MyBatis

熟悉MyBatis

jar包:

<!--mysql驱动-->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.18</version>
</dependency>
<!--mybatis-->
<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.5.2</version>
</dependency>
<!--junit-->
<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.12</version>
</dependency>
<!--lombok-->
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.18.10</version>
</dependency>

由于maven中约定大于配置（配置文件需要写在resources目录下），所以要配置资源导出：

<!--在build中配置resource，来防止我们资源导出失败的问题-->
<build>
    <resources>
        <resource>
            <directory>src/main/resources</directory>
            <includes>
                <include>**/*.properties</include>
                <include>**/*.xml</include>
            </includes>
            <filtering>true</filtering>
        </resource>
        <resource>
            <directory>src/main/java</directory>
            <includes>
                <include>**/*.properties</include>
                <include>**/*.xml</include>
            </includes>
            <filtering>true</filtering>
        </resource>
    </resources>
</build>

编写工具类:

package com.hitenine.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;

//sqlSessionFactory --> sqlSession
public class MybatisUtils {

    private static SqlSessionFactory sqlSessionFactory;

    static {
        try {
            //使用mybatis的第一步获取sqlSessionFactory对象
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    //既然有了 SqlSessionFactory，顾名思义，
    // 我们就可以从中获得 SqlSession 的实例了。
    // SqlSession 完全包含了面向数据库执行 SQL 命令所需的所有方法。
    public static SqlSession getSqlSession() {
        return sqlSessionFactory.openSession();
    }

}

配置文件：

注意xml配置中的顺序：

properties?,settings?,typeAliases?,typeHandlers?,objectFactory?,objectWrapperFactory?,reflectorFactory?,plugins?,environments?,databaseIdProvider?,mappers?

<?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核心配置文件-->
<configuration>

<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>


        <!--    每一个Mapper.xml都需要在MyBatis核心配置文件中注册！注意"/"-->
    </environments>
    <mappers>
        <mapper resource="com/hitenine/dao/UserMapper.xml"/>
    </mappers>
</configuration>

driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis?useSSL=true&useUnicode=true&characterEncoding=utf-8
username=root
password=123456

实体类：

package com.hitenine.pojo;

//实体类
public class User {
    private int id;
    private String name;
    private String pwd;

    public User() {
    }

    public User(int id, String name, String pwd) {
        this.id = id;
        this.name = name;
        this.pwd = pwd;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", pwd='" + pwd + '\'' +
                '}';
    }
}

写接口：

package com.hitenine.dao;

import com.hitenine.pojo.User;

import java.util.List;

public interface UserDao {

    List<User> getUserList();

}

写mapper.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">
<!--namespace=绑定一个对应的Dao/Mapper接口-->
<mapper namespace="com.hitenine.dao.UserDao">

    <!--id为方法名  返回类型：SQL语句的返回值-->
    <select id="getUserList" resultType="com.hitenine.pojo.User">
    select * from mybatis.user
  </select>
</mapper>

使用Junit测试，文件目录最好与src下一样：

package com.hitenine.dao;

import com.hitenine.pojo.User;
import com.hitenine.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserDaoTest {

    @Test
    public void test() {

        //第一步：获得SqlSession对象
        SqlSession sqlSession;
        sqlSession = MybatisUtils.getSqlSession();
        //执行SQL 方式一：getMapper  官方推荐！！
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        List<User> userList = mapper.getUserList();

        //方式二： 不推荐
//        List<User> userList = sqlSession.selectList("com.hitenine.dao.UserDao.getUserList");

        for (User user : userList) {
            System.out.println(user);
        }

        //关闭SqlSessoin
        sqlSession.close();
    }

    /*
    官方建议这样做
    //第一步：获得SqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();;
        try {
            //执行SQL 方式一：getMapper  官方推荐！！
            UserDao mapper = sqlSession.getMapper(UserDao.class);
            List<User> userList = mapper.getUserList();

            //方式二： 不推荐
//        List<User> userList = sqlSession.selectList("com.hitenine.dao.UserDao.getUserList");

            for (User user : userList) {
                System.out.println(user);
            }

