Mybatis介绍(一)
这里介绍的mybatis比较简单, 我做为一个初学者, 记录下个人在学习中方法, 如果那里出错, 希望读者朋友们见谅.
首先这里介绍一下我们下面用的表结构：
author表是保存了作者的个人信息, 因为我们在这里做测试, 所以就简单的定义几个字段.
blog表是保存谁写了博客的内容, 这里也是几个简单的字段.
comment表是保存对哪篇博客评论, 也是几个简单的字段.
注意: 这三张表的id都是自增型, 你也可以做其他的改变, 这里是为了方便.
下面给出了几张表格创建的sql语句:
CREATE TABLE `author` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(25) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
`age` int(5) NULL DEFAULT NULL,
`email` varchar(30) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
`country` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
PRIMARY KEY (`id`)
); CREATE TABLE `blog` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`authorid` int(11) NULL DEFAULT NULL,
`title` varchar(35) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
`mainbody` text CHARACTER SET utf8 COLLATE utf8_general_ci NULL,
`creattime` varchar(70) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
PRIMARY KEY (`id`)
); CREATE TABLE `comment` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`blogid` int(11) NULL DEFAULT NULL,
`content` text CHARACTER SET utf8 COLLATE utf8_general_ci NULL,
`creattime` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
PRIMARY KEY (`id`)
);
使用maven+springmvc+mabatis+spring搭建web环境, 可以参考博客: https://www.cnblogs.com/jay36/p/7762448.html, 这里就不详细的介绍了.
这里主要介绍mybatis的用法, 首先使用Mybatis Generator生成pojo/dao/mapping三个文件, 即实体类、DAO接口和Mapping映射文件.
可以参考博客: https://blog.csdn.net/zhshulin/article/details/23912615, 下面就开始简单介绍Mybatis的使用.
1. 看一下三个表pojo(Plain Ordinary Java Object), 即实体类
package com.springdemo.pojo;
public class Author {
private Integer id;
private String name;
private Integer age;
private String email;
private String country;
/* getting and setting function */
}
package com.springdemo.pojo;
public class Blog {
private Integer id;
private Integer authorid;
private String title;
private String creattime;
private String mainbody;
/* getting and setting function */
}
package com.springdemo.pojo;
public class Comment {
private Integer id;
private Integer blogid;
private String creattime;
private String content;
/* getting and setting function */
}
2. 再看一下三个表的dao(Data Access Object), 即dao接口
package com.springdemo.dao
public interface AuthorMapper {
int deleteByPrimaryKey(Integer id);
int insert(Author record);
int insertSelective(Author record);
Author selectByPrimaryKey(Integer id);
int updateByPrimaryKeySelective(Author record);
int updateByPrimaryKey(Author record);
}
package com.springdemo.dao
public interface BlogMapper {
int deleteByPrimaryKey(Integer id);
int insert(Blog record);
int insertSelective(Blog record);
Blog selectByPrimaryKey(Integer id);
int updateByPrimaryKeySelective(Blog record);
int updateByPrimaryKeyWithBLOBs(Blog record);
int updateByPrimaryKey(Blog record);
}
package com.springdemo.dao
public interface CommentMapper {
int deleteByPrimaryKey(Integer id);
int insert(Comment record);
int insertSelective(Comment record);
Comment selectByPrimaryKey(Integer id);
int updateByPrimaryKeySelective(Comment record);
int updateByPrimaryKeyWithBLOBs(Comment record);
int updateByPrimaryKey(Comment record);
}
3. 再看一下三个表的mapping, 即Mapping映射
<?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.springdemo.dao.AuthorMapper" >
<resultMap id="BaseResultMap" type="com.springdemo.pojo.Author" >
<id column="id" property="id" jdbcType="INTEGER" />
<result column="name" property="name" jdbcType="VARCHAR" />
<result column="age" property="age" jdbcType="INTEGER" />
<result column="email" property="email" jdbcType="VARCHAR" />
<result column="country" property="country" jdbcType="VARCHAR" />
</resultMap>
<sql id="Base_Column_List" >
id, name, age, email, country
</sql>
<select id="selectByPrimaryKey" resultMap="BaseResultMap" parameterType="java.lang.Integer" >
select
<include refid="Base_Column_List" />
from author
where id = #{id,jdbcType=INTEGER}
</select>
<delete id="deleteByPrimaryKey" parameterType="java.lang.Integer" >
