Mybatis 框架搭建实例
前言
MyBatis是一个优秀的持久层框架。原生的jdbc操做存在大量的重复性代码（如注册驱动，建立链接，建立statement，结果集检测等）。框架的做用就是把这些繁琐的代码封装。java
MyBatis经过XML或者注解的方式将要执行的sql语句配置起来，并经过java对象和sql语句映射成最终执行的sql语句。最终由MyBatis框架执行sql，并将结果映射成java对象并返回。mysql
正文
准备jar包sql
- mybatis-3.4.6.jar
- mysql-connector-java-5.1.47.jar
mysql数据库为firstdb，表名为xtb,表结构以下数据库
1.新建java project MybatisPro ，项目结构图：
一共五个文件apache
在src下新建com.domain包，在新建User.java
package com.domain;
public class User {
private Integer user_id;
private String user_name;
private String user_sex;
private String user_phone;
public String toString() {
return "User [user_id=" + user_id + ", user_name=" + user_name + ", user_sex=" + user_sex + ", user_phone="
+ user_phone + "]";
}
public String getUser_phone() {
return user_phone;
}
public void setUser_phone(String user_phone) {
this.user_phone = user_phone;
}
public String getUser_sex() {
return user_sex;
}
public void setUser_sex(String user_sex) {
this.user_sex = user_sex;
}
public String getUser_name() {
return user_name;
}
public void setUser_name(String user_name) {
this.user_name = user_name;
}
public Integer getUser_id() {
return user_id;
}
public void setUser_id(Integer user_id) {
this.user_id = user_id;
}
}
在src下新建com.Dao包，而后新建Interface文件，UserMapper.java
package com.Dao;
import com.domain.*;
public interface UserMapper {
public User findUserById(int id) throws Exception;
public void insertUser(User user) throws Exception;
}
在src下新建全局配置文件SqlMapConfig.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>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/firstdb"/><!--用本身的数据库名字 -->
<property name="username" value="root"/> <!-- 用本身的用户名密码 -->
<property name="password" value=""/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="UserMapper.xml"/> <!-- 这里配置映射文件 -->
</mappers>
</configuration>
新建映射配置文件UserMpper.xml
<?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标签要指定namespace属性，否则会报错，可看作包名-->
<mapper namespace="com.Dao.UserMapper">
<select id="findUserById" parameterType="int" resultType="com.domain.User">
select * from xtb where user_id = #{id}
</select>
<insert id="insertUser" parameterType="com.domain.User">
insert into xtb(user_name,user_sex,user_phone) values(#{user_name},#{user_sex},#{user_phone})
</insert>
</mapper>
最后，新建测试类Test.java
package com.test;
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.Dao.UserMapper;
import com.domain.User;
public class Test{
public static void main(String[] args) throws Exception {
testInsertUser();
SelectByid();
}
public static void SelectByid() throws Exception{
String resource = "SqlMapConfig.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession session = factory.openSession();
//---------------
UserMapper userMapper = session.getMapper(UserMapper.class);
User user = userMapper.findUserById(2);
System.out.println(user);
//--------------
session.close();
}
public static void testInsertUser() throws Exception{
String resource = "SqlMapConfig.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession session = factory.openSession();
//---------------------
User user = new User();
user.setUser_name("lalala");
user.setUser_sex("women");
user.setUser_phone("0123345");
UserMapper mapper = session.getMapper(UserMapper.class);
mapper.insertUser(user);
session.commit();
//----------------------
session.close();
}
}
运行程序，查看结果：
常见错误解决：
基本上都是UserMapper.xml和接口UserMap.java的对应关系没有配置好，我把UserMapper.xml和UserMap.java拼在一块儿能够看下本身的配置是否正确：session
简单来讲就是：接口的包名，类名，参数，返回值分别对应着映射文件的namespace，id，parameterType，resultType。mybatis
总结原理：
mybais运用了代理技术，实例化出接口UserMapper的实例，而后经过根据配置文件调用sql.app
具体流程：框架
1.读取配置文件SqlMapConfig.xml 获取连数据库的相关信息dom
2.有了这些信息就能建立SqlSessionFactory
3.SqlSessionFactory创建SqlSession
4.SqlSession 经过代理建立出UserMapper接口的实例，并从userMapper.xml中读取信息
5.经过userMapper.xml中的信息，执行sql语句
6.返回结果，关闭session