Mybatis系列（三）简单示例

Mybatis系列之简单示例

经过前两篇文章《Mybatis系列之入门》和《Mybatis系列之配置》的介绍，我们对Mybatis有了一定的了解，下面就接合一个实例学习案例，来巩固一下我们前面学习的知识。

环境搭建

IDE: STS(Spring Tools Suite)
Java Version: 1.6
Spring Version:3.1.1
Mybatis Version: 3.3.0
Database: Mysql 5.1.36
JUnit Version: 4.7

数据库

在Mysql中创建数据库mybatis，并在其中创建两张数据表，DDL语句如下：
CREATE TABLE `sys_user` (
`user_id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`user_name` varchar(64) NOT NULL,
`user_password` varchar(32) NOT NULL,
`nick_name` varchar(64) NOT NULL,
`email` varchar(128) DEFAULT NULL,
`user_type_id` smallint(4) NOT NULL,
`is_valid` tinyint(1) NOT NULL DEFAULT '1',
`created_time` datetime NOT NULL,
`update_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
`last_login_time` datetime DEFAULT NULL,
`online` tinyint(4) NOT NULL DEFAULT '0',
`language` varchar(6) NOT NULL DEFAULT 'zh-cn',
`psd_changed_date` datetime DEFAULT NULL,
`mphone` varchar(12) DEFAULT NULL,
PRIMARY KEY (`user_id`),
UNIQUE KEY `user_name` (`user_name`) USING BTREE
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8

CREATE TABLE `communicator` (
`communicator_id` int(10) NOT NULL AUTO_INCREMENT,
`communicator_name` varchar(64) NOT NULL,
`phone` varchar(32) DEFAULT NULL,
`fax` varchar(32) DEFAULT NULL,
`email` varchar(100) DEFAULT NULL,
`user_id` int(10) DEFAULT NULL,
`report_to` int(10) DEFAULT '0',
`is_valid` tinyint(4) NOT NULL DEFAULT '1',
`created_time` datetime DEFAULT NULL,
`update_time` timestamp NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
PRIMARY KEY (`communicator_id`),
UNIQUE KEY `communicator_name` (`communicator_name`) USING BTREE
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8

Mybatis 配置

<?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>
<properties resource="mybatis-mysql.properties">
<property name="driver-mysql" value="com.mysql.jdbc.Driver"></property>
<property name="url" value="jdbc:mysql://127.0.0.1:3306/etao" ></property>
<property name="username" value="root"></property>
<property name="password" value="cope9020"></property>
</properties>

<settings>
<!-- 将数据库字段命名规则A_COLUMN转换为Java使用的驼峰式命名规则aCloumn -->
<setting name="mapUnderscoreToCamelCase" value="true" />
</settings>

<typeAliases>
<typeAlias alias="User" type="com.emerson.learning.pojo.User" />
</typeAliases>

<environments default="development">
<environment id="development">
<transactionManager type="JDBC" />
<dataSource type="POOLED">
<property name="driver" value="${driver-mysql}" />
<property name="url" value="${url}" />
<property name="username" value="${username}" />
<property name="password" value="${password}" />
</dataSource>
</environment>

<environment id="product">
<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="cope9020" />
</dataSource>
</environment>
</environments>

<mappers>
<mapper resource="com/emerson/learning/mapping/User.xml" />
<mapper class="com.emerson.learning.dao.ICommunicatorDao" />
</mappers>
</configuration>

数据表映射文件

为了体验Mybatis配置的灵活性和多样性，这里个案例中使用了不同的数据映射方式。
数据表User，使用外部XML文件进行映射，而另一张数据表Communicator则使用了注解映射。
这里仅用于测试，因为在实际使用中，注解还是写在Java代码上的，所有当有变化时，还是需要重新编译程序的，这一点与Mybatis的初衷是背道而驰的。

<?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.emerson.learning.mapping.user">
<!-- 根据传入的Id值，到数据库中查询记录 -->
<select id="getByID" parameterType="int" resultType="User">
SELECT user_id, user_name, user_password, nick_name, email, is_valid, created_time, updated_time
FROM sys_user WHERE user_id = #{id}
</select>

<!-- 按用户名进行模糊查询 -->
<select id="queryByName" parameterType="User" resultType="User">
SELECT user_id, user_name, user_password, nick_name, email, is_valid, created_time, updated_time
FROM sys_user
<where>
<if test="userName != null">user_name like '%' #{userName} '%'</if>
</where>
</select>