delete from author
where id = #{id,jdbcType=INTEGER}
</delete>
<insert id="insert" parameterType="com.springdemo.pojo.Author" >
insert into author (id, name, age,
email, country)
values (#{id,jdbcType=INTEGER}, #{name,jdbcType=VARCHAR}, #{age,jdbcType=INTEGER},
#{email,jdbcType=VARCHAR}, #{country,jdbcType=VARCHAR})
</insert>
<insert id="insertSelective" parameterType="com.springdemo.pojo.Author" >
insert into author
<trim prefix="(" suffix=")" suffixOverrides="," >
<if test="id != null" >
id,
</if>
<if test="name != null" >
name,
</if>
<if test="age != null" >
age,
</if>
<if test="email != null" >
email,
</if>
<if test="country != null" >
country,
</if>
</trim>
<trim prefix="values (" suffix=")" suffixOverrides="," >
<if test="id != null" >
#{id,jdbcType=INTEGER},
</if>
<if test="name != null" >
#{name,jdbcType=VARCHAR},
</if>
<if test="age != null" >
#{age,jdbcType=INTEGER},
</if>
<if test="email != null" >
#{email,jdbcType=VARCHAR},
</if>
<if test="country != null" >
#{country,jdbcType=VARCHAR},
</if>
</trim>
</insert>
<update id="updateByPrimaryKeySelective" parameterType="com.springdemo.pojo.Author" >
update author
<set >
<if test="name != null" >
name = #{name,jdbcType=VARCHAR},
</if>
<if test="age != null" >
age = #{age,jdbcType=INTEGER},
</if>
<if test="email != null" >
email = #{email,jdbcType=VARCHAR},
</if>
<if test="country != null" >
country = #{country,jdbcType=VARCHAR},
</if>
</set>
where id = #{id,jdbcType=INTEGER}
</update>
<update id="updateByPrimaryKey" parameterType="com.springdemo.pojo.Author" >
update author
set name = #{name,jdbcType=VARCHAR},
age = #{age,jdbcType=INTEGER},
email = #{email,jdbcType=VARCHAR},
country = #{country,jdbcType=VARCHAR}
where id = #{id,jdbcType=INTEGER}
</update>
</mapper> <?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.springdemo.dao.BlogMapper" >
<resultMap id="BaseResultMap" type="com.springdemo.pojo.Blog" >
<id column="id" property="id" jdbcType="INTEGER" />
<result column="authorid" property="authorid" jdbcType="INTEGER" />
<result column="title" property="title" jdbcType="VARCHAR" />
<result column="creattime" property="creattime" jdbcType="VARCHAR" />
</resultMap>
<resultMap id="ResultMapWithBLOBs" type="com.springdemo.pojo.Blog" extends="BaseResultMap" >
<result column="mainbody" property="mainbody" jdbcType="LONGVARCHAR" />
</resultMap>
<sql id="Base_Column_List" >
id, authorid, title, creattime
</sql>
<sql id="Blob_Column_List" >
mainbody
</sql>
<select id="selectByPrimaryKey" resultMap="ResultMapWithBLOBs" parameterType="java.lang.Integer" >
select
<include refid="Base_Column_List" />
,
<include refid="Blob_Column_List" />
from blog
where id = #{id,jdbcType=INTEGER}
</select>
<delete id="deleteByPrimaryKey" parameterType="java.lang.Integer" >
delete from blog
where id = #{id,jdbcType=INTEGER}
</delete>
<insert id="insert" parameterType="com.springdemo.pojo.Blog" >
insert into blog (id, authorid, title,
creattime, mainbody)
values (#{id,jdbcType=INTEGER}, #{authorid,jdbcType=INTEGER}, #{title,jdbcType=VARCHAR},
#{creattime,jdbcType=VARCHAR}, #{mainbody,jdbcType=LONGVARCHAR})
</insert>
<insert id="insertSelective" parameterType="com.springdemo.pojo.Blog" >
insert into blog
<trim prefix="(" suffix=")" suffixOverrides="," >
<if test="id != null" >
id,
</if>
<if test="authorid != null" >
authorid,
</if>
<if test="title != null" >
title,
</if>
<if test="creattime != null" >
creattime,
</if>
<if test="mainbody != null" >
mainbody,
</if>
</trim>
<trim prefix="values (" suffix=")" suffixOverrides="," >
<if test="id != null" >
#{id,jdbcType=INTEGER},
</if>
<if test="authorid != null" >
#{authorid,jdbcType=INTEGER},
</if>
<if test="title != null" >
#{title,jdbcType=VARCHAR},
</if>
<if test="creattime != null" >
#{creattime,jdbcType=VARCHAR},
</if>
<if test="mainbody != null" >
#{mainbody,jdbcType=LONGVARCHAR},
</if>
</trim>
</insert>
