Java的MyBatis框架项目搭建与hellow world示例

新建项目（我使用的是maven项目）mybatis-study-01

一、加入mybatis与mysql-connector依赖包到pom文件

<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>mybatis</groupId>
<artifactId>mybatis-study-01</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>mybatis-01</name>
<url>http://maven.apache.org</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.10</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.2.3</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.27</version>
</dependency>
</dependencies>
</project>

二、创建数据库mybatis-test
新建一张user表用于测试。建表sql如下：

CREATE TABLE `user` (
`id` int(11) NOT NULL auto_increment,
`password` varchar(255) default NULL,
`user_name` varchar(50) default NULL,
`user_age` int(11) default NULL,
`user_address` varchar(200) default NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `userName` (`user_name`)
) EN

插入一条数据

INSERT INTO `user` VALUES ('1', '123131', 'summer', '100', 'shanghai,pudong');

三、在项目中编写pojo对象。

package com.zf.mybatis.pojo;
public class User {
private int id;
private String password ;
private String userName;
private String 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 String getUserAge() {
return userAge;
}
public void setUserAge(String userAge) {
this.userAge = userAge;
}
public String getUserAddress() {
return userAddress;
}
public void setUserAddress(String userAddress) {
this.userAddress = userAddress;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}

四、编写pojo对应的映射文件User.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 namespace="com.zf.mybatis.pojo.UserMapper">
<!-- 使用sql标签可以将公共的sql提取出来复用 -->
<sql id="queryFields">
id , password , user_name as userName , user_age as userAge , user_address as userAddress
</sql>
<select id="selectByID" parameterType="int" resultType="User">
select
<include refid="queryFields"/>
from `user` where id = #{id}
</select>
<insert id="add" parameterType="User" useGeneratedKeys="true" keyProperty="id" >
insert into `user`
(password , user_name , user_age , user_address)
values(#{password} , #{userName} , #{userAge} , #{userAddress} )
</insert>
<update id="update" parameterType="User" >
update `user`
set password = #{password} , user_name = #{userName}, user_age = #{userAge}, user_address = #{userAddress}
where id = #{id}
</update>
<delete id="deleteById" parameterType="int">
delete from `user` where id = #{id}
</delete>
</mapper>

注意：上面的namespace的值为com.zf.mybatis.pojo.UserMapper，可以自定义 ，UserMapper不是一个类，不需要存在的。
另外，mybatis会将从数据库查询出来的记录根据列名与pojo中的字段进行匹配， 所以上面的user_name，user_age ,user_address这几个字段都取了别名，跟pojo中的字段相对应。 如果不起别名， 查询出来的对象，这几个字段是没有值的。

五、编写mybatis的配置文件mybatis-config.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>
<!-- 配置别名 -->
<typeAliases>
<typeAlias alias="User" type="com.zf.mybatis.pojo.User"/>
</typeAliases>
<!-- 数据库配置信息 -->
<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-test"/>
<property name="username" value="root"/>
<property name="password" value="root"/>
</dataSource>
</environment>
</environments>
<!-- 映射文件 -->
<mappers>
<mapper resource="conf/User.xml"/>
</mappers>
</configuration>

在该配置文件中配置了数据库的链接方式，以及注册所有的映射文件，还可以设置mybatis的一些参数。

现在就可以编写测试类了。来测试一下。

package com.zf.mybatis;
import java.io.IOException;
import java.io.Reader;
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.Before;
import org.junit.Test;
import com.zf.mybatis.pojo.User;
public class TestMyBatis {
private SqlSessionFactory sqlSessionFactory;
private Reader reader;
@Before
public void init(){
try {
reader = Resources.getResourceAsReader("mybatis-config.xml");
sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
} catch (IOException e) {
e.printStackTrace();
}
}
@Test
public void testQueryUser(){
SqlSession session = sqlSessionFactory.openSession();
try {
User user = (User) session.selectOne("com.zf.mybatis.pojo.UserMapper.selectByID" ,1);
System.out.println(user.getUserAddress());
System.out.println(user.getUserName());
} finally {
session.close();
}
}
@Test
public void testInsertUser(){
SqlSession session = sqlSessionFactory.openSession();
try {
User user = new User() ;
user.setUserName("abcde");
user.setUserAge(15) ;
user.setUserAddress("hangzhou/zhejiang");
user.setPassword("123456");
//返回值是记录条数
int resultCount = session.insert("com.zf.mybatis.pojo.UserMapper.add", user );
session.commit() ;
System.out.printf("userID:%d,总记录条数:%d" , user.getId() , resultCount); //获取插入对象的id
} finally {
session.close();
}
}
@Test
public void testUpdateUser(){
SqlSession session = sqlSessionFactory.openSession();
try {
User user = new User() ;
user.setId(5) ;
user.setUserName("updateName");
user.setUserAge(101) ;
user.setUserAddress("shenzhen/guangdong");
user.setPassword("000000");
//返回值是修改条数
int updateCount = session.update("com.zf.mybatis.pojo.UserMapper.update", user );
session.commit() ;
System.out.printf("修改条数:%d" ,updateCount);
} finally {
session.close();
}
}
@Test
public void testDelete(){
SqlSession session = sqlSessionFactory.openSession();
try {
//返回值是删除条数
int deleteCount = session.update("com.zf.mybatis.pojo.UserMapper.deleteById", 4 );
session.commit() ;
System.out.printf("删除条数:%d" ,deleteCount );
} finally {
session.close();
}
}
}

运行testQueryUser结果如下：

shanghai,pudong
summer

到此，一个mybatis的helloworld类型的小程序就出来了。

PS：MyBaits配置文件报错解决
Mybaits的配置文件校验很诡异，节点的位置还有要求
如下，会报错：

The content of element type "configuration" must match "(properties?,settings?,typeAliases?,typeHandlers?,objectFactory?,objectWrapperFactory?,plugins?,environments?,mappers?)".
<?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="oracle.jdbc.driver.OracleDriver"/>
<property name="url" value="jdbc:oracle:thin:@xx:1521:xx"/>
<property name="username" value="ireport"/>
<property name="password" value="xxxx"/>
</dataSource>
</environment>
</environments>
<typeAliases>
<typeAlias type="com.ice.stat.online.model.EventFlag" alias="EventFlag"/>
</typeAliases>
<mappers>
<mapper resource="com/ice/stat/online/model/hbm/EventFlagMapper.xml"/>
</mappers>
</configuration>

 
把typeAliases放到最上面就好了说：

<?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>
<typeAliases>
<typeAlias type="com.ice.stat.online.model.EventFlag" alias="EventFlag"/>
</typeAliases>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="oracle.jdbc.driver.OracleDriver"/>
<property name="url" value="jdbc:oracle:thin:@xx:1521:xx"/>
<property name="username" value="ireport"/>
<property name="password" value="xxxx"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="com/ice/stat/online/model/hbm/EventFlagMapper.xml"/>
</mappers>
</configuration>

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