<!-- 创建新用户，并写入到数据表中 -->
<!-- 写入新记录并返回主键值，注意，这里的KeyProperty应该是Java类里的属性名称，而非数据表中的字段名 -->
<insert id="insertUser" parameterType="User" useGeneratedKeys="true"
keyProperty="userId">
INSERT INTO sys_user(user_name, user_password, nick_name,
user_type_id,
is_valid, created_time)
VALUES(#{userName},
#{userPassword}, #{nickName}, #{userTypeId}, #{isValid},
#{createdTime})
</insert>

<!-- 更新用户信息，并写回到数据表中 -->
<update id="udpateUser" parameterType="User">
UPDATE sys_user
SET
user_name = #{userName}, user_password = #{userPassword}, nick_name =
#{nickName}, user_type_id = #{userTypeId}, is_valid, = #{isValid}
WHERE user_id = #{id}
</update>

<!-- 根据传入的Id值，删除单条记录 -->
<delete id="deleteById" parameterType="int">
DELETE FROM sys_user WHERE
user_id = #{id}
</delete>

<!-- 根据传入的Id值列表，删除多条记录 -->
<delete id="deleteBatch" parameterType="java.util.List">
DELETE FROM sys_user WHERE user_id in
<foreach collection="list" item="item" index="index" open="("
close=")" separator=",">
#{item}
</foreach>
</delete>
</mapper>

package com.emerson.learning.dao;

import java.util.List;

import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;

import com.emerson.learning.pojo.Communicator;

public interface ICommunicatorDao {
@Select("SELECT * FROM communicator WHERE communicator_id=#{id}")
public Communicator getById(@Param(value = "id") int id);

@Select("SELECT * FROM vw_communicator ORDER BY communicator_name")
public List<Communicator> getAll();
}

Java POJO类

创建用于封装数据表记录的值对象，有的朋友喜欢叫entity，有的叫domain，有的叫pojo，叫什么无所谓了，根据自己的喜好来吧 ：）
package com.emerson.learning.pojo;

import java.sql.Timestamp;

public class User {
/**
*
*/
private int userId;

/**
*
*/
private String userPassword;

/**
*
*/
private String userName;

/**
*
*/
private String nickName;

/**
*
*/
private int userTypeId;

/**
*
*/
private String email;

/**
*
*/
private int isValid;

/**
*
*/
private Timestamp createdTime;

/**
*
*/
private Timestamp updatedTime;

public int getIsValid() {
return isValid;
}

public void setIsValid(int isValid) {
this.isValid = isValid;
}

public Timestamp getCreatedTime() {
return createdTime;
}

public void setCreatedTime(Timestamp createdTime) {
this.createdTime = createdTime;
}

public Timestamp getUpdatedTime() {
return updatedTime;
}

public void setUpdatedTime(Timestamp updatedTime) {
this.updatedTime = updatedTime;
}

public int getUserId() {
return userId;
}

public void setUserId(int userId) {
this.userId = userId;
}

public String getUserName() {
return userName;
}

public void setUserName(String userName) {
this.userName = userName;
}

public String getNickName() {
return nickName;
}

public void setNickName(String nickName) {
this.nickName = nickName;
}

public String getEmail() {
return email;
}

public void setEmail(String eamil) {
this.email = eamil;
}

public String getUserPassword() {
return userPassword;
}

public void setUserPassword(String userPassword) {
this.userPassword = userPassword;
}

public User() {
this.createdTime = new Timestamp(System.currentTimeMillis());
}

public int getUserTypeId() {
return userTypeId;
}

public void setUserTypeId(int userTypeId) {
this.userTypeId = userTypeId;
}

@Override
public String toString() {
return "User [userId=" + userId + ", userName=" + userName + ", nickName=" + nickName + ", eamil=" + email
+ ", isValid=" + isValid + ", createdTime=" + createdTime + ", updatedTime=" + updatedTime + "]";
}
}

package com.emerson.learning.pojo;

import java.sql.Timestamp;

public class Communicator {

/**
*
*/
private long communicatorId;

/**
*
*/
private String communicatorName;

/**
*
*/
private String phone;

/**
*
*/
private String fax;

/**
*
*/
private String email;

/**
*
*/
private int reportTo;

/**
*
*/
private String reportToName;

