatis-dao开发
学而时习之，不亦说乎！
--《论语》
本文以前文“mybatis-入门”为基础，同时再次提醒最佳参考资料：
http://www.mybatis.org/mybatis-3/zh/index.html
DAO开发说明：
mybatis的DAO开发分为两种方式：原始开发方式和Mapper代理开发方式。
原始开发方式指先写一个dao接口，然后写一个dao实现类，在dao实现类中注入SqlSessionFactory对象，获取SqlSession，最后执行代码。
Mapper代理开发方式指写好一个dao接口，然后写mapper映射文件，通过代理生成实现类。
原始开发方式：
create database mybatis;
use mybatis;
create table user (
id int primary key auto_increment comment '主键id',
name varchar(30) comment '姓名',
age int comment '年龄',
birthday date comment '生日',
address varchar(200) comment '地址'
)default charset utf8;
insert into user(name,age,birthday,address) values('zby',24,'1993-05-05','四川省成都市');
insert into user(name,age,birthday,address) values('zby',24,'1993-05-05','四川省成都市');
insert into user(name,age,birthday,address) values('zby',24,'1993-05-05','四川省成都市');
insert into user(name,age,birthday,address) values('zby',24,'1993-05-05','四川省成都市');
insert into user(name,age,birthday,address) values('zby',24,'1993-05-05','四川省成都市');
select * from user;
2）项目整体结构如下：
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.zby</groupId> <artifactId>mybatis</artifactId> <version>0.0.1-SNAPSHOT</version> <dependencies> <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis --> <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>3.4.0</version> </dependency> <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java --> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.34</version> </dependency> <!-- https://mvnrepository.com/artifact/log4j/log4j --> <dependency> <groupId>log4j</groupId> <artifactId>log4j</artifactId> <version>1.2.17</version> </dependency> </dependencies> </project>
import java.util.Date;
/**
*
* @描述:对应数据库user表的实体类
* @类名:
* @作者: zby
* @创建时间: 2017年5月22日 上午10:23:21
* @版本: v1.0
*/
public class User {
private Integer id;
private String name;
private Integer age;
private Date birthday;
private String address;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "User [id=" + id + ", name=" + name + ", age=" + age + ", birthday=" + birthday + ", address=" + address
+ "]";
}
}
<?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> <!-- 配置mybatis的环境信息 --> <environments default="development"> <environment id="development"> <!-- 配置JDBC事务控制，由mybatis进行管理 --> <transactionManager type="JDBC"></transactionManager> <!-- 配置数据源，采用mybatis连接池 --> <dataSource type="POOLED"> <property name="driver" value="com.mysql.jdbc.Driver" /> <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useUnicode=true&characterEncoding=utf8" /> <property name="username" value="root" /> <property name="password" value="123456" /> </dataSource> </environment> </environments> <!-- 加载映射文件 --> <mappers> <mapper resource="mapper/UserMapper.xml" /> </mappers> </configuration>
<?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：命名空间，对statement的信息进行分类管理 -->
<!-- 注意：在mapper代理时，它具有特殊及重要的作用 -->
<mapper namespace="test">
<!-- 根据用户ID查询用户信息 -->
<!-- select：表示一个MappedStatement对象 -->
<!-- id：statement的唯一标示 -->
<!-- #{}：表示一个占位符？ -->
<!-- #{id}：里面的id表示输入参数的参数名称，如果该参数是简单类型，那么#{}里面的参数名称可以任意 -->
<!-- parameterType：输入参数的java类型 -->
<!-- resultType：输出结果的所映射的java类型（单条结果所对应的java类型） -->
<select id="findUserById" parameterType="int"
resultType="com.zby.domain.User">
SELECT * FROM USER WHERE id =#{id}
</select>
</mapper>
7)为了看到日志打印，在src/main/resources文件夹下加入log4j.properties配置文件,内容如下：
# Global logging configuration log4j.rootLogger=DEBUG, stdout # Console output... log4j.appender.stdout=org.apache.log4j.ConsoleAppender log4j.appender.stdout.layout=org.apache.log4j.PatternLayout log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n
8)编写UserDao类：
package com.zby.dao;
import com.zby.domain.User; /** * * @描述:用户DAO接口 * @类名: UserDao * @作者: zby * @创建时间: 2017年5月27日 下午2:30:45 * @版本: v1.0 */ public interface UserDao { User findUserById(Integer id); }
9）编写UserDaoImpl类：
package com.zby.dao.impl;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import com.zby.dao.UserDao;
import com.zby.domain.User;
public class UserDaoImpl implements UserDao {
private SqlSessionFactory sqlSessionFactory;
public UserDaoImpl(SqlSessionFactory sqlSessionFactory) {
this.sqlSessionFactory = sqlSessionFactory;
}
public User findUserById(Integer id) {
SqlSession sqlSession = sqlSessionFactory.openSession();
User user = sqlSession.selectOne("test.findUserById", id);
sqlSession.close();
return user;
}
}
10）编写测试类：
package com.zby;
import java.io.InputStream;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import com.zby.dao.UserDao;
import com.zby.dao.impl.UserDaoImpl;
import com.zby.domain.User;
public class Application {
public static void main(String[] args) throws Exception {
// 1、读取配置文件
String resource = "SqlMapConfig.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
// 2、根据配置文件创建SqlSessionFactory
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
// 创建UserDao实例，模拟spring注入SqlSessionFactory
UserDao userDao = new UserDaoImpl(sqlSessionFactory);
// 使用DAO
User user = userDao.findUserById(1);
System.out.println(user);
}
}
11）输出结果：
DEBUG [main] - Logging initialized using 'class org.apache.ibatis.logging.log4j.Log4jImpl' adapter.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - Opening JDBC Connection
DEBUG [main] - Created connection 193297871.
