mybatis项目CRUD步骤实例详解

 

mybatis项目CRUD步骤

1.pom.xml引入相应的依赖

  <?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
<!--父工程-->
    <groupId>org.example</groupId>
    <artifactId>demo1</artifactId>
    <packaging>pom</packaging>
    <version>1.0-SNAPSHOT</version>
    <modules>
        <module>demo01</module>
        <module>demo02</module>
        <module>demo03</module>
        <module>demo04</module>
    </modules>
    <!--    导入依赖-->
     <dependencies>
         <dependency>
             <groupId>mysql</groupId>
             <artifactId>mysql-connector-java</artifactId>
             <version>8.0.28</version>
         </dependency>
<!--         导入lombok依赖-->
         <dependency>
             <groupId>org.projectlombok</groupId>
             <artifactId>lombok</artifactId>
             <version>1.18.22</version>
         </dependency>
         <dependency>
             <groupId>org.mybatis</groupId>
             <artifactId>mybatis</artifactId>
             <version>3.5.9</version>
         </dependency>
         <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
             <version>4.13</version>
             <scope>test</scope>
         </dependency>
         <dependency>
             <groupId>org.mybatis.caches</groupId>
             <artifactId>mybatis-ehcache</artifactId>
             <version>1.2.1</version>
         </dependency>
     </dependencies>
<!--maven资源导出,约定大于配置-->
    <build>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties
                    </include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties
                    </include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
        </resources>
    </build>


</project>

2. 在resources目录下写配置文件

  • 数据库连接配置
  • db.properties
  driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis?useSSL=true&useUnicode=true&characterEncoding=UTF-8
username=root
password=123456
  • mybatis配置
  • mybatis-config.xml
  <?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>
<!--    引入外部配置文件-->
    <properties resource="db.properties">

    </properties>

    <settings>
        <!--    开启日志-->
        <setting name="logImpl" value="STDOUT_LOGGING"/>
        <!--显示的开启缓存-->
        <setting name="cacheEnabled" value="true"/>
    </settings>
<!--    类型别名:可以给实体类起别名-->
    <typeAliases>
<!--        固定别名-->
<!--        <typeAlias type="com.wyc.pojo.User" alias="User"></typeAlias>-->

<!--        扫描包:扫描实体类的包,它的默认别名就为这个类的类名,首字母小写!-->
        <package name="com.wyc.pojo"/>
    </typeAliases>

    <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>
<!--    注册mapper-->
    <mappers>
        <mapper class="com.wyc.dao.UserMapper"/>
    </mappers>
</configuration>

  • 自定义缓存配置
  • ehcache.xml
  <?xml version="1.0" encoding="UTF-8"?>
<ehcache xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:noNamespaceSchemaLocation="http://ehcache.org/ehcache.xsd"
         updateCheck="false">

    <diskStore path="./tmpdir/Tmp_EhCache"/>

    <defaultCache
            eternal="false"
            maxElementsInMemory="10000"
            overflowToDisk="false"
            diskPersistent="false"
            timeToIdleSeconds="1800"
            timeToLiveSeconds="259200"
            memoryStoreEvictionPolicy="LRU"/>

    <cache
            name="cloud_user"
            eternal="false"
            maxElementsInMemory="5000"
            overflowToDisk="false"
            diskPersistent="false"
            timeToIdleSeconds="1800"
            timeToLiveSeconds="1800"
            memoryStoreEvictionPolicy="LRU"/>
</ehcache>

3. 创建相应的包

img

各个层的含义

img

4. 在utils层

获取获取sqlSessionFactory对象

  package com.wyc.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 MybayisUtils {
    private static SqlSessionFactory sqlSessionFactory;
    static {
        try{
            //使用mybatis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();
            }
    }
    public static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession(true);


    }
}

5. 在pojo层创建实体类,类名与数据库表一致

  package com.wyc.pojo;

import lombok.Data;

@Data   //自动生成get set 等方法,详细点击 右边的Structure
public class User {
    private int id;
    private String name;
    private String pwd;
}

6.在dao层编写Mapper接口,和Mapper.xml sql语法

UserMapper

  package com.wyc.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 MybayisUtils {
    private static SqlSessionFactory sqlSessionFactory;
    static {
        try{
            //使用mybatis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();
            }
    }
    public static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession(true);