        } catch (Exception e) {
            e.printStackTrace();

        } finally {
            //关闭SqlSessoin
            sqlSession.close();
        }
     */
}

Mybatis中的CRUD

package com.hitenine.dao;

import com.hitenine.pojo.User;

import java.util.List;
import java.util.Map;

public interface UserMapper {
    //查询用户
    List<User> getUserList();

    //根据id查询用户
    User getUserById(int id);

    //插入用户
    int addUser(User user);

    //用map添加
    int addUser2(Map<String, Object> map);

    //修改任我
    int updateUser(User user);

    //删除用户
    int deletUser(int id);
}

<?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">
<!--namespace=绑定一个对应的Dao/Mapper接口-->
<mapper namespace="com.hitenine.dao.UserMapper">

<!--    id为方法名  返回类型为：com.hitenine.pojo.User-->
    <select id="getUserList" resultType="com.hitenine.pojo.User">
    select * from mybatis.user
  </select>
    <select id="getUserById" parameterType="int" resultType="com.hitenine.pojo.User">
        select * from mybatis.user where id = #{id}
    </select>

<!--    对象中的属性可以直接取出来-->
    <insert id="addUser" parameterType="com.hitenine.pojo.User">
        insert into mybatis. user(id, name, pwd) values (#{id}, #{name},#{pwd});
    </insert>

    <insert id="addUser2" parameterType="map">
        insert into mybatis. user(id, name, pwd) values (#{userid}, #{username},#{password});
    </insert>

    <update id="updateUser" parameterType="com.hitenine.pojo.User">
        update mybatis.user set name = #{name}, pwd = #{pwd} where id = #{id};
    </update>

    <!--参数类型为int的时候可以不写-->
    <delete id="deletUser" parameterType="int">
        delete from mybatis.user where id = #{id};
    </delete>

</mapper>

package com.hitenine.dao;

import com.hitenine.pojo.User;
import com.hitenine.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class UserMapperTest {

   // @Test
    public void test() {

        //第一步：获得SqlSession对象
        SqlSession sqlSession;
        sqlSession = MybatisUtils.getSqlSession();
        //执行SQL 方式一：getMapper  官方推荐！！
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> userList = mapper.getUserList();

        //方式二： 不推荐
//        List<User> userList = sqlSession.selectList("com.hitenine.dao.UserDao.getUserList");

        for (User user : userList) {
            System.out.println(user);
        }

        //关闭SqlSessoin
        sqlSession.close();
    }

    /*
    官方建议这样做
    //第一步：获得SqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();;
        try {
            //执行SQL 方式一：getMapper  官方推荐！！
            UserDao mapper = sqlSession.getMapper(UserDao.class);
            List<User> userList = mapper.getUserList();

            //方式二： 不推荐
//        List<User> userList = sqlSession.selectList("com.hitenine.dao.UserDao.getUserList");

            for (User user : userList) {
                System.out.println(user);
            }

        } catch (Exception e) {
            e.printStackTrace();

        } finally {
            //关闭SqlSessoin
            sqlSession.close();
        }
     */

    //@Test
    public void getUserByIdTest() {
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        User user = mapper.getUserById(3);

        System.out.println(user);

        sqlSession.close();

    }

    //增删改需要提交事务
   // @Test
    public void addUserTest() {
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        int res = mapper.addUser(new User(5, "hah", "123"));
        if (res > 0) {
            System.out.println("插入成功！");
        }

        //提交事务
        sqlSession.commit();
        sqlSession.close();

    }

    //增删改需要提交事务
     @Test
    public void addUser2Test() {
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

         Map<String, Object> map = new HashMap<>();
         map.put("userid", 5);
         map.put("username", "hello");
         map.put("password", "12345");


         mapper.addUser2(map);


        //提交事务
        sqlSession.commit();
        sqlSession.close();

    }

    //修改用户
    //@Test
    public void updateUserTest() {
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        int updateUser = mapper.updateUser(new User(4, "哈哈", "1234"));

        if (updateUser > 0) {
            System.out.println("更新成功！");
        }

        //提交事务
        sqlSession.commit();
        sqlSession.close();