DEBUG [main] - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@b857dcf]
DEBUG [main] - ==> Preparing: SELECT * FROM USER WHERE id =?
DEBUG [main] - ==> Parameters: 1(Integer)
DEBUG [main] - <== Total: 1
DEBUG [main] - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@b857dcf]
DEBUG [main] - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@b857dcf]
DEBUG [main] - Returned connection 193297871 to pool.
User [id=1, name=zby, age=24, birthday=Wed May 05 00:00:00 CST 1993, address=四川省成都市]
12)总结:这种方式开发DAO跟入门的Demo其实区别不大，也是传统的开发流程。
Mapper代理开发方式：
mapper代理开发方式实际就是传统开发方式的简化，不过简化的同时，需要我们准守一定的规范：
1、 mapper接口的全限定名要和mapper映射文件的namespace值一致。
2、 mapper接口的方法名称要和mapper映射文件的statement的id一致。
3、 mapper接口的方法参数类型要和mapper映射文件的statement的parameterType的值一致，而且它的参数是一个。
4、 mapper接口的方法返回值类型要和mapper映射文件的statement的resultType的值一致。
现在我们在传统开发模式基础上进行修改：
1.删除UserDaoImpl类和所在的包；
2.修改UserMapper.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">
<!-- 1、namespace的值跟UserDao的全限定名相同 -->
<mapper namespace="com.zby.dao.UserDao">
<!-- 2、id跟UserDao中的方法名相同 -->
<!-- 3、parameterType的类型跟UserDao中对应的方法的参数相同 -->
<!-- 4、resultType的类型跟UserDao中对应的方法的返回类型相同 -->
<select id="findUserById" parameterType="int" resultType="com.zby.domain.User">
select * from User where id=#{id}
</select>
</mapper>
3）编写测试类：
package com.zby;
import java.io.InputStream;
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 com.zby.dao.UserDao;
import com.zby.domain.User;
public class Application {
public static void main(String[] args) throws Exception {
// 1、读取配置文件
String resource = "SqlMapConfig.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
// 2、根据配置文件创建SqlSessionFactory
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
// 获取代理对象
UserDao userDao = sqlSession.getMapper(UserDao.class);
// 使用DAO
User user = userDao.findUserById(1);
System.out.println(user);
}
}
4）运行结果：
DEBUG [main] - Logging initialized using 'class org.apache.ibatis.logging.log4j.Log4jImpl' adapter. DEBUG [main] - PooledDataSource forcefully closed/removed all connections. DEBUG [main] - PooledDataSource forcefully closed/removed all connections. DEBUG [main] - PooledDataSource forcefully closed/removed all connections. DEBUG [main] - PooledDataSource forcefully closed/removed all connections. DEBUG [main] - Opening JDBC Connection DEBUG [main] - Created connection 114388565. DEBUG [main] - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@6d16e55] DEBUG [main] - ==> Preparing: select * from User where id=? DEBUG [main] - ==> Parameters: 1(Integer) DEBUG [main] - <== Total: 1 User [id=1, name=zby, age=24, birthday=Wed May 05 00:00:00 CST 1993, address=四川省成都市]
5）其实还可以使用注解代替UserMapp.xml文件，但是，这样存在硬编码，而且不方便开发，有兴趣就自己去研究吧。