/**
*
*/
private int isValid;

/**
*
*/
private Timestamp createdTime;

/**
*
*/
private Timestamp updatedTime;

public long getCommunicatorId() {
return communicatorId;
}

public void setCommunicatorId(long communicatorId) {
this.communicatorId = communicatorId;
}

public String getCommunicatorName() {
return communicatorName;
}

public void setCommunicatorName(String communicatorName) {
this.communicatorName = communicatorName;
}

public String getPhone() {
return phone;
}

public void setPhone(String phone) {
this.phone = phone;
}

public String getFax() {
return fax;
}

public void setFax(String fax) {
this.fax = fax;
}

public String getEmail() {
return email;
}

public void setEmail(String email) {
this.email = email;
}

public int getReportTo() {
return reportTo;
}

public void setReportTo(int reportTo) {
this.reportTo = reportTo;
}

public String getReportToName() {
return reportToName;
}

public void setReportToName(String reportToName) {
this.reportToName = reportToName;
}

public int getIsValid() {
return isValid;
}

public void setIsValid(int isValid) {
this.isValid = isValid;
}

public Timestamp getCreatedTime() {
return createdTime;
}

public void setCreatedTime(Timestamp createdTime) {
this.createdTime = createdTime;
}

public Timestamp getUpdatedTime() {
return updatedTime;
}

public void setUpdatedTime(Timestamp updatedTime) {
this.updatedTime = updatedTime;
}

@Override
public String toString() {
return "Communicator [communicatorId=" + communicatorId + ", communicatorName=" + communicatorName + ", phone="
+ phone + ", fax=" + fax + ", email=" + email + ", reportTo=" + reportTo + ", reportToName="
+ reportToName + ", isValid=" + isValid + ", createdTime=" + createdTime + ", updatedTime="
+ updatedTime + "]";
}

}

测试

一切基础工作做好后，就可以着手编写测试代码了。这里使用了JUnit测试框架，如果有朋友不了解，请自行补充学习。
我们先对使用外部XML文件进行映射的User表进行测试，测试代码如下。
package com.emerson.learning.mapping;

import java.io.IOException;
import java.io.Reader;
import java.util.ArrayList;
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.After;
import org.junit.Before;
import org.junit.Test;

import com.emerson.learning.pojo.User;

public class UserMappingTest {

private Reader reader;
private SqlSessionFactory sqlSessionFactory;

@Before
public void setUp() throws Exception {
try {
reader = Resources.getResourceAsReader("mybatis.xml");
} catch (IOException e) {
e.printStackTrace();
}
sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
}

@After
public void tearDown() throws Exception {
}

/**
* 下面使用的是直接从映射配置文件中读取相应的SQL语句并执行 返回的是Object对象，需要对其进行强类型转换后才可使用
*
* 该实现方便需要为每个实体类编写一个映射文件
* <mapper namespace="com.emerson.learning.mapping.user">
* <select id="getByID" parameterType="int" resultType="User">
* SELECT user_id, user_name, nick_name, email FROM sys_user WHERE user_id = #{id}
* </select>
* </mapper>
*
* 并注册到Mybatis配置文件中的mappers节中
* <mappers>
* <mapper resource="com/emerson/learning/mapping/User.xml" />
* </mappers>
*
*/
@Test
public void testGetById() {
SqlSession session = sqlSessionFactory.openSession();
try {
User user;

Object obj = session.selectOne("com.emerson.learning.mapping.user.getByID", 1);
if (null == obj) {
System.out.println("the result is null.");
} else {
user = (User) obj;
System.out.println(user.getUserName());
System.out.println(user.getNickName());
System.out.println(user);
}
} finally {
session.close();
}
}

/**
* 测试模糊查询
*/
@Test
public void testQueryByName() {
SqlSession session = sqlSessionFactory.openSession();
try {
User user = new User();
user.setUserName("mao");
List<User> list = session.selectList("com.emerson.learning.mapping.user.queryByName", user);
System.out.println(list.size());
for(User u: list) {
System.out.println(u);
}
} finally {
session.close();
}
}

