maven中使用mybatis

1、Mybatis优缺点

优点： Mybatis实现了对Dao层的封装，隔离了SQL语句，便于管理，避免了像JDBC那样操作数据集，便于扩展等等。

缺点： Mybatis属于?半自动“ORM”，比Hibernate的工作做得要多很多，对象参数传递比较麻烦，没有Hibernate对象操作的概念。

2、Mybatis的实现方式

Mybatis提供两种应用实现：XML配置和注解。

2.1配置主要依赖实体对象的xml文件，将对象以<resultMap>形式注入，并提供给<insert > <delete > <select> <update> 语句引用。

2.2使用注解来的比配置XML文件要简单得多。只需要在接口上添加相应的注解并附上SQL语句就行了，如：

插入语句：@insert(" insert into table_user ..")

修改语句： @update(" update table_user set ....")

删除语句：@delete(" delete from table_user .....")

查询语句：@select(" select * from table_user .....")

3、下载mybatis的jar包：mybatis-3.1.1-bundle.zip?，网址：http://code.google.com/p/mybatis/

Maven的pom.xml依赖配置如下：

<dependency>
   <groupId>org.mybatis</groupId>
   <artifactId>mybatis</artifactId>
   <version>3.1.1</version>
 </dependency>

依赖仓库配置：

<repository>
    <id>mybatis-snapshot</id>
    <name>MyBatis Snapshot Repository</name>
    <url>https://oss.sonatype.org/content/repositories/snapshots</url>
</repository>

4、构建自己的mybatis项目,如图所示：

展开文件展示：

5、mybatis-config.xml:配置数据源和隐射文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration PUBLIC "-//ibatis.apache.org//DTD Config 3.0//EN" "http://ibatis.apache.org/dtd/ibatis-3-config.dtd">
<configuration>
    <environments default="environment">
        <environment id="environment">
            <transactionManager type="JDBC" />
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url"
                    value="jdbc:mysql://localhost:3306/mybatis?characterEncoding =UTF-8" />
                <property name="username" value="root" />
                <property name="password" value="root" />
            </dataSource>
        </environment>
    </environments>
       <!-- <mappers> <mapper resource="mybatis/User.xml"/> </mappers> -->
</configuration>

注：<!-- <mappers> <mapper resource="mybatis/User.xml"/> </mappers> -->是使用实体配置的实现，如果使用注解则不需要添加。

6、使用注解实现CRUD操作-此处以实现用户管理为例

6.1编写接口（interface）：实际上就是官方文档所述的Mapper

public interface UserService {
     @Insert(" insert into users (id,username,password) values (#{id},#{username},#{password})")
     void add(@Param("id")String id,@Param("username") String username,@Param("password")String password);

     @Delete(" delete from users where id=#{id}")
     void delete(String id);

     @Update(" update users set username=#{username},password=#{password} where id=#{id}")
     int update(@Param("username") String username,@Param("password")String password,@Param("id")String id);

     @Select(" select * from users where id=#{id}")
     User getUser(String id);

     @Select(" select * from users order by id asc ")
     List<User> getUsers();

     @Select(" select * from users order by id asc limit #{pageSize} offset #{offset} ")
     List<User> getUsersByPage(@Param("offset")int offset,@Param("pageSize") int pageSize);//offset=pageSize*(page-1)}?
}

注：使用注解时接口的方法不能重载，否者会产生Mapped Statements collection does not contain value for 异常,另外还应尽量避免配置和注解混合使用的情况。

6.2获取数据源

public class GetSqlSessionFactory
{
    private static SqlSessionFactory sqlSessionFactory = null;

    private static GetSqlSessionFactory getSqlSessionFactory = null;

    private GetSqlSessionFactory()
    {
        String rs = "mybatis-config.xml";
        Reader reader = null;
        try
        {
            reader = Resources.getResourceAsReader(rs);
        } catch (IOException e)
        {
            e.printStackTrace();
        }
        sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
        // 注解方式查询时需要注册mapper
        sqlSessionFactory.getConfiguration().addMapper(UserService.class);
    }

    public static GetSqlSessionFactory getInstance()
    {
        if (getSqlSessionFactory == null)
            getSqlSessionFactory = new GetSqlSessionFactory();
        return getSqlSessionFactory;
    }

    public static SqlSessionFactory getSqlSessionFactory()
    {
        return sqlSessionFactory;
    }