    }
}

UserMapper.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">
<mapper namespace="com.wyc.dao.UserMapper">
    <insert id="add">

    </insert>
    <insert id="addUser" parameterType="com.wyc.pojo.User">
    insert into mybatis.user (id,name,pwd) value (#{id},#{name},#{pwd})
    </insert>
    <insert id="addUser2" parameterType="map">
    insert into mybatis.user (id,name,pwd) value (#{userid},#{username},#{userpwd})
    </insert>
    <update id="update" parameterType="com.wyc.pojo.User">
    update mybatis.user set name =#{name},pwd=#{pwd} where id = #{id} ;
    </update>
    <delete id="deleteUser">
        delete from mybatis.user where id = #{id}
    </delete>
    <select id="getUserList" resultType="com.wyc.pojo.User">
    select * from mybatis.user
  </select>
    <select id="getUserById" resultType="com.wyc.pojo.User" parameterType="int">
    select * from mybatis.user where id = #{id}
    </select>
    <select id="getUserById2" resultType="com.wyc.pojo.User" parameterType="map">
    select * from mybatis.user where id = #{id} and name = #{name};
    </select>
    <select id="getUserLike" resultType="com.wyc.pojo.User">
    select * from mybatis.user where name like "%"#{value}"%"

    </select>
        
        
<!--    在当前mapper.xml中开启二级缓存-->
    <cache eviction="FIFO"
           flushInterval="60000"
           size="512"
           readOnly="true"
    ></cache>

<!--自定义缓存-->
<cache type="org.mybatis.caches.ehcache.EhcacheCache"/>
<!--useCache="true":使用开启缓存-->
    <select id="queryUserById" parameterType="int" resultType="user" useCache="true">
        select * from mybatis.user where id = #{id}
    </select>
</mapper>

BlogMapper

img

BlogMapper.xml

  <?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.wyc.dao.BlogMapper">
    <insert id="addBlog" parameterType="blog">
        insert into mybatis.blog (id,title,author,create_time,views)
        value (#{id},#{title},#{author},#{createTime},#{views});
    </insert>
    <sql id="if-title-author">                     //if语句
        <if test="title != null">
            and title = #{title}
        </if>
        <if test="author != null">
            and author = #{author}
        </if>
    </sql>
    <select id="queryBlogIf" parameterType="map" resultType="blog">
    select * from mybatis.blog where 1=1
    <where>
        <include refid="if-title-author"></include>
    </where>
    </select>



    <select id="queryBlogChoose" parameterType="map" resultType="blog">   //choose语句
    select * from mybatis.blog
    <where>
        <choose>
            <when test="title != null">
                 title = #{title}
            </when>
            <when test="title != null">
                 and author = #{author}
            </when>
            <otherwise>
                and views = #{views}
            </otherwise>
        </choose>
    </where>
    </select>
<!--我们现在传入一个万能的map,这个map可以存一个集合
          select * from mybatis.blog where 1=1 and (id=1 or id=2 or id=3)
-->
    <select id="queryBlogForeach" parameterType="map" resultType="blog">   //foreach语句
    select * from mybatis.blog
     <where>
            <foreach collection="ids" item="id" open="and (" close=")" separator="or">  separator  拼接sql
                id = #{id}
            </foreach>
     </where>
    </select>


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

7.编写测试类test,进行测试

1. UserTest

  package com.wyc.dao;

import com.wyc.pojo.User;
import com.wyc.utils.MybayisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

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

public class UserDaoTest {
    @Test
    //查询所有用户
    public void test(){
        //第一步:获得SqlSession对象
        SqlSession sqlSession = MybayisUtils.getSqlSession();
        //执行sql  方式一:getMapper
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> userList = mapper.getUserList();
        for (User user : userList) {
            System.out.println(user);

        }

    }
    @Test
    public void testlike(){
        SqlSession sqlSession = MybayisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> userLike = mapper.getUserLike("zhang%");  //%最好在sql中拼接
        for (User user : userLike) {
            System.out.println("______________________");
            System.out.println(user);
        }
    }
    @Test
    //根据id查询
    public void test1(){
        SqlSession sqlSession = MybayisUtils.getSqlSession();
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        User userById = mapper.getUserById(1);
        System.out.println(userById);

