MyBatis入门教程

MyBatis作为持久性框架，能够简化我们的编程。下面我们学一下如何利用MyBatis进行数据库连接
首先：应该导入myBatis的jar包mybatis-xxx和mysql驱动包mysql-connector-java-x.x.x-bin

1：
2创建与数据表对应的POJO Role ，字段名要与属性名一致。

package pojo;public class Role {    private Long id;    private String roleName;    public Long getId() {        return id;    }    public void setId(Long id) {        this.id = id;    }    public String getRoleName() {        return roleName;    }    public void setRoleName(String roleName) {        this.roleName = roleName;    }    public String getNote() {        return note;    }    public void setNote(String note) {        this.note = note;    }    private String note;}

3：采用XML形式构建映射器，包含一个接口和一个XML
3.1 创建接口RoleMapper ，里面的方法是对Role对象进行操作

package mapper;import java.util.List;import pojo.Role;public interface RoleMapper {    public int insertRole(Role role);    public int deleteRole(Long id);    public int updateRole(Role role);    public Role getRole(Long id);    public List<Role> findRoles(String roleName);}

3.2：创建XML文件，与接口形成映射
RoleMapper.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="mapper.RoleMapper"> <insert id="insertRole" parameterType="role">    insert into role(roleName,note) values(#{roleName},#{note}) </insert> <delete id="deleteRole" parameterType="long">  delete from role where id=#{id} </delete> <update id="updateRole" parameterType="role"> update role set roleName=#{roleName},note=#{note} where id=#{id} </update> <select id="getRole" parameterType="long" resultType="role"> select id,roleName,note from role where id=#{id} <!--id是方法中传递进来的参数--> </select> <select id="findRoles" parameterType="string" resultType="role"> select id,roleName,note from role where roleName=#{roleName} </select> </mapper>

4:配置mybatis-config.xml文件，用于创建SqlSessionFactory对象

<?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 >        <!-- 别名方式1，一个一个的配置 type中放置的是类的全路径，alias中放置的是类别名        <typeAliase  alias="role" type="pojo.Role"/> -->        <!-- 别名方式2，自动扫描，将JAVA类的类名作为类的类别名 -->        <package name="pojo"/>   </typeAliases>   <environments default="development">     <environment id="development">       <transactionManager type="JDBC" />       <!-- 配置数据库连接信息 -->       <dataSource type="POOLED">         <property name="driver" value="com.mysql.jdbc.Driver" />         <property name="url" value="jdbc:mysql://localhost:3306/ssm"/>         <property name="username" value="root" />         <property name="password" value="1367356" />       </dataSource>     </environment>   </environments>    <mappers>    <!-- 注册RoleMapper.xml文件，     RoleMapper.xml位于mapper这个包下，所以resource写成mapper/RoleMapper.xml-->    <mapper resource="mapper/RoleMapper.xml"/>  </mappers> </configuration>

5使用SqlSessionFactoryBuilder来构建SqlSessionFactory
SqlSessionFactoryUtils.java

package utils;import java.io.InputStream;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 SqlSessionFactoryUtils {    private final static Class<SqlSessionFactoryUtils> Lock = SqlSessionFactoryUtils.class;    private static SqlSessionFactory SqlSessionFactory = null;    // 构造函数    private SqlSessionFactoryUtils() {    }    public static SqlSessionFactory getSqlSessionFactory() {        synchronized (Lock) {            if (SqlSessionFactory != null) {                return SqlSessionFactory;            }            String resource = "mybatis-config.xml";            InputStream inputStream;            try {                inputStream = Resources.getResourceAsStream(resource);                SqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);            } catch (Exception e) {                // TODO: handle exception                e.printStackTrace();                return null;            }            return SqlSessionFactory;        }    }    public static SqlSession openSqlSession() {        if (SqlSessionFactory == null) {            getSqlSessionFactory();        }        return SqlSessionFactory.openSession();    }}

6创建测试类
Chapter3Main.java

package main;import org.apache.ibatis.session.SqlSession;import mapper.RoleMapper;import pojo.Role;import utils.SqlSessionFactoryUtils;public class Chapter3Main {    public static void main(String[] args) {        SqlSession sqlSession=null;        try {            sqlSession=SqlSessionFactoryUtils.openSqlSession();            RoleMapper roleMapper=sqlSession.getMapper(RoleMapper.class);            Role role=roleMapper.getRole(1L);            System.out.println(role.getRoleName());        } finally {            // TODO: handle finally clause            if(sqlSession!=null){                sqlSession.close();            }        }    }}

7:层次结构图