}

6.3DAO层：数据访问

public class UserDao
{
    @SuppressWarnings("static-access")
    public void add(String id, String username, String password)
    {
        SqlSession session = GetSqlSessionFactory.getInstance().getSqlSessionFactory().openSession();
        try
        {
            session.getMapper(UserService.class).add(id, username, password);
            session.commit();// 提交事务
        } catch (Exception e)
        {
            e.printStackTrace();
        } finally
        {
            session.close();
        }
    }

    @SuppressWarnings("static-access")
    public void delete(String id)
    {
        SqlSession session = GetSqlSessionFactory.getInstance().getSqlSessionFactory().openSession();
        try
        {
            session.getMapper(UserService.class).delete(id);
            session.commit();// 提交事务
        } catch (Exception e)
        {
            e.printStackTrace();
        } finally
        {
            session.close();
        }
    }

    @SuppressWarnings("static-access")
    public int update(String username, String password, String id)
    {
        int count = 0;
        SqlSession session = GetSqlSessionFactory.getInstance().getSqlSessionFactory().openSession();
        try
        {
            // Map<String, Object> map=new HashMap<String, Object>();
            // map.put("username", user.getUsername());
            // map.put("password", user.getPassword());
            // session.update("updateUser", map);
            count = session.getMapper(UserService.class).update(username, password, id);
            session.commit();// 提交事务
        } catch (Exception e)
        {
            count = 0;
            e.printStackTrace();
        } finally
        {
            session.close();
        }
        return count;
    }

    @SuppressWarnings("static-access")
    public List<User> getUsers(int offset, int pageSize)
    {
        List<User> users = new ArrayList<User>();
        SqlSession session = GetSqlSessionFactory.getInstance().getSqlSessionFactory().openSession();
        try
        {
            // users=session.selectList("user_list_page", new User(),new
            // RowBounds(offset,pageSize));//未测试过
            // 注解方式查询
            users = session.getMapper(UserService.class).getUsersByPage(offset, pageSize);
        } catch (Exception e)
        {
            e.printStackTrace();
        } finally
        {
            session.close();
        }
        return users;
    }
}

6.4servlet实现数据跳转访问

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
    {
        response.setContentType("text/html;charset=utf-8");
        UserService userService = new UserServiceImpl();
        PrintWriter out = response.getWriter();
        String method = request.getParameter("method");
        String returnString = "";
        // 方法入口
        if (method.equals("users"))
        {
            returnString = new JsonUtil<User>().getJsonByListObj(userService.getUsers());
        } else if (method.equals("user"))
        {
            String id = request.getParameter("id");
            returnString = new JsonUtil<User>().getJsonByEntity(userService.getUser(id));
        } else if (method.equals("delete"))
        {
            String id = request.getParameter("id");
            Map<String, Object> map = new HashMap<String, Object>();
            map.put("event", method);
            map.put("param", id);
            returnString = new JsonUtil<User>().getJsonByObject(map);
        } else if (method.equals("update"))
        {
            String id = request.getParameter("id");
            String username = request.getParameter("username");
            String password = request.getParameter("password");
            Map<String, Object> map = new HashMap<String, Object>();
            int count = userService.update(username, password, id);
            map.put("status", count == 0 ? false : true);
            map.put("event", method);
            map.put("param", id);
            returnString = new JsonUtil<User>().getJsonByObject(map);
        } else if (method.equals("paginate"))
        {
            int limit = Integer.valueOf(request.getParameter("pageSize"));
            int offset = Integer.valueOf(request.getParameter("offset"));
            returnString = new JsonUtil<User>().getJsonByListObj(userService.getUsersByPage(offset, limit));
        }
        // 输出JSON数据
        out.print(returnString);
        out.flush();
        out.close();
    }