    }

    //删除用户
    @Test
    public void deletUserTest() {
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int i = mapper.deletUser(4);

        if (i > 0) {
            System.out.println("删除成功！");
        }

        //提交事务
        sqlSession.commit();
        sqlSession.close();

    }

}

Map的强大

//用map添加
int addUser2(Map<String, Object> map);

<insert id="addUser2" parameterType="map">
    insert into mybatis. user(id, name, pwd) values (#{userid}, #{username},#{password});
</insert>

    public void addUser2Test() {
        SqlSession sqlSession = MybatisUtils.getSqlSession();
	UserMapper mapper = sqlSession.getMapper(UserMapper.class);

     Map<String, Object> map = new HashMap<>();
     map.put("userid", 5);
     map.put("username", "hello");
     map.put("password", "12345");
	mapper.addUser2(map);
	//提交事务
    sqlSession.commit();
    sqlSession.close();
}

熟练掌握Map

Map传递参数，直接在sql中取出key即可！ parameterType="map"

对象传递参数，直接在sql中取对象的属性即可 parameterType="Object"

只有一个基本类型参数的情况下，可以直接在sql中取到 parameterType可以忽略

多个参数用Map，或注解

模糊查询：

java代码执行的时候，传递通配符% %

List<User> userLike = mapper.getUserLike("%h%");

在sql拼接中使用通配符

select * from mybatis.user where name like "%"#{value}"%";

<select id="getUserByLike" resultType="userDto">
    select * from hi_test02.t_user
    <where>
        <if test="username != null">
            username like concat('%', #{username} ,'%')
        </if>
        limit #{offset},#{limit}
    </where>
</select>

ResultMap结果集映射

<!--结果集映射-->
<resultMap id="UserMap" type="User">
    <!--column数据库中的字段，property实体类中的属性-->
    <!--<result column="id" property="id"/>-->
    <!--<result column="name" property="name"/>-->
    <result column="pwd" property="password"/>
</resultMap>

<!--可以省略resultType-->
<select id="getUserById" resultMap="UserMap">
    select * from mybatis.user where id = #{id}
</select>

日志

注意xml顺序，大小写，是否多空格

日志工厂：

<settings>
    <setting name="logImpl" value="STDOUT_LOGGING"/>
</settings>

Log4j：

先导入log4j的jar包<!--

<dependency>
    <groupId>log4j</groupId>
    <artifactId>log4j</artifactId>
    <version>1.2.17</version>
</dependency>

log4j.properties

#将等级为DEBUG的日志信息输出到console和file这两个目的地，console和life的定义在下面的代码
log4j.rootLogger=DEBUG,console,file

#控制台输出的相关设置
log4j.appender.console = org.apache.log4j.ConsoleAppender
log4j.appender.console.Target = System.out
log4j.appender.console.Threshold=DEBUG
log4j.appender.console.layout = org.apache.log4j.PatternLayout
log4j.appender.console.layout.ConversionPattern = [%c]-%m%n

#文件传输出的相关设置
log4j.appender.file = org.apache.log4j.RollingFileAppender
log4j.appender.file.File = ./log/hitenine.log
log4j.appender.file.MaxFileSize=10Mb
log4j.appender.file.Threshold=DEBUG
log4j.appender.file.layout = org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=[%p][%d{yy-MM-dd}][%c]%m%n

#日志输出级别
log4j.logger.org.mybatis=DEBUG
log4j.logger.java.sql=DEBUG
log4j.logger.java.sql.Statement=DEBUG
log4j.logger.java.sql.ResultSet=DEBUG
log4j.logger.java.sql.PreparedStatement=DEBUG

配置log4j为日志的实现

<settings>
    <setting name="logImpl" value="LOG4J"/>
</settings>

Log4j的使用，直接测试

简单使用

在要使用Log4j 的类中，导入org.apache.log4j.Logger;

日志对象，加载参数为当前类的class

 static Logger logger = Logger.getLogger(UserDaoTest.class);

