【JAVAEE框架】Mybatis常用操作（CRUD）

心已赠人 2024-05-23 18:59 53阅读 0赞

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> 哈喽~大家好呀，这篇来看看使用的常用操作。
> 
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**目录**

一、准备工作

二、查询所有用户信息

三、按 xx 进行查询

四、模糊查询

五、增删改操作

六、联合查询

七、分页查询

--------------------

## 一、准备工作 ##

如何新建 Mybatis 项目，可以看看上一篇的讲解——[【JAVAEE框架】Mybatis项目起步讲解][JAVAEE_Mybatis]

> 准备 tb\_brand 表，字段id（id）、品牌名（brand\_name）、公司名（company\_name）、排序顺序（ordered）、描述信息（description）、状态（status）。
> 
> ![e93842efc3f646f99c2677ee52b41e48.png][]

项目结构在上篇有所讲解，这里就不重复了，直接上代码讲解。

## 二、查询所有用户信息 ##

我们常见的 xx 管理系统最常见的操作之一，查看所有的记录。

**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.itxzw.dao.IBrandDao">
    
        <select id="getUserList" resultType="Brand">
            select * from tb_brand
        </select>
    
    </mapper>

**IBrandDao**

public interface IBrandDao {
    
        public List<Brand> getUserList() throws Exception;
    
    }

> 接着上次的讲，上次我们讲到SqlSession是dao与db建立的一次会话，就像 servlet 的 session 一样，但，有没有想过，我们以后一个项目有成千上万的访问者访问页面（获取 db 的信息），那么岂不是要建立成千上万次会话？这是很不合理的。所以就有了 MyBatisUtil，就像 jdbc 的 Util 一样

**MyBatisUtil**

public class MyBatisUtil {
    
        private static SqlSessionFactory factory;
    
        static {
    
            try {
                SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
    
                InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
    
                factory = builder.build(is);
            } catch (IOException e) {
                e.printStackTrace();
            }
    
        }
    
        public static SqlSession openSession(){
            return factory.openSession();
        }
    
        public static SqlSession openSession(boolean autoCommit){
            return factory.openSession(autoCommit);
        }
    
    }

**实体类(Brand)**

public class Brand {
        // id 主键
        private Integer id;
        // 品牌名称
        private String brand_name;
        // 企业名称
        private String company_name;
        // 排序字段
        private Integer ordered;
        // 描述信息
        private String description;
        // 状态：0：禁用  1：启用
        private Integer status;
    
        public Brand() {
        }
    
        public Brand(Integer id, String brand_name, String company_name, Integer ordered, String description, Integer status) {
            this.id = id;
            this.brand_name = brand_name;
            this.company_name = company_name;
            this.ordered = ordered;
            this.description = description;
            this.status = status;
        }
    
        public Integer getId() {
            return id;
        }
    
        public void setId(Integer id) {
            this.id = id;
        }
    
        public String getBrand_name() {
            return brand_name;
        }
    
        public void setBrand_name(String brand_name) {
            this.brand_name = brand_name;
        }
    
        public String getCompany_name() {
            return company_name;
        }
    
        public void setCompany_name(String company_name) {
            this.company_name = company_name;
        }
    
        public Integer getOrdered() {
            return ordered;
        }
    
        public void setOrdered(Integer ordered) {
            this.ordered = ordered;
        }
    
        public String getDescription() {
            return description;
        }
    
        public void setDescription(String description) {
            this.description = description;
        }
    
        public Integer getStatus() {
            return status;
        }
    
        public void setStatus(Integer status) {
            this.status = status;
        }
    
        @Override
        public String toString() {
            return "Brand{" +
                    "id=" + id +
                    ", brand_name='" + brand_name + '\'' +
                    ", company_name='" + company_name + '\'' +
                    ", ordered=" + ordered +
                    ", description='" + description + '\'' +
                    ", status=" + status +
                    '}';
        }
    }

**测试**

public class TestMyBatis {
    
        @Test
        public void test01() throws Exception {
    
            IBrandDao userDao = new BrandDao();
    
            List<Brand> userList = userDao.getUserList();
    
            for (Brand brand : userList) {
                System.out.println(brand);
            }
    
    
        }
    
    }

**效果**

![662bf88e05ff4a32b02d0544d2f08856.png][]

## 三、按 xx 进行查询 ##

常见的按照姓名查询、按照 id 查询等，这里就演示 id 查询

**mapper**

<select id="getBrandById" resultType="Brand" parameterType="java.lang.String">
            select * from tb_brand where id = #{id}
        </select>