至此，注解方式的实现就全部完成了。

7、User.xml实体对象配置

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//ibatis.apache.org//DTD Mapper 3.0//EN" "http://ibatis.apache.org/dtd/ibatis-3-mapper.dtd">
<mapper namespace="com.boonya.mybatis.entity.User">
    <resultMap id="UserResultMap" type="com.boonya.mybatis.entity.User">
        <result property="id" column="id" jdbcType="VARCHAR" javaType="string" />
        <result property="name" column="name" javaType="string"
            jdbcType="VARCHAR" />
        <result property="createtime" column="createtime" javaType="string"
            jdbcType="VARCHAR" />
        <result property="tilepath" column="tilepath" javaType="string"
            jdbcType="VARCHAR" />
        <result property="lastlogintime" column="lastlogintime"
            javaType="string" jdbcType="VARCHAR" />
        <result property="nickname" column="nickname" javaType="string"
            jdbcType="VARCHAR" />
        <result property="password" column="password" javaType="string"
            jdbcType="VARCHAR" />
        <result property="picture" column="picture" javaType="string"
            jdbcType="VARCHAR" />
        <result property="sex" column="sex" javaType="string" jdbcType="VARCHAR" />
        <result property="username" column="username" javaType="string"
            jdbcType="VARCHAR" />
    </resultMap>
    <span style="color:#ff0000"><!-- 一般的SQL查询或操作语句配置 --></span>
    <select id="user" parameterType="int" resultType="com.boonya.mybatis.entity.User"
        resultMap="UserResultMap">select * from users where id=#{id} </select>
    <select id="users" resultMap="UserResultMap">select * from users order by id asc
    </select>
    <insert id="addUser" parameterType="com.boonya.mybatis.entity.User"
        parameterMap="UserResultMap">insert into users
        (id,name,createtime,email,tilepath,lastloginip,lastlogintime,nickname,password,picture,sessionid,sex,tel,username)
        values
        (#{id},#{name},#{createtime},#{email},#{tilepath},#{lastloginip},#{lastlogintime},#{nickname},#{password},#{picture},#{sessionid},#{sex},#{tel},#{username})
    </insert>
    <span style="color:#ff0000"><!-- Dynamic SQL 这里的方法未经测试 -->
    <!-- IF --></span>
    <select id="dynamic_user" resultMap="UserResultMap">
        select * from users where username=#{username}
        <if test="name!=null">and name=#{name}</if>
    </select>
    <span style="color:#ff0000"><!-- FOREACH --></span>
    <select id="dynamic_users" resultMap="UserResultMap">
        select * from users name=#{name} and createtime in
        <foreach collection="list" item="classTimeList" open="("
            separator="," close=")"> #{classTimeList} </foreach>
    </select>
    <span style="color:#ff0000"><!-- choose when otherwise --></span>
    <select id="dynamic_findNameLike" resultMap="UserResultMap">
        SELECT * FROM USERS WHERE NAME IS NOT NULL
        <choose>
            <when test="nickname!=null">AND nickname like #{nickname}</when>
            <when test="picture!=null ">AND picture like #{picture}</when>
            <otherwise>AND lastlogintime > #{lastlogintime}</otherwise>
        </choose>
    </select>
    <span style="color:#ff0000"><!-- WHERE --></span>
    <select id="dynamic_findUSERSLike" resultMap="UserResultMap">
        select * from users
        <where>
            <if test="name!=null">WHERE name LIKE #{name}</if>
        </where>
    </select>
</mapper>

注：如果使用配置需将mybatis-config.xml文件的mapper去掉注释：

<!-- <mappers>

         <mapper resource="mybatis/User.xml"/>

</mappers> -->

并且注释掉使用注解的mapper隐射：

//注解方式查询时需要注册mapper

sqlSessionFactory.getConfiguration().addMapper(UserService.class);

配置方式是根据SQL语句的隐射去访问的 如UserDao 中的getUsers方法：

//xml方式查询

//users=session.selectList("users");

8、测试数据是否能够正常访问

8-1、数据库mybatis创建users表并添加数据

/*
Navicat MySQL Data Transfer

Source Server         : localhost
Source Server Version : 50513
Source Host           : localhost:3306
Source Database       : mybatis

Target Server Type    : MYSQL
Target Server Version : 50513
File Encoding         : 65001

Date: 2012-12-17 18:25:15
*/

SET FOREIGN_KEY_CHECKS=0;

