MyBatis 是支持普通 SQL 查询,存储过程和高级映射的优秀持久层框架。是开发人员常用的框架之一，它能通过在任何映射SQL语句中，那mybatis怎么操作数据库?下面来我们就来给大家讲解一下。
对一个User表的CRUD操作：
User表：
-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --Table structure
for `user`-- -- -- -- -- -- -- -- -- -- -- -- -- -- --DROP TABLE IF EXISTS `user`;
CREATE TABLE `user`(
`id`
int(11) NOT NULL AUTO_INCREMENT
, `userName`
varchar(50) DEFAULT NULL
, `userAge`
int(11) DEFAULT NULL
, `userAddress`
varchar(200) DEFAULT NULL
, PRIMARY KEY(`id`)
) ENGINE = InnoDB AUTO_INCREMENT = 6 DEFAULT CHARSET = utf8;
-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --Records of user-- -- -- -- -- -- -- -- -- -- -- -- -- -- --INSERT INTO `user`
VALUES('1', 'summer', '30', 'shanghai');
INSERT INTO `user`
VALUES('2', 'test2', '22', 'suzhou');
INSERT INTO `user`
VALUES('3', 'test1', '29', 'some place');
INSERT INTO `user`
VALUES('4', 'lu', '28', 'some place');
INSERT INTO `user`
VALUES('5', 'xiaoxun', '27', 'nanjing');在Src目录下建一个mybatis的xml配置文件Configuration.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> <!-- mybatis别名定义 --> <typeAliases> <typeAlias alias="User" type="com.mybatis.test.User"/> </typeAliases> <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://127.0.0.1:3306/mybatis" /> <property name="username" value="root"/> <property name="password" value="admin"/> </dataSource> </environment> </environments> <!-- mybatis的mapper文件，每个xml配置文件对应一个接口 --> <mappers> <mapper resource="com/mybatis/test/User.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">
<mapper namespace="com.mybatis.test.IUserOperation">
<!-- select语句 -->
<select id="selectUserByID" parameterType="int" resultType="User">
select * from `user` where user.id = #{id}
</select>
<!-- 定义的resultMap，可以解决类的属性名和数据库列名不一致的问题-->
<!-- <resultMap type="User" id="userResultMap">
<id property="id" column="user_id" />
<result property="userName" column="user_userName" />
<result property="userAge" column="user_userAge" />
<result property="userAddress" column="user_userAddress" />
</resultMap> -->
<!-- 返回list的select语句，注意 resultMap的值是指向前面定义好的 -->
<!-- <select id="selectUsersByName" parameterType="string" resultMap="userResultMap">
select * from user where user.userName = #{userName}
</select> -->
<select id="selectUsersByName" parameterType="string" resultType="User">
select * from user where user.userName = #{userName}
</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。
useGeneratedKeys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User的id属性-->
<insert id="addUser" parameterType="User"
useGeneratedKeys="true" keyProperty="id">
insert into user(userName,userAge,userAddress)
values(#{userName},#{userAge},#{userAddress})
</insert>
<update id="updateUser" parameterType="User" >
update user set userName=#{userName},userAge=#{userAge},userAddress=#{userAddress} where id=#{id}
</update>
<delete id="deleteUser" parameterType="int">
delete from user where id=#{id}
</delete>
</mapper>配置文件实现了接口和SQL语句的映射关系。selectUsersByName采用了2种方式实现，注释掉的也是一种实现，采用resultMap可以把属性和数据库列名映射关系定义好，property为类的属性，column是表的列名，也可以是表列名的别名!
User类的定义：
package com.mybatis.test;
public class User
{
private int id;
private String userName;
private int userAge;
private String userAddress;
public int getId()
{
return id;
}
public void setId(int id)
{
this.id = id;
}
public String getUserName()
{
return userName;
}
public void setUserName(String userName)
{
this.userName = userName;
}
public int getUserAge()
{
return userAge;
}
public void setUserAge(int userAge)
{
this.userAge = userAge;
}
public String getUserAddress()
{
return userAddress;
}
public void setUserAddress(String userAddress)
{
this.userAddress = userAddress;
}
@Override
public String toString()
{
return this.userName + " " + this.userAge + " " + this.userAddress;
}IUserOperaton定义：
package com.mybatis.test;
import java.util.List;
public interface IUserOperation
{
public User selectUserByID(int id);
public List < User > selectUsersByName(String userName);
public void addUser(User user);
public void updateUser(User user);
public void deleteUser(int id);
}IUserOperation为操作接口，函数名和mybatis的xml配置文件中的操作id名对应。
测试类Test：
package com.mybatis.test;
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 Test
{
private static SqlSessionFactory sqlSessionFactory;
private static Reader reader;
static
{
try
{
reader = Resources.getResourceAsReader("Configuration.xml");
sqlSessionFactory = new SqlSessionFactoryBuilder()
.build(reader);
}
catch (Exception e)
{
e.printStackTrace();
}
}
public static SqlSessionFactory getSession()
{
return sqlSessionFactory;
}
public void getUserByID(int userID)
{
SqlSession session = sqlSessionFactory.openSession();
try
{
IUserOperation userOperation = session
.getMapper(IUserOperation.class);
User user = userOperation.selectUserByID(userID);
if (user != null)
{
System.out.println(user.getId() + ":" + user.getUserName() +
":" + user.getUserAddress());
}
}
finally
{
session.close();
}
}
public void getUserList(String userName)
{
SqlSession session = sqlSessionFactory.openSession();
try
{
IUserOperation userOperation = session
.getMapper(IUserOperation.class);
List < User > users = userOperation.selectUsersByName(userName);
for (User user: users)
{
System.out.println(user.getId() + ":" + user.getUserName() +
":" + user.getUserAddress());
}
}
finally
{
session.close();
}
}
/**
* 增加后要commit
*/
public void addUser()
{
User user = new User();
user.setUserAddress("place");
user.setUserName("test_add");
user.setUserAge(30);
SqlSession session = sqlSessionFactory.openSession();
try
{
IUserOperation userOperation = session
.getMapper(IUserOperation.class);
userOperation.addUser(user);
session.commit();
System.out.println("新增用户ID：" + user.getId());
}
finally
{
session.close();
}
}
/**
* 修改后要commit
*/
public void updateUser()
{
SqlSession session = sqlSessionFactory.openSession();
try
{
IUserOperation userOperation = session
.getMapper(IUserOperation.class);
User user = userOperation.selectUserByID(1);
if (user != null)
{
user.setUserAddress("A new place");
userOperation.updateUser(user);
session.commit();
}
}
finally
{
session.close();
}
}
/**
* 删除后要commit.
*
* @param id
*/
public void deleteUser(int id)
{
SqlSession session = sqlSessionFactory.openSession();
try
{
IUserOperation userOperation = session
.getMapper(IUserOperation.class);
userOperation.deleteUser(id);
session.commit();
}
finally
{
session.close();
}
}
public static void main(String[] args)
{
try
{
Test test = new Test();
// test.getUserByID(1);
// test.getUserList("test1");
// test.addUser();
// test.updateUser();
// test.deleteUser(6);
}
catch (Exception e)
{
System.out.println(e.getMessage());
}
}
}这样就完成了Mybatis增删改查的步骤，Mybatis的使用很灵活，它不会对应用程序或者数据库的现有设计强加任何影响，能够满足操作数据库的所有需求，最后大家如果想要了解更多java架构师知识，敬请关注奇Q工具网。
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