**IBrandDao**

这里就全部给了，这小节就不多写 IBrandDao 了

public interface IBrandDao {
    
        public List<Brand> getBrandList();
    
        public Brand getBrandById(String id);
    
        public List<Brand> getBrandListByCondition(Brand conn);
    
        public List<Brand> getBrandListByCondition(Map<String,String> conn);
    
        public Integer addBrand(Brand brand);
    
        public Integer updateBrand(Brand brand);
    
        public Integer deleteBrand(Brand brand);
    
        public Integer getBrandByCondition(Brand brand);
    
    }

**测试**

@Test
        public void test02(){
            IBrandDao dao = new BrandDao();
    
            Brand brandList = dao.getBrandById("142");
    
            System.out.println(brandList);
    
        }

**效果**

![7587a3baaa0e4a05a9de94b907ae5e14.png][]

## 四、模糊查询 ##

查询品牌含有8的品牌名

**mapper**

**测试**

@Test
        public void test03(){
            SqlSession sqlSession = MyBatisUtil.openSession();
    
            IBrandDao mapper = sqlSession.getMapper(IBrandDao.class);
    
            Brand brand = new Brand();
            brand.setBrand_name("8");
    //        brand.setCompany_name("小米");
    
            List<Brand> brandList = mapper.getBrandListByCondition(brand);
    
            for (int i = 0; i < brandList.size(); i++) {
                System.out.println(brandList.get(i));
            }
    
        }

**效果**

![2b1d6ef5b680405096ab9e343f398f1f.png][]

> **扩：**
> 
> <!\[CDATA\[\]\]> 用法
> 
> 在使用mybatis 时我们sql是写在xml 映射文件中，如果写的sql中有一些特殊的字符的话，在解析xml文件的时候会被转义，但我们不希望他被转义，所以我们要使用<!\[CDATA\[ \]\]>来解决。
> 
> eg：> < 这两个符号

## 五、增删改操作 ##

**mapper**

**测试**

@Test
        public void test04(){
            SqlSession sqlSession = MyBatisUtil.openSession();
    
            IBrandDao mapper = sqlSession.getMapper(IBrandDao.class);
    
            Brand brand = new Brand(null, "菠萝手机","菠萝",100,"美国有苹果,中国有菠萝",0);
    
            Integer integer = mapper.addBrand(brand);
            sqlSession.commit();
    
            System.out.println(integer);
    
        }
    
    
        @Test
        public void test05(){
            SqlSession sqlSession = MyBatisUtil.openSession();
    
            IBrandDao mapper = sqlSession.getMapper(IBrandDao.class);
    
            Brand brand = new Brand();
            brand.setId(191);
            brand.setCompany_name("大菠萝手机");
    
            Integer integer = mapper.updateBrand(brand);
            sqlSession.commit();
    
            System.out.println(integer);
    
        }
    
        @Test
        public void test06(){
            SqlSession sqlSession = MyBatisUtil.openSession();
    
            IBrandDao mapper = sqlSession.getMapper(IBrandDao.class);
    
            Brand brand = new Brand();
            brand.setId(195);
    
            Integer integer = mapper.deleteBrand(brand);
            sqlSession.commit();
    
            System.out.println(integer);
    
        }

**效果**

![b1dece5ef32a45d78b962f248fec59fb.png][]

![0434ef2e9baa44f08e6743a21c835989.png][]

![cf3d04995c084f099a3798543b8163e9.png][]

![2e26cd92d78c4ac6ac4375ef4eadc118.png][]

![776e86f8b0e14f0d9aafb46c3e51e13c.png][]

## 六、联合查询 ##

**mapper**

**IUserDao**

public List<SmbmsUser> getUserListByCondition(UserCondition conn);

**测试**

@Test
        public void test01(){
    
            SqlSession sqlSession = MyBatisUtil.openSession();
    
            IUserDao mapper = sqlSession.getMapper(IUserDao.class);
    
    
            UserCondition conn = new UserCondition();
    
            List<SmbmsUser> userList = mapper.getUserListByCondition(conn);
            for (SmbmsUser smbmsUser : userList) {
                System.out.println(smbmsUser);
            }
    
    
            sqlSession.close();
        }

**效果**

![c104aec501364a3a9b1351b138f70dd1.png][]

## 七、分页查询 ##

**mapper**

<select id="selectByPage" parameterType="Brand" resultType="Brand">
            select * from tb_brand limit #{begin}, #{size}
        </select>

**IUserDao**

public List<Brand> selectByPage(@Param("begin") int begin, @Param("size") int size);

**测试**

@Test
        public void test01() {
    
            SqlSession sqlSession = MyBatisUtil.openSession();
    
            IUserDao mapper = sqlSession.getMapper(IUserDao.class);
    
            List<Brand> pageBean = mapper.selectByPage(1, 10);
    
            for (Brand brand : pageBean) {
                System.out.println(brand);
            }
    
            sqlSession.close();
        }

**效果**

![152380da67634b65a69c44588bfd2519.png][]

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