<update id="updateByPrimaryKeySelective" parameterType="com.springdemo.pojo.Blog" >
update blog
<set >
<if test="authorid != null" >
authorid = #{authorid,jdbcType=INTEGER},
</if>
<if test="title != null" >
title = #{title,jdbcType=VARCHAR},
</if>
<if test="creattime != null" >
creattime = #{creattime,jdbcType=VARCHAR},
</if>
<if test="mainbody != null" >
mainbody = #{mainbody,jdbcType=LONGVARCHAR},
</if>
</set>
where id = #{id,jdbcType=INTEGER}
</update>
<update id="updateByPrimaryKeyWithBLOBs" parameterType="com.springdemo.pojo.Blog" >
update blog
set authorid = #{authorid,jdbcType=INTEGER},
title = #{title,jdbcType=VARCHAR},
creattime = #{creattime,jdbcType=VARCHAR},
mainbody = #{mainbody,jdbcType=LONGVARCHAR}
where id = #{id,jdbcType=INTEGER}
</update>
<update id="updateByPrimaryKey" parameterType="com.springdemo.pojo.Blog" >
update blog
set authorid = #{authorid,jdbcType=INTEGER},
title = #{title,jdbcType=VARCHAR},
creattime = #{creattime,jdbcType=VARCHAR}
where id = #{id,jdbcType=INTEGER}
</update>
</mapper> <?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.springdemo.dao.CommentMapper" >
<resultMap id="BaseResultMap" type="com.springdemo.pojo.Comment" >
<id column="id" property="id" jdbcType="INTEGER" />
<result column="blogid" property="blogid" jdbcType="INTEGER" />
<result column="creattime" property="creattime" jdbcType="VARCHAR" />
</resultMap>
<resultMap id="ResultMapWithBLOBs" type="com.springdemo.pojo.Comment" extends="BaseResultMap" >
<result column="content" property="content" jdbcType="LONGVARCHAR" />
</resultMap>
<sql id="Base_Column_List" >
id, blogid, creattime
</sql>
<sql id="Blob_Column_List" >
content
</sql>
<select id="selectByPrimaryKey" resultMap="ResultMapWithBLOBs" parameterType="java.lang.Integer" >
select
<include refid="Base_Column_List" />
,
<include refid="Blob_Column_List" />
from comment
where id = #{id,jdbcType=INTEGER}
</select>
<delete id="deleteByPrimaryKey" parameterType="java.lang.Integer" >
delete from comment
where id = #{id,jdbcType=INTEGER}
</delete>
<insert id="insert" parameterType="com.springdemo.pojo.Comment" >
insert into comment (id, blogid, creattime,
content)
values (#{id,jdbcType=INTEGER}, #{blogid,jdbcType=INTEGER}, #{creattime,jdbcType=VARCHAR},
#{content,jdbcType=LONGVARCHAR})
</insert>
<insert id="insertSelective" parameterType="com.springdemo.pojo.Comment" >
insert into comment
<trim prefix="(" suffix=")" suffixOverrides="," >
<if test="id != null" >
id,
</if>
<if test="blogid != null" >
blogid,
</if>
<if test="creattime != null" >
creattime,
</if>
<if test="content != null" >
content,
</if>
</trim>
<trim prefix="values (" suffix=")" suffixOverrides="," >
<if test="id != null" >
#{id,jdbcType=INTEGER},
</if>
<if test="blogid != null" >
#{blogid,jdbcType=INTEGER},
</if>
<if test="creattime != null" >
#{creattime,jdbcType=VARCHAR},
</if>
<if test="content != null" >
#{content,jdbcType=LONGVARCHAR},
</if>
</trim>
</insert>
<update id="updateByPrimaryKeySelective" parameterType="com.springdemo.pojo.Comment" >
update comment
<set >
<if test="blogid != null" >
blogid = #{blogid,jdbcType=INTEGER},
</if>
<if test="creattime != null" >
creattime = #{creattime,jdbcType=VARCHAR},
</if>
<if test="content != null" >
content = #{content,jdbcType=LONGVARCHAR},
</if>
</set>
where id = #{id,jdbcType=INTEGER}
</update>
<update id="updateByPrimaryKeyWithBLOBs" parameterType="com.springdemo.pojo.Comment" >
update comment
set blogid = #{blogid,jdbcType=INTEGER},
creattime = #{creattime,jdbcType=VARCHAR},
content = #{content,jdbcType=LONGVARCHAR}
where id = #{id,jdbcType=INTEGER}
</update>
<update id="updateByPrimaryKey" parameterType="com.springdemo.pojo.Comment" >
update comment
set blogid = #{blogid,jdbcType=INTEGER},
creattime = #{creattime,jdbcType=VARCHAR}
where id = #{id,jdbcType=INTEGER}
</update>
</mapper>
mybatis的使用, 关键在于要要写好mapping映射, 使用工具生成的是最简单的curd的方法, 现在我们来增加一个我们自定义的方法.