日志级别

logger.info("info:进入了testLog4j方法");
logger.debug("debug:进入了testLog4j");
logger.error("error:进入了testLog4j");

多对一处理

按照查询嵌套处理

<select id="getStudent" resultMap="StudentTeacher">
    select * from student
</select>
<resultMap id="StudentTeacher" type="Student">
    <result property="id" column="id"/>
    <result property="name" column="name"/>
    <!--复杂的属性我们需要单独处理
    对象：association
    集合：collection
    -->
    <association property="teacher" column="tid" javaType="Teacher" select="getTeacher"/>
</resultMap>
<select id="getTeacher" resultType="Teacher">
    select * from teacher where id = #{id}
</select>

按照结果嵌套处理

<select id="getStudent2" resultMap="StudentTeacher2">
    select s.id sid,s.name sname,t.name tname
    from mybatis.student s,mybatis.teacher t
    where s.tid = t.id
</select>
<resultMap id="StudentTeacher2" type="Student">
    <result property="id" column="sid"/>
    <result property="name" column="sname"/>
    <association property="teacher" javaType="Teacher">
        <result property="name" column="tname"/>
    </association>
</resultMap>

一对多处理

按照查询嵌套处理

<select id="getTeacher" resultMap="TeacherStudent">
    select s.id sid, s.name sname, t.name tname, t.id tid
    from student s,
    teacher t
    where s.tid = t.id and t.id = #{tid};
</select>

<resultMap id="TeacherStudent" type="Teacher">
    <result property="id" column="tid"/>
    <result property="name" column="tname"/>
    <!--复杂的属性，我们需要处理 对象：association 集合：collection
        javaType="" 指定属性的类型
        集合中的泛型信息，我们使用ofType获取
        -->
    <collection property="students" ofType="Student">
        <result property="id" column="sid"/>
        <result property="name" column="sname"/>
        <result property="tid" column="tid"/>
    </collection>
</resultMap>

按照结果嵌套处理

<select id="getTeacher2" resultMap="TeacherStudent2">
    select * from mybatis.teacher where id = #{tid}
</select>
<resultMap id="TeacherStudent2" type="Teacher">
    <!--<result property="id" column="id"/>-->
    <!--<result property="name" column="name"/>-->
    <collection property="students" javaType="ArrayList" ofType="Student" select="getStudentByTeacherId" column="id"/>
</resultMap>
<select id="getStudentByTeacherId" resultType="Student">
    select * from mybatis.student where tid = #{tid}
</select>

驼峰命名转换

creat_time -- > creatTime

<setting name="mapUnderscoreToCamelCase" value="true"/>

动态SQL

什么事动态SQL：动态SQL就是指根据不同的条件生成不同的SQL语句

利用动态SQL这一特性可以彻底摆脱这种痛苦

动态 SQL 元素和 JSTL 或基于类似 XML 的文本处理器相似。在 MyBatis 之前的版本中，有很多元素需要花时间了解。MyBatis 3 大大精简了元素种类，现在只需学习原来一半的元素便可。MyBatis 采用功能强大的基于 OGNL 的表达式来淘汰其它大部分元素。

if
choose (when, otherwise)
trim (where, set)
foreach

搭建环境

CREATE TABLE `bolg`(
	`id` VARCHAR(50) NOT NULL COMMENT '博客id',
	`title` VARCHAR(100) not null comment '博客标题',
	`author` VARCHAR(30) not null comment '博客作者',
	`creat_time` datetime not null comment '创建时间',
	`views` int(30) not null comment '浏览量'
)ENGINE=InnoDB DEFAULT CHARSET=utf8

创建一个基础工程

导包
编写配置文件

编写实体类

@Data
public class Blog {
    private int id;
    private String title;
    private String author;
    private Date creatTime;
    private int views;
}

编写实体类对应的Mapper接口和Mapper.xml

IF

<select id="queryBlogIF" parameterType="map" resultType="com.rui.pojo.Blog">
    select * from mybatis.bolg where 1=1
    <if test="title != null">
        and title = #{title}
    </if>
    <if test="author != null">
        and author = #{author}
    </if>
</select>