/**
* 测试写入数据
*/
@Test
public void testInsertUser() {
SqlSession session = sqlSessionFactory.openSession();
try {
User user = new User();
user.setEmail("chris.mao.zb@###.com");
user.setNickName("Mybatis Tester");
user.setUserName("cmzb");
user.setIsValid(1);
user.setUserPassword("5f4dcc3b5aa765d61d8327deb882cf99");

session.insert("com.emerson.learning.mapping.user.insertUser", user);
System.out.println("New Id is " + user.getUserId()); //打印出新增记录的Id值
session.commit(); //这里一定要使用commit，否则事务不会被提交，数据操作不会反映到数据表中
} finally {
session.close();
}
}

/**
* 测试更新数据
*/
@Test
public void testUpdateUser() {
SqlSession session = sqlSessionFactory.openSession();
try {
User user = session.selectOne("com.emerson.learning.mapping.user.getByID", 2);
user.setEmail("chris.mao.zb@＃＃＃.com");
user.setNickName("ChrisMao");
user.setIsValid(0);

session.update("com.emerson.learning.mapping.user.updatetUser", user);
session.commit();//这里一个要commit，否则更新是不会写入到数据表中的
} finally {
session.close();
}
}

/**
* 测试单条删除
*/
@Test
public void testDeleteById() {
SqlSession session = sqlSessionFactory.openSession();
try {
session.delete("com.emerson.learning.mapping.user.deleteById", 3);
session.commit();
} finally {
session.close();
}
}

/**
* 测试批量删除
*/
@Test
public void testDeleteBatch() {
SqlSession session = sqlSessionFactory.openSession();
try {
List<Integer> idList = new ArrayList<Integer>();
idList.add(1);
idList.add(2);
session.delete("com.emerson.learning.mapping.user.deleteBatch", idList);
session.commit();
} finally {
session.close();
}
}
}
下在是对使用注解映射的数据表Communicator表进行测试。
package com.emerson.learning.dao;

import java.io.IOException;
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;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import com.emerson.learning.pojo.Communicator;

public class CommunicatorDaoTest {
private Reader reader;
private SqlSessionFactory sqlSessionFactory;

@Before
public void setUp() throws Exception {
try {
reader = Resources.getResourceAsReader("mybatis.xml");
} catch (IOException e) {
e.printStackTrace();
}
sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
}

@After
public void tearDown() throws Exception {
}

/**
* 下面使用了接口和注解的方式来执行同样的代码 定义一个操作数据实体表的接口，并使用注解方式把SQL查询语句与接口方法进行绑定 public
* interface ICommunicatorDao { @Select(
* "SELECT * FROM communicator WHERE communicator_id=#{id}") public
* Communicator getById(@Param(value = "id") int id); }
*
* 然后将接口注册到Mybatis的配置文件中即可
* <mappers> <mapper class="com.emerson.learning.inter.ICommunicatorDao" />
* </mappers>
*
* 当数据表很多的时候，需要写很多的映射关系，这样也比较麻烦，Mybatis3.2.1提供了 一种更加简洁的方法，可以一次指定多个映射接口
* <mappers> <package namee="com.emerson.learning.inter" /> </mappers>
*
*/
@Test
public void testGetById() {
SqlSession session = sqlSessionFactory.openSession();
try {
ICommunicatorDao cp = session.getMapper(ICommunicatorDao.class);
Communicator c = cp.getById(1);
if (null == c) {
System.out.println("the result is null.");
} else {
System.out.println(c);
}
} finally {
session.close();
}
}

@Test
public void testGetAll() {
SqlSession session = sqlSessionFactory.openSession();
try {
ICommunicatorDao cp = session.getMapper(ICommunicatorDao.class);
List<Communicator> list = cp.getAll();
for (Communicator c : list) {
System.out.println(c);
}
} finally {
session.close();
}
}
}

总结

至此，对Mybatis的单表测试代码部分已全部完成。对于上述案例进行如下总结：

Mybatis大大减少了码农的编码工作，提高了工和效率
让程序猿可以把更多精力放在业务逻辑处理上，与数据库打交道的工作交由Mybatis完成
对于业务表的映射关系尽量使用外部文件进行配置
对于变动极小的基础数据表的映射可以考虑使用注解方式完成

最后，附上项目目录结构图。

 

附录

《Mybatis系列（一）入门》《Mybatis系列（二）配置》《Mybatis系列（四）映射文件》《Mybatis系列（五）动态SQL》《Mybatis系列（六）接口式编程》《Mybatis系列（七）关联映射》《Mybatis系列（八）集合映射》《Mybatis系列（九）Spring & Mybatis整合》