-- ----------------------------
-- Table structure for `users`
-- ----------------------------
DROP TABLE IF EXISTS `users`;
CREATE TABLE `users` (
  `id` varchar(50) NOT NULL,
  `username` varchar(30) DEFAULT NULL,
  `password` varchar(20) DEFAULT NULL,
  `name` varchar(30) DEFAULT NULL,
  `nickname` varchar(30) DEFAULT NULL,
  `sex` varchar(10) DEFAULT NULL,
  `picture` varchar(255) DEFAULT NULL,
  `createtime` varchar(20) DEFAULT NULL,
  `lastlogintime` varchar(50) DEFAULT NULL,
  `tilepath` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of users
-- ----------------------------
INSERT INTO `users` VALUES ('HUSDHSHFSD_00001', 'BOONYA', '123456', 'BOONYA_U', 'BOONYA_*', '男', 'images/inde.png', '2012-12-17 15:30:23', '1832928398932', 'this/home/index.tile');
INSERT INTO `users` VALUES ('HUSDHSHFSD_000010', 'BOONYA', '123456', 'BOONYA_U', 'BOONYA_*', '男', 'images/inde.png', '2012-12-17 15:30:23', '1832928398932', 'this/home/index.tile');
INSERT INTO `users` VALUES ('HUSDHSHFSD_00002', 'BOONYA', '123456', 'BOONYA_U', 'BOONYA_*', '女', 'images/inde.png', '2012-12-17 15:30:23', '1832928398932', 'this/home/index.tile');
INSERT INTO `users` VALUES ('HUSDHSHFSD_00003', 'BOONYA', '123456', 'BOONYA_U', 'BOONYA_*', '男', 'images/inde.png', '2012-12-17 15:30:23', '1832928398932', 'this/home/index.tile');
INSERT INTO `users` VALUES ('HUSDHSHFSD_00004', 'BOONYA', '123456', 'BOONYA_U', 'BOONYA_*', '男', 'images/inde.png', '2012-12-17 15:30:23', '1832928398932', 'this/home/index.tile');
INSERT INTO `users` VALUES ('HUSDHSHFSD_00005', 'BOONYA', '123456', 'BOONYA_U', 'BOONYA_*', '女', 'images/inde.png', '2012-12-17 15:30:23', '1832928398932', 'this/home/index.tile');
INSERT INTO `users` VALUES ('HUSDHSHFSD_00006', 'BOONYA', '123456', 'BOONYA_U', 'BOONYA_*', '男', 'images/inde.png', '2012-12-17 15:30:23', '1832928398932', 'this/home/index.tile');
INSERT INTO `users` VALUES ('HUSDHSHFSD_00007', 'BOONYA', '123456', 'BOONYA_U', 'BOONYA_*', '男', 'images/inde.png', '2012-12-17 15:30:23', '1832928398932', 'this/home/index.tile');
INSERT INTO `users` VALUES ('HUSDHSHFSD_00008', 'BOONYA', '123456', 'BOONYA_U', 'BOONYA_*', '男', 'images/inde.png', '2012-12-17 15:30:23', '1832928398932', 'this/home/index.tile');
INSERT INTO `users` VALUES ('HUSDHSHFSD_00009', 'BOONYA', '123456', 'BOONYA_U', 'BOONYA_*', '女', 'images/inde.png', '2012-12-17 15:30:23', '1832928398932', 'this/home/index.tile');

8-2、修改web.xml的servlet的配置

<!DOCTYPE web-app PUBLIC
 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>
  <display-name>Archetype Created Web Application</display-name>
  <servlet>
    <servlet-name>DefaultUserListHandler</servlet-name>
    <display-name>DefaultUserListHandler</display-name>
    <description></description>
    <servlet-class>com.boonya.mybatis.servlet.DefaultUserListHandler</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>DefaultUserListHandler</servlet-name>
    <url-pattern>/userservice</url-pattern>
  </servlet-mapping>

  <welcome-file-list>
         <welcome-file>index.html</welcome-file>
 </welcome-file-list>

</web-app>

将mybatis项目部署到Tomcat服务器中，启动服务器，在浏览器输入：http://localhost:8080/mybatis/userservice?method=users会看到如下图所示的结果：