Mybatis
1.搭建环境
https://mybatis.org/mybatis-3/zh/index.html
创建一个mavan项目
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导入依赖
<dependencies> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.47</version> </dependency> <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>3.5.2</version> </dependency> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.12</version> </dependency> </dependencies>
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修改配置，能够自动导入所有xml和properties 文件
<build> <resources> <resource> <directory>src/main/resources</directory> <includes> <include>**/*.xml</include> <include>**/*.properties</include> </includes> </resource> <resource> <directory>src/main/java</directory> <includes> <include>**/*.xml</include> <include>**/*.properties</include> </includes> </resource> </resources> </build> -
在resources 配置mysql数据库
<?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> <environments default="development"> <environment id="development"> <transactionManager type="JDBC"/> <dataSource type="POOLED"> <property name="driver" value="${driver}"/> <property name="url" value="${url}"/> <property name="username" value="${username}"/> <property name="password" value="${password}"/> </dataSource> </environment> </environments> <mappers> <mapper resource="org/mybatis/example/BlogMapper.xml"/> </mappers> </configuration>- ${driver} : 使用的驱动 一般使用com.mysql.jdbc.Driver
- ${url}:数据库地址
- ${username}:用户名
- ${password}:密码
<?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> <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/blogData?useSSL=false&useUnicode=true&characterEncoding=UTF-8"/> <property name="username" value="root"/> <property name="password" value="123456"/> </dataSource> </environment> </environments> <mappers> </mappers> </configuration> -
创建一个数据库
CREATE DATABASE blogData; -
创建数据表
use blogData; CREATE TABLE IF NOT EXISTS `Category`( `id` INT UNSIGNED AUTO_INCREMENT, `name` VARCHAR(100) NOT NULL, PRIMARY KEY(`id`) ) ENGINE =InnoDB DEFAULT CHARSET =utf8; CREATE TABLE IF NOT EXISTS `Tag`( `id` INT UNSIGNED AUTO_INCREMENT, `name` VARCHAR(100) NOT NULL , PRIMARY KEY (`id`) )ENGINE = InnoDB DEFAULT CHARSET = utf8; CREATE TABLE IF NOT EXISTS `Post`( `id` INT UNSIGNED AUTO_INCREMENT, `content` VARCHAR(1000) NOT NULL, `author` VARCHAR(100) NOT NULL, `cid` INT UNSIGNED, `tid` INT UNSIGNED, PRIMARY KEY (id), FOREIGN KEY (cid) REFERENCES Category(id), FOREIGN KEY (tid) REFERENCES Tag(id) ) ENGINE=InnoDB DEFAULT CHARSET = utf8; -
创建实体类
- 在src下创建一个pojo目录
image-20200529003522307.png
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编写实体类
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这里可以使用lombok插件
<dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <version>1.18.10</version> </dependency> -
代码：
package com.test.pojo; import lombok.Data; @Data public class Category { int id; String name; }package com.test.pojo; import lombok.Data; @Data public class Tag { int id; String name; }package com.test.pojo; import lombok.Data; import java.util.List; @Data public class Post { int id; String author; String content; Category category; Tag tag; }
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注意 ： 类名和属性名要和数据表匹配
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创建工具类
- 创建一个utils包
image-20200529135921661.png
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创建MyBatisUtils 获取sqlsession
package com.test.utils; import org.apache.ibatis.io.Resources; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder; import java.io.IOException; import java.io.InputStream; public class MyBatisUtils { private static SqlSessionFactory sqlSessionFactory; static { try{ String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); } catch (IOException e) { e.printStackTrace(); } } public static SqlSession getSqlSession(){ return sqlSessionFactory.openSession(true); } } openSession(true) :可以设置自动提交
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创建一个mapper包
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编写实体类的映射类
- 使用注解开发
package com.test.mapper; import com.test.pojo.Category; import org.apache.ibatis.annotations.Delete; import org.apache.ibatis.annotations.Insert; import org.apache.ibatis.annotations.Select; import org.apache.ibatis.annotations.Update; public interface CategoryMapper { @Select("select * from Category") Category getCategorys(); @Insert("insert into Category values(#{id},#{name})") void addCategory(Category category); @Delete("delete from Category where id=#{id}") void deleteCatogory(int id); @Update("update Category set name=#{name} where id=#{id}") void updateCategory(Category category); }-
使用xml 映射
package com.test.mapper; import com.test.pojo.Tag; import java.util.List; public interface TagMapper { List<Tag> getTags(); void addTag(Tag tag); void deleteTag(int id); void updateTag(Tag tag); }<?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.test.mapper.TagMapper"> <select id="getTags" resultType="com.test.pojo.Tag"> select * from tag; </select> <insert id="addTag" parameterType="com.test.pojo.Tag"> insert into tag values (#{id}, #{name}); </insert> <delete id="deleteTag"> delete from tag where id=#{id}; </delete> <update id="updateTag" parameterType="com.test.pojo.Tag"> update tag set name=#{name} where id=#{id}; </update> </mapper>xml 文件：
- namespace: 命名空间，就是映射类的包名+类名
类型别名：使用类型别名可以简化 类的导入
<!--mybatis-config.xml --> <typeAliases> <typeAlias type="com.test.pojo.Category" alias="Category" /> <typeAlias type="com.test.pojo.Tag" alias="Tag" /> </typeAliases><?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.test.mapper.TagMapper"> <select id="getTags" resultType="Tag"> select * from tag; </select> <insert id="addTag" parameterType="com.test.pojo.Tag"> insert into tag values (#{id}, #{name}); </insert> <delete id="deleteTag"> delete from tag where id=#{id}; </delete> <update id="updateTag" parameterType="com.test.pojo.Tag"> update tag set name=#{name} where id=#{id}; </update> </mapper>-
一对多和多对一：
<?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.test.mapper.PostMapper"> <resultMap id="getPosts" type="com.test.pojo.Post"> <association property="category" column="cid" select="getCategory" /> <association property="tag" column="tid" select="getTag" /> </resultMap> <select id="getPosts" resultMap="getPosts"> select * from post; </select> <insert id="addPost" parameterType="com.test.pojo.Tag" useGeneratedKeys="true"> insert into post(content, author, cid, tid) values ( #{content},#{author},#{category.id},#{tag.id}); </insert> <delete id="deletePost"> delete from post where id=#{id}; </delete> <update id="updatePost" parameterType="com.test.pojo.Post"> update post set content=#{content}, author=#{author}, cid=#{category.id}, tid=#{tag.id}; </update> <select id="getCategory" resultType="com.test.pojo.Category"> select * from category where id=#{cid}; </select> <select id="getTag" resultType="com.test.pojo.Tag"> select * from tag where id=#{tid}; </select> </mapper>package com.test.mapper; import com.test.pojo.Post; import java.util.List; public interface PostMapper { List<Post> getPosts(); void addPost(Post post); void deletePost(int id); void updatePost(Post post); }
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其他内容
动态sql+map 做多条件查询
<select id="getPost" resultMap="getPosts">
select * from post where 1=1
<if test="author!=null" >
and author=#{author}
</if>
<if test="content!=null">
and content like '%#{content}%'
</if>
</select>