首先在mapping的文件中写一个映射, 我们就在BlogMapper.xml文件中写,代码如下:
<?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.springdemo.dao.BlogMapper" >
......
<insert id="insertBlogByList" useGeneratedKeys="true"
keyProperty="id" parameterType="java.util.List">
insert into blog (authorid, title, creattime, mainbody) values
<foreach item="item" collection="list" separator=",">
(#{item.authorid,jdbcType=INTEGER}, #{item.title,jdbcType=VARCHAR},
#{item.creattime,jdbcType=VARCHAR}, #{item.mainbody,jdbcType=LONGVARCHAR})
</foreach>
</insert>
......
</mapper> 这段xml的代码主要就是批量插入数据, 而且id是自增长的, 数据以list的形式传入进来, 然后循环插入到blog表中.
然后我们要在BlogMapper.java的dao中加一个接口, 代码如下:
package com.springdemo.dao;
public interface BlogMapper {
......
int insertBlogByList(List<Blog> listBlog);
......
}
注意这里的接口名字要和我们之前在xml中加入的id值相同才行, 因为这样mybatis才会映射.
即在BlogMapper.xml中写的insert语句id是insertBlogByList,
那么这里的定义的接口必须也是这个, 而且参数的类型也必须一样, 这一点切记。
最后我们要在controller中去调用(因为这里我是用springmvc写的,所有用mvc思想去写调用,你也可以随便写一个方法去调用, 这里给出我的调用方法):
//下面是BlogController.java的代码
package com.springdemo.controller; @Controller
@RequestMapping(value = "/blog")
public class BlogController { private static final Logger LOG = LogManager.getLogger(); @Autowired
private BlogService blogService; //这里是把前端的值获取到,然后再存入到数据库中, 最后返回状态
@RequestMapping(value="/insert", method = RequestMethod.POST)
public void insertBlog(HttpServletRequest request, HttpServletResponse response) {
String status = "{\"status\":\"failure\"}";
int authorid = Integer.parseInt(request.getParameter("authorid"));
String title = String.valueOf(request.getParameter("title"));
String mainbody = String.valueOf(request.getParameter("mainbody")); SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Date now = new Date();
String creattime = df.format(now); List<Blog> listBlog = new ArrayList<Blog>();
Blog blog = new Blog();
blog.setAuthorid(authorid);
blog.setTitle(title);
blog.setMainbody(mainbody);
blog.setCreattime(creattime);
listBlog.add(blog); int affectRow = blogService.insertBlogByList(listBlog);
if (affectRow != 0) {
status = "{\"status\":\"success\"}";
} response.setContentType("text/html;UTF-8");
try (PrintWriter writer = response.getWriter();) {
writer.write(status);
writer.flush();
} catch (IOException e) {
LOG.error(e.getMessage(), e);
}
}
} ----------------------------------------------------------
// 下面是BlogService.java的代码
package com.springdemo.service;
import java.util.List;
// 这里不需要继承BlogMapper接口, 通过spring注解直接使用
@Service(value="blogService")
public class BlogService { @Resource
private BlogMapper blogMapper; public int insertBlogByList(List<Blog> listBlog) {
int affectRow = 0;
affectRow = this.blogMapper.insertBlogByList(listBlog);
return affectRow;
} }
这样就简单的完成了在xml中建立sql语句, 然后通过映射转换到java中, 最后去执行.
待续......
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