Mybatis初学

Mybatis简介大家可以自行google之。官网为：http://code.google.com/p/mybatis/

我也刚刚开始初学，先来一个小例子：

创建一个User.java文件，代码如下：

package com.rollen;

public class User {
	private String name;
	private int age;
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	@Override
	public String toString() {
		
		return "Name:"+name+"Age"+age;
	}
	
	
}

　　上面的java文件位于com.rollen包中，然后在这个包中建立generator.xml文件，代码为：

<?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 alias="User" type="com.rollen.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://localhost:3306/user_db" />  
                <property name="username" value="root" />  
                <property name="password" value="root" />  
            </dataSource>  
        </environment>  
    </environments>  
    <mappers>  
        <mapper resource="com/rollen/user.xml" />  
    </mappers>  
</configuration>  

　　在com.rollen包下面创建user.xml文件，代码为：

<?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.rollen.User">
	<select id="selectUser" parameterType="int" resultType="User" >
		 select * from user where age = #{age} 
	</select>
</mapper>

我们最后编写一个测试类，代码如下“：

package com.rollen;
import java.io.*;

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 {
	public static void main(String[] args) {
		String resource="com/rollen/generatorConfig.xml";
		Reader reader = null;
		try {
			reader = Resources.getResourceAsReader(resource);
		} catch (IOException e) {
			e.printStackTrace();
		}
		SqlSessionFactory factory=new SqlSessionFactoryBuilder().build(reader);
		SqlSession sqlSession = factory.openSession();
		
		try {
			User user=sqlSession.selectOne("selectUser", 10);
			System.out.println(user);
		}finally{
			sqlSession.close();
		}
		
	}
}

　　在上面的generateConfig.xml文件中，也可以改为这样：

<?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>
		<property name="username" value="root" />
	</properties>
	<typeAliases>
		<typeAlias alias="User" type="com.rollen.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://localhost:3306/user_db" />
				<property name="username" value="${username}" />
				<property name="password" value="root" />
			</dataSource>
		</environment>
	</environments>
	<mappers>
		<mapper resource="com/rollen/user.xml" />
	</mappers>
</configuration>  

　　注意，和上面的区别是我们添加了：

<properties>
		<property name="username" value="root" />
	</properties>

　　并且修改了这行代码：

<property name="username" value="${username}" />

　　还可以有如下的修改方法，新建一个config.properties文件，文件内容为：

password=root

　　然后将generatorconfig.xml文件的内容改为：

<?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="com/rollen/config.properties">
		<property name="username" value="root" />
	</properties>
	<typeAliases>
		<typeAlias alias="User" type="com.rollen.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://localhost:3306/user_db" />
				<property name="username" value="${username}" />
				<property name="password" value="${password}" />
			</dataSource>
		</environment>
	</environments>
	<mappers>
		<mapper resource="com/rollen/user.xml" />
	</mappers>
</configuration>  

　　需要注意的是如下的两行代码：

<properties resource="com/rollen/config.properties">
....
<property name="password" value="${password}" />