@Test
public void queryBlogIF(){
    SqlSession sqlSession = MyBatisUtils.getSqlSession();
    BlogMapper mapper = sqlSession.getMapper(BlogMapper.class);
    HashMap map = new HashMap();
    map.put("author","尹锐");
    List<Blog> blogs = mapper.queryBlogIF(map);
    for (Blog blog : blogs) {
        System.out.println(blog);
    }
    sqlSession.close();
}

choose (when, otherwise)

<select id="queryBlogChoose" parameterType="map" resultType="com.rui.pojo.Blog">
    select * from mybatis.bolg
    <where>
        <choose>
            <when test="title != null">
                title=#{title}
            </when>
            <when test="author!=null">
                and author = #{author}
            </when>
            <otherwise>
                and views = #{views}
            </otherwise>
        </choose>
    </where>
</select>

trim, (where, set)

select * from mybatis.bolg
<where>
<if test="title != null">
    title = #{title}
</if>
<if test="author != null">
    and author = #{author}
</if>
</where>

<update id="updateBlog" parameterType="map">
    update mybatis.bolg
    <set>
        <if test="title != null">
            title = #{title},
        </if>
        <if test="author != null">
            author = #{author},
        </if>
    </set>
    where id = #{id}
</update>

所谓的动态SQL，本质还是SQL语句，只是我们可以在SQL层面，去执行一些逻辑代码

Where,set,choose,when

SQL片段

有的时候，我们可能会将一些公共的部分抽取出来，方便复用！

使用SQL标签抽取公共的部分

<sql id="if-title-author">
    <if test="title != null">
        title = #{title}
    </if>
    <if test="author != null">
        and author = #{author}
    </if>
</sql>

在需要使用的地方使用Include标签引用即可

<select id="queryBlogIF" parameterType="map" resultType="com.rui.pojo.Blog">
    select * from mybatis.bolg
    <where>
        <include refid="if-title-author"></include>
    </where>
</select>

注意事项：

最好基于单表来定义SQL片段！
不要存在where或者set标签，片段里尽量只有if就好了

Foreach

select * from user where 1=1 and 
  <foreach item="id" index="index" collection="ids"
      open="(" separator="or" close=")">
        #{id}
  </foreach>

(id=1 or id=2 or id=3)

<!--
select * from mybatis.bolg where 1=1 and (id=1 or id=2 or id=3)

我们现在传递一个万能的map，这个map中可以存在一个map
-->
<select id="queryBlogForeach" parameterType="map" resultType="com.rui.pojo.Blog">
    select * from mybatis.bolg

    <where>
    <foreach collection="ids" item="id" open="(" close=")" separator="or">
        id = #{id}
    </foreach>
    </where>
</select>

动态SQL就是在拼接SQL语句，我们只要保证SQL的正确性，按照SQL的格式，去排列组合就可以了

建议：

先在Mysql中写出完整的SQL，在对应的去修改称为我们的动态SQL

foreach

<delete id="deleteUser" parameterType="list">
        delete from hi_test02.t_user where id in
        <if test="list!=null and list.size()>0">
            <foreach collection="list" item="id" open="(" separator="," close=")">
                #{id}
            </foreach>
        </if>
</delete>

posted @ 2020-01-18 18:07 Nine_Hite 阅读(148) 评论(0) 收藏举报

刷新页面返回顶部

Nine_Hite

MyBatis

熟悉MyBatis

jar包:

由于maven中约定大于配置（配置文件需要写在resources目录下），所以要配置资源导出：

编写工具类:

配置文件：

实体类：

写接口：

写mapper.xml：

使用Junit测试，文件目录最好与src下一样：

Mybatis中的CRUD

模糊查询：

ResultMap结果集映射

日志

日志工厂：

Log4j：

简单使用

多对一处理

按照查询嵌套处理

按照结果嵌套处理

一对多处理

按照查询嵌套处理

按照结果嵌套处理

驼峰命名转换

动态SQL

搭建环境

IF

choose (when, otherwise)

trim, (where, set)

SQL片段

Foreach

foreach

公告