DevOps
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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
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：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：
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：
注：刚开始学习mybatis的使用很多地方或细节不是很在意，如某些地方存在问题希望指点一二！
