Java's MyBatis framework project construction and hellow world example

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,pudongsummer

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>