使用mybatis访问mysql数据库之二

在使用mybatis访问mysql数据库的第一版中，我们需要在main代码中指定对应的SQL的ID和参数，这样就不太灵活了。下面，我们做一个新版的访问mysql数据库的程序。该版本使用了接口技术，将接口与对应的SQL的ID进行关联，在main代码中只需要使用接口中的方法就可以直接操作数据库，mybatis真是太好用了！
基础表的配置略。与《使用mybatis访问mysql数据库之一》中的表一致。

User.java的代码如下。各个字段需要与表中的字段名称一致。

package com.baby.javaStudy.mybatis.v2;

public class User {
private int id;
private int classification;
private String name;
private String address;
private String remark;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public int getClassification() {
return classification;
}
public void setClassification(int classification) {
this.classification = classification;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
public String getRemark() {
return remark;
}
public void setRemark(String remark) {
this.remark = remark;
}
@Override
public String toString() {
return "User [id=" + id + ", classification=" + classification + ", name=" + name + ", address=" + address
+ ", remark=" + remark + "]";
}
}

对数据库的user表建立配置文件。这个文件中主要定义了SQL语句。对应的文件名称为User.xml，内容如下：
<?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.baby.javaStudy.mybatis.v2.IUserOperation">
<select id="selectByID" parameterType="int" resultType="User">
select *
from user where id = #{id}
</select>

<!-- 为了返回list 类型而定义的returnMap -->
<resultMap type="User" id="UserList">
<id column="id" property="id" />
<result column="classification" property="classification" />
<result column="name" property="name" />
<result column="address" property="address" />
<result column="remark" property="remark" />
</resultMap>

<!-- 返回list 的select 语句，注意 resultMap 的值是指向前面定义好的 -->
<select id="selectByName" parameterType="string" resultMap="UserList">
select * from user where name like #{name}
</select>

<!--执行增加操作的SQL语句。id和parameterType 分别与IUserOperation接口中的addUser方法的名字和 参数类型一致。以#{name}的形式引用Student参数
的name属性，MyBatis将使用反射读取Student参数 的此属性。#{name}中name大小写敏感。引用其他 的gender等属性与此一致。seGeneratedKeys设置
为"true"表明要MyBatis获取由数据库自动生成的主 键；keyProperty="id"指定把获取到的主键值注入 到Student的id属性 -->
<insert id="add" parameterType="User" useGeneratedKeys="true"
keyProperty="id">
insert into user(classification,name,address,remark)
values(#{classification},#{name},#{address},#{remark})
</insert>

<update id="updateRemark" parameterType="User">
update user set remark=#{remark} where id=#{id}
</update>

<delete id="delete" parameterType="int">
delete from user where id=#{id}
</delete>
</mapper>

建立一个对user表操作的接口IUserOperation.java，接口中的方法的名称，需要与User.xml中对应的SQL的ID一样。内容如下：
package com.baby.javaStudy.mybatis.v2;

import java.util.List;

public interface IUserOperation {

public User selectByID(int id);
public List<User> selectByName(String name);
public void add(User book);
public void updateRemark(User book);
public void delete(int id);
}


数据库访问测试程序：
package com.baby.javaStudy.mybatis.v2;

import java.io.Reader;
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;

public class UserTestV2 {

public static void main(String[] args) {
SqlSession session = null;

try {
Reader reader = Resources.getResourceAsReader("com/baby/javaStudy/mybatis/v2/Configuration.xml");
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
session = sqlSessionFactory.openSession();

IUserOperation userOperation = session.getMapper(IUserOperation.class);

System.out.println("========selectByID() test========");
User user = userOperation.selectByID(2);
System.out.println(user);

System.out.println("========selectByName() test========");
List<User> users = userOperation.selectByName("%wang%");
for(User user2 : users){
System.out.println(user2);
}

System.out.println("========add() test========");
User user3 = new User();
user3.setClassification(1);
user3.setName("baby");
user3.setAddress("beijing");
user3.setRemark("added from userTestv2.java");
System.out.println("new user info is: "+user3);
userOperation.add(user3);
session.commit();

System.out.println("========updateRemark() test========");
User user4 = userOperation.selectByID(2);
System.out.println("old user info is "+user4);
user4.setRemark("modified from userTestV2.java");
userOperation.updateRemark(user4);
session.commit();
user4 = userOperation.selectByID(2);
System.out.println("new user info is "+user4);

System.out.println("========delete() test========");
User user5 = userOperation.selectByID(2);
System.out.println("user need delete info is "+user5);
userOperation.delete(user5.getId());
session.commit();
} catch (Exception e) {
e.printStackTrace();
} finally {
session.close();
}
}

}


运行上面的程序，然后在数据库中查询对应的表，即可用看到程序对表中数据的增加或者修改。