    }
    @Test
    //添加用户 增删改查需要提交事物
    public void test2(){
        SqlSession sqlSession = MybayisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int addUser = mapper.addUser(new User(5,"HH","123"));
        sqlSession.commit();

    }
    @Test
    public void add(){
        SqlSession sqlSession = MybayisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        Map<String, Object> map = new HashMap<String, Object>();
        map.put("userid",7);
        map.put("username","zhangsan");
        mapper.addUser2(map);
        sqlSession.commit();

    }
    @Test
    //修改用户
    public void test3(){
        SqlSession sqlSession = MybayisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int update = mapper.update(new User(3, "rr", "1234"));
        sqlSession.commit();
    }
    @Test
    //删除用户
    public void test4(){
        SqlSession sqlSession = MybayisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int user = mapper.deleteUser(2);
        sqlSession.commit();

    }
}

2. BlogTest

  import com.wyc.dao.BlogMapper;
import com.wyc.dao.UserMapper;
import com.wyc.pojo.Blog;
import com.wyc.pojo.User;
import com.wyc.utils.IDutils;
import com.wyc.utils.MybayisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;

public class MyTest {
    @Test
    public void test(){
        SqlSession sqlSession = MybayisUtils.getSqlSession();
        BlogMapper mapper = sqlSession.getMapper(BlogMapper.class);
        Blog blog = new Blog();
        blog.setId(IDutils.getId());
        blog.setTitle("mybatis如此简单");
        blog.setAuthor("狂神说");
        blog.setCreateTime(new Date());
        blog.setViews(9999);
        mapper.addBlog(blog);

        blog.setId(IDutils.getId());
        blog.setTitle("java如此简单");
        mapper.addBlog(blog);

        blog.setId(IDutils.getId());
        blog.setTitle("spring如此简单");
        mapper.addBlog(blog);

        blog.setId(IDutils.getId());
        blog.setTitle("微服务如此简单");
        mapper.addBlog(blog);

        sqlSession.commit();

    }
    @Test
    public void test2(){
        SqlSession sqlSession = MybayisUtils.getSqlSession();
        BlogMapper mapper = sqlSession.getMapper(BlogMapper.class);
        HashMap map = new HashMap();
        map.put("author","狂神说");
        List<Blog> blogs = mapper.queryBlogIf(map);
        for (Blog blog : blogs) {
            System.out.println(blog);
        }

    }
    @Test
    public void test3(){
        SqlSession sqlSession = MybayisUtils.getSqlSession();
        BlogMapper mapper = sqlSession.getMapper(BlogMapper.class);
        HashMap map = new HashMap();
        map.put("views",9999);
        List<Blog> blogs = mapper.queryBlogChoose(map);
        for (Blog blog : blogs) {
            System.out.println(blog);
        }

    }
    @Test
    public void test4(){
        SqlSession sqlSession = MybayisUtils.getSqlSession();
        BlogMapper mapper = sqlSession.getMapper(BlogMapper.class);
        HashMap map = new HashMap();
//        map.put("views",9999);
        map.put("id","aaee3fee53d041ef93f51ff42d432d");
        map.put("author","超哥说");
        map.put("title","编程如此简单");
        mapper.updateBlog(map);
        sqlSession.commit();

    }
    @Test
    public void test5(){
        SqlSession sqlSession = MybayisUtils.getSqlSession();
        BlogMapper mapper = sqlSession.getMapper(BlogMapper.class);
        HashMap map = new HashMap();
        ArrayList<Integer> ids = new ArrayList<Integer>();
        ids.add(1);
        map.put("ids",ids);
        List<Blog> blogs = mapper.queryBlogForeach(map);
        for (Blog blog : blogs) {
            System.out.println(blog);
        }
        sqlSession.commit();

    }
    @Test
    public void queryUserById(){
        SqlSession sqlSession = MybayisUtils.getSqlSession();
        SqlSession sqlSession2 = MybayisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        User user = mapper.queryUserById(1);
        System.out.println(user);
        sqlSession.close();
        UserMapper mapper2 = sqlSession2.getMapper(UserMapper.class);
        User user2 = mapper2.queryUserById(1);
        System.out.println(user2);
    }
}

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 了解下这两个文件类型.java文件是给人看的.class是给计算机看的程序员编写的是.java文件,经编译后生成.class文件给计算执行。相信这